Impact of learning on representation of parts and wholes in monkey inferotemporal cortex.

Chris I Baker,Marlene Behrmann,Carl R Olson

doi:10.1038/nn960

Abstract

Here we investigated the impact of visual discrimination training on neuronal responses to parts of images and to whole images in inferotemporal (IT) cortex. Monkeys were trained to discriminate among 'baton' stimuli consisting of discrete top and bottom parts joined by a vertical stem. With separate features at each end, we were able to manipulate the two parts of each baton independently. After training the monkeys, we used single-cell recording to compare neuronal responses to learned and unlearned batons. Responses to learned batons, though not enhanced in strength, were enhanced in selectivity for both individual parts and for whole batons. Whole-baton selectivity arose from a form of conjunctive encoding whereby two parts together exerted a greater influence on neuronal activity than predicted by the additive influence of each part considered individually. These results indicate a possible neural mechanism for holistic or configural effects in expert versus novice observers.

Highlights

We investigated the impact of visual discrimination training on neuronal responses to parts of images and to whole images in inferotemporal (IT) cortex
Visual object recognition is thought to depend on experienceinduced changes in inferotemporal (IT) cortex, such that neurons become more selective for learned images[1,2,3,4]. This view is consistent with evidence showing that lesions in IT interfere with pattern recognition[5,6], that neurons in IT are pattern- selective[5,6] and that IT is a site of experience-dependent plasticity
By monitoring neuronal responses elicited by the batons in these tetrads, we were able to determine whether the neuron was selective for the parts or for the wholes

Summary

Introduction

We investigated the impact of visual discrimination training on neuronal responses to parts of images and to whole images in inferotemporal (IT) cortex. Whole-baton selectivity arose from a form of conjunctive encoding whereby two parts together exerted a greater influence on neuronal activity than predicted by the additive influence of each part considered individually These results indicate a possible neural mechanism for holistic or configural effects in expert versus novice observers. Visual object recognition is thought to depend on experienceinduced changes in inferotemporal (IT) cortex, such that neurons become more selective for (or more responsive to) learned images[1,2,3,4] This view is consistent with evidence showing that lesions in IT interfere with pattern recognition[5,6], that neurons in IT are pattern- selective[5,6] and that IT is a site of experience-dependent plasticity. The dark line running through the cortex is a shadow surrounding an electrode that was placed at the most medial recording site

Methods

Results

Conclusion