Effect of Image Orientation and Size on Object Recognition: Responses of Single Units in the Macaque Monkey Temporal Cortex

Abstract

This study examined how cells in the temporal cortex code orientation and size of a complex object. The study focused on cells selectively responsive to the sight of the head and body but unresponsive to control stimuli. The majority of cells tested (19/26, 73%) were selectively responsive to a particular orientation in the picture plane of the static whole body stimulus, 7/26 cells showed generalisation responding to all orientations (three cells with orientation tuning superimposed on a generalised response). Of all cells sensitive to orientation, the majority (15/22, 68%) were tuned to the upright image. The majority of cells tested (81%, 13/16) were selective for stimulus size. The remaining cells (3/16) showed generalisation across four-fold decrease in size from life-sized. All size-sensitive cells were tuned to life-sized stimuli with decreasing responses to stimuli reduced from life-size. These results do not support previous suggestions that cells responsive to the head and body are selective to view but generalise across orientation and size. Here, extensive selectivity for size and orientation is reported. It is suggested that object orientation and size-specific responses might be pooled to obtain cell responses that generalise across size and orientation. The results suggest that experience affects neuronal coding of objects in that cells become tuned to views, orientation, and image sizes that are commonly experienced. Models of object recognition are discussed.

Action Recognition by Motion Detection in Posture Space

“…On the other hand, as the parameters of the posture-selective neurons have to match the retinal size of the stimulus, one needs templates of different sizes or ways to establish size invariance, as for other types of object recognition. Indeed, body-shape-selective neurons have only limited size invariance (Ashbridge et al, 2000), suggesting that indeed posture-selective neurons for different sizes might be needed.…”

Parallel and distributed neural models of the ideomotor principle: An investigation of imitative cortical pathways

“…The neural implementation of the two models is inspired by neurophysiological evidence suggesting a continuous representation of stimuli in feature maps (Ashbridge et al, 2000;Cisek & Kalaska, 2005;Schwartz et al, 1988). In such neural populations, neurons generally respond to external stimuli with broad tuning curves of activity.…”

Effects of varying stimulus size on object recognition in pigeons.

“…These data suggest that, for normal recognition tasks, size is not encoded. Ashbridge, Perrett, Oram, and Jellema (2000) tested for size invariance in single cells of the object recognition area of rhesus macaques. They first recorded from 16 cells in the anterior part of the superior temporal sulcus that responded selectively to images of human forms; they later presented these images at several different sizes.…”