Averaged cortical evoked responses to auditory and somatosensory stimuli were recorded in elderly depressives, dements, patients with a combination of depression and dementia and normal elderly controls. The subjects were also given a battery of cognitive tests and clinical ratings at stated intervals.
The latency of the auditory response was significantly longer in dements than in controls. Depressives had intermediate latencies which did not return to normal after recovery. Although somatosensory stimuli produced the results that pointed in the same direction, the mean response latencies were not statistically significant. Mixed cases were too few for separate statistical analysis but their latencies fell between those of the dements and those of the depressives.
Significant correlations emerged between latencies of auditory responses and some cognitive tests, but not with measures of depressive symptomatology.
The delay in response to auditory stimuli may be a useful adjunct to diagnosis: in depressives it may reflect organic cerebral change playing a part in the emergence of depressive symptoms in old age.