Models of Simple and Complex Cells

The aim of the present study was to characterize the spatial and temporal features of synaptic and discharge receptive fields (RFs), and to quantify their relationships, in cat area 17. For this purpose, neurons were recorded intracellularly while high-frequency flashing bars were used to generate RFs maps for synaptic and spiking responses. Comparison of the maps shows that some features of the discharge RFs depended strongly on those of the synaptic RFs, whereas others were less dependent. Spiking RF duration depended poorly and spiking RF amplitude depended moderately on those of the underlying synaptic RFs. At the other extreme, the optimal spatial frequency and phase of the discharge RFs in simple cells were almost entirely inherited from those of the synaptic RFs. Subfield width, in both simple and complex cells, was less for spiking responses compared with synaptic responses, but synaptic to discharge width ratio was relatively variable from cell to cell. When considering the whole RF of simple cells, additional variability in width ratio resulted from the presence of additional synaptic subfields that remained subthreshold. Due to these additional, subthreshold subfields, spatial frequency tuning predicted from synaptic RFs appears sharper than that predicted from spiking RFs. Excitatory subfield overlap in spiking RFs was well predicted by subfield overlap at the synaptic level. When examined in different regions of the RF, latencies appeared to be quite variable, but this variability showed negligible dependence on distance from the RF center. Nevertheless, spiking response latency faithfully reflected synaptic response latency.

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Substructure of Direction-Selective Receptive Fields in Macaque V1

Journal of Neurophysiology ◽

10.1152/jn.00822.2002 ◽

2003 ◽

Vol 89 (5) ◽

pp. 2743-2759 ◽

Cited By ~ 33

Author(s):

Margaret S. Livingstone ◽

Bevil R. Conway

Keyword(s):

Receptive Fields ◽

Direction Selectivity ◽

Positive Interactions ◽

Null Direction ◽

Simple Cells ◽

Complex Cells ◽

Preferred Direction ◽

Orientation Axis ◽

Interaction Regions ◽

Simple And Complex Cells

We used two-dimensional (2-D) sparse noise to map simultaneous and sequential two-spot interactions in simple and complex direction-selective cells in macaque V1. Sequential-interaction maps for both simple and complex cells showed preferred-direction facilitation and null-direction suppression for same-contrast stimulus sequences and the reverse for inverting-contrast sequences, although the magnitudes of the interactions were weaker for the simple cells. Contrast-sign selectivity in complex cells indicates that direction-selective interactions in these cells must occur in antecedent simple cells or in simple-cell-like dendritic compartments. Our maps suggest that direction selectivity, and on andoff segregation perpendicular to the orientation axis, can occur prior to receptive-field elongation along the orientation axis. 2-D interaction maps for some complex cells showed elongated alternating facilitatory and suppressive interactions as predicted if their inputs were orientation-selective simple cells. The negative interactions, however, were less elongated than the positive interactions, and there was an inflection at the origin in the positive interactions, so the interactions were chevron-shaped rather than band-like. Other complex cells showed only two round interaction regions, one negative and one positive. Several explanations for the map shapes are considered, including the possibility that directional interactions are generated directly from unoriented inputs.

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Tangential segregation of simple and complex cells in the visual cortex and their connections. A universal neocortical module

Neuroscience and Behavioral Physiology ◽

10.1007/bf02461396 ◽

2000 ◽

Vol 30 (1) ◽

pp. 89-96

Author(s):

S. A. Chebkasov

Keyword(s):

Visual Cortex ◽

Complex Cells ◽

Simple And Complex Cells

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Image statistics at the point of gaze during human navigation

Visual Neuroscience ◽

10.1017/s0952523808080978 ◽

2009 ◽

Vol 26 (1) ◽

pp. 81-92 ◽

Cited By ~ 16

Author(s):

CONSTANTIN A. ROTHKOPF ◽

DANA H. BALLARD

Keyword(s):

Visual System ◽

Selection Process ◽

Human Subjects ◽

Image Features ◽

Complex Cells ◽

Cell Responses ◽

Active Selection ◽

Active Nature ◽

Simple And Complex Cells ◽

Distinct Features

AbstractTheories of efficient sensory processing have considered the regularities of image properties due to the structure of the environment in order to explain properties of neuronal representations of the visual world. The regularities imposed on the input to the visual system due to the regularities of the active selection process mediated by the voluntary movements of the eyes have been considered to a much lesser degree. This is surprising, given that the active nature of vision is well established. The present article investigates statistics of image features at the center of gaze of human subjects navigating through a virtual environment and avoiding and approaching different objects. The analysis shows that contrast can be significantly higher or lower at fixation location compared to random locations, depending on whether subjects avoid or approach targets. Similarly, significant differences in the distribution of responses of model simple and complex cells between horizontal and vertical orientations are found over timescales of tens of seconds. By clustering the model simple cell responses, it is established that gaze was directed toward three distinct features of intermediate complexity the vast majority of time. Thus, this study demonstrates and quantifies how the visuomotor tasks of approaching and avoiding objects during navigation determine feature statistics of the input to the visual system through the combined influence on body and eye movements.

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