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This is talk 10 of 31 at the Conference on Brain Network Dynamics held at the University of California at Berkeley on January 26-27, 2007. Speaker is David A. Leopold, Unit on Cognitive Neurophysiology and Imaging, National Institute of Mental Health, Bethesda, MD. http://intramural.nimh.nih.gov/research/pi/pi_leopold_d.html . Abstract: The role of the striate cortex (area V1) in shaping our perception of visual patterns and scenes is of fundamental importance in understanding how we see. Visual illusions where a salient stimulus can be temporarily rendered invisible have provided a paradigm by which neuroscientists can isolate neural processes directly involved in perception. This approach has been applied to study electrophysiological activity in monkeys, as well as fMRI activation patterns in humans. Interestingly, the different types of studies have provided divergent results regarding the role of V1 in perceptual processing. Human neuroimaging (fMRI) studies have repeatedly shown that during perceptual suppression there is a marked decrease in the BOLD response in V1. In contrast, single unit studies in monkeys have reported the near absence of such suppression in the firing of individual V1 neurons. Here I will present new data in which we directly compare neurophysiological and fMRI responses during perceptual suppression in monkey area V1. By monitoring the two signals in a variety of conditions within the very same monkeys, we found that the single-unit and BOLD activation specifically ceased to be correlated during periods of perceptual suppression. Slow changes in some bands of the local field potential reflected perception, but only over short time scales. I will discuss how the spatiotemporal pattern of neural events in V1 might contribute to shaping the BOLD response, and will argue that the fMRI signal provides a complementary, rather than incorrect, perspective on neural processing within a cortical area.

This article is from Nature Communications , volume 5 . Abstract Propagating waves occur in many excitable media and were recently found in neural systems from retina to neocortex. While propagating waves are clearly present under anaesthesia, whether they also appear during awake and conscious states remains unclear. One possibility is that these waves are systematically missed in trial-averaged data, due to variability. Here we present a method for detecting propagating waves in noisy multichannel recordings. Applying this method to single-trial voltage-sensitive dye imaging data, we show that the stimulus-evoked population response in primary visual cortex of the awake monkey propagates as a travelling wave, with consistent dynamics across trials. A network model suggests that this reliability is the hallmark of the horizontal fibre network of superficial cortical layers. Propagating waves with similar properties occur independently in secondary visual cortex, but maintain precise phase relations with the waves in primary visual cortex. These results show that, in response to a visual stimulus, propagating waves are systematically evoked in several visual areas, generating a consistent spatiotemporal frame for further neuronal interactions.

We propose a theory for ocular dominance (OD) patterns in mammalian primary visual cortex. This theory is based on the premise that OD pattern is an adaptation to minimize the length of intra-cortical wiring. Thus we can understand the existing OD patterns by solving a wire length minimization problem. We divide all the neurons into two classes: left-eye dominated and right-eye dominated. We find that segregation of neurons into monocular regions reduces wire length if the number of connections with the neurons of the same class differs from that with the other class. The shape of the regions depends on the relative fraction of neurons in the two classes. If the numbers are close we find that the optimal OD pattern consists of interdigitating stripes. If one class is less numerous than the other, the optimal OD pattern consists of patches of the first class neurons in the sea of the other class neurons. We predict the transition from stripes to patches when the fraction of neurons dominated by the ipsilateral eye is about 40%. This prediction agrees with the data in macaque and Cebus monkeys. This theory can be applied to other binary cortical systems.

We compare several ConvNets with different depth and regularization techniques with multi-unit macaque IT cortex recordings and assess the impact of the same on representational similarity with the primate visual cortex. We find that with increasing depth and validation performance, ConvNet features are closer to cortical IT representations.

We compare several ConvNets with different depth and regularization techniques with multi-unit macaque IT cortex recordings and assess the impact of the same on representational similarity with the primate visual cortex. We find that with increasing depth and validation performance, ConvNet features are closer to cortical IT representations.

As of 2020 the role of glutathione as a novel neurotransmitter or neuromodulator remains tantalizingly undetermined. See: Multiple Roles of Glutathione in the Nervous System by Christopher Shaw in: Glutathione in the Nervous System edited by Christopher Shaw, 1998 [https://books.google.ca/books?id=7SZhDwAAQBAJ], and Glutathione and Signal Transduction in the Mammalian CNS by Janaky et al., J. Neurochem. 1999 Sep;73(3):889-902.  [Note on name change: In 1994 Stephen Arthur legally changed his name from Stephen Arthur Bowlsby, which is the name cited by Shaw (thesis and Soc. Neurosci. Abstracts 12:75, 1991).] https://en.wikipedia.org/wiki/Glutathione#Potential_neurotransmitters

We present computer simulations of how the visual cortex may discriminate objects based on depth-from-occlusion. We propose neural mechanisms for how the visual system binds edges into contours, and binds contours and surfaces into objects. The model is simulated by a system of physiologically- based neural networks which feature feedback connections from higher to lower cortical areas, a distributed representation of depth, and phase-locked cortical neuronal firing. The system demonstrates psychophysical properties consistent with human perception of real and illusory visual scenes. The model addresses both the binding problem and the problem of object segmentation.

This article is from PLoS ONE , volume 9 . Abstract It is believed that human primary visual cortex (V1) increases activity with increasing temporal frequency of a visual stimulus. Two kinds of visual stimulus were used in the previous studies, one is patterned-flash stimulus with a fixed onset period and an increasing average luminance with the increase of temporal frequency, the other is contrast reversing flickering checkerboard or grating with a constant average luminance across different temporal frequencies. That hemodynamic responses change as a function of reversal frequency of contrast reversing checkerboard is at odds with neurophysiological studies in animals and neuroimaging studies in humans. In the present study, we addressed the relationship between reversal frequency of contrast reversing checkerboard and hemodynamic response in human V1 using an event-related experimental paradigm and found that the transient characteristics of blood oxygenation level dependent response in human V1 depended very little on the reversal frequency of a contrast reversing checkerboard.

This article is from PLoS ONE , volume 9 . Abstract Novel stimuli often require a rapid reallocation of sensory processing resources to determine the significance of the event, and the appropriate behavioral response. Both the amygdala and the visual cortex are central elements of the neural circuitry responding to novelty, demonstrating increased activity to new as compared to highly familiarized stimuli. Further, these brain areas are intimately connected, and thus the amygdala may be a key region for directing sensory processing resources to novel events. Although knowledge regarding the neurocircuit of novelty detection is gradually increasing, we still lack a basic understanding of the conditions that are necessary and sufficient for novelty-specific responses in human amygdala and the visual cortices, and if these brain areas interact during detection of novelty. In the present study, we investigated the response of amygdala and the visual cortex to novelty, by comparing functional MRI activity between 1st and 2nd time presentation of a series of emotional faces in an event-related task. We observed a significant decrease in amygdala and visual cortex activity already after a single stimulus exposure. Interestingly, this decrease in responsiveness was less for subjects with a high score on state anxiety. Further, novel faces stimuli were associated with a relative increase in the functional coupling between the amygdala and the inferior occipital gyrus (BA 18). Thus, we suggest that amygdala is involved in fast sensory boosting that may be important for attention reallocation to novel events, and that the strength of this response depends on individual state anxiety.

