The effects of frontal and temporal-parietal lesions on the auditory evoked potential in man.

We compared the properties of long-latency auditory evoked potentials (AEPs) in patients with unilateral lesions of the dorsolateral frontal cortex (N = 10) or temporal-parietal cortex (N = 10) to those of a group of age-matched normal subjects. Extensive lesions of the frontal cortex had no effect on AEP amplitudes, scalp distributions or refractory properties. However, following frontal lesions AEPs were larger to tones presented in the ear contralateral to the lesion than they were for tones presented ipsilaterally. Following unilateral temporal-parietal lesions, the N1 component (98 msec latency) was markedly reduced in amplitude at all scalp sites, and no increase in N1 amplitude occurred with lengthening ISIs. The P2 component (200 msec), however, showed the same amplitude and refractory properties as in the normal subjects. The results underline the critical role played by the cortex of the posterior-superior temporal plane and the adjacent cortex of the parietal lobe in the production of the N1 component.