Sex-related differences in event-related potentials, face recognition, and facial affect processing in prepubertal children

Thirty-five prepubertal children, 17 boys and 18 girls, between the ages of 8 and 11 years, were studied to examine electrophysiological and cognitive sex differences during a face-recognition-memory (FRM) task and a facial-affect-identification task (FAIT). All participants were prepubertal, as determined by J. M. Tanner's (1962) staging and endocrine evaluation. Sex-dependent event-related potential (ERP) amplitude asymmetries were found during FRM. Boys displayed greater right versus left ERP amplitude to auditory tone probes during the task, whereas girls displayed the opposite pattern. In addition, positive correlations were obtained between ERP amplitude during FRM and FAIT accuracy scores for boys, but not for girls. Results suggest that girls and boys may use different neuronal systems in the processing of faces and facial affect. Findings are consistent with developmental theories regarding sex differences in visuospatial processing.     

Working memory and processing speed deficits in systemic lupus erythematosus as measured by the paced auditory serial addition test.

As many as 66% of systemic lupus erythematosus (SLE) patients have been reported to have cognitive deficits. These deficits are often associated with information processing speed and working memory. Similarly, processing speed and working memory impairments are the hallmark of cognitive dysfunction in multiple sclerosis (MS). The Paced Auditory Serial Addition Test (PASAT) places high demands on processing speed and working memory. Fisk and Archibald, however, demonstrated that the total score of the PASAT does not accurately reflect impairments in these cognitive processes. They found that MS patients used a chunking strategy to obtain correct responses and reduce the cognitive demands of the task. In the present study, PASAT performance was examined for 45 SLE patients and 27 controls using alternative scoring procedures. Although the total number of correct responses did not differ between SLE and controls at the 2.4 or 2.0 s presentation rates, SLE patients had fewer dyads (correct consecutive responses) than controls at the faster rate, and more chunking responses than controls at both rates. Disease activity, disease duration, depression, fatigue, and corticosteroids could not account for these differences. The findings suggest that SLE patients, like MS patients, chunk responses more often than controls, and that this scoring procedure may better reflect the working memory and processing speed deficits present in SLE.     

Working memory deficits in multiple sclerosis: comparison between the n-back task and the Paced Auditory Serial Addition Test.

Working memory (WM) deficits are common in multiple sclerosis (MS). The Paced Auditory Serial Addition Test (PASAT) is used frequently to measure WM in clinical settings. The n-back paradigm is used often in experimental studies of WM. One unique component of the n-back task is that it provides a measure of reaction time (RT), an additional behavioral index of processing speed and task difficulty. Despite the use of both tasks to measure WM, their common variance has not been documented. We tested 32 MS patients and 20 controls; performance measures were obtained for both tasks. Compared with controls, MS patients generally had poorer performance on both the PASAT and n-back task. MS patients also had slower RTs on the n-back than controls and showed more slowing than controls as a function of WM load. Correlational analyses showed a high correspondence between performance measures on the PASAT and n-back. Principal components analysis pointed to a common feature of the PASAT, n-back, and specific other neuropsychological measures, that is, processing speed. Although the PASAT and n-back were shown to have a significant amount of shared variance, each test has specific advantages and disadvantages for use in clinical populations.     

Cerebral resuscitation with succinate and fructose-1, 6-diphosphate

To test the hypotheses that succinate or fructose-1, 6-diphosphate may have a beneficial effect in global cerebral ischemia, we induced complete global cerebral ischemia for 5 minutes in rabbits by occlusion of the ascending aorta and the superior and inferior vena cavae. Fifteen minutes after restoration of cerebral blood flow, animals received an intravenous bolus of either succinate or fructose-1,6-diphosphate followed by continuous infusion. Another group of animals received fructose-1, 6-diphosphate beginning prior to aortic occlusion. Control animals received intravenous glucose by bolus, followed by infusion. Cerebrospinal fluid lactate levels were measured before occlusion and at 2 1/2 hours after occlusion, when the animals were sacrificed. In all animals electrocortical silence was demonstrated for the 5 minutes of global ischemia. The percent change in cerebrospinal fluid lactate levels in all groups was statistically similar. Only two of seven of the control animals recovered electroencephalogram amplitude during the 2 1/2 hour observation period. Time for recovery of amplitude on the electroencephalogram in animals receiving fructose-1, 6-diphosphate either before or after ischemia was statistically similar to controls. In the succinate treated group, all seven animals regained preocclusion levels of electroencephalogram amplitude within 36 minutes of the restoration of cerebral blood flow. Succinate administered after complete global cerebral ischemia resulted in significantly increased recovery of cerebral electrical activity (Fischer's exact test, p less than 0.05).     

