Scene perception: inferior temporal cortex neurons encode the positions of different objects in the scene

Abstract

Inferior temporal cortex (IT) neurons have reduced receptive field sizes in complex natural scenes. This facilitates the read-out of information about individual objects from IT, but raises the question of whether more than the single object present at the fovea is represented by the firing of IT neurons, as would be important for whole scene perception in which several objects may be located without eye movements. Recordings from IT neurons with five simultaneously presented objects, each subtending 7 degrees , with one object at the fovea and the other four centred 10 degrees eccentrically in the parafovea, showed that although 38 IT neurons had their best response to an effective stimulus at the fovea, eight IT neurons had their best response to an object when it was located in one or more of the parafoveal positions. Moreover, of 54 neurons tested for asymmetric parafoveal receptive fields, 35 (65%) had significantly different responses for different parafoveal positions. The asymmetry was partly related to competition within the receptive fields, as only 21% of the neurons had significant asymmetries when tested with just one object present located at the same parafoveal positions. The findings thus show that some evidence is conveyed by a population of IT neurons about the relative positions of several simultaneously presented objects in a scene extending well into the parafovea during a single fixation, and this is likely to be important in whole scene perception with multiple objects, including specifying the relative positions of different objects in a scene.