Extrapersonal spatial orientation: The role of posterior parietal, anterior frontal, and inferotemporal cortex

The present study indicates that the posterior parietal cortex is essentially involved in coding spatial relations between external objects, and the anterior frontal cortex mediates a function superordinate to a spatial factor.

Abstract

Rhesus monkeys with ablations of posterior parietal, anterior frontal, or inferotemporal cortex, and normal controls were tested on two tasks of extrapersonal spatial orientation. Both tasks measured the monkey's ability to perceive the spatial relationship between external objects. One task involved reversal learning, maximizing perseverative interference effects (landmark discrimination reversal task); the other eliminated a spatial separation of the cue from the reward-response location, minimizing shifts in the focus of attention (patterned string problems). Monkeys with parietal lesions were significantly impaired on both extrapersonal spatial tasks, whereas those with frontal lesions were not impaired on either one. Monkeys with inferotemporal lesions demonstrated a significant and increasingly greater deficit with each successive reversal on the landmark reversal task, but no impairment on the patterned string problems. In the context of prior research, the present study indicates that the posterior parietal cortex is essentially involved in coding spatial relations between external objects, and the anterior frontal cortex mediates a function superordinate to a spatial factor. The role of the inferotemporal cortex in spatial functions depends on the extent to which visual discrimination learning is involved.