Basal forebrain amnesia: does the nucleus accumbens contribute tohuman memory?

摘要

OBJECTIVE—To analyse amnesia caused by basal forebrain lesions.
METHODS—A single case study of a patient with amnesia after bleeding into the anterior portion of the left basal ganglia. Neuropsychological examination included tests of attention, executive function, working memory, recall, and recognition of verbal and non-verbal material, and recall from remote semantic and autobiographical memory. The patient's MRI and those of other published cases of basal forebrain amnesia were reviewed to specify which structures within the basal forebrain are crucial for amnesia.
RESULTS—Attention and executive function were largely intact. There was anterograde amnesia for verbal material which affected free recall and recognition. With both modes of testing the patient produced many false positive responses and intrusions when lists of unrelated words had been memorised. However, he confabulated neither on story recall nor in day to day memory, nor in recall from remote memory. The lesion affected mainly the nucleus accumbens, but encroached on the inferior limb of the capsula interna and the most ventral portion of the nucleus caudatus and globuspallidus, and there was evidence of some atrophy of the head of thecaudate nucleus. The lesion spared the nucleus basalis Meynert, thediagnonal band, and the septum, which are the sites of cholinergic cell concentrations.
CONCLUSIONS—It seemsunlikely that false positive responses were caused by insufficientstrategic control of memory retrieval. This speaks against a major roleof the capsular lesion which might disconnect the prefrontal cortexfrom the thalamus. It is proposed that the lesion of the nucleusaccumbens caused amnesia.