A physiological change in the homotopic cortex following left posterior temporal lobe infarction.

We investigated the relationship between cerebral activity (measured with positron emission tomography) and word rate in normal subjects and aphasic patients listening to monosyllabic words at rates up to those encountered in normal speech. By measuring the slope of the regression of the individual activity-word rate responses in the temporal cortex in normal subjects, we identified a functional asymmetry in the posterior superior temporal sulcus. The response was greater (steeper) on the left. Using the same study design, we identified a steeper activity-word rate response in the right posterior superior temporal sulcus of patients who had recovered single-word auditory comprehension after infarction of the left posterior temporal cortex. This response was significantly different from that observed in both normal subjects and a group of patients with left hemisphere infarcts that spared the posterior temporal cortex. The results demonstrated a change in physiological responsiveness in the contralateral homotopic cortex after posterior temporal infarction.