Cognitive and White Matter Tract Differences in MS and Diffuse Neuropsychiatric Systemic Lupus Erythematosus

BACKGROUND AND PURPOSE

Multiple sclerosis and neuropsychiatric systemic lupus erythematosus are autoimmune diseases with similar CNS inflammatory and neurodegenerative characteristics. Our aim was to investigate white matter tract changes and their association with cognitive function in patients with MS and those with neuropsychiatric systemic lupus erythematosus compared with healthy controls by using diffusion tensor imaging.

MATERIALS AND METHODS

Thirty patients with relapsing-remitting MS and 23 patients with neuropsychiatric systemic lupus erythematosus matched for disease severity and duration and 43 healthy controls were scanned with 3T MR imaging. The DTI was postprocessed, corrected for lesions, and analyzed with tract-based spatial statistics. Cognitive assessment included examination of processing speed; visual, auditory/verbal, and visual-spatial memory; and sustained attention and executive function. Differences were considered significant at P < .05.

RESULTS

Tract-based spatial statistics analysis revealed significantly decreased fractional anisotropy and increased mean diffusivity in patients with MS compared with healthy controls, decreased fractional anisotropy in patients with MS compared with those with neuropsychiatric systemic lupus erythematosus, and an increased mean diffusivity in patients with neuropsychiatric systemic lupus erythematosus compared with healthy controls. Patients with MS showed decreased fractional anisotropy throughout central WM pathways, including the corpus callosum and the inferior longitudinal and fronto-occipital fasciculi compared with those with neuropsychiatric systemic lupus erythematosus. Altered cognitive scores in patients with MS were significantly associated with decreased fractional anisotropy and increased mean diffusivity in all examined domains, while in patients with diffuse neuropsychiatric systemic lupus erythematosus, only decreased fractional anisotropy in the superior WM pathways showed significant association with executive function.

CONCLUSIONS

Patients with MS and neuropsychiatric systemic lupus erythematosus showed widespread WM tract alterations outside overt lesions, though more severe changes were identified in patients with MS. The WM tract changes were associated with cognitive dysfunction in all explored domains only in patients with MS.

Multimodal imaging in systemic lupus erythematosus patients with diffuse neuropsychiatric involvement

OBJECTIVES

The objective of this paper is to investigate conventional and nonconventional brain magnetic resonance imaging (MRI) findings in systemic lupus erythematosus (SLE) patients with diffuse neuropsychiatric involvement (dNPSLE) compared to healthy controls (HCs).

METHODS

Twenty-six (26) SLE patients with one or more diffuse NP syndromes related to the central nervous system (CNS) (dNPSLE) and 36 age- and sex-matched HCs were scanned on a 3T MRI using a multimodal imaging approach. Univariate and multivariate analyses were used to determine MRI-specific measure differences between dNPSLE and HCs for lesion burden, tissue-specific atrophy, magnetization transfer ratio (MTR) and diffusion-tensor imaging (DTI) outcomes.

RESULTS

In univariate analyses, dNPSLE patients showed significantly increased T1 lesion number (p = .001) and T1-lesion volume (LV, p = .008) compared to HCs. dNPSLE patients showed decreased whole brain volume (p < .0001), gray matter volume (p < .0001), cortical volume (p < .0001) and increased lateral ventricle volume (p = .004) compared to HCs. dNPSLE patients had increased axial diffusivity (AD) of NAWM (p = .008) and NA brain tissue (p = .017) compared to HCs. In the multivariate regression analysis, decreased cortical volume was associated with SLE (R (2) = 0.59, p < .0001).

CONCLUSIONS

This study shows that cortical and central atrophy are associated with SLE patients with diffuse CNS syndromes. Microscopic tissue injury in the NAWM on AD DTI measures in SLE patients indicates a predominant reduction of axonal density.

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.

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.

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.

