The spatial organization and dynamic interactions between excitatory and inhibitory synaptic inputs that define the receptive field (RF) of simple cells in the cat primary visual cortex (V1) still raise the following paradoxical issues: (1) stimulation of simple cells in V1 with drifting gratings supports a wiring schema of spatially segregated sets of excitatory and inhibitory inputs activated in an opponent way by stimulus contrast polarity and (2) in contrast, intracellular studies using flashed bars suggest that although ON and OFF excitatory inputs are indeed segregated, inhibitory inputs span the entire RF regardless of input contrast polarity. Here, we propose a biologically detailed computational model of simple cells embedded in a V1-like network that resolves this seeming contradiction. We varied parametrically the RF-correlation-based bias for excitatory and inhibitory synapses and found that a moderate bias of excitatory neurons to synapse onto other neurons with correlated receptive fields and a weaker bias of inhibitory neurons to synapse onto other neurons with anticorrelated receptive fields can explain the conductance input, the postsynaptic membrane potential, and the spike train dynamics under both stimulation paradigms. This computational study shows that the same structural model can reproduce the functional diversity of visual processing observed during different visual contexts.SIGNIFICANCE STATEMENT Identifying generic connectivity motives in cortical circuitry encoding for specific functions is crucial for understanding the computations implemented in the cortex. Indirect evidence points to correlation-based biases in the connectivity pattern in V1 of higher mammals, whereby excitatory and inhibitory neurons preferentially synapse onto neurons respectively with correlated and anticorrelated receptive fields. A recent intracellular study questions this push-pull hypothesis, failing to find spatial anticorrelation patterns between excitation and inhibition across the receptive field. We present here a spiking model of V1 that integrates relevant anatomic and physiological constraints and shows that a more versatile motif of correlation-based connectivity with selectively tuned excitation and broadened inhibition is sufficient to account for the diversity of functional descriptions obtained for different classes of stimuli.

• Keywords
• circuits, conductance analysis, cortex, primary visual cortex, push–pull, spiking model,
• MeSH
• Action Potentials physiology   MeSH
• Cats MeSH
• Models, Neurological * MeSH
• Synaptic Transmission physiology   MeSH
• Neural Inhibition physiology   MeSH
• Neurons physiology   MeSH
• Synapses physiology   MeSH
• Visual Perception physiology   MeSH
• Visual Pathways physiology   MeSH
• Visual Cortex physiology   MeSH
• Animals MeSH
• Check Tag
• Cats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH

To understand how anatomy and physiology allow an organism to perform its function, it is important to know how information that is transmitted by spikes in the brain is received and encoded. A natural question is whether the spike rate alone encodes the information about a stimulus (rate code), or additional information is contained in the temporal pattern of the spikes (temporal code). Here we address this question using data from the cat Lateral Geniculate Nucleus (LGN), which is the visual portion of the thalamus, through which visual information from the retina is communicated to the visual cortex. We analyzed the responses of LGN neurons to spatially homogeneous spots of various sizes with temporally random luminance modulation. We compared the Firing Rate with the Shannon Information Transmission Rate , which quantifies the information contained in the temporal relationships between spikes. We found that the behavior of these two rates can differ quantitatively. This suggests that the energy used for spiking does not translate directly into the information to be transmitted. We also compared Firing Rates with Information Rates for X-ON and X-OFF cells. We found that, for X-ON cells the Firing Rate and Information Rate often behave in a completely different way, while for X-OFF cells these rates are much more highly correlated. Our results suggest that for X-ON cells a more efficient "temporal code" is employed, while for X-OFF cells a straightforward "rate code" is used, which is more reliable and is correlated with energy consumption.

• Keywords
• Cat LGN, Entropy, Firing rate, Neural coding, ON–OFF cells, Shannon information theory,
• MeSH
• Action Potentials physiology   MeSH
• Mental Processes physiology   MeSH
• Cats MeSH
• Geniculate Bodies cytology   physiology   MeSH
• Neurons physiology   MeSH
• Photic Stimulation methods   MeSH
• Visual Pathways cytology   physiology   MeSH
• Visual Cortex cytology   physiology   MeSH
• Animals MeSH
• Check Tag
• Cats MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH
• Comparative Study MeSH

