The functional anatomy of frontal lobe neglect in the monkey: behavioral and quantitative 2-deoxyglucose studies

A syndrome of hemisensory neglect follows damage to frontal association areas in monkeys and humans. To study the syndrome we removed frontal association cortex from the right hemisphere of macaque monkeys. After operation, behavioral testing showed conditional deficits in visual, somatosensory, and motor responses contralateral to the lesion. Brains of animals were studied with [14C]2-deoxyglucose autoradiography to evaluate functional neuroanatomical changes. Ipsilateral striatal and selected thalamic and midbrain nuclei exhibited depression of glucose utilization (10 to 60%). No consistent glucose utilization changes appeared in cortex or in primary motor or sensory pathways. Brains from unoperated control animals did not exhibit these changes, nor did brains from operated animals with behavioral recovery from neglect. We conclude that the symptoms of frontal lobe neglect in the monkey are the result of dysfunction within a widely distributed system of subcortical centers. The distribution of the dysfunction provides an explanation for some of the clinical features of neglect.