Multiple object response normalization in monkey inferotemporal cortex

TitleMultiple object response normalization in monkey inferotemporal cortex
Publication TypeJournal Article
Year of Publication2005
AuthorsZoccolan D, Cox DD, DiCarlo JJ
JournalThe Journal of Neuroscience: The Official Journal of the Society for Neuroscience
Date Publishedsep
KeywordsAnimals, Brain Mapping, Macaca mulatta, Male, Photic Stimulation, Posture, Recognition {(Psychology), Visual Pathways, Visual Perception, } Temporal Lobe

The highest stages of the visual ventral pathway are commonly assumed to provide robust representation of object identity by disregarding confounding factors such as object position, size, illumination, and the presence of other objects (clutter). However, whereas neuronal responses in monkey inferotemporal cortex {(IT)} can show robust tolerance to position and size changes, previous work shows that responses to preferred objects are usually reduced by the presence of nonpreferred objects. More broadly, we do not yet understand multiple object representation in {IT.} In this study, we systematically examined {IT} responses to pairs and triplets of objects in three passively viewing monkeys across a broad range of object effectiveness. We found that, at least under these limited clutter conditions, a large fraction of the response of each {IT} neuron to multiple objects is reliably predicted as the average of its responses to the constituent objects in isolation. That is, multiple object responses depend primarily on the relative effectiveness of the constituent objects, regardless of object identity. This average effect becomes virtually perfect when populations of {IT} neurons are pooled. Furthermore, the average effect cannot simply be explained by attentional shifts but behaves as a primarily feedforward response property. Together, our observations are most consistent with mechanistic models in which {IT} neuronal outputs are normalized by summed synaptic drive into {IT} or spiking activity within {IT} and suggest that normalization mechanisms previously revealed at earlier visual areas are operating throughout the ventral visual stream.

Refereed DesignationRefereed

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