Differential imaging of ocular dominance and orientation selectivity in monkey striate cortex

Abstract

Differential images of ocular dominance, acquired by comparing responses to the two eyes, reveal dark and light bands where cortical cells are dominated by the right and left eyes. These include most (but not all) histochemically stained cytochrome oxidase blobs in their centers. Differential images of orientation, acquired by comparing responses to orthogonal orientations, reveal dark and light bands that are reminiscent of the "orientation columns" reported earlier, on the basis of 2-deoxyglucose (2DG) autoradiograms (Hubel et al., 1978). However, they are shorter and more fragmented because they do not include regions lacking selectivity for orientation. Even though these "bands" derive from orientation-selective areas, comparisons with differential images of other orientations reveal that regions along their centers prefer different orientations. Hence, the orientation preferences inferred from "bands" in single differential images, or single 2DG autoradiograms, are not necessarily incorrect. Interactions between ocular dominance and orientation were investigated by comparing differential images of orientation obtained with binocular and monocular stimulation, as well as by comparing differential images of ocular dominance obtained with different orientations. In both cases, the elicited interactions were minimal, indicating a remarkable and unexpected independence that subsequent experiments revealed arises, at least in part, from a lateral segregation of regions most selective for one eye and regions most selective for one orientation, in the centers and edges of ocular dominance columns. Since this can also be viewed as a lateral correlation between binocularity and orientation selectivity, it fits with the simultaneous emergence of these properties in layers receiving input from layer 4c, and suggests that each of these properties requires the other.

Efficient coding in heterogeneous neuronal populations

“…Thus, it is well known that the local network environment, not only the responses of individual neurons, is heterogeneous in the way it represents specific aspects of the sensory input. For instance, within primary visual cortex, neurons are clustered according to their orientation preference in orientation domains that converge at singularities or pinwheel centers (31)(32)(33). The structure of the orientation map in V1 implies that the orientation distribution of local connections would vary with a neuron's position within the map: Neurons in pinwheel centers are likely to be connected to neurons of a broader range of orientations than neurons in orientation domains (9) to possibly influence information coding.…”

Optical imaging of visually evoked responses in prosimian primates reveals conserved features of the middle temporal visual area

“…By using WINMIX software (Optical Imaging), all activity images associated with stimuli of the same orientation were summed and divided by the ''pure blank'' obtained by summing the images of the blank control to create single-condition maps. In addition, the summed activity images acquired during the presentation of one orientation were divided by the summed activity images acquired during presentation of the orthogonal orientation to create differential maps (5). Custom programs written in MAT-LAB were used to further process the data.…”

Oriented Axon Projections in Primary Visual Cortex of the Monkey

“…Our surgical procedures are detailed in Blasdel (1992) and only briefly reviewed here. T welve hours before each experiment, the animal was fasted and given a prophylactic dose of dexamethasone (4 mg / kg).…”

“…In some animals, we used a voltage-sensitive dye (N K2367; Nippon KankohShikiso, Kenkyusho, L td., Okayama, Japan), and in other animals we imaged without dye. Details of the imaging technique are given in Blasdel (1992); here we present only those methods that have been adopted for these experiments.…”