The neuropsychological phenotype in Turner syndrome

Numerous studies have demonstrated a significant depression in performance IQ (PIQ) in Turner Syndrome (TS) females, but the neuropsychological interpretation of this finding remains unclear. The present study addressed the following questions regarding the neurospychological phenotype in TS: (1) Are TS women neuropsychologically impaired? (2) Is the impairment lateralized and (3) How consistent is the neuropsychological phenotype across TS individuals? Unlike previous studies, the present study utilized both normal and brain damaged female controls. All subjects were given an extended Halstead-Reitan neuropsychological battery.The TS females were significantly worse than normals but not significantly different from brain damaged females in their overall level of neuropsychological functioning. However, their impairment was not lateralized. Their pattern of lateralizing findings was similar to that found in the Diffuse and Normal groups, but significantly different from either the right or left unilateral lesion groups. Fairly consistent deficits were found on tests of visuospatial skills and long term memory, but there was considerable variability in all the other test findings among TS individuals. The results are discussed in relation to the recent findings (Inglis and Lawson, 1981) that verbal-performance IQ discrepancies may be unreliable indicators of lateralized cerebral dysfunction in females. Hence the depressed PIQ in TS appears not to indicate predominantly right hemisphere dysfunction and may not even indicate a consistent underlying neuropsychological phenotype.     

Suppression of water intake by immune complex formation in the hypothalamus : Implications for Systemic Lupus Erythematosus

Immune complex formation in the perifornical region of the hypothalamus resulted in depressed water consumption in rats, but did not consistently alter body temperature. The antibody with an unrelated antigen did not affect water consumption or body temperature. These results support the notion that immune complex reactions with the central nervous system can alter behavior.     

An event-related potential study of attention deficits in posttraumatic stress disorder during auditory and visual Go/NoGo continuous performance tasks

Posttraumatic stress disorder (PTSD) is characterized by disturbances in attention, such as increased arousal and hypervigilance. This study examined the event-related potential (ERP) P3 component to target detection (Go), response inhibition (NoGo) and irrelevant nontarget stimuli during auditory and visual A-X continuous performance tasks. NoGo N2 amplitude effects were also analyzed. Participants were 23 Vietnam veterans with PTSD and 13 civilian controls. No group differences were present for N2 or P3 amplitude to Go and NoGo stimuli. The PTSD group, however, had longer P3 latency to NoGo stimuli than controls, regardless of modality. The PTSD group also had greater frontal P3 amplitude to irrelevant nontarget stimuli than controls. Significant P3 amplitude and latency findings were associated with higher hyperarousal and reexperiencing scores from the Clinician-Administered PTSD Scale. The findings suggest that attentional problems in PTSD are related to slowed central processing when response inhibition is required, and to an impaired ability to screen irrelevant information. This study provides further evidence that the attentional impairments in PTSD are not confined to trauma-related stimuli. Heightened arousal appears to enhance the attentional dysregulation seen in PTSD.     

Comparison of neuropsychological impairment and vocational outcomes in systemic lupus erythematosus and multiple sclerosis patients

Systemic lupus erythematosus (SLE) and multiple sclerosis (MS) are chronic immunologic diseases that can cause cognitive dysfunction. MS is a central nervous system (CNS) disease characterized by demyelination and progressive brain atrophy. SLE is an autoimmune disease capable of damaging multiple organ systems, including the CNS. Cognitive disturbances are seen in both SLE and MS. The present study is concerned with understanding the similarities and differences between the cognitive profiles of SLE and MS as well as the relationship between cognitive impairment and vocational disability in these patients. We examined 47 SLE patients, 47 MS patients, and 44 healthy controls. The groups were well matched on demographics and the patient groups were also matched on disease duration and severity. Group comparisons revealed that generative verbal fluency and visual-spatial memory are more profoundly affected in MS than SLE; whereas depression, fatigue, and working memory deficits are similarly involved in both diseases. Logistic regression analysis revealed that executive function, in particular, was predictive of vocational outcomes in SLE and MS patients.     

Stimulus modality and Go/NoGo effects on P3 during parallel visual and auditory continuous performance tasks

Task and modality effects on P3 latency, amplitude, and scalp topography were studied during parallel versions of visual (VCPT) and auditory (ACPT) continuous performance tasks using a Go/NoGo paradigm (A-X CPT). Both the ACPT and VCPT incorporated five conditions including Go and NoGo stimulus sequences as well as three other nontarget conditions. The goal was to evaluate the functional significance and modality specificity of the P300 response and the NoGo P3. Analyses were performed using both raw and normalized data to make comparisons across modalities. For both modalities, the Target X (Go) and three nontarget conditions elicited maximum P3 amplitudes over the posterior scalp sites and qualified as classical P300 responses. The NoGo condition was associated with an increase in central-frontal amplitude compared to the Target X condition. The scalp topography of the P300/P3 for Go and NoGo conditions, as well as all other conditions, was the same for both modalities, supporting the modality independent nature of both P300 and the NoGo P3. Min-Max normalization of P3 amplitudes did not change the condition-topography relationships.