Motor sequencing deficits in schizophrenia: a comparison with Parkinson's disease.

Motor abnormalities occur in schizophrenia (SZ) and may arise from striatal dysfunction. This study examined whether the pattern of performance on simple and complex motor abilities in SZ was similar to that of patients with Parkinson's disease (PD). Quantitative tests of speeded movement and motor and cognitive sequencing were used to assess 25 SZ, 16 PD, and 84 normal controls (NCs). Sequencing performance was also examined with motor rigidity taken into account. Compared with the NC group, the SZ and PD groups were impaired on measures of motor rigidity and motor sequencing. With rigidity accounted for, the SZ group was significantly more impaired than the PD group on motor sequencing; cognitive and motor processes contributed to the motor deficit. Cognitive sequencing performance predicted motor sequencing performance in PD but not SZ. Although both SZ and PD resulted in significant motor and cognitive sequencing deficits, the pattern and correlates of these deficits differ, suggesting that the affected neural systems underlying motor deficits in SZ are different from those involved in PD.

Prediction of functional status from neuropsychological tests in community-dwelling elderly individuals.

Age-related dysfunction of frontal systems can result in deficits in planning, organization, self-control, and awareness of problems, which are likely to affect the ability to care for one's self. The purpose of this study was to determine the relationship between age-related frontal/executive deficits and impairment in instrumental activities of daily living (IADLs) in elderly individuals. Twenty-seven community-dwelling individuals were administered a comprehensive battery of neuropsychological tests and a performance-based evaluation of IADLs. Multiple regression analyses indicated that executive function and depression severity accounted for a significant proportion of variance in IADLs, with executive function making the greatest contribution. Tests measuring other cognitive functions, such as memory, language, and spatial skills, did not contribute significantly to the prediction of functional status. Furthermore, executive measures accounted for more variance than other demographic characteristics such as general health status, age, and educational level. The results of this study indicate that executive dysfunction in normal aging may be the best predictor of functional decline. A better understanding of the mechanisms that underlie IADL skills will ultimately aid in the development of compensatory and intervention strategies designed to delay the onset of assisted living and nursing home placement.

Structural brain correlates of verbal and nonverbal fluency measures in Alzheimer's disease.

This study examined the relationships between regional brain volumes and semantic, phonological, and nonverbal fluency in 32 participants with Alzheimer's disease (AD). Object but not animal semantic fluency correlated with frontal and temporal gray matter volumes. Phonological fluency was not significantly associated with any brain volume examined. Nonverbal fluency was selectively associated with bilateral frontal gray matter volumes. Hippocampal volumes, although markedly reduced in these patients, were not related to any of the fluency measures. Results lend evidence to the importance of the frontal lobes in the directed generation of nonverbal and verbal exemplars by AD patients. Furthermore, both left- and right-hemisphere regions contribute to the generation of verbal and nonverbal exemplars.

Brain structural and cognitive correlates of clock drawing performance in Alzheimer's disease.

The Clock Drawing Test (CDT) is widely used in the assessment of dementia and is known to be sensitive to the detection of deficits in neurodegenerative disorders such as Alzheimer's disease (AD). CDT performance is dependent not only on visuospatial and constructional abilities, but also on conceptual and executive functioning; therefore, it is likely to be mediated by multiple brain regions. The purpose of the present study was to identify component cognitive processes and regional cortical volumes that contribute to CDT performance in AD. In 29 patients with probable AD, CDT performance was significantly related to right-, but not left-hemisphere, regional gray matter volume. Specifically, CDT score correlated significantly with the right anterior and posterior superior temporal lobe volumes. CDT scores showed significant relationships with tests of semantic knowledge, executive function, and visuoconstruction, and receptive language. These results suggest that in AD patients, CDT performance is attributable to impairment in multiple cognitive domains but is related specifically to regional volume loss of right temporal cortex.