In the early visual cortex, information is processed within functional maps whose layout is thought to underlie visual perception. However, the precise organization of these functional maps as well as their interrelationships remains unresolved. Here, we show that spatial frequency representation in cat areas 17 and 18 exhibits singularities around which the map organizes like an electric dipole potential. These singularities are precisely co-located with singularities of the orientation map: the pinwheel centers. We first show, using high resolution optical imaging, that a large majority (around 80%) of pinwheel centers exhibit in their neighborhood semi-global extrema in the spatial frequency map. These extrema created a sharp gradient that was confirmed with electrophysiological recordings. Based on an analogy with electromagnetism, a mathematical model of a dipolar structure is proposed, that was accurately fitted to optical imaging data for two third of pinwheel centers with semi-global extrema. We conclude that more than half of orientation pinwheel centers form spatial frequency dipoles in cat early visual cortex. Given the functional specificities of neurons at singularities in the visual cortex, it is argued that the dipolar organization of spatial frequency around pinwheel centers could be fundamental for visual processing.

This article is from BMC Neuroscience , volume 15 . Abstract None

This article is from PLoS ONE , volume 9 . Abstract Neurofeedback based on real-time functional magnetic resonance imaging (fMRI) is a new approach that allows training of voluntary control over regionally specific brain activity. However, the neural basis of successful neurofeedback learning remains poorly understood. Here, we assessed changes in effective brain connectivity associated with neurofeedback training of visual cortex activity. Using dynamic causal modeling (DCM), we found that training participants to increase visual cortex activity was associated with increased effective connectivity between the visual cortex and the superior parietal lobe. Specifically, participants who learned to control activity in their visual cortex showed increased top-down control of the superior parietal lobe over the visual cortex, and at the same time reduced bottom-up processing. These results are consistent with efficient employment of top-down visual attention and imagery, which were the cognitive strategies used by participants to increase their visual cortex activity.

Development of stimulus selectivity in primary sensory cortex of higher vertebrates is considered in a general mathematical framework. A synaptic evolution scheme of a new kind is proposed in which incoming patterns rather than converging afferents compete. The change in efficacy of a given synapse depends not only on instantaneous pre and postsynaptic activities but also on a slowly varying time-averaged value of the postsynaptic activity. Assuming an appropriate nonlinear form for this dependence, development of selectivity is obtained under quite general conditions on the sensory environment. One does not require nonlinearity of the neuron's integrative power nor does one need to assume any particular form for intracortical circuitry. This is illustrated in simple cases, e.g. when the environment consists of only two different stimuli presented alternately in a random manner. The following formal statement then holds: the state of the system converges with probability 1 to points of maximum selectivity in the state space. We next consider the problem of early development of orientation selectivity and binocular interaction in primary visual cortex. Giving the environment an appropriate form, we obtain orientation tuning curves and ocular dominance comparable to what is observed in normally reared adult cats or monkeys. Simulations with binocular input and various types of normal or altered environments show good agreement with relevant experimental data.

Concurrent with the recent developments in neural network theories of learning and memory has been the experimental demonstration of experience- dependent synaptic plasticity at the highest level of the mammalian nervous system, the cerebral cortex. A neurobiological problem of extraordinary interest is to identify the molecular mechanisms which underlie this process of cortical modification. For the complex forms of plasticity evoked in neocortex by changes in the sensory environment, an essential first step in sorting out the various possibilities is to derive a set of rules that can adequately account for the observed modifications. These rules serve as a guide towards identifying candidate mechanisms that can then be tested experimentally. Hence, it can be seen that two lines of inquiry on concerning neural network theory, the other concerning molecular mechanisms of synapse modification-- converge at the level of the modification rule. We have proposed such a modification rule to explain the rich body of experimental evidence available on the experience-dependent plasticity of the feline visual cortex during early postnatal development. This theoretical form of modification is able to account for the results of a wide variety of deprivation experiments, and has led to a number of predictions that appear to have been confirmed by more recent experiments. In this chapter we shall illustrate how this theory has interacted with experiment to suggest a possible molecular basis for synapse modification in the visual cortex.

This article is from Frontiers in Neural Circuits , volume 7 . Abstract Two theories have influenced our understanding of cortical development: the integrated network theory, where synaptic development is coordinated across areas; and the cascade theory, where the cortex develops in a wave-like manner from sensory to non-sensory areas. These different views on cortical development raise challenges for current studies aimed at comparing detailed maturation of the connectome among cortical areas. We have taken a different approach to compare synaptic development in rat visual, somatosensory, and frontal cortex by measuring expression of pre-synaptic (synapsin and synaptophysin) proteins that regulate vesicle cycling, and post-synaptic density (PSD-95 and Gephyrin) proteins that anchor excitatory or inhibitory (E-I) receptors. We also compared development of the balances between the pairs of pre- or post-synaptic proteins, and the overall pre- to post-synaptic balance, to address functional maturation and emergence of the E-I balance. We found that development of the individual proteins and the post-synaptic index overlapped among the three cortical areas, but the pre-synaptic index matured later in frontal cortex. Finally, we applied a neuroinformatics approach using principal component analysis and found that three components captured development of the synaptic proteins. The first component accounted for 64% of the variance in protein expression and reflected total protein expression, which overlapped among the three cortical areas. The second component was gephyrin and the E-I balance, it emerged as sequential waves starting in somatosensory, then frontal, and finally visual cortex. The third component was the balance between pre- and post-synaptic proteins, and this followed a different developmental trajectory in somatosensory cortex. Together, these results give the most support to an integrated network of synaptic development, but also highlight more complex patterns of development that vary in timing and end point among the cortical areas.

This article is from BMC Neuroscience , volume 14 . Abstract Background: Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables (syl) per second - exceeding by far the maximum performance level of normal-sighted listeners (ca. 8 syl/s). To further elucidate the brain mechanisms underlying this extraordinary skill, functional magnetic resonance imaging (fMRI) was performed in blind subjects of varying ultra-fast speech comprehension capabilities and sighted individuals while listening to sentence utterances of a moderately fast (8 syl/s) or ultra-fast (16 syl/s) syllabic rate. Results: Besides left inferior frontal gyrus (IFG), bilateral posterior superior temporal sulcus (pSTS) and left supplementary motor area (SMA), blind people highly proficient in ultra-fast speech perception showed significant hemodynamic activation of right-hemispheric primary visual cortex (V1), contralateral fusiform gyrus (FG), and bilateral pulvinar (Pv). Conclusions: Presumably, FG supports the left-hemispheric perisylvian “language network”, i.e., IFG and superior temporal lobe, during the (segmental) sequencing of verbal utterances whereas the collaboration of bilateral pulvinar, right auditory cortex, and ipsilateral V1 implements a signal-driven timing mechanism related to syllabic (suprasegmental) modulation of the speech signal. These data structures, conveyed via left SMA to the perisylvian “language zones”, might facilitate – under time-critical conditions – the consolidation of linguistic information at the level of verbal working memory.