Neuropsychological effects of interferon beta-1a in relapsing multiple sclerosis. Multiple Sclerosis Collaborative Research Group

Cognitive dysfunction is common in multiple sclerosis (MS), yet few studies have examined effects of treatment on neuropsychological (NP) performance. To evaluate the effects of interferon beta-1a (IFNbeta-1a, 30 microg administered intramuscularly once weekly [Avonex]) on cognitive function, a Comprehensive NP Battery was administered at baseline and week 104 to relapsing MS patients in the phase III study, 166 of whom completed both assessments. A Brief NP Battery was also administered at 6-month intervals. The primary NP outcome measure was 2-year change on the Comprehensive NP Battery, grouped into domains of information processing and learning/memory (set A), visuospatial abilities and problem solving (set B), and verbal abilities and attention span (set C). NP effects were most pronounced in cognitive domains vulnerable to MS: IFNbeta-1a had a significant beneficial effect on the set A composite, with a favorable trend evident on set B. Secondary outcome analyses revealed significant between-group differences in slopes for Brief NP Battery performance and time to sustained deterioration in a Paced Auditory Serial Addition Test processing rate, favoring the IFNbeta-1a group. These results support and extend previous observations of significant beneficial effects of IFNbeta-1a for relapsing MS.

Validity of neural network in sleep apnea

Clinical assessment of obstructive sleep apnea (OSA) is poor. Overnight polysomnography (OPG) is the standard reference test, but it is expensive and time-consuming. We developed an artificial neural network (ANN) using anthropomorphic measurements and clinical information to predict the apnea-hypopnea index (AHI). All patients completed a questionnaire about sleep symptoms, sleep behavior, and demographic information prior to undergoing OPG. Neck circumference, height, and weight were obtained on presentation to the sleep center. Twelve variables were used as inputs. The output was an estimate of the AHI. The network was trained with a back-propagation algorithm on 189 patients and validated prospectively on 80 additional patients. Data from the derivation group was used to calculate the 95% confidence interval of the estimated AHI. Predictive accuracy at different AHI thresholds was assessed by the c-index, which is equivalent to the area under the receiver operator characteristic curve. The c-index for predicting OSA in the validation set was 0.96 +/- 0.0191 SE, 0.951 +/- 0.0203 SE, and 0.935 +/- 0.0274 SE, using thresholds of > 10, > 15, and > 20/hour respectively. The actual AHI of the 80 patients in the validation data set fell within the 95% confidence limits of the values predicted by the ANN. This study suggests that ANN may be useful as a predictive tool for OSA.

An electrophysiological study of infants' sensitivity to the sound patterns of English speech

The study explores 10- to 11-month-old infants' sensitivity to the phonological characteristics of their native language. Event-related potentials (ERPs) were obtained for tones that were superimposed on two versions of a story: an Unmodified version containing normal English function morphemes, and a Modified version in which the prosodic and segmental properties of a subset of function morphemes were changed to make them atypical. The 11-month-olds exhibited significantly lower amplitude ERPs to the tones during the Modified story than to the Unmodified story, whereas the 10-month-olds showed no differences. These results suggest that the 11-month-olds discriminated the two versions of the story based on their representations of the phonological properties of English. Further, the tone-probe ERP method can successfully be used to study the development of speech perception in the pre-linguistic infant.

The immune system can affect learning: chronic immune complex disease in a rat model

Evidence is presented that the immune system can affect central nervous system functioning, leading to changes in learning. Immune complex disease is induced in rats and their behavior tested using a Lashley maze. Significant differences in behavior were found between the animals with high disease activity and those with low disease activity and the non-disease controls. These changes were not due to uremia and are most likely due to the immune response. There is some evidence immune complex deposits in the choroid plexus may play some role, but not the sole or major role in the behavioral changes. This provides a model by which immunologic processes can cause neuropsychiatric manifestations in autoimmune diseases like lupus, as well as showing that immune processes can affect behavioral functioning.

Functional neuroimaging of attention in the auditory modality

Previous functional neuroimaging studies of attention have emphasized the visual modality. We developed an auditory version of the continuous performance test (CPT) that included simple, focused and divided attention conditions. Positron emission tomographic (PET) scans were acquired during CPT performance in normal young adults and then submitted to statistical parametric mapping. Simple attention brought about a large region of activation involving the anterior cingulate gyrus and the right anterior/mesial frontal lobe. Focused and divided attention CPT conditions were compared but there were few significant differences. The findings are consistent with activation of an anterior attention network during auditory attention, without involvement of posterior attention structures which are more likely to vary in accordance with sensory modality.

