Claudia Kraiuhin

The differential diagnosis of dementia using P300 latency

The P300 component was elicited by an auditory oddball paradigm in 55 normal adults from a wide age range: 19 patients with dementia, 17 patients with depression, and 15 patients with schizophrenia. Normal P300 latency at a given age was predicted by using an age regression equation that had been calculated on the basis of the entire normal sample. Using this procedure, an abnormal delay in latency (greater than 2 SD) was found in approximately 80% of the dementia patients. However, when normal latency was predicted with a slightly greater degree of reliability according to separate equations for adults younger and older than 63 years, an abnormal delay in P300 was found to be less sensitive and specific to dementia. Suggestions for enhancing the diagnostic utility of the P300 component are proposed.

The P300 ERP component: an index of cognitive dysfunction xin depression?

A number of measures of brain function have suggested that depression is associated with cerebral hypoactivity. This study examines the late components of the event-related potential (ERP), in particular the P300 component, in depression. The P300 component is thought to index the updating of neurocognitive models which are concerned with the prediction of future events. Cognitive theories of depression include the proposition that depression may be characterized by abnormalities in the prediction of future events. The P300 component may therefore provide one neurophysiological index of cognitive dysfunction in depression. Twenty-seven subjects (14 medicated, 13 drug-free) fulfilling DSM-III criteria for Major Depression were compared to 27 age- and sex-matched normal controls. The amplitudes and latencies of N100, P200, N200 and P300 ERP components, reaction time and task accuracy were recorded during a standard auditory discrimination task. No significant differences were found in any ERP component measure or in reaction-time between the groups. Depressed subjects performed the experimental task significantly less accurately than normal controls, but this was not reflected in the ERPs.

Normal latency of the P300 event-related potential in mild-to-moderate alzheimer's disease and depression

A two-tone-discrimination task was used to elicit the P300 component of event-related (brain) potentials (ERPs) from patients with presumed Alzheimers dementia of mild or moderate severity, depressed patients of older age, and cognitively normal individuals. Although the average P300 latency of the Alzheimer patients was greater than that of the depressed patients, which in turn was greater than that of older aged normals, none of the group differences in latency were statistically significant. Moreover, when latency was examined on an individual basis, less than one-quarter of the Alzheimer patients had an abnormally delayed P300 for their age. Reaction times and the percentage of correct behavioral responses to the tones did distinguish the Alzheimer from the normal group; on both measures the patients scores were significantly worse. It was concluded that the performance of a simple tone discrimination task requiring a button-press response does not sufficiently tax those cognitive functions impaired in the earlier stages of Alzheimers dementia to result in abnormally slowed cognitive processing of the kind reflected in P300 latency.

P300 and the effects of aging: Relevance to the diagnosis of dementia

A tone discrimination task was used to elicit the P300 component of event related potentials in 55 normal subjects aged between 15 and 89 years. The age/latency relationship in the total sample was significant, but contrary to the reports of some others was statistically better described at CZ by a linear and not a curvilinear age regression function. Adults over 45 had steeper age regression slopes and larger age/latency correlations frontally and centrally than younger adults, but there was no difference in amplitude between these groups. The effect of age on latency seemed slightly more pronounced frontally in older adults, and there was significantly more latency variability in this group. Overall, the age/latency relationship in adults was statistically best described by separate linear age regression functions for adults less than or equal to 45 and greater than 45. It is suggested that latency variability may account for some of the discrepancy in the age/P300 literature, and the clinical implications of this are discussed.

A neurophysiological study of somatization disorder.

Abstract This article examines the possibility of neurophysiological dysfunction in somatization disorder. It draws on neurophysiological theories of hysteria, which suggest this disorder is associated with impairments of attention and stimulus processing. The possibility that somatization disorder is associated with similar impairments was investigated using a tone-discrimination event-related potential paradigm. Fifteen patients with somatization disorder and 15 age and sex matched normals were investigated, but for neither group was there a differential P1, N1, P2, or N2 component response to rare and frequent tones. No significant group differences were found on the P3 component either. However, there was a trend for N1 amplitudes to be larger in the somatization group, and this is tentatively interpreted in terms of an impairment in stimulus filtering. It is suggested that a more demanding task of selective attention may be used to further investigate the possibility of impaired stimulus processing in somatization disorder.

The prediction of normal P3 latency and the diagnosis of dementia

The relationship between age and the latency of the P3 (auditory evoked response potential) component was best described in 55 normals aged 15-89 by separate linear regression equations for those younger and those older than 63. Twelve out of 19 patients with dementia had P3 latencies at FZ and CZ which were delayed by more than two standard errors from the normal latency for their age predicted using the above equations, and were thus correctly identified. However, an equation calculated across the entire adult age range provided a better patient identification rate. The potential usefulness of P3 measures in clarifying the nature of cognitive impairment in dementia is discussed.

Auditory evoked response potentials in somatization disorder.

Event related potentials to frequently and infrequently occurring tones were recorded from 15 patients with somatization disorder, 10 patients with anxiety disorders and 15 normals. P3 component responses were of normal latency and amplitude in the somatizers, which suggests they had no apparent difficulty with certain aspects of processing novel, task-relevant stimuli. However, their N1 component responses to the frequent tones, which subjects had been instructed to ignore, were enhanced relative to each of the other groups. Moreover, there was no difference in N1 amplitude to the two types of tones among the somatizers, whereas each of the other groups had significantly larger N1 amplitudes to the infrequent tones. These preliminary results may suggest that somatization disorder is associated with an impaired ability to filter out and not respond to relatively meaningless afferent stimuli.

Whose Hysteria: Briquet's, Janet's or Freud's?

Somatisation disorder (Briquets syndrome) is a recent addition to psychiatric nosology. It represents an attempt to describe a syndrome of ‘hysteria’, the term initially applied to this polysymptomatic disorder by Guze and his colleagues. The manner of identification of this syndrome, however, has been the subject of criticism. This brief review suggests that the ideas of Janet, who worked at Salpetriere 30 to 40 years after Briquet, may provide a more precise approach to diagnosis. Furthermore, his hypotheses about predisposition to this disorder are seen to offer a preliminary way towards its understanding. Recent experimental evidence lends some support to Janets hypotheses.

The type A behaviour Pattern and Physique

This study examines the possibility that Type A behaviour is related to physique, and thus, is secondary to physique as a risk factor for coronary heart disease (CHD). Scores on a modified version of the 1966 Jenkins Activity Survey were correlated with a number of physical parameters. Age was found to have the highest correlation of -0.177. When the effects of age were adjusted for, only 7.1% of variation in JAS scores was explained by the body measurements used to define physique. In addition, when high and low scorers on the JAS were compared, no significant differences were found between the groups on any of the body measurements. Since this study found no significant relationship between JAS scores and physique, the results do not controvert the supposition that Type A behaviour is an independent risk factor for CHD.