摘要:

ObjectiveIn a sample of right-handed adults, volumetric magnetic resonance imaging (MRI) was used to reinvestigate hemispheric and sex-linked differences in Sylvian fissure (SF) morphology.BackgroundAsymmetries of the SF exist with a predominant leftward asymmetry consistently reported in postmortem studies. These anatomic asymmetries may reflect asymmetric allocation of adjacent opercula, with some investigators positing a relationship with planum temporale asymmetries, as the postcentral SF is more asymmetric than the anterior segment. Sex-related differences have also been reported with reduced asymmetries in women relative to men.MethodUsing in vivo MRI surface renderings, SF asymmetries were studied in a group of consistently right-handed men (n = 12) and women (n = 12). Anterior and postcentral SF lengths were measured.ResultsOverall, there was a significant leftward asymmetry of the horizontal SF (anterior and postcentral) in men and women. Whereas there was a significant leftward asymmetry of the postcentral SF, there was no significant asymmetry of the anterior SF. There was an increase in the parietal operculum anterior to the posterior ascending ramus (PAR) in the left hemisphere and posterior to the PAR in the right hemisphere when SF asymmetries were leftward, with the length of the anterior parietal operculum positively correlated with postcentral SF length.ConclusionsThese findings demonstrate that the SF is asymmetric but that clear sex-related effects do not exist in consistently right-handed subjects.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveThe objective of this study was to investigate cerebral asymmetries for the detection of brief temporal events in a group of 22 dextrals using psychophysical measures.BackgroundBy combining electrophysiologic and psychophysical measures, it should be possible to demonstrate that the right ear advantage reported in previous studies is the result of a left hemisphere temporal processing advantage rather than a rightward attentional bias.MethodBursts of white noise lasting 300 milliseconds were delivered unilaterally to the participants' ears. Half of the stimuli contained a gap lasting either 4 or 6 milliseconds. Participants indicated whether or not the noise burst contained a gap. Asymmetries in alpha and beta activity at left and right temporal lobe sites were measured during the task.ResultsThe psychophysical data confirmed previous reports of faster response times (RTs) and lower levels of error for the right ear (RE). There was no asymmetry in alpha activity between the left and right temporal lobes; however, there was a higher level of beta activity in the left temporal lobe.ConclusionsThe electrophysiological data suggest that the perceptual asymmetry is not the result of a nonspecific rightward attentional bias but that of a left hemisphere specialization for the detection of brief temporal events. The relation between atypical temporal processing asymmetries and developmental learning disorders is discussed.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveThis article reviews research on the main characteristics of mismatch negativity (MMN) and its applications in neuropsychiatry.BackgroundEvent-related potentials (ERPs) have been used to study many aspects of information processing. Mismatch negativity is an early auditory ERP that has been identified as an index of an automatic (preconscious) alerting mechanism stimulating an individual to attend to unexpected environmental events. Disturbances of MMN may relate to abnormalities of auditory information processing contributing to the pathophysiology of neuropsychiatric conditions.MethodThe authors review (1) studies that have evaluated the electrophysiological aspects of MMN and (2) studies that have investigated the different applications of MMN in neuropsychiatry.ResultsThe first part of this article describes the characteristics of MMN, its cerebral origins, and electrophysiological parameters. We then discuss the role of “echoic memory” as well as that of attention and vigilance. In the second part of the article, disturbances in MMN associated with schizophrenia, depressive illness, dementing processes, and other neuropsychiatric states are discussed.ConclusionsMMN is a preconscious cognitive ERP, the main generators and functions of which are well defined. Observations relating to the origins of MMN and its role in early auditory information processing together with its possible behavioral significance, combined with observations of MMN aberrations in psychiatric conditions, may provide novel insights into the pathophysiology of neuropsychiatric states.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveThis study was designed to determine whether young and older adults differ in the spatial pattern of omission errors on random-array letter cancellation tasks.BackgroundAging is associated with declines in the speed or efficiency of visual information processing. It is unclear whether the spatial characteristics of visual exploration also change with aging.MethodThirty young adults and 30 older adults each completed 21 random-array cancellation forms. Forms were systematically varied in paper size, target-to-distractor ratio, stimulus density, and target number.ResultsThe spatial distribution of errors was not random for older adults. Younger adults expressed a trend toward nonrandom error location, but the spatial distribution did not differ between groups. There was also a strong trend toward more errors per subject in the older group. Older subjects required more time for task completion.ConclusionsThe findings are consistent with a generalized age-related decline in the speed or efficiency of visual search, but the spatial properties of directed attention do not appear to be different between young and older adults.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveThis consecutive multiple case study was designed to determine whether cortical lesion sites can predict occurrence of mood or psychomotor disorders in adults and children.BackgroundMost of a large body of research supports the contention that left hemisphere lesions result more often than right ones in depression, and that the inverse occurs in mania. However, it is not clear how psychomotor status fits into this picture, nor whether children respond to the same lesions in a similar manner.MethodPublished (n = 88) and unpublished (n = 31) cases of school-aged child and adult patients with focal unilateral cortical lesions and psychomotor agitation or lethargy with or without corresponding mania or depression were reviewed systematically to determine whether lesion location relates systematically to any of those psychiatric conditions. No patients had symptoms prior to detection of their lesion. Manic-depressives and agitated depressives were also excluded.ResultsPatients with mania and/or psychomotor agitation had predominantly right hemisphere lesions. Postlesion hyperactivity (without mania) in children was common but was not more related to lesions in one or the other hemisphere. Adult and child patients with depression and/or psychomotor lethargy had predominantly left hemisphere lesions. The intrahemispherical site of the lesion did not significantly predict the type of mood or psychomotor disorder. Nevertheless, the nonsignificant trend was for right posterorolandic lesions to predict mania or agitation and for left frontal lesions to predict depression or psychomotor lethargy.ConclusionsThese findings support the neuropsychiatric approach to mood and psychomotor disorder in children and adults.