This article is from BMC Neuroscience , volume 14 . Abstract Background: Individuals suffering from vision loss of a peripheral origin may learn to understand spoken language at a rate of up to about 22 syllables (syl) per second - exceeding by far the maximum performance level of normal-sighted listeners (ca. 8 syl/s). To further elucidate the brain mechanisms underlying this extraordinary skill, functional magnetic resonance imaging (fMRI) was performed in blind subjects of varying ultra-fast speech comprehension capabilities and sighted individuals while listening to sentence utterances of a moderately fast (8 syl/s) or ultra-fast (16 syl/s) syllabic rate. Results: Besides left inferior frontal gyrus (IFG), bilateral posterior superior temporal sulcus (pSTS) and left supplementary motor area (SMA), blind people highly proficient in ultra-fast speech perception showed significant hemodynamic activation of right-hemispheric primary visual cortex (V1), contralateral fusiform gyrus (FG), and bilateral pulvinar (Pv). Conclusions: Presumably, FG supports the left-hemispheric perisylvian “language network”, i.e., IFG and superior temporal lobe, during the (segmental) sequencing of verbal utterances whereas the collaboration of bilateral pulvinar, right auditory cortex, and ipsilateral V1 implements a signal-driven timing mechanism related to syllabic (suprasegmental) modulation of the speech signal. These data structures, conveyed via left SMA to the perisylvian “language zones”, might facilitate – under time-critical conditions – the consolidation of linguistic information at the level of verbal working memory.

This article is from PLoS ONE , volume 9 . Abstract The mammalian striatum receives inputs from many cortical areas, but the existence of a direct axonal projection from the primary visual cortex (V1) is controversial. In this study we use anterograde and retrograde tracing techniques to demonstrate that V1 directly innervates a topographically defined longitudinal strip of dorsomedial striatum in mice. We find that this projection forms functional excitatory synapses with direct and indirect pathway striatal projection neurons (SPNs) and engages feed-forward inhibition onto these cells. Importantly, stimulation of V1 afferents is sufficient to evoke phasic firing in SPNs. These findings therefore identify a striatal region that is functionally innervated by V1 and suggest that early visual processing may play an important role in striatal-based behaviors.

This article is from PLoS ONE , volume 9 . Abstract The mammalian striatum receives inputs from many cortical areas, but the existence of a direct axonal projection from the primary visual cortex (V1) is controversial. In this study we use anterograde and retrograde tracing techniques to demonstrate that V1 directly innervates a topographically defined longitudinal strip of dorsomedial striatum in mice. We find that this projection forms functional excitatory synapses with direct and indirect pathway striatal projection neurons (SPNs) and engages feed-forward inhibition onto these cells. Importantly, stimulation of V1 afferents is sufficient to evoke phasic firing in SPNs. These findings therefore identify a striatal region that is functionally innervated by V1 and suggest that early visual processing may play an important role in striatal-based behaviors.

Human-level visual performance has remained largely beyond the reach of engineered systems despite decades of research and significant advances in problem formulation, algorithms and computing power. We posit that significant progress can be made by combining existing technologies from machine vision, insights from theoretical neuroscienee and large-scale distributed computing. Such claims have been made before and so it is quite reasonable to ask what are the new ideas we bring to the,table that might make a difference this time around. From a theoretical standpoint, our primary point of departure from current practice is our reliance on exploiting time in order to turn an otherwise intractable unsupervised problem into a locally semi-supervised, and plausibly tractable, learning problem. From a pragmatic perspective, our system architecture follows what we know of conical neuroanatomy and provides a solid foundation for scalable hierarchical inference. This combination of features provides the framework for implementing a wide range of robust object-recognition capabilities.

This is talk 19 (of 31) at the Conference on Brain Network Dynamics held at the University of California at Berkeley on January 26-27, 2007. Speaker is Friedrich T. Sommer, from the Redwood Center for Theoretical Neuroscience, University of California Helen Wills Neuroscience Institute, Berkeley, CA. http://redwood.berkeley.edu/wiki/Fritz_Sommer Abstract: Visually evoked changes in retinal firing rate convey information downstream to the thalamus and to cortex. It is widely held that retinal spike trains code information about the visual stimulus solely by a process that depends on how reproducibly firing rates lock to stimulus onset, that is, by stimulus-locked coding. Yet retinal firing patterns are not only influenced by external stimuli but also by dynamics of intrinsic neuronal networks. In fact, work in other systems suggests that information can be encoded by stimulus-induced changes in ongoing oscillatory activity. Thus it is natural to ask if the early visual system processes sensory information not only by means of stimulus-locked coding but also by a mechanism that compares spike timing to intrinsic activity. To address this question we used whole-cell recording in vivo to record retinal EPSPs and the spikes they evoke from relay cells in the lateral geniculate nucleus of the thalamus in response to naturalistic stimuli. Using information theory to interpret the results, we found that visual information can indeed be transmitted by two separate channels. The first channel transmits stimulus locked information about patterns within the receptive field and is limited to relaying visual signals slower than 30 Hz. The second, novel, channel uses spike timing relative to intrinsic retinal oscillations at fine temporal scales, corresponding to the gamma band (50-70 Hz). Remarkably, the amount of information in the second channel could match or even exceed that conveyed by the first, a result that we were able to reproduce in a simple model of a relay cell. Because retinal oscillations involve large-scale networks, the novel channel could convey distributed, contextual aspects of the stimulus that complement stimulus-locked information about local features.

This article is from Frontiers in Computational Neuroscience , volume 8 . Abstract The primary visual cortex is an excellent model system for investigating how neuronal populations encode information, because of well-documented relationships between stimulus characteristics and neuronal activation patterns. We used two-photon calcium imaging data to relate the performance of different methods for studying population coding (population vectors, template matching, and Bayesian decoding algorithms) to their underlying assumptions. We show that the variability of neuronal responses may hamper the decoding of population activity, and that a normalization to correct for this variability may be of critical importance for correct decoding of population activity. Second, by comparing noise correlations and stimulus tuning we find that these properties have dissociated anatomical correlates, even though noise correlations have been previously hypothesized to reflect common synaptic input. We hypothesize that noise correlations arise from large non-specific increases in spiking activity acting on many weak synapses simultaneously, while neuronal stimulus response properties are dependent on more reliable connections. Finally, this paper provides practical guidelines for further research on population coding and shows that population coding cannot be approximated by a simple summation of inputs, but is heavily influenced by factors such as input reliability and noise correlation structure.

This article is from Frontiers in Computational Neuroscience , volume 8 . Abstract The primary visual cortex is an excellent model system for investigating how neuronal populations encode information, because of well-documented relationships between stimulus characteristics and neuronal activation patterns. We used two-photon calcium imaging data to relate the performance of different methods for studying population coding (population vectors, template matching, and Bayesian decoding algorithms) to their underlying assumptions. We show that the variability of neuronal responses may hamper the decoding of population activity, and that a normalization to correct for this variability may be of critical importance for correct decoding of population activity. Second, by comparing noise correlations and stimulus tuning we find that these properties have dissociated anatomical correlates, even though noise correlations have been previously hypothesized to reflect common synaptic input. We hypothesize that noise correlations arise from large non-specific increases in spiking activity acting on many weak synapses simultaneously, while neuronal stimulus response properties are dependent on more reliable connections. Finally, this paper provides practical guidelines for further research on population coding and shows that population coding cannot be approximated by a simple summation of inputs, but is heavily influenced by factors such as input reliability and noise correlation structure.