UNLABELLED: Single cases may lead to unexpected hypotheses in psychology. We retrospectively analyzed single case studies that suggested organizational principles along the early visual pathway, which have remained unanswered until now. FIRST CASE: In spite of the inhomogeneity of sensitivity, paradoxically the visual field on the subjective level appears to be homogeneous; constancy of brightness of supra-threshold stimuli throughout the visual field is claimed to be responsible for homogeneity; specific summation properties of retinal ganglion cells are hypothesized to guarantee this effect. SECOND CASE: With a brain-injured patient having suffered a partial visual field loss it can be shown that color induction is a retinal phenomenon; lateral inhibitory processes at the level of amacrine cells are hypothesized as neural network. Third case: In a patient having suffered a bilateral occipital lobe infarction, some functional recovery has been demonstrated; divergence and convergence of projection in the ascending neural pathway are suggested as a structural basis for recovery. Slowed down binocular rivalry discloses a sequential mechanism in the construction of a visual percept. Fourth case: The pre-wired projection of the retina to the visual cortex in spite of a severe squint of one eye is confirmed, but paradoxically some local neuroplasticity is also suggested. Fifth case: Using habituation of local sensitivity in the visual field and its resetting by interhemispheric interactions as an experimental paradigm, it is suggested that spatial attention is controlled at the midbrain level. Sixth case: Observations on residual vision or "blindsight" support the hypothesis that the visual cortex is the one and only structure responsible for visual perception on a conscious level. The unifying principle of these retrospective analyses is that subjective visual phenomena can lead to unexpected but testable hypotheses of neural processing on the structural and functional level in the early visual pathway.

• Keywords
• attentional control, binocular rivalry, blindsight, brightness perception, color perception, consciousness, eccentricity effect, habituation, neuroplasticity, restitution of function,
• MeSH
• Humans MeSH
• Geniculate Bodies physiology   MeSH
• Brain Infarction physiopathology   MeSH
• Brain Injuries physiopathology   MeSH
• Attention physiology   MeSH
• Retina physiology   MeSH
• Retrospective Studies MeSH
• Blindness physiopathology   MeSH
• Photic Stimulation MeSH
• Color Perception MeSH
• Visual Fields * MeSH
• Visual Pathways physiology   MeSH
• Visual Cortex physiology   MeSH
• Check Tag
• Humans MeSH
• Publication type
• Journal Article MeSH
• Case Reports MeSH

Animals often change their habitat throughout ontogeny; yet, the triggers for habitat transitions and how these correlate with developmental changes - e.g. physiological, morphological and behavioural - remain largely unknown. Here, we investigated how ontogenetic changes in body coloration and of the visual system relate to habitat transitions in a coral reef fish. Adult dusky dottybacks, Pseudochromis fuscus, are aggressive mimics that change colour to imitate various fishes in their surroundings; however, little is known about the early life stages of this fish. Using a developmental time series in combination with the examination of wild-caught specimens, we revealed that dottybacks change colour twice during development: (i) nearly translucent cryptic pelagic larvae change to a grey camouflage coloration when settling on coral reefs; and (ii) juveniles change to mimic yellow- or brown-coloured fishes when reaching a size capable of consuming juvenile fish prey. Moreover, microspectrophotometric (MSP) and quantitative real-time PCR (qRT-PCR) experiments show developmental changes of the dottyback visual system, including the use of a novel adult-specific visual gene (RH2 opsin). This gene is likely to be co-expressed with other visual pigments to form broad spectral sensitivities that cover the medium-wavelength part of the visible spectrum. Surprisingly, the visual modifications precede changes in habitat and colour, possibly because dottybacks need to first acquire the appropriate visual performance before transitioning into novel life stages.

• Keywords
• Co-expression, Colour change, Development, Gene duplication, Opsin, Vision,
• MeSH
• Color MeSH
• Models, Biological MeSH
• Time Factors MeSH
• Ecosystem * MeSH
• Phylogeny MeSH
• Adaptation, Physiological MeSH
• Coral Reefs * MeSH
• Skin cytology   MeSH
• Quantitative Trait, Heritable MeSH
• Biological Mimicry * MeSH
• Opsins genetics   MeSH
• Pigmentation physiology   MeSH
• Predatory Behavior MeSH
• Gene Expression Regulation MeSH
• Fishes growth & development   physiology   MeSH
• Vision, Ocular physiology   MeSH
• Visual Pathways physiology   MeSH
• Animals MeSH
• Check Tag
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Geographicals
• Australia MeSH
• Names of Substances
• Opsins MeSH