Slowed reaction time during a continuous performance test in children with Tourette's syndrome

The phenomonology of Tourette's syndrome (TS) not only includes tics but also apparent deficits in attention. These attentional deficits in TS likely involve anomalies in frontal-striatal circuits. In this study, performance of 22 boys with TS and 22 age-matched boys without TS was compared on a continuous performance test (CPT) of attention. TS children demonstrated a normal capacity for discriminating targets from nontargets during the task, but showed significantly slower reaction times than controls. Severity of complex vocal tics was predictive of reaction time performance. Possible explanations for these findings are discussed and include the presence of attentional difficulties in TS, interference associated with tic suppression, a conservative strategy taken by TS children, and a general impairment of motor performance.

Effects of low level lead exposure on cognitive function in children: a review of behavioral, neuropsychological and biological evidence

Low level lead exposure, at levels currently found in significant numbers of children in the U.S., has been associated with decreases in IQ and other cognitive test scores in children, as well as with decreases in developmental test scores in infants. The precise nature of the cognitive deficits is not clear. This paper reviews epidemiological and developmental neurocognitive effects of lead and addresses methodological issues that may have contributed to differences in interpretation of previous research. In an attempt to provide a rationale for the lead-related deficits reported for humans, we have reviewed studies of lead-related behavioral and electrophysiological effects seen in animals as well as findings from studies that have examined the effects of lead exposure on neurochemical subcellular and cellular mechanisms. Based on these data, future strategies are suggested for determining the possible effects of low-level lead exposure on neurocognitive functioning in children.

Slowed reaction time during a continuous performance test in children with Tourette's syndrome

The phenomonology of Tourette's syndrome (TS) not only includes tics but also apparent deficits in attention. These attentional deficits in TS likely involve anomalies in frontal-striatal circuits. In this study, performance of 22 boys with TS and 22 age-matched boys without TS was compared on a continuous performance test (CPT) of attention. TS children demonstrated a normal capacity for discriminating targets from nontargets during the task, but showed significantly slower reaction times than controls. Severity of complex vocal tics was predictive of reaction time performance. Possible explanations for these findings are discussed and include the presence of attentional difficulties in TS, interference associated with tic suppression, a conservative strategy taken by TS children, and a general impairment of motor performance.

Single-trial latency variability does not contribute to fast habituation of the long-latency averaged auditory evoked potential in the albino rat

Fast habituation (FH) is defined as a general reduction in long-latency, vertex-recorded, averaged auditory evoked potential (AEP) amplitude that occurs in response to the second of a pair of acoustic stimuli. Our laboratory has been studying FH in a variety of human populations with different paradigms and has interpreted it to be a measure of neural attentional mechanism(s) and/or resource allocation related to the processing of cognitive information. We have also reported an analogous phenomenon in the rat. In the present investigation, we examined the relationship between FH (viz., averaged AEP component amplitude decrement) and the single-trial latency variability of the AEP peaks comprising that component. Specifically, AEPs were obtained to 60 paired-tone stimuli from unanesthetized and restrained albino rats previously implanted with chronic skull electrodes. Using a template-matching algorithm similar to that used by Michalewski et al. (Electroenceph. clin. Neurophysiol., 1986,65:59-71), the latency variability for each animal was computed for the N1 and P2 peaks of the single-trial AEPs that were used to compose the averaged wave form. Findings indicated that (a) there was no difference in single-trial latency variability for these peaks either within or across tones, and (b) there was no relationship between single-trial latency variability for either the N1 or the P2 peaks and the overall peak-to-peak amplitude (N1-P2) of the averaged wave from in response to the second tone. Thus, FH of the N1-P2(i.e. Peak 2) amplitude in the rat is not due to an increase in latency variability across tones.

