On familial factors in the attentional deficit in schizophrenia: a review and report of two new subject samples.
We review the literature on attentional impairment in schizophrenics and their first-degree relatives and present new information from ongoing family studies of the disorder in Ireland and Israel. Subjects were administered a neuropsychological test battery (the NIMH Attention Battery) intended to measure four different elements of attention: encode, focus/execute, sustain, and shift. Results from both samples indicated that schizophrenic subjects performed most poorly on the tests, the control subjects performed best, and the scores of the relatives fell somewhere between the other two groups. Separation among subject groups was most significant for those tests comprising the focus/execute and sustain elements. Some of the results indicate, as well, that tests of auditory sustained attention may be the most discriminating of all. Overall comparison of the Irish and Israeli cohorts revealed striking differences. While within cohort differences remained, subjects from the Irish sample performed more poorly on many of the tests than Israeli subjects. This between-cohort difference was not found in the sustain element, as measured by the Continuous Performance Test. The socio-cultural implications of these findings are discussed with respect to future neuropsychological studies of schizophrenia.