Audio-visual integration has been shown to be present in a wide range of different conditions, some of which are processed through the dorsal, and others through the ventral visual pathway. Whereas neuroimaging studies have revealed integration-related activity in the brain, there has been no imaging study of the possible role of segregated visual streams in audio-visual integration. We set out to determine how the different visual pathways participate in this communication. We investigated how audio-visual integration can be supported through the dorsal and ventral visual pathways during the double flash illusion. Low-contrast and chromatic isoluminant stimuli were used to drive preferably the dorsal and ventral pathways, respectively. In order to identify the anatomical substrates of the audio-visual interaction in the two conditions, the psychophysical results were correlated with the white matter integrity as measured by diffusion tensor imaging.The psychophysiological data revealed a robust double flash illusion in both conditions. A correlation between the psychophysical results and local fractional anisotropy was found in the occipito-parietal white matter in the low-contrast condition, while a similar correlation was found in the infero-temporal white matter in the chromatic isoluminant condition. Our results indicate that both of the parallel visual pathways may play a role in the audio-visual interaction.

• Keywords
• DTI, Doubleflash, MRI, Multisensory, TBSS,
• MeSH
• Acoustic Stimulation MeSH
• Anisotropy MeSH
• White Matter physiology   MeSH
• Adult MeSH
• Humans MeSH
• Brain Mapping MeSH
• Auditory Perception physiology   MeSH
• Photic Stimulation MeSH
• Signal Detection, Psychological physiology   MeSH
• Diffusion Tensor Imaging MeSH
• Imaging, Three-Dimensional MeSH
• Visual Perception physiology   MeSH
• Visual Pathways physiology   MeSH
• Check Tag
• Adult MeSH
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Inconsistent information from different modalities can be delusive for perception. This phenomenon can be observed with simultaneously presented inconsistent numbers of brief flashes and short tones. The conflict of bimodal information is reflected in double flash or fission, and flash fusion illusions, respectively. The temporal resolution of the vision system plays a fundamental role in the development of these illusions. As the parallel, dorsal and ventral pathways have different temporal resolution we presume that these pathways play different roles in the illusions. We used pathway-optimized stimuli to induce the illusions on separately driven visual streams. Our results show that both pathways support the double flash illusion, while the presence of the fusion illusion depends on the activated pathway. The dorsal pathway, which has better temporal resolution, does not support fusion, while the ventral pathway which has worse temporal resolution shows fusion strongly.

• MeSH
• Acoustic Stimulation MeSH
• Time Factors MeSH
• Illusions * MeSH
• Humans MeSH
• Young Adult MeSH
• Psychometrics MeSH
• Auditory Perception MeSH
• Photic Stimulation methods   MeSH
• Signal Detection, Psychological MeSH
• Visual Perception * MeSH
• Visual Pathways physiology   MeSH
• Visual Cortex physiology   MeSH
• Check Tag
• Humans MeSH
• Young Adult MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

An electrophysiological study on the effect of aging on the visual pathway and various levels of visual information processing (primary cortex, associate visual motion processing cortex and cognitive cortical areas) was performed. We examined visual evoked potentials (VEPs) to pattern-reversal, motion-onset (translation and radial motion) and visual stimuli with a cognitive task (cognitive VEPs - P300 wave) at luminance of 17 cd/m(2). The most significant age-related change in a group of 150 healthy volunteers (15-85 years of age) was the increase in the P300 wave latency (2 ms per 1 year of age). Delays of the motion-onset VEPs (0.47 ms/year in translation and 0.46 ms/year in radial motion) and the pattern-reversal VEPs (0.26 ms/year) and the reductions of their amplitudes with increasing subject age (primarily in P300) were also found to be significant. The amplitude of the motion-onset VEPs to radial motion remained the most constant parameter with increasing age. Age-related changes were stronger in males. Our results indicate that cognitive VEPs, despite larger variability of their parameters, could be a useful criterion for an objective evaluation of the aging processes within the CNS. Possible differences in aging between the motion-processing system and the form-processing system within the visual pathway might be indicated by the more pronounced delay in the motion-onset VEPs and by their preserved size for radial motion (a biologically significant variant of motion) compared to the changes in pattern-reversal VEPs.

