Functional Micro-Organization of Primary Visual Cortex: Receptive-Field Analysis of Nearby Neurons
Gregory C. DeAngelis, Geoffrey M. Ghose, Izumi Ohzawa, and Ralph D. Freeman (1999)
Functional Micro-Organization of Primary Visual Cortex: Receptive-Field Analysis of Nearby Neurons.
Journal of Neuroscience 19: 4046-4064.
(19 pages, 17 figures, 1 table):
visual cortex, receptive field, neuron, correlation, columnar organization, reverse correlation, phase coding
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It is well established that multiple stimulus dimensions (e.g.,
orientation and spatial frequency) are mapped onto the surface of
striate cortex. However, the detailed organization of neurons
within a local region of striate cortex remains unclear. Within a
vertical column, do all neurons have the same response selectivities?
And if not, how do they most commonly differ and why? To address
these questions, we recorded from nearby pairs of simple cells and
made detailed spatiotemporal maps of their receptive fields. From
these maps, we extracted and analyzed a variety of response metrics.
Our results provide new insights into the local organization of
striate cortex. First, we show that nearby neurons seldom have
very similar receptive fields, when these fields are characterized
in space and time. Thus, there may be less redundancy within a
column than previously thought. Moreover, we show that correlated
discharge increases with receptive field similarity; thus, the local
dissimilarity between neurons may allow for noise reduction by
response pooling. Second, we show that several response variables
are clustered within striate cortex, including some that have not
received much attention such as response latency and temporal
frequency. We also demonstrate that other parameters are not
clustered, including the spatial phase (or symmetry) of the receptive
field. Third, we show that spatial phase is the single parameter
that accounts for most of the difference between receptive fields
of nearby neurons. We consider the implications of this local
diversity of spatial phase for population coding and construction
of higher-order receptive fields.