Fast habituation of the long-latency auditory evoked potential in the awake albino rat

Fast habituation of the long-latency, vertex-recorded auditory evoked potential (AEP) peaks in humans was first described by Callaway (1973) as a reduction in AEP amplitude that occurs to the second of a pair of acoustic stimuli when both stimuli are presented with an interstimulus interval (ISI) of no more than 10 sec. When acoustic stimuli are presented in pairs with an ISI of 2 sec and an interpair interval (IPI) of approximately 10 sec, reduction in amplitude to the second tone occurs by as much as 30-50%. Fast habituation may depend somewhat on a subject's anticipation of the stimulus and on other factors related to attention and orienting. Studies in our laboratory have demonstrated this amplitude decrement to the second tone of a pair in human infants, children and adults and have explored the implications of this finding with respect to attentional processes and the allocation of cerebral resources. In the present investigation we describe an animal model of fast habituation. Here, vertex-recorded AEPs were obtained to paired tone stimuli delivered to awake adult male Sprague-Dawley rats chronically implanted with skull electrodes. Findings showed: (a) an AEP wave form with 8 distinct peaks, (b) for one component there was a marked decrement in amplitude from tone 1 to tone 2 in recordings obtained from an electrode placed slightly to the right of midline, and (c) that there were no significant differences in peak latencies across tones. This methodology may further our understanding of fast habituation in humans and may prove useful for studies of attention, orienting, and resource allocation using techniques that are not possible for use with human subjects.

Sleep apnea

The diagnosis of sleep apnea should be considered when a patient complains of snoring and excessive daytime somnolence. Middle-aged obese men are at particular risk, although apnea can occur in women and the elderly, as well as in persons who are not obese. An overnight polysomnographic sleep study can reveal the degree and type of apnea. Effective medical therapy can provide prompt clinical improvement. General treatment measures include weight loss and, in mild cases, training the patient to sleep in a side-lying position. Continuous positive airway pressure administered by masks worn at night is especially effective. Surgical treatment can help properly selected patients. Uvulopalatopharyngoplasty, which increases the volume of the oropharynx, requires follow-up polysomnographic studies. Tracheostomy is extremely effective and can be lifesaving in severe obstructive apnea. Effective therapeutic options make early recognition and treatment of this disorder vital and successful.

Sequential use of standard and ambulatory EEG in neonatal seizures

Adequate predictors do not exist to indicate whether seizures are likely to continue beyond the neonatal period. Thirteen neonates with seizures occurring after 7 days of age were evaluated with standard short-term electroencephalography (SEEG) during the initial seizures and with ambulatory EEG (AEEG) when each infant was within 37-44 weeks corrected age (i.e., gestational age plus chronologic age). Eight of 13 SEEGs, 10 of 13 AEEGs, and 12 of 13 with the combined use of both SEEGs and AEEGs accurately predicted the occurrence of seizures at 3-4 months corrected age. Results with SEEG and AEEG did not produce significantly different outcomes. Combined analysis of SEEG and AEEG produced significantly different results from those calculated when the two EEG types were analyzed independently (Z = 3.98, p less than 0.001). The findings indicate that the use of both of these tests may improve the ability to predict continued seizure activity in infants with neonatal seizures when compared to the use of each measure separately.

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 significance of MRI abnormalities in children with neurofibromatosis

We prospectively evaluated 47 children with neurofibromatosis to determine whether the previously reported high signals on magnetic resonance imaging (MRI) (prolonged T2) correlated with CT, brainstem auditory evoked responses (BAER), EEG, clinical examinations, cognitive abilities, or seizure disorder. Thirty percent of children had a history of seizures and 70% had either learning disabilities or mental retardation. Overall, 74% had an abnormal MRI examination. Sixty-two percent had high signals (prolonged T2) on T2-weighted images. Abnormal signals were located primarily in the basal ganglia, brainstem, and cerebellum. Twenty-five percent of patients had abnormal EEGs, 28% had abnormal CTs, and 27% had abnormal BAER examinations. The abnormal signals on MRI did not consistently relate to findings on CT, BAER, EEG, school placement, or clinical examination. The abnormal signals presumably reflect areas of abnormal brain parenchyma, either hamartomas, heterotopias, or local areas of brain dysplasia.

