Evaluation of the supervisory system in elderly subjects with and without disinhibition

Disinhibition and irritability, defined as loss of behavioral and emotional control, are frequent in the elderly. The working hypothesis for this stud y was that these disorders are associated with a cognitive alteration of co ntrol processes that manifests as non-routine behavior because of the dysfu nction of a general executive component known as the supervisory attentiona l system (SAS). Methods - A total of 28 elderly subjects with mild cognitive impairment wer e recruited and divided into two groups using the Neuropsychiatric inventor y. Fourteen subjects were allocated to the disinhibited group and 14 subjec ts matched for age, sex and educational level formed a disinhibition-free c ontrol group. The neuropsychological battery included the following tests: Mini Mental Score Evaluation, Boston Naming test, Token test, Trail Making and Verbal Fluency. Two tasks were specifically designed to stress the SAS: 1) A specific verbal sentence arrangement task in which subjects had to us e sequential reasoning with verbal material. Each test sequence consisted o f a series of words shown in jumbled order. The construction of some sequen ces had to be done by using familiar routine associations (valid conditions ). in contrast, other sequences required the overriding selection of famili ar routine associations, which were inappropriate within the general contex t of the task (invalid conditions). 2) Using the Continuous Performance Tes t, four aspects were evaluated: sustained, selective, preparation and suppr essive attention. Results -The only group differences in neuropsychological test results were the following: 1) the sentence arrangement task. In comparison with the co ntrol group, the disinhibited group was impaired in invalid conditions and the calculated difference between the number of correct responses in invali d conditions minus that in Valid conditions was significantly higher; and 2 ) the GPT. Disinhibited subjects had a significantly lower number of hits, exclusively in the 'suppressive attention' paradigm. These results suggest that subjects with disinhibition have impaired superv isory system function. (C) 2000 Editions scientifiques et medicates Elsevie r SAS.