This article is from Frontiers in Computational Neuroscience , volume 8 . Abstract The primary visual cortex is an excellent model system for investigating how neuronal populations encode information, because of well-documented relationships between stimulus characteristics and neuronal activation patterns. We used two-photon calcium imaging data to relate the performance of different methods for studying population coding (population vectors, template matching, and Bayesian decoding algorithms) to their underlying assumptions. We show that the variability of neuronal responses may hamper the decoding of population activity, and that a normalization to correct for this variability may be of critical importance for correct decoding of population activity. Second, by comparing noise correlations and stimulus tuning we find that these properties have dissociated anatomical correlates, even though noise correlations have been previously hypothesized to reflect common synaptic input. We hypothesize that noise correlations arise from large non-specific increases in spiking activity acting on many weak synapses simultaneously, while neuronal stimulus response properties are dependent on more reliable connections. Finally, this paper provides practical guidelines for further research on population coding and shows that population coding cannot be approximated by a simple summation of inputs, but is heavily influenced by factors such as input reliability and noise correlation structure.

It's a chilling thought - losing the sense of sight because of severe injury or damage to the brain's visual cortex. But, is it possible to train a damaged or injured brain to "see" again after such a catastrophic injury? Yes, according to Tony Ro, a neuroscientist at The City College of New York, who is artificially recreating a condition called Blindsight in his lab. "Blindsight is a condition that some patients experience after having damage to the primary visual cortex in the back of their brains. What happens in these patients is they go cortically blind, yet they can still discriminate visual information, albeit without any awareness." explains Ro. While no one is ever going to say Blindsight is 20/20, Ro says it holds tantalizing clues to the architecture of the brain. With support from the National Science Foundation, Ro is developing a clearer picture of how other parts of the brain, besides the visual cortex, respond to visual stimuli. He says understanding and mapping those alternative pathways might be the key to new rehabilitative therapies.

In this project, we will examine the effects of offline continuous theta burst stimulation to dorsolateral prefrontal cortex (dlPFC) on metacognition and the interaction between visual working memory and perception. Continuous theta burst stimulation is a transcranial magnetic stimulation (TMS) protocol whereby 50Hz “bursts” of TMS pulse triplets are delivered to a single cortical site in a continuous chain, with a carrier frequency of 5Hz (i.e. five 50hz triplets per second). Continuous theta burst stimulation has been found to elicit short-term alterations to cortical excitability, functional connectivity, and associated task behaviour, and has been routinely applied to dlPFC and visual areas under both clinical and experimental conditions. We will deliver offline neuronavigated continuous theta burst stimulation (cTBS) to area p9-46v (dlPFC) and primary motor cortex (M1), defined using individualised fMRI data (based on resting-state connectivity), and manual mapping of motor excitability with single-pulse TMS over the scalp, respectively. We will use a multi-featural visual working memory task involving change detection for dot motion stimuli. Subjects must remember the speed, orientation, and dot density of an initial motion pattern (pattern 1), before identifying the perceived orientation of a second motion pattern (pattern 2). Next, subjects are shown two test patterns (pattern 3 and pattern 4) and asked to select which of the two test patterns is the same pattern that they remembered (where the other pattern on each trial has been altered in one of three visual feature dimensions: either speed, orientation, or dot density). We refer to this as a 2-alternative-forced-choice (2AFC) change detection task, which is used to assess working memory precision (for pattern 1) in this study. Here, we first aim to replicate a known motion repulsion effect whereby subjects mis-judge the direction of pattern 2 as being oriented further away (clockwise or anticlockwise) from the true pattern 2 direction, respective to the angular separation of pattern 2 from pattern 1 (Kang et al., 2012, doi: 10.3758/s13423-011-0126-5). For example, if subjects remember motion pattern 1 with orientation 45 degrees, and are subsequently presented with motion pattern 2 with orientation 75 degrees, subjects are likely to mis-judge the perceived orientation of pattern 2 as being greater than 75 degrees. Second, we will also measure subjects’ individual change detection thresholds independently for three motion feature dimensions: speed, orientation, and dot density (which will be independently titrated throughout the experimental task using adaptive staircases to maintain the difficulty of the task at approximately 79% correct performance in the 2AFC change detection task). We will also collect trial-by-trial confidence ratings for the 2AFC change detection task. We will measure the effects of continuous theta burst stimulation (cTBS) to dlPFC on 1) the magnitude of the motion repulsion effect, 2) change detection stimulus thresholds (i.e. change magnitude required to keep subjects at 75% correct in the 2AFC change detection task), and 3) metacognitive performance (correspondence between confidence and accuracy; see details in below sections), by comparing the relevant metrics pre- and post-stimulation, within an experimental session. We will examine the anatomical specificity of the effects by comparing these outcomes across stimulation sites (area p9-46v/dlPFC compared to M1, where M1 will serve as a control stimulation site).

Despite immense variability across languages, people can learn to understand any human language, spoken or signed. What neural mechanisms allow people to comprehend language across sensory modalities? When people listen to speech, electrophysiological oscillations in auditory cortex entrain to slow (<8 Hz) fluctuations in the acoustic envelope. Entrainment to the speech envelope may reflect mechanisms specialized for auditory perception. Alternatively, flexible entrainment may be a general-purpose cortical mechanism that optimizes sensitivity to rhythmic information regardless of modality. Here we test these proposals by examining cortical coherence to visual information in sign language. First, we develop a metric to quantify visual change over time. We find quasi-periodic fluctuations in sign language, characterized by lower frequencies than fluctuations in speech. Next, we test for entrainment of neural oscillations to visual change in sign language, using electroencephalography (EEG) in fluent speakers of American Sign Language (ASL) as they watch videos in ASL. We find significant cortical entrainment to visual oscillations in sign language below 5 Hz, peaking at about 1 Hz. Coherence to sign is strongest over occipital and parietal cortex, in contrast to speech, where coherence is strongest over the auditory cortex. Non-signers also show coherence to sign language but entrainment at frontal sites is reduced relative to fluent signers. These results demonstrate that flexible cortical entrainment to language does not depend on neural processes that are specific to auditory speech perception. Low-frequency oscillatory entrainment may reflect a general cortical mechanism that maximizes sensitivity to informational peaks in time-varying signals. [This paper was published in "Proceedings of the National Academy of Sciences" v114 n24 p6352-6357 2017.]

The object of our research is to find principles of development and organization of neural networks that can account both for experimental data on the cellular level and, when applied to large numbers of neurons that receive sensory and/or interneuronal information, for various higher level systems properties. Networks of neurons already have been constructed that can organize themselves to display some cognitive properties. Although these are still primitive compared to what animals or even machines in some cases can presently do, it is significance that these networks are self-organizing, that the global cognitive properties are the result of local modifications of the network components -- learning (so to speak) on a cellular level. This learning comes about through the modification of synaptic junctions (connections) between neurons. One crucial hypothesis concerns the form of this synaptic modification by applying them to the development of selectivity and ocular dominance in cat visual cortex, where much experimental data has been obtained in the last twenty years. This leads to a theory of synaptic evolution based on sets of coupled non-linear stochastic differential equations. Analysis and computer simulations show this theory is in good agreement with classical experimental results. In addition we obtain some new predictions that can be tested.