Brain-reactive autoantibody levels in the sera of ageing autoimmune mice

Brain-reactive autoantibodies are thought to play an important role in mediating central nervous system (CNS) disorders in systemic lupus erythematosus (SLE). In this paper the developmental occurrence of these antibodies in the sera of autoimmune mice, i.e. NZB, NZB/W, MRL/l and BXSB mice were examined. All murine strains tested, whether autoimmune or not, showed some degree of serum reactivity toward brain antigens. Autoimmune mice, however, displayed higher levels of serum brain-reactive antibodies, and at earlier ages, than non-autoimmune mice. Immunofluorescence assays against brain sections and adsorption assays, with both neural and non-neural tissue, indicated a heterogeneity in the specificity of the populations of brain-reactive antibodies present. These studies provide an important step in characterizing the appearance and diversity of brain-reactive autoantibodies, with the goal of better understanding their significance and potential role in mediating CNS dysfunction in SLE.

Auditory event-related potentials in waking infants and adults: a developmental perspective

Auditory event-related potentials (AERPs) were recorded in waking 1 month olds, 3 month olds, 6 month olds and adults in order to study the morphology and development of the wave form in the waking subject. Previous data were generally obtained in sleeping or drowsy infants. The findings indicated that there were 3 quantitative changes in the AERP over the first 6 months of life in waking infants: an increase in the latency of peaks, an increase in peak amplitude, and a decrease in intersubject variability. Adult peak latencies were generally shorter than those for 3 month olds and 6 month olds. Further, latencies of earlier AERP peaks for 1 and 6 month olds, in the present study, were comparable to those reported in previous investigations with sleeping infants. However, latencies of later AERP peaks differed from those of previous reports and were closer to those reported for waking adults. With respect to the amplitude, the 6 month olds, in general, had the highest amplitudes, the 1 month olds the lowest, and the 3 month olds and adults fell in between the two groups. Some differences were present between early and late components. The findings of this study are significant in that the AERPs were quantitatively different from those reported in earlier work with sleeping or drowsy infants. If cognitive and perceptual development is to be studied, it is necessary to obtain data on waking subjects. The data presented in this report are consistent with behavioral studies of biobehavioral shifts that are associated with changes in responsivity of the organism to stimuli during the first 6 months of life.

Pentobarbital-induced changes in the mouse brainstem auditory evoked potential as a function of click repetition rate and time postdrug

The effects of pentobarbital (80 mg/kg, i.p.) and saline injections on the BAEP were studied in 10 adult female BDF1 mice. Pentobarbital anesthesia induced statistically significant increases in the amplitudes and latencies of various BAEP components relative to preinjection and saline control values. These pentobarbital-induced changes were maximal shortly after drug administration and dissipated over time in a pattern similar to a drug elimination curve. Since pentobarbital and fast stimulus repetition rates are considered to be 'synaptic stressors', it was predicted that pentobarbital anesthesia and click repetition rate would have combined effects on the BAEP. This prediction was partially supported in that pentobarbital-induced changes in P4 amplitude and latency were significantly dependent on click repetition rate. The pentobarbital-induced effects on earlier BAEP components, however, proved to be largely independent of click rate. Pentobarbital-associated changes in the BAEP were not due to such factors as core temperature changes, circadian variations, and stress. The importance of anesthetic-induced changes in the BAEP for clinical and experimental studies is discussed.

Theophylline-induced changes in the mouse brainstem auditory evoked potential

Because theophylline is a widely used analeptic, there is interest in its possible ototoxic and neurotoxic effects. The present study used the brainstem auditory evoked potential (BAEP) to evaluate the acute effects of theophylline on auditory electrophysiology in mice. Adult female C57BL/6 mice were injected intraperitoneally with 150 mg/kg theophylline or saline. The BAEP thresholds and latency-intensity profiles suggested that theophylline induced a rather slight but statistically significant change in auditory function that was suggestive of a temporary recruitment-type sensorineural deficit. This observation raises concerns about the possible ototoxic effects of theophylline, particularly in asthmatic patients and apneic preterm neonates who receive this drug chronically. While there was BAEP evidence of ototoxic effects for theophylline, there was no evidence of neurotoxic effects.

Age-related hearing loss in BDF1 mice as evidenced by the brainstem auditory evoked potential

Age-related hearing loss was studied in unanesthetized female BDF1 mice using brainstem auditory evoked potential (BAEP) latency-intensity (L-I) profiles and BAEP thresholds. The mice were divided into 5 age-related groups: 3-4 months, 5.5-7 months, 9-10 months, 12 months and 18 months. Relative to the youngest group, BAEP threshold data indicated shifts in auditory sensitivity ranging from +6 dB for the 5.5- to 7-month-old group to +71 dB for the 18-month-old group. The BAEP L-I profiles of older mice were consistent with recruitment-type sensorineural (cochlear) hearing losses. No evidence of retrocochlear involvement was observed.