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveThe objective of this study was to determine whether the pathophysiological changes associated with Parkinson's disease (PD) lead to an increased vulnerability to react to negative emotional stimuli and hence to depression. It is hypothesized that nondepressed PD patients will demonstrate, associated with particular PD and/or cognitive variables, vulnerability to the interfering effects of negative words on the Emotional (sad) Stroop task (EST).BackgroundDepression has been reported to occur frequently in PD, but there is controversy regarding its pathophysiology: psychosocial factors versus neurobiologic ones.MethodThirty nondepressed/nondemented patients with idiopathic PD attending a specialist movement disorders clinic were assessed from their emotional state (Beck's Depression Inventory [BDI], and Hospital Anxiety and Depression Scale) and from their cognitive state (Mini-Mental State Examination, Stroop tasks [including the EST], Modified Card Sorting Test, Word Fluency tasks, Digit Span, and Trail Making tests). In addition, information was gathered on PD-related variables such as severity (Hoehn and Yahr scale), duration of the disease, and type of motor response to dopaminergic drugs. The sample was split into two groups according to the median BDI score to allow for comparisons. One-way ANOVA techniques were used to look for significant differences between variables in the two groups. Bivariate correlations were used to look for significant relationships between variables in each group.ResultsThe two groups only differed in parameters measuring emotional state. Only the subjects with higher BDI scores showed significant correlations between EST performance and cognitive and PD-related variables.ConclusionsThose PD patients with more severe forms of illness and a greater level of prefrontal cognitive dysfunction are more vulnerable to the distracting effects of external negative stimuli. According to the cognitive model of depression, this may ultimately lead to the development of clinical depression.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveTo better understand apathy and disengagement in patients with Alzheimer's disease (AD), the authors investigated possible behavioral mechanisms underlying diminished novelty-seeking activity in patients with probable AD.BackgroundApathy and disengagement have been shown to be the most common behavioral changes associated with AD.MethodPatients and age-matched normal controls had their eye movements recorded while pairs of line drawings pitting an incongruous figure against a congruous figure were shown on a screen for 12 seconds. Characteristics of a subset of AD patients who were indifferent to novel visual stimuli as measured by exploratory eye movements were compared to those of a subset of AD patients who were attracted to novel stimuli to a degree similar to that of normal controls.ResultsThe indifferent patients were judged by informants, who completed a personality questionnaire, to exhibit a greater degree of apathy. The two AD groups did not differ in overall dementia severity or performance on a Saccade-to-Target Task that required shifts of attention and gaze. In a separate task, the indifferent patients were able to accurately identify the more novel stimuli in 97.5% of trials. Normal control subjects exhibited a strong bias toward processing novel stimuli, directing a higher proportion of their first fixations and dwell time to the incongruous stimuli whether the analysis was run for 3, 6, or 12 seconds of viewing. Indifferent patients did not direct their initial fixation toward novel stimuli and distributed their looking time evenly between incongruous and congruous stimuli throughout all measured intervals.ConclusionsThe results suggest that the indifference to novelty observed in some patients with probable AD cannot simply be attributed to global cognitive decline, more elementary attentional deficits, more rapid habituation of response to novel stimuli, or an inability to discriminate upon demand between stimuli of varying degrees of novelty. It is more likely that their behavior reflects a disruption, by AD pathology, of neural systems that modulate behavioral engagement and maintain attentional bias toward novel events in the environment.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveThis study attempted a systematic investigation of incidence, type, and circumstances of anomalous perceptual experiences in a highly specialized group of healthy subjects, extreme-altitude climbers.BackgroundThere is anecdotal evidence for a high incidence of anomalous perceptual experiences during mountain climbing at high altitudes.MethodIn a structured interview, we asked eight world-class climbers, each of whom has reached altitudes above 8500 m without supplementary oxygen, about hallucinatory experiences during mountain climbing at various altitudes. A comprehensive neuropsychological, electroencephalographic, and magnetic resonance imaging evaluation was performed within a week of the interview (8).ResultsAll but one subject reported somesthetic illusions (distortions of body scheme) as well as visual and auditory pseudohallucinations (in this order of frequency of occurrence). A disproportionately large number of experiences above 6000 m as compared to below 6000 m were reported (relative to the total time spent at these different altitudes). Solo climbing and (in the case of somesthetic illusions) life-threatening danger were identified as probable triggers for anomalous perceptual experiences. No relationship between the number of reported experiences and neuropsychological impairment was found. Abnormalities in electroencephalographic (3 climbers) and magnetic resonance imaging (2 climbers) findings were likewise unrelated to the frequency of reported hallucinatory experiences.ConclusionsThe results confirm earlier anecdotal evidence for a considerable incidence of hallucinatory experiences during climbing at high altitudes. Apart from hypoxia, social deprivation and acute stress seem to play a role in the genesis of these experiences.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