Temporal dynamics are a well known feature of synaptic transmission. Recently temporal dynamics of synaptic transmission has been reported in neocortex. Here we examine the possible effects of these dynamics on the spatio-temporal receptive fields of simple cells in VI. We do this by examining a simple model of a cortical neuron that depends on an oriented thalamocortical projection. In our model, the receptive field (RF) structure is encoded either as a structured presynaptic probability of release or as a structured postsynaptic efficacy. We show that these different assumptions about the origin of receptive field structure lead to very different spatio-temporal dynamics. The structured efficacy model (SE) leads to tuning curves that are unimodal, and although the response magnitude changes in time, the preferred orientation does not. On the other hand, the structured probability model (PR) leads to tuning curves which are not unimodal and change their preferred orientation in time. We show that the temporal code induced by the dynamic synapses can be used for distinguishing between different input that induce the same average firing rate.

We introduce a novel set of features for robust object recognition. Each element of this set is a complex feature obtained by combining position- and scale-tolerant edge-detectors over neighboring positions and multiple orientations. Our system's architecture is motivated by a quantitative model of visual cortex. We show that our approach exhibits excellent recognition performance and outperforms several state-of-the-art systems on a variety of image datasets including many different object categories. We also demonstrate that our system is able to learn from very few examples. The performance of the approach constitutes a suggestive plausibility proof for a class of feedforward models of object recognition in cortex.

This is a record of the sixteenth symposium sponsored by the Center for Visual Science at the University of Rochester on June 15-18, 1988. It consists of abstracts from the papers presented at the meeting and a list of the participants. Five topical sessions each included four papers. The sessions were: early visual processing, parallel channels cortical processing (approaches), levels of cortical processing, and visuomotor integration. Keywords: Symposia; Visual cortex; Vision; Visual perception.

Firing fields of grid cells in medial entorhinal cortex show compression or expansion after manipulations of the location of environmental barriers. This compression or expansion could be selective for individual grid cell modules with particular properties of spatial scaling. We present a model for differences in the response of modules to barrier location that arise from different mechanisms for the influence of visual features on the computation of location that drives grid cell firing patterns. These differences could arise from differences in the position of visual features within the visual field. When location was computed from the movement of visual features on the ground plane (optic flow) in the ventral visual field, this resulted in grid cell spatial firing that was not sensitive to barrier location in modules modeled with small spacing between grid cell firing fields. In contrast, when location was computed from static visual features on walls of barriers, i.e. in the more dorsal visual field, this resulted in grid cell spatial firing that compressed or expanded based on the barrier locations in modules modeled with large spacing between grid cell firing fields. This indicates that different grid cell modules might have differential properties for computing location based on visual cues, or the spatial radius of sensitivity to visual cues might differ between modules.

. Automatic object recognition from still imagery, insensitive to clutter and partial occlusion, is an unsolved computer vision problem with countless applications to military readiness. Ambiguity of segmentation of complex images into objects is the major stumbling block. Incorporation of certain structural features of the primate early visual system into computational models has been suggested as a potential solution. However, little is known about effects of these features on segmentation performance of either humans or computational models

This report used a combination of physiological and anatomical approaches to elucidate the functional organization of visual cortex in the macaque monkey. One project was a single cell analysis of texture vision, using texture patterns of the type developed by Julesz for human psychophysical studies. Many cells tested in area V2 responded to static or moving texture gradients in ways which were not predictable on the basis of responses to individual texture elements and which correlated with the preattentive discriminability of these texture patterns to human observers. A second project involved the development of a computerized technique for generating two-dimensional maps of cerebral cortex. An algorithm based on simulated annealing procedures was used to construct a complete map of primary visual cortex, thereby demonstrating its suitability for dealing with anatomical data from highly convoluted regions of cortex. A third project involved the use of voltage-sensitive dyes to monitor activity patterns in visual cortex. This technique offers great promise for analyzing the organization of large neural ensembles with high spatial and temporal resolution. Keywords: Cerebral cortex; Pattern recognition; Cortical mapping; Single neuron physiology.

This article is from Frontiers in Psychology , volume 5 . Abstract Stimulation using weak electrical direct currents has shown to be capable of inducing polarity-dependent diminutions or elevations in motor and visual cortical excitability. The aim of the present study was to test if reading during transcranial direct current stimulation (tDCS) is able to modify stimulation-induced plasticity in the visual cortex. Phosphene thresholds (PTs) in 12 healthy subjects were recorded before and after 10 min of anodal, cathodal, and sham tDCS in combination with reading. Reading alone decreased PTs significantly, compared to the sham tDCS condition without reading. Interestingly, after both anodal and cathodal stimulation there was a tendency toward smaller PTs. Our results support the observation that tDCS-induced plasticity is highly dependent on the cognitive state of the subject during stimulation, not only in the case of motor cortex but also in the case of visual cortex stimulation.

This article is from Frontiers in Psychology , volume 5 . Abstract Stimulation using weak electrical direct currents has shown to be capable of inducing polarity-dependent diminutions or elevations in motor and visual cortical excitability. The aim of the present study was to test if reading during transcranial direct current stimulation (tDCS) is able to modify stimulation-induced plasticity in the visual cortex. Phosphene thresholds (PTs) in 12 healthy subjects were recorded before and after 10 min of anodal, cathodal, and sham tDCS in combination with reading. Reading alone decreased PTs significantly, compared to the sham tDCS condition without reading. Interestingly, after both anodal and cathodal stimulation there was a tendency toward smaller PTs. Our results support the observation that tDCS-induced plasticity is highly dependent on the cognitive state of the subject during stimulation, not only in the case of motor cortex but also in the case of visual cortex stimulation.

This article is from Frontiers in Psychology , volume 5 . Abstract Stimulation using weak electrical direct currents has shown to be capable of inducing polarity-dependent diminutions or elevations in motor and visual cortical excitability. The aim of the present study was to test if reading during transcranial direct current stimulation (tDCS) is able to modify stimulation-induced plasticity in the visual cortex. Phosphene thresholds (PTs) in 12 healthy subjects were recorded before and after 10 min of anodal, cathodal, and sham tDCS in combination with reading. Reading alone decreased PTs significantly, compared to the sham tDCS condition without reading. Interestingly, after both anodal and cathodal stimulation there was a tendency toward smaller PTs. Our results support the observation that tDCS-induced plasticity is highly dependent on the cognitive state of the subject during stimulation, not only in the case of motor cortex but also in the case of visual cortex stimulation.