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 neuropsychological phenotype in TS: Are TS women neuropsychologically impaired? Is the impairment lateralized and 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.

Effects of impeded breathing on auditory brainstem responses in conscious man

Auditory brainstem responses (ABR) recorded in two groups of 10 normal volunteers were compared under conditions of impeded and unimpeded breathing. Impedance to breathing was accomplished by adding inspiratory flow-resistive loads of varying magnitude. Loaded breathing selectively augmented the amplitude of ABR components generated in the vicinity of the pontomidbrain junction. Peak latencies and other peak amplitudes of the ABR were unaffected. These findings suggest that the ABR procedure may serve as a direct noninvasive approach to the assessment of brainstem respiratory functions in conscious humans.

Central nervous system effects of antiasthma medication--an EEG study

The relationship between electroencephalographic (EEG) abnormalities (in particular paroxysmal activity) and theophylline alone or in combination with corticosteroids and/or ephedrine was examined in 161 adult and 93 pediatric patients. For each patient, total theophylline dosage was calculated and a theophylline blood level was obtained at the time of EEG recording. The major findings indicated: The presence of EEG paroxysmal activity in a greater percentage of the population studied than that which has been reported in a group of nonhospitalized individuals of similar age in the general population. There is a greater probability of EEG paroxysmal activity among patients with higher theophylline blood levels or total dosages than among those with lower blood levels or total dosages. There is an increase in EEG abnormalities with the addition of ephedrine. There is a possible protective effect of steroids against theophylline-related central nervous system disturbances.

A method for chronically recording brain-stem and cortical auditory evoked potentials from unanesthetized mice

Anesthetizing or sedating animals affords control over movement artifact during electrophysiological recording. However, the use of chemical restraint leads to unwanted side effects such as drug-induced hypothermia. Hypothermia is problematic because BAEP amplitudes and latencies are affected significantly by core temperature changes. Moreover, several recent studies have indicated that anesthetics and sedatives may significantly alter the BAEP and CAEP even in thermoregulated subjects. There is a need, therefore, to develop a practical technique for obtaining chronic BAEPs and CAEPs in restrained, unanesthetized animals. The present report describes a technique that permits the gathering of consistent, reliable evoked potential recordings over time in unanesthetized mice. The preparation is useful for studying the CNS effects of pharmacological agents, pathological conditions, aging and development in the mouse and could be adapted for use with other small animals as well.

Event-related brain potentials differentiate normal and disabled readers

Auditory event-related potentials (AERPs) recorded to irrelevant tone pairs while subjects performed visual, reading-related cognitive tasks differed significantly between normal and disabled readers. Disabled readers as compared with normal readers showed significantly lower amplitude right hemisphere AERP responses during tasks that involved visual-phonemic transfer of information and simple pattern recognition. Disabled readers as compared with normal readers also showed significantly higher amplitude left hemisphere responses during the visual-phonemic task. In both experimental conditions the reading-disabled subjects showed significantly lower amplitude right than left hemisphere AERP responses. Task-related strategies did not differ between groups. The pattern of AERP amplitude asymmetry found for disabled readers, which was opposite to that found for normal readers, suggests that the same reading-related tasks activated different cerebral processes in the two groups studied.

The use of a control or baseline condition in electrophysiological studies of hemispheric specialization of function

Asymmetries in event-related potential (ERP) measures between the two cerebral hemispheres in humans may not be apparent when the absolute values of left and right hemisphere recordings are only considered within the context of one experimental condition. ERP asymmetries may only emerge when results obtained during experimental conditions designed to differentially activate the two cerebral hemispheres are compared to a baseline or control condition involving low-level cognitive demands. Both theoretical and empirical considerations of such a baseline condition are discussed.

