Sixteen normal volunteers were studied with [F-18] fluorodeoxyglucose and positron emission tomography scans during behavioral activation with a verbal fluency test, and 35 age-matched controls were studied with resting-state scans. There was an overall increase of the cerebral glucose metabolic rate of 23.3% during verbal fluency activation, compared to the resting state, with the greatest activation in bilateral temporal and frontal lobes. A negative correlation between test performance scores and indices of metabolism was found in frontal, temporal, and parietal regions. Damage to the left frontal lobe maximally affects scores on verbal fluency tests, but performing the test activates a network of regions, of which the left frontal lobe is only one. Proficient performance in verbal fluency seems to require less metabolic activation than poor performance, perhaps because of the efficiency of cognitive strategies employed.
Homelessness is associated with multiple adversities that might impact upon brain function. We performed a review of published work to assess evidence of cognitive dysfunction among adults who are homeless. Despite liberal inclusion criteria only seventeen publications were identified, these describing eighteen samples mainly from the USA. Although the total number of individuals studied is small (about 3300) and the samples are heterogeneous, most studies indicate a considerable burden of cognitive dysfunction among homeless people. Such dysfunction might be expected to impact upon their ability to reintegrate into society, thereby undermining policies of inclusiveness. In clinical practice, assessment of homeless adults should include their cognitive state.
Homelessness is associated with multiple adversities that might impact upon brain function. We performed a review of published work to assess evidence of cognitive dysfunction among adults who are homeless. Despite liberal inclusion criteria only seventeen publications were identified, these describing eighteen samples mainly from the USA. Although the total number of individuals studied is small (about 3300) and the samples are heterogeneous, most studies indicate a considerable burden of cognitive dysfunction among homeless people. Such dysfunction might be expected to impact upon their ability to reintegrate into society, thereby undermining policies of inclusiveness. In clinical practice, assessment of homeless adults should include their cognitive state.
Disordered time perception has been reported in schizophrenia. We investigated time perception dysfunction and its neuropsychological correlates in patients with schizophrenia. Thirty-eight patients and thirty-eight age and sex matched healthy volunteers were compared in an auditory temporal bisection paradigm using two interval ranges (a 400/800ms condition and a 1000/2000ms condition). In the temporal bisection, subjects were required to categorise a probe duration as short or long, based upon the similarity with two reference durations. All subjects also completed a battery of neuropsychological tests measuring sustained attention, shortand long-term memory and executive function. In the 400/800ms condition, patients judged durations significantly shorter than did control subjects. Patients also exhibited decreased temporal sensitivity in both conditions. We found in both groups a negative association between temporal sensitivity and sustained attention for the 400/800ms condition, and between temporal sensitivity and long-term memory for the 1000/200ms condition. In patients, short-term memory performance was negatively associated with duration judgement in both conditions, while executive dysfunction was correlated to a general performance deficit in the 400/800ms condition. These findings suggest the possibility that time perception abnormalities in schizophrenia are part of neuropsychological dysfunction and are likely to adversely impact upon activity of daily living.
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