This article is from Frontiers in Human Neuroscience , volume 8 . Abstract Working memory (WM) is central to human cognition as it allows information to be kept online over brief periods of time and facilitates its usage in cognitive operations (Luck and Vogel, 2013). How this information maintenance actually is implemented is still a matter of debate. Several independent theories of WM, derived, respectively, from behavioral studies and neural considerations, advance the idea that items in WM decay over time and must be periodically reactivated. In this proposal, we show how recent data from intracranial EEG and attention research naturally leads to a simple model of such reactivation in the case of sensory memories. Specifically, in our model the amplitude of high-frequency activity (>50 Hz, in the gamma-band) underlies the representation of items in high-level visual areas. This activity decreases to noise-levels within 500 ms, unless it is reactivated. We propose that top-down attention, which targets multiple sensory items in a cyclical or rhythmic fashion at around 6–10 Hz, reactivates these decaying gamma-band representations. Therefore, working memory capacity is essentially the number of representations that can simultaneously be kept active by a rhythmically sampling attentional spotlight given the known decay rate. Since attention samples at 6–10 Hz, the predicted WM capacity is 3–5 items, in agreement with empirical findings.

This article is from Frontiers in Neuroanatomy , volume 8 . Abstract Calretinin is a calcium-binding protein often used as a marker for a subset of inhibitory interneurons in the mammalian neocortex. We studied the labeled cells in offspring from a cross of a Cre-dependent reporter line with the CR-ires-Cre mice, which express Cre-recombinase in the same pattern as calretinin. We found that in the mature visual cortex, only a minority of the cells that have expressed calretinin and Cre-recombinase during their lifetime is GABAergic and only about 20% are immunoreactive for calretinin. The reason behind this is that calretinin is transiently expressed in many cortical pyramidal neurons during development. To determine whether neurons that express or have expressed calretinin share any distinct functional characteristics, we recorded their visual response properties using GCaMP6s calcium imaging. The average orientation selectivity, size tuning, and temporal and spatial frequency tuning of this group of cells, however, match the response profile of the general neuronal population, revealing the lack of functional specialization for the features studied.

This paper is in the public domain in USA. Metadata comes from the CrossRef API, see full record in the source URL below.

This paper is in the public domain in USA. Metadata comes from the CrossRef API, see full record in the source URL below.

This article is from Frontiers in Psychology , volume 4 . Abstract Age-related performance declines in visual tasks have been attributed to reductions in processing efficiency. The neural basis of these declines has been explored by comparing the blood-oxygen-level-dependent (BOLD) index of neural activity in older and younger adults during visual task performance. However, neural activity is one of many factors that change with age and lead to BOLD signal differences. We investigated the origin of age-related BOLD changes by comparing blood flow and oxygen metabolic constituents of BOLD signal. Subjects periodically viewed flickering annuli and pressed a button when detecting luminance changes in a central fixation cross. Using magnetic resonance dual-echo arterial spin labeling and CO2 ingestion, we observed age-equivalent (i.e., similar in older and younger groups) fractional cerebral blood flow (ΔCBF) in the presence of age-related increases in fractional cerebral metabolic rate of oxygen (ΔCMRO2). Reductions in ΔCBF responsiveness to increased ΔCMRO2 in elderly led to paradoxical age-related BOLD decreases. Age-related ΔCBF/ΔCMRO2 ratio decreases were associated with reaction times, suggesting that age-related slowing resulted from less efficient neural activity. We hypothesized that reduced vascular responsiveness to neural metabolic demand would lead to a reduction in ΔCBF/ΔCMRO2. A simulation of BOLD relative to ΔCMRO2 for lower and higher neurometabolic-flow coupling ratios (approximating those for old and young, respectively) indicated less BOLD signal change in old than young in relatively lower CMRO2 ranges, as well as greater BOLD signal change in young compared to old in relatively higher CMRO2 ranges. These results suggest that age-comparative studies relying on BOLD signal might be misinterpreted, as age-related BOLD changes do not merely reflect neural activity changes. Age-related declines in neurometabolic-flow coupling might lead to neural efficiency reductions that can adversely affect visual task performance.

This article is from PLoS ONE , volume 8 . Abstract This work describes an approach inspired by the primary visual cortex using the stimulus response of the receptive field profiles of binocular cells for disparity computation. Using the energy model based on the mechanism of log-Gabor filters for disparity encodings, we propose a suitable model to consistently represent the complex cells by computing the wide bandwidths of the cortical cells. This way, the model ensures the general neurophysiological findings in the visual cortex (V1), emphasizing the physical disparities and providing a simple selection method for the complex cell response. The results suggest that our proposed approach can achieve better results than a hybrid model with phase-shift and position-shift using position disparity alone.

This article is from Frontiers in Neuroscience , volume 8 . Abstract Previous imaging studies on the brain mechanisms of spatial hearing have mainly focused on sounds varying in the horizontal plane. In this study, we compared activations in human auditory cortex (AC) and adjacent inferior parietal lobule (IPL) to sounds varying in horizontal location, distance, or space (i.e., different rooms). In order to investigate both stimulus-dependent and task-dependent activations, these sounds were presented during visual discrimination, auditory discrimination, and auditory 2-back memory tasks. Consistent with previous studies, activations in AC were modulated by the auditory tasks. During both auditory and visual tasks, activations in AC were stronger to sounds varying in horizontal location than along other feature dimensions. However, in IPL, this enhancement was detected only during auditory tasks. Based on these results, we argue that IPL is not primarily involved in stimulus-level spatial analysis but that it may represent such information for more general processing when relevant to an active auditory task.

This article is from BMC Neuroscience , volume 15 . Abstract None

This article is from Frontiers in Aging Neuroscience , volume 5 . Abstract There is considerable interest in understanding food cravings given the obesogenic environment of Western Society. In this paper we examine how the imagery of palatable foods affects cravings and functional connectivity in the visual cortex for people who differ on the power of food scale (PFS). Fourteen older, overweight/obese adults came to our laboratory on two different occasions. Both times they ate a controlled breakfast meal and then were restricted from eating for 2.5 h prior to scanning. On 1 day they consumed a BOOST® liquid meal after the period of food restriction, whereas on the other day they only consumed water (NO BOOST® condition). After these manipulations, they had an fMRI scan in which they were asked to image both neutral objects and their favorite snack foods; they also completed visual analog scales for craving, hunger, and the vividness of the imagery experiences. Irrespective of the BOOST® manipulation, we observed marked increases in food cravings when older, overweight/obese adults created images of favorite foods in their minds as opposed to creating an image of neutral objects; however, the increase in food craving following the imagery of desired food was more pronounced among those scoring high than low on the PFS. Furthermore, local efficiency within the visual cortex when imaging desired food was higher for those scoring high as compared to low on the PFS. The active imagery of desired foods seemed to have overpowered the BOOST® manipulation when evaluating connectivity in the visual cortex.

Lecture delivered by Nobel prize winner Dr. David Hubel at Wellesley College, April 2009.