Permeability of the blood cerebrospinal fluid barrier during acute immune complex disease

Changes in the permeability of the blood-brain barrier (BBB) and blood-cerebrospinal fluid (blood-CSF) barrier in rabbits were assessed by using a sensitive double isotope technique at different times after the induction of acute immune complex disease (AICD). Induction of AICD was done with a single large dose of bovine serum albumin, whereas controls received only saline. Animals were sacrificed 6, 9, 12, 15, and 18 days after induction. Extravasation of protein was measured by injecting rabbits i.v. with 131I-rabbit serum albumin (RSA) 24 hr before sacrifice. In order to correct for intravascular blood volume, 125I-RSA was injected 5 min before sacrifice. Extravascular blood equivalents (EVBE), a measure of barrier permeability, were elevated in the CSF of rabbits sacrificed on days 12 and 15. None of the brain regions from any of the animal groups showed any changes or significant differences from controls in EVBE values on these days. These results indicate that there was an increase in the permeability of the blood-CSF barrier to radiolabeled albumin but not in the BBB proper during the time that CSF IgG levels were elevated in AICD. The potential significance of these findings for the mechanisms mediating central nervous system involvement in systemic lupus erythematosus is discussed.

Permeability of the blood cerebrospinal fluid barrier during acute immune complex disease

Changes in the permeability of the blood-brain barrier (BBB) and blood-cerebrospinal fluid (blood-CSF) barrier in rabbits were assessed by using a sensitive double isotope technique at different times after the induction of acute immune complex disease (AICD). Induction of AICD was done with a single large dose of bovine serum albumin, whereas controls received only saline. Animals were sacrificed 6, 9, 12, 15, and 18 days after induction. Extravasation of protein was measured by injecting rabbits i.v. with 131I-rabbit serum albumin (RSA) 24 hr before sacrifice. In order to correct for intravascular blood volume, 125I-RSA was injected 5 min before sacrifice. Extravascular blood equivalents (EVBE), a measure of barrier permeability, were elevated in the CSF of rabbits sacrificed on days 12 and 15. None of the brain regions from any of the animal groups showed any changes or significant differences from controls in EVBE values on these days. These results indicate that there was an increase in the permeability of the blood-CSF barrier to radiolabeled albumin but not in the BBB proper during the time that CSF IgG levels were elevated in AICD. The potential significance of these findings for the mechanisms mediating central nervous system involvement in systemic lupus erythematosus is discussed.

Changes in patterns of hemispheric electrophysiological activity as a function of instructional set

Investigations of differential hemispheric functioning which have used auditory event-related potentials (AERPs) typically employ paradigms in which two or more conditions are used. In these paradigms, conditions typically differ from each other with respect to both the physical aspects of the stimuli and the operations the subject must perform on these stimuli. Because both the subject's task and the physical properties of the stimuli change from one condition to another, it is unclear whether different patterns of AERP cerebral asymmetries obtained between conditions are primarily a function of differences in the stimuli (e.g., verbal vs. musical stimuli) or of endogenous factors such as the subject's cognitive approach to the processing of the stimuli. In the present study, two conditions with identical stimuli were employed but different instructions were given about how to process these stimuli. Music and paired tones were simultaneously presented in both conditions. In the Music Condition, subjects performed a task which involved attending to the music and ignoring the tones. In the Tones Sequence Condition, subjects counted specified sequences of tones and ignored the music. The results indicated that there were different patterns of left-right hemispheric AERP relationships between the two conditions. These findings support the hypothesis that endogeneous factors play a significant role in differential hemispheric functioning and that the AERP technique employed in this paradigm is a sensitive index of changes in electrophysiological activity associated with these endogeneous factors.

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 within the central nervous system can alter behavior.

Evoked potentials to auditory probes as indices of cerebral specialization of function--replication and extension

This study was an attempt to replicate findings from previous work in our laboratory as well as to study the relationship between vertex-referenced and linked mastoid-referenced responses under conditions purported to produce differential hemispheric activation. Auditory evoked potentials were recorded between T4-Cz, T3-Cz, T4-A1A2, and T3-A1A2 to task-irrelevant tone pips superimposed on a baseline condition and on two experimental conditions (verbal and music) hypothesized to differentially activate areas of the left and right cerebral hemispheres. Significant AEP amplitude asymmetries were obtained as a function of the ongoing tasks, replicating our previous findings. Higher amplitude AEPs were recorded from temporal-to-vertex leads from the hemisphere thought to be most involved in the ongoing task. In addition, temporal-linked mastoids placements showed an effect opposite to that seen for the vertex-referenced leads with lower amplitude AEPs occurring from the hemisphere purported to be most activated by the task. Mastoid-referenced placements were also less sensitive to task effects than vertex-referenced placements.