摘要:

ObjectiveThe goal of this study was to more precisely define the nature of the cognitive processing deficits in the patients with Lyme disease.BackgroundLyme disease has been associated with cognitive disturbances.MethodSixteen patients who met the Centers for Disease Control's case definition for Lyme disease and 15 age-and education-matched control subjects completed two computerized assessments. The first was a matching procedure that assessed perceptual/motor speed. The second task was an alphabet-arithmetic (AA) test that measured the speed of mental arithmetic. On the matching task, subjects judged as true or false simple identity equations (e.g., B + 0 = B). On the AA task, subjects indicated the veracity of equations of the same form as those of the matching task but which required mental arithmetic (e.g., A + 3 = D). The use of this paradigm permits sensory or motor slowing to be distinguished from slowed cognitive processing speed. Also, the tests do not involve automated or overlearned responses.ResultsLyme disease patients and healthy controls did not differ in perceptual/motor speed. However, Lyme disease patients' response times were significantly longer than those of healthy controls during the AA task, demonstrating specific impairments in mental activation speed.ConclusionsThese results suggest that Lyme disease patients show specific deficits when initiating a cognitive process. These impairments are independent of sensory, perceptual, or motor deficits.

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID

ISSN:0894-878X    

出版商:OVID    

年代:1999

数据来源: OVID