Topographic analysis of auditory event-related potentials associated with acoustic and semantic processing.

The topography of auditory event-related potentials (ERPs) was examined during 3 kinds of tasks: selection of a specified real word or nonsense syllable from a list; simple detection of each of the same stimuli without discrimination; and classification of a set of words according to a specified semantic category. The potentials that were associated with the additional processing required by the discriminative tasks were disclosed by subtracting the wave forms obtained in the detection condition from those obtained during discriminative performance. Difference wave forms were also derived between the semantic classification and verbal discriminative ERP to delineate the changes associated with the extraction of word meaning. The topography of the ERP associated with stimulus detection was comparable to that found in previous studies of evoked potentials to non-speech stimuli. This distribution was consistent with 2 cortical generators, one within the supratemporal plane and the other on the lateral surface of the superior temporal gyrus. When discriminative performance was required on the basis of acoustic stimulus properties, the topography of the difference wave form that reflected this discriminative processing extended more posteriorly over temporal cortex. Semantic processing elicited a further posterior extension of ERP components by 330 msec after stimulus onset, as well as longer latency potentials that were not present in the verbal selection task. These differences imply that a more extensive portion of language cortex is engaged in semantic classification than in verbal identification.

Developmental abnormalities in children with acquired immunodeficiency syndrome (AIDS): a follow-up study.

Developmental abnormalities in 16 pediatric patients with AIDS or AIDS-Related Complex (ARC) were previously described. Neurological deterioration was in evidence on follow-up in 9 of the children, 5 died since the original assessments were performed. Ten patients were reevaluated 14 months later by cognitive testing. Two showed greater progress than expected on the basis of earlier test results; 6 showed the expected level of developmental progress; and the remaining 2 showed regression in cognitive functioning. All patients who exhibited regression in their developmental course showed deterioration in their neurological examinations. Developmental progression was noted in some children who on follow-up serial examinations exhibited a clinically deteriorating neurological picture. Pediatric AIDS patients manifest variable neurodevelopmental courses. As a result, rehabilitative intervention services must be tailored to meet individual needs.

Circulating thymulin and thymosin-alpha 1 activity in pediatric acquired immune deficiency syndrome: in vivo and in vitro studies.

Twenty-five children with acquired immune deficiency syndrome (AIDS) or AIDS-related complex had a characteristic pattern of T cell deficiency. Abnormally low plasma thymulin levels preceded the development of peripheral blood T cell abnormalities. In contrast to patients with congenital T cell deficiencies, our patients had elevated serum levels of thymosin-alpha 1. Treatment with thymosin fraction 5 in three children with AIDS resulted in only transient clinical and immunologic improvement.

AIDS: calcification of the basal ganglia in infants and children.

CT or postmortem examination demonstrated calcification of the basal ganglia in eight infants and children with acquired immune deficiency syndrome. Serial CT studies documented progression of both bilateral symmetric calcium densities and cerebral atrophy. Clinical features included progressive encephalopathy with dementia, and pyramidal tract signs. Postmortem examination of four children revealed variable degrees of calcific vasopathy of the basal ganglia, involving predominantly the putamen and globus pallidus.

Restoration of suppressor T-cell functions in children with AIDS following intravenous gamma globulin treatment.

Suppressor T-cell function was analyzed in seven children with acquired autoimmunodeficiency syndrome (AIDS) or AIDS-related complex (ARC). Four of the patients had markedly increased serum IgG levels. All patients had elevated percentages and absolute numbers of peripheral blood T8 cells. In vitro concanavalin A generation of suppressor cells for T-cell mitogenic responses and suppression of pokeweed mitogen-driven immunoglobulin secretion were diminished in all patients. After intravenous treatment with gamma globulin, four patients regained in vitro suppression of pokeweed mitogen-driven gamma globulin secretion. Treatment with intravenous gamma globulin also modified in vitro suppressor T-cell functions in children with AIDS or ARC.

Neurological complications in infants and children with acquired immune deficiency syndrome.