Semantic comprehension in infancy: a signal detection analysis

The purpose of this study was to validate a paradigm by which an infant's comprehension of concrete nouns could be assessed while controlling for (a) response bias, (b) stimulus preference, and (c) maternal cuing. More specifically, we sought to determine whether 11- and 13-month-old infants directed their eye fixations to the referent of an object word said by the mother and to determine whether there was a developmental shift in responding to object words at these 2 ages, as some previous research suggests. Duration of looking at each of 4 corners of an apparatus was measured while the mother (unable to see what the child was doing) uttered a word she felt the infant knew, 1 she felt he/she did not know, and a nonsense word. Analyses based on signal detection theory using "known" words as signal trials and nonsense words as noise revealed that 13-month-olds directed their looking time significantly longer at the referent of the known word when that word was uttered than when the nonsense word was uttered. At neither age did looking at the referent of the unknown word exceed control values. No significant effects were obtained at 11 months of age, nor were there any sex effects.

Simple apparatus for blocking small animal brains

A modification of previously described devices for blocking small animal brains is presented. The apparatus is easily constructed and allows for blocking at varous angles of both fixed and unfixed tissue of most small laboratory animals.

Chronic immune complex disease: behavioral and immunological correlates

Using a fear avoidance paradigm, behavioral effects were seen in Sprague-Dawley rats in which chronic immune complex disease was induced. These effects were related to changes in urine protein that developed during the course of the experiment. Experimental animals also had glomerular deposits of rat gamma globulin and BSA as determined by immunofluorescence; C3 deposits were observed in half of these animals. BSA and/or rat gamma-globulin, but not C3, was seen in the choroid plexus of half of the experimental animals. This is the first study to report behavioral changes associated with the induction of chronic immune complex disease in experimental animals.

A naturally occurring antibody in New Zealand mice cytotoxic to dissociated cerebellar cells

A spontaneously occurring antibody cytotoxic to dissociated cells of the neonate mouse cerebellum was found in the sera of some New Zealand (NZ) mice. No significant activity was found in the sera of six non-autoimmune mouse strains. The degree of cytotoxicity was similar towards both allogeneic and syngeneic cells. Absorption of the cytotoxic sera with brain and kidney homogenates removed the reactivity, while liver removed less reactivity. Absorptions with thymocytes and several other tissue homogenates and cells had no effect on the cytotoxicity levels, nor was there a correlation between the levels of thymocytotoxicity and cerebellar cell cytotoxicity. The antibody cytotoxic for cerebellar cells could not be demonstrated in the cerebrospinal fluid (CSF) of any mice examined, including a mouse with high serum cytotoxic levels. Gel filtration of reactive sera indicated that the antibody is of the IgM class.

Auditory evoked potentials as probes of hemispheric differences in cognitive processing

The amplitude of auditory evoked potentials recorded from the cerebral hemispheres to pairs of task-irrelevant tones was related to differential hemispheric engagement in ongoing cognitive activity (for example, verbal versus musical). The hemisphere hypothesized to be most engaged in the ongoing cognitive task, as compared to the unengaged hemisphere, produced a greater potential difference between the temporal and reference electrode to the second of the tone pairs. These findings are related to "fast habituation" and "recovery cycle.".

Atropine-induced bradycardia in the guinea pig: dose-response

The effect of atropine sulfate on the heart rate of the unanesthetized guinea pig was studied using a wide range of doses injected via a chronic jugular cannula; dose-response data are presented for the range of 5 mg/kg to 50 mg/kg. A long-lasting dose-dependent bradycardia was produced. This finding is in contrast to the clasically reported effect of atropine in man and dog: tachycardia sometimes preceded by a transient bradycardia. Thus, the guinea pig may be an excellent model for the study of parasympathomimetic, bradycardia-producing effects of atropine.