Memory failures in progressive idiopathic dementia.

Fourteen patients with progressive idiopathic dementia (PID) were compared with 14 normal controls on psychometric and laboratory measures of cognitive processes. The patients had significantly lower scores than controls did on the Wechsler Memory Scale (p < .001) and the Wechsler Adult Intelligence Scale (WAIS) Performance IQ (p < .01) but not on WAIS Verbal or Full Scale IQ nor on Digit Span tests. The patients performed more poorly on learning and memory tasks than controls. Unlike the latter, the patients' recall of categorized word lists was no better than their recall of unrelated words and they did not consistently remember information that had been previously recalled. Patients also were unable to generate as many words that start with a given letter (p < .01) or that belong to a given category (p < .001) as controls did. The data are interpreted as showing that while many intellectual functions are preserved, PID patients are unable to access structures in semantic memory and therefore fail to effectively encode episodic events so that they are memorable. Differences in cognitive dysfunction in PID and in depression are discussed.