This article is from Frontiers in Neural Circuits , volume 7 . Abstract Prolonged viewing of high contrast gratings alters perceived stimulus contrast, and produces characteristic changes in the contrast response functions of neurons in the primary visual cortex (V1). This is referred to as contrast adaptation. Although contrast adaptation has been well-studied, its underlying neural mechanisms are not well-understood. Therefore, we investigated contrast adaptation in mouse V1 with the goal of establishing a quantitative description of this phenomenon in a genetically manipulable animal model. One interesting aspect of contrast adaptation that has been observed both perceptually and in single unit studies is its specificity for the spatial and temporal characteristics of the stimulus. Therefore, in the present work we determined if the magnitude of contrast adaptation in mouse V1 neurons was dependent on the spatial frequency and temporal frequency of the adapting grating. We used protocols that were readily comparable with previous studies in cats and primates, and also a novel contrast ramp stimulus that characterized the spatial and temporal specificity of contrast adaptation simultaneously. Similar to previous work in higher mammals, we found that contrast adaptation was strongest when the spatial frequency and temporal frequency of the adapting grating matched the test stimulus. This suggests similar mechanisms underlying contrast adaptation across animal models and indicates that the rapidly advancing genetic tools available in mice could be used to provide insights into this phenomenon.

David Heeger, New York University: "What fMRI Can Tell Us about How Visual Cortex Works" This is the 7th talk given at the Redwood Center for Theoretical Neuroscience Inaugural Symposium UC Berkeley, October 7, 2005

This article is from Neural Systems & Circuits , volume 1 . Abstract Background: The statistical structure of the visual world offers many useful clues for understanding how biological visual systems may understand natural scenes. One particularly important early process in visual object recognition is that of grouping together edges which belong to the same contour. The layout of edges in natural scenes have strong statistical structure. One such statistical property is that edges tend to lie on a common circle, and this 'co-circularity' can predict human performance at contour grouping. We therefore tested the hypothesis that long-range excitatory lateral connections in the primary visual cortex, which are believed to be involved in contour grouping, display a similar co-circular structure. Results: By analyzing data from tree shrews, where information on both lateral connectivity and the overall structure of the orientation map was available, we found a surprising diversity in the relevant statistical structure of the connections. In particular, the extent to which co-circularity was displayed varied significantly. Conclusions: Overall, these data suggest the intriguing possibility that V1 may contain both co-circular and anti-cocircular connections.

1Uncle Remus

By Joel Chandler Harris

Many readers will already be familiar with Uncle Remus’ favorite animal characters – Br’er Rabbit and Br’er Fox among them – and some of the popular tales concerning them. (To this day, “tar baby” as an expression for a particularly sticky situation that is almost impossible to solve, has passed into the English language and common use.) Even people who have never read any of these tales will know exactly why you don’t throw a rabbit into a briar patch, mainly because Walt Disney produced his first movie ever to use professional actors with animation, called “Song of the South”, based on the Uncle Remus tales.<br /><br /> Joel Chandler Harris, a newsman in Georgia, grew up listening to folktales told by the local black population. Later, he published his version of these tales in a series of stories printed in the “Atlanta Constitution.” The tales of, and by, Harris’ chief character Uncle Remus, an old black man scrabbling to make his living in the post-Civil War South, were extremely popular and widely read. Harris’ use of innovative spelling to give the reader a sense of the black dialect was considered novel.<br /><br /> While this is not a book that will pass a current political correctness test, due to its use of labels for black folks which have gone out of polite conversation, Uncle Remus is a largely sympathetic look at post-war plantation life. Uncle Remus himself is a warm, folksy man of good humor and dry wit, and after finishing his animal stories, the remaining sayings and tales are a moment of history frozen in amber. (Summary by Mark)

2Life in a Thousand Worlds

By William Shuler Harris

A jolly romp, which could be perhaps be described as Gulliver’s Travels Through Our Solar System and Beyond, as written by a great admirer of C. S. Lewis, on a rainy Sunday afternoon, after one too many mugs of cocoa. Includes some thought on alien philosophies and how to apply them to moral and social problems here on Planet Earth.<br><br> Unrelated to the book, this was also the one-thousandth project to be started at LibriVox. — (Non-summary by Cori Samuel.)

3Oscar Wilde: His Life and Confessions

By Frank Harris

Consumers of biography are familiar with the division between memoirs of the living or recently dead written by those who "knew" the subject more or less intimately, and the more objective or scholarly accounts produced by later generations.<br /><br /> In the case of Wilde, as presented to us by Frank Harris, we are in a way doubly estranged from the subject. We meet with Oscar the charismatic talker, whose tone of voice can never be reproduced – even if a more scrupulous biographer had set down his words accurately – and we are perhaps already aware of him as Wilde the self-destructive celebrity who uneasily fills the place of the premier gay icon and martyr in our contemporary view.<br /><br /> Neither of these images will do. We need to read as many accounts as possible. Harris, though himself a self-advertising literary and sexual buccaneer, takes a wincingly representative view of Wilde’s homophile activity: for him it is a patrician excrescence, the abominable vice of the few, contracted at English boarding schools – though thankfully “not infectious” as far as he himself is concerned.<br /><br /> What a long road we have to travel to arrive at the essentially gay man of today! But there are many shortcuts to take us back to where we came from… (Summary by Martin Geeson)

4Uncle Remus and Brer Rabbit

By Joel Chandler Harris

Uncle Remus' stories feature a trickster hero called Br'er Rabbit ("Brother" Rabbit), who uses his wits to slide out of trouble and gain the advantage over the slower witted other animals, many of whom are trying to eat him. Br'er Rabbit stories were mostly collected directly from the afro-american oral story-telling tradition and are said to be a direct interpretation of Yoruba tales of Hare. This book contains 11 unique stories and was the last one published before the author's death. (Introduction by Phil Chenevert)

5Nights With Uncle Remus

By Joel Chandler Harris

That the little boy loved Uncle Remus and his stories was so obvious that the tale-spinning sessions began drawing additional listeners. Daddy Jack, an old "Africa man" visiting from down-state; Sis Tempy, the strong chief of the mansion's servants; and Tildy, a young and pretty servant-girl - all found their way to Uncle Remus' rude cabin when their duties or interests permitted, to sit around the hearth and hear the wonderful tales of the animals, and foremost among them, Brer Rabbit and Brer Fox.<br></br>It turned out that some of the tales had different ways of telling, and the visitors took their turns at being the story-teller. Always one or more clever animals humbled or hornswoggled others among their community with flattery, wide-eyed mystery, or outright fraud.<br></br>After the success of Harris' "Uncle Remus: His Songs and His Sayings" ( http://librivox.org/uncle-remus-by-joel-chandler-harris/ ), he went on to write eight more books compiling the tales he himself had heard on the plantation in his young days. This is the first of those sequels.