• MeSH
• Adult MeSH
• Cognition physiology   MeSH
• Middle Aged MeSH
• Humans MeSH
• Adolescent MeSH
• Young Adult MeSH
• Reaction Time physiology   MeSH
• Pattern Recognition, Visual physiology   MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Aging physiology   MeSH
• Photic Stimulation methods   MeSH
• Motion Perception physiology   MeSH
• Visual Pathways physiology   MeSH
• Evoked Potentials, Visual physiology   MeSH
• Visual Cortex physiology   MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Adolescent MeSH
• Young Adult MeSH
• Male MeSH
• Aged, 80 and over MeSH
• Aged MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

We performed a systematic study to check whether neurons in the area TE (the anterior part of inferotemporal cortex) in rhesus monkey, regarded as the last stage of the ventral visual pathway, could be modulated by auditory stimuli. Two fixating rhesus monkeys were presented with visual, auditory or combined audiovisual stimuli while neuronal responses were recorded. We have found that the visually sensitive neurons are also modulated by audiovisual stimuli. This modulation is manifested as the change of response rate. Our results have shown also that the visual neurons were responsive to the sole auditory stimuli. Therefore, the concept of inferotemporal cortex unimodality in information processing should be re-evaluated.

• MeSH
• Acoustic Stimulation MeSH
• Time Factors MeSH
• Macaca mulatta MeSH
• Neurons physiology   MeSH
• Reaction Time MeSH
• Auditory Pathways cytology   physiology   MeSH
• Evoked Potentials, Auditory MeSH
• Auditory Cortex cytology   physiology   MeSH
• Photic Stimulation MeSH
• Visual Pathways physiology   MeSH
• Evoked Potentials, Visual MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH

Event related potentials (ERPs) provide an insight into sensory and cognitive processes in health and disease. Studies of an ERP negative amplitude deflection elicited by a change in a series of auditory stimuli is known as mismatch negativity (MMN). The generation of MMN is impaired in schizophrenia. Its deficit is associated with lower everyday functioning and may be also interpreted as the marker of progression in schizophrenia. MMN elicited by visual stimuli (vMMN) was described by several research teams, but it has not been investigated in schizophrenia as yet. Using a motion-direction paradigm, we elicited visual MMN in 24 patients with schizophrenia and schizoaffective disorder. The vMMN was computed as differences in areas under curve of visual ERPs to standard and deviant motion-direction stimuli recorded from midline derivations at the interval of 100-200 ms. They were compared between groups of patients with schizophrenia and healthy controls. The significantly smaller vMMN indicated an impaired generation of mismatch negativity in patients with schizophrenia. In secondary analyses there was an association of vMMN impairment among patients with higher dose of medication, lower level of functioning and the presence of deficit syndrome. This impairment appears analogous to the impairment of MMN in the auditory domain and is probably related to early visual information processing. Its relationship to cognitive functioning of patients with schizophrenia deserves further attention.

• MeSH
• Adult MeSH
• Electroencephalography statistics & numerical data   MeSH
• Functional Laterality physiology   MeSH
• Cognition Disorders diagnosis   physiopathology   MeSH
• Control Groups MeSH
• Middle Aged MeSH
• Humans MeSH
• Brain physiology   MeSH
• Neuropsychological Tests MeSH
• Memory physiology   MeSH
• Area Under Curve MeSH
• Attention physiology   MeSH
• Cross-Sectional Studies MeSH
• Psychotic Disorders diagnosis   physiopathology   MeSH
• Reaction Time physiology   MeSH
• Schizophrenic Psychology MeSH
• Schizophrenia diagnosis   physiopathology   MeSH
• Photic Stimulation methods   MeSH
• Motion Perception physiology   MeSH
• Visual Perception physiology   MeSH
• Visual Pathways physiology   MeSH
• Evoked Potentials, Visual physiology   MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Comparative Study MeSH

The processing of visual motion was tested by means of event related potentials recording (ERP) using a paradigm designed to produce a visual mismatch negativity effect. The stimuli were unattended and presented in the peripheral visual field (outside the central 15 degrees). The standard stimulus consisted of an up/down motion sequence, whilst the deviant stimulus of a down/up motion sequence. Significant ERP differences between the standard and deviant conditions were found in 8 out of 10 adult subjects already in 80 ms and prevailingly in interval 145-260 ms from the initial stimulus presentation. The results demonstrate that the magnocellular information undergoes processing capable of detecting differences in the sequence of unattended peripheral motion stimuli.

• MeSH
• Adult MeSH
• Electroencephalography MeSH
• Evoked Potentials MeSH
• Middle Aged MeSH
• Humans MeSH
• Attention physiology   MeSH
• Photic Stimulation methods   MeSH
• Motion Perception physiology   MeSH
• Visual Fields physiology   MeSH
• Visual Pathways physiology   MeSH
• Check Tag
• Adult MeSH
• Middle Aged MeSH
• Humans MeSH
• Male MeSH
• Female MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH