Adaptive sampling of visual stimuli in thalamic and cortical neurons

Recent work suggests that synchronization of neuronal activity could serve to define functionally relevant relationships between spatially distributed cortical neurons. At present, it is not known to what extent this hypothesis is compatible with the widely supported notion of coarse coding, which assumes that features of a stimulus are represented by the graded responses of a population of optimally and suboptimally activated cells. To resolve this issue we investigated the temporal relationship between responses of optimally and suboptimally stimulated neurons in area 17 of cat visual cortex. We find that optimally and suboptimally activated cells can synchronize their responses with a precision of a few milliseconds. However, there are consistent and systematic deviations of the phase relations from zero phase lag. Systematic variation of the orientation of visual stimuli shows that optimally driven neurons tend to lead over suboptimally activated cells. The observed phase lag depends linearly on the stimulus orientation and is, in addition, proportional to the difference between the preferred orientations of the recorded cells. Similar effects occur when testing the influence of the movement direction and the spatial frequency of visual stimuli. These results suggest that binding by synchrony can be used to define assemblies of neurons representing a coarse-coded stimulus. Furthermore, they allow a quantitative test of neuronal network models designed to reproduce physiological results on stimulus-specific synchronization.

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Receptive-field properties of neurons in binocular and monocular segments of striate cortex in cats raised with binocular lid suture

Journal of Neurophysiology ◽

10.1152/jn.1978.41.2.322 ◽

1978 ◽

Vol 41 (2) ◽

pp. 322-337 ◽

Cited By ~ 36

Author(s):

D. W. Watkins ◽

J. R. Wilson ◽

S. M. Sherman

Keyword(s):

Receptive Field ◽

Cortical Neurons ◽

Striate Cortex ◽

Ocular Dominance ◽

Visual Stimuli ◽

Receptive Fields ◽

Total Sample ◽

Orientation Selectivity ◽

Peak Response ◽

Response Properties

1. We studied the receptive fields of 171 striate cortical neurons from 17 cats raised with binocular lid suture. Of these, 102 fields were within 10 degrees of the area centralis and the remaining 69 were at least 38 degrees from the vertical meridian. 2. Based on their different response properties, cells were divided into three broad groups: the mappable cells (49%) had clearly defined receptive fields, the unmappable cells (31%) were activated by visual stimuli but had diffuse fields which could not be hand plotted, and the visually inexcitable cells (20%) could not be activated by visual stimuli. Very few (less than or equal to 12% of the total sample) normal simple or complex cells could be found. 3. Orientation selectivity was assessed in these cells. Only 12% displayed orientation selectivity within normal bounds, and these were all mappable cells. None of the unmappable cells had discernible orientation selectivity. 4. Ocular dominance was assessed for 62 of the centrally located receptive fields. Among mappable cells, there was an abnormally low proportion of binocular fields, while no such abnormality was seen for unmappable cells. 5. For 47 of the neurons, average response histograms were compiled for moving stimuli of various parameters in an effort to evoke the maximum discharge or peak response. This peak response was normal for mappable cells but reduced for unmappable cells. 6. We devised a technique for studying potential inhibitory receptive-field zones in these neurons, validated the method in normal striate cortex, and used it to test 20 mappable cells in the lid-sutured cats. None showed the pattern of strong inhibitory side bands seen in normal simple cells, although six showed weak or abnormal inhibitory zones. Interestingly, six of the seven visually inexcitable cells tested by this method had purely inhibitory receptive fields. 7. The effects of binocular suture were essentially identical for the binocular and monocular segments since the cell types and their response properties did not differ between these two areas of cortex. Furthermore, the cortical monocular segments of these cats seemed qualitatively different from the deprived cortical monocular segment after monocular suture. This extends an analogous difference for these cats reported for the monocular segments of the lateral geniculate nucleus. We thus conclude that monocularly and binocularly sutured cats develop by qualitatively different mechanisms. For the former, competition between central synapses related to each eye is a prominent feature of geniculocortical development, whereas, for the latter, such specific forms of geniculocortical development may not obtain.

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Differential effect of anesthesia on visual cortex neurons with diverse population coupling

10.1101/2020.06.13.150284 ◽

2020 ◽

Author(s):

Heonsoo Lee ◽

Sean Tanabe ◽

Shiyong Wang ◽

Anthony G. Hudetz

Keyword(s):

Visual Cortex ◽

Cortical Neurons ◽

Neural Circuit ◽

Tuning Curve ◽

Visual Stimuli ◽

Early Response ◽

Spike Timing ◽

Late Response ◽

Pairwise Correlation ◽

Deep Layers

AbstractIntroductionFiring rate (FR) and population coupling (PC) are intrinsic properties of cortical neurons. Neurons with different FR and PC have diverse excitability to stimulation, tuning curve, and synaptic plasticity. Therefore, investigation of the effect of anesthesia on neurons with different FR and PC would be important to understand state-dependent information processing in neuronal circuits.MethodsTo test how anesthesia affects neurons with diverse PC and FR, we measured single-unit activities in deep layers of primary visual cortex at three levels of anesthesia with desflurane and in wakefulness. Based on PC and FR in wakefulness, neurons were classified into three distinct groups: high PC-high FR (HPHF), low PC-high FR (LPHF), and low PC-low FR (LPLF) neurons.ResultsApplying repeated light flashes as visual stimuli, HPHF neurons showed the strongest early response (FR at 20-150ms post-stimulus) among the three groups, whereas the response of LPHF neurons persisted longest (up to 440ms). Anesthesia profoundly altered PC and FR, and differently affected the three neuron groups: (i) PC and FR became strongly correlated suppressing population-independent spike activity; (ii) Pairwise correlation of spikes between neurons could be predicted by a PC-based raster model suggesting uniform neuron-to-neuron coupling; (iii) Contrary to evoked-potential studies under anesthesia, the flash-induced early response of HPHF neurons was attenuated, and their spike timing was split and delayed; (iv) Late response (FR at 200-400ms post-stimulus) was suppressed both in HPHF and LPHF neurons.ConclusionsAnesthetic-induced association between PC and FR suggests reduced information content in the neural circuit. Altered response of HPHF neurons to visual stimuli suggests that anesthesia interferes with conscious sensory processing in primary sensory cortex.

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