The recollections of a British infantryman who served in the British army during the Napoleonic Wars. (Summary by Graham Keeling)

26 of Uncle Remus's stories put into verse and song. With the exception of the Tar Baby story, they were all new to this publication of 1904 and cover a variety of humorous subjects from Adan and Eve (De Appile Tree) to Brer Rabbit's Gigglin' Place. There are also genuine Camp Meeting Songs and a Corn Shuckin' Song. (Summary by Phil Chenevert)

Uncle Remus tells these 11 stories but to the son of the original "little boy" who is visiting his grandmother on the plantation. As always Uncle Remus can be relied upon to provide funny and pointed insight into human personalities through his story telling. These were all published in the Uncle Remus magazine from 1905 and 1906 and gathered together in this book by the author. (Summary by Phil Chenevert)

9Uncle Remus & Friends

By Joel Chandler Harris

Uncle Remus, that genial old storyteller, knows how to spin these wonderful tales about the 'criteers' that the little 6 year old boy (and many of us adults!) love to listen to. Yet the 'Brer Rabbit and 'Brer Fox and the others sound a lot like the people all around us. They tell stories about personalities and faults and virtues in a way that is unique to Uncle Remus. As the shadows grow longer outside, draw up a rocking chair next to the little boy, settle back and listen to the wise old man tell these stories. These 17 stories were specially chosen from Uncle Remus: His Songs and Sayings and include The Wonderful Tar-Baby Story, Miss Cow falls a Victim to Mr. Rabbit; Mr. Fox and the Deceitful Frogs; Mr. Rabbit grossly deceives Mr. Fox and lots of others. (Summary by phil chenevert)

While detective work always makes for exciting stories, the circumstances under which the detective works play a huge role in the thrill. The stories in this collection follow detectives as they unravel mysteries in times of war, where danger awaits them at every turn. - Summary by Carolin

11Honey-Bee: Its Nature, Homes and Products

By William Hetherington Harris

"In these days of intense business-pressure, it is a good thing for men to cultivate hobbies. We say this, notwithstanding the fact that men with hobbies are likely to become bores, from thinking and talking too incessantly of their pet occupations, or are apt to run into extravagant expenditure of time and money, which could be better utilised. Now, in recommending apiculture, or bee-keeping, as a recreation from more serious pursuits, we feel that we incur little risk of increasing the number of bores in society, or of inducing an undue outlay of hours or pounds on the part of those who follow our suggestions. For, on the one hand, the facts likely to be spoken of by enthusiastic apiarians to casual hearers could not fail to interest; while the practical results of bee-keeping will certainly, to say the least, repay in hard cash all reasonable outlay on the part of any one who is possessed of ordinary good sense, and who learns to manage his hives according to modern methods." - From the book Introduction

An allegory that describes the sad journey of Miss Church-Member who thinks she is traveling on a more convenient way to heaven, but she does not realize that she is traveling on the Broad Highway to destruction with her polite, yet, fiendish companion, Mr. World. - Summary by James En

The Guerra del Rif—the Rif War. 1921 to 1926. It was the slogging bloody 5-year long climax of Spain’s effort to secure dominion over a territory in North Africa allotted them by France; A chapter instigated over a cause no less profane than a mining concession and which would prove to be an unmitigated disaster for all involved; the Spanish, the French and the Iriffiyen. <br><br> This attempted salve for a nation’s wounded prestige would leave more than forty thousand Spaniards as casualties, the nation humiliated and irrevocably destabilize the Spanish state—directly leading to the dethronement of Alfonso XIII, civil war and the rise of Franco. The French Republic would be sucked into the conflict while enforcing their own colonial designs on Morocco and would suffer—only—eighteen thousand casualties. The war evoked widespread condemnation from the left in France and provided an exemplar for anti-colonial revolt which would go on to haunt them for many decades hence. <br><br> Finally, Abd El-Krim’s Republic of the Rif would (eventually) be crushed under the weight of an opposing army of almost half-a-million soldiers as well as hundreds of tanks and aircraft. During the war, the Spanish and French widely employed chemical weapons against Rifian civilian populations. As a side note, also during the war Spain and France signed the Geneva Protocol prohibiting the use of chemical weapons—though the treaty didn’t come into effect until 1928. <br><br> <i>⸮ It is one thing to make a stand on moral principle, after all, but quite another to let perfectly good stockpiles of phosgene and mustard gas go to waste.~</i> <br><br> Throughout the duration of this particularly brutal and senseless war the correspondent covering it for The Times was Walter Burton Harris, British expat and author of this book, who had deep connections in Morocco having settled there in 1887 and travelled widely within the country. <br><br> This is his account. - Summary by Alister<br><br> <b>Part 2</b> can be found at: <a href="https://librivox.org/france-spain-and-the-rif-part-2-by-walter-burton-harris/">https://librivox.org/france-spain-and-the-rif-part-2-by-walter-burton-harris/</a>

14Story of Coventry

By Mary Dormer Harris

Nowadays best known for its bombing in WWII, the English city of Coventry was founded in the early Middle Ages. Earl Leofric and his wife Lady Godiva (famously riding naked through the streets) founded a Benedictine monastery in 1043, and over time, the city became a major pilgrimage center. During the Wars of the Roses (1455 - 1487), the Royal Court was moved to Coventry and parliament was held in the city as well. In this book Mary Dormer Harris follows Coventry's history through the Middle Ages. While looking at famous people from Coventry and their influence on the city's architecture, she also details the daily lives of the common townsfolk, the guild, and their contributions to the city's thriving economy. This book is part of the "Mediaeval Town" series published in the early 20th century. (Summary by Availle)

The Guerra del Rif—the Rif War. 1921 to 1926. It was the slogging bloody 5-year long climax of Spain’s effort to secure dominion over a territory in North Africa allotted them by France; A chapter instigated over a cause no less profane than a mining concession and which would prove to be an unmitigated disaster for all involved; the Spanish, the French and the Iriffiyen. <br><br> This attempted salve for a nation’s wounded prestige would leave more than forty thousand Spaniards as casualties, the nation humiliated and irrevocably destabilize the Spanish state—directly leading to the dethronement of Alfonso XIII, civil war and the rise of Franco. The French Republic would be sucked into the conflict while enforcing their own colonial designs on Morocco and would suffer—only—eighteen thousand casualties. The war evoked widespread condemnation from the left in France and provided an exemplar for anti-colonial revolt which would go on to haunt them for many decades hence. <br><br> Finally, Abd El-Krim’s Republic of the Rif would (eventually) be crushed under the weight of an opposing army of almost half-a-million soldiers as well as hundreds of tanks and aircraft. During the war, the Spanish and French widely employed chemical weapons against Rifian civilian populations. As a side note, also during the war Spain and France signed the Geneva Protocol prohibiting the use of chemical weapons—though the treaty didn’t come into effect until 1928. <br><br> <i>⸮ It is one thing to make a stand on moral principle, after all, but quite another to let perfectly good stockpiles of phosgene and mustard gas go to waste.~</i> <br><br> Throughout the duration of this particularly brutal and senseless war the correspondent covering it for The Times was Walter Burton Harris, British expat and author of this book, who had deep connections in Morocco having settled there in 1887 and travelled widely within the country. <br><br> This is his account. - Summary by Alister<br><br> <b>Part 1</b> can be found at: <a href="https://librivox.org/france-spain-and-the-rif-part-1-by-walter-burton-harris/">https://librivox.org/france-spain-and-the-rif-part-1-by-walter-burton-harris/</a>

Wholesome Cooking, A Practical Book for a Practical Cook, Two Hundred Well-Tested Recipes selected by Ethel Harris. Ten chapters from soup to cakes with such intriguing dishes as rabbit stew, fricassee parsnips, and snow pudding. Recipes are given in the older narrative style with general instructions for each type of dish. - Summary by Larry Wilson

17Persephone of Eleusis

By Clare Winger Harris

A romance of Ancient Greece featuring the hero's journey and evil plotting. Will either succeed? - Summary by Christine Rottger