Neurological complications occurred in 6 children, aged 6 months to 5 years, with acquired immune deficiency syndrome who were followed for 14 months. The most frequent manifestations included encephalopathies, acquired microcephaly, and pyramidal tract signs. Computed tomographic examinations showed variable degrees of cortical atrophy with ventricular dilatation and calcification. Electrophysiological abnormalities were demonstrated. Two children had documented central nervous system infections. Neurological deterioration resulted in dementia in 3 children. Cognitive impairment and developmental delays were evident in the other 3. Postmortem examination of the 3 children who died showed subacute cytomegalovirus encephalitis in 1; nonspecific hemispheric white matter changes, calcific vasopathy of the basal ganglia, and striking bilateral corticospinal tract degeneration in the second; and extensive calcific vasopathy of the basal ganglia and frontal centrum semiovale, and bilateral attenuation of the frontopontine and corticospinal tracts in the third.

Developmental abnormalities in infants and children with acquired immune deficiency syndrome (AIDS) and AIDS-related complex.

Children with acquired immune deficiency syndrome (AIDS) display two types of clinical picture: a full-blown AIDS characterized by the presence of opportunistic infections and/or Kaposi's sarcoma and a prodromal stage now identified as AIDS-related complex (ARC). Neurological complications have been identified in infants and children with the disease. This paper discusses the developmental abnormalities in 16 pediatric patients, seven with AIDS and nine with ARC, ranging in age from six months to six years. In all cases, the mothers of these children either had ARC, AIDS and/or used intravenous drugs. Developmental histories showed delayed acquisition of milestones in most children following the diagnosis of AIDS or ARC, with delayed motor milestones consistently noted in both groups. Several children with AIDS actually lost milestones as their illness progressed; this has not occurred in the ARC group. Psychometric testing revealed more severe cognitive dysfunction in the group with AIDS. Involvement of the central nervous system was documented clinically, radiologically, and/or electrophysiologically in all patients with AIDS. In the ARC group the course of the illness has shown greater variability. Medical and social factors that may contribute to the developmental abnormalities are discussed.

Bacterial infection in the acquired immunodeficiency syndrome of children.

We have followed 46 children with acquired immunodeficiency syndrome and acquired immunodeficiency syndrome-related complex. Twenty-six patients had at least one episode of serious bacterial infection. Twenty-seven episodes of sepsis were documented in 21 patients. Soft tissue infection was common in both the presence and the absence of documented bacteremia. Urinary tract infection commonly presented as worsening diarrhea in the absence of sepsis. Organisms commonly isolated included Streptococcus pneumoniae, Haemophilus influenzae and Salmonella sp. Staphylococcal infection accompanied episodes of cellulitis/abscess. Escherichia coli commonly caused urinary tract infection in the absence of sepsis. Enteric and nosocomial sepsis was limited to hospitalized, instrumented patients or to individuals who had received prior antibiotic therapy as outpatients. We conclude that bacterial infection causes serious morbidity in acquired immunodeficiency syndrome and acquired immunodeficiency syndrome-related complex and may be further evidence for altered humoral immunity in the disorder.

Event-related potentials associated with the discrimination of acoustic and semantic aspects of speech.

Analysis of a word's acoustic structure must precede identification of its meaning. Therefore, these aspects of speech processing could be associated with event-related potential (ERP) components that differed in their timing. To identify electrophysiologic indices of the cortical processing of acoustic and semantic features of speech, we recorded ERPs to the random presentation of nonsense or real words in four conditions designed to manipulate the extent to which the speech sounds were processed. In one condition subjects responded to all stimuli; in a second and third, to a designated nonsense or real word; and in the final condition to words within a specified semantic category. To define the cortical activity associated with acoustic processing, ERPs obtained when no discrimination was required were subtracted from those recorded during the identification of a specified speech target. The difference waveforms exhibited a negative potential that began about 50 msec after stimulus onset and lasted about 200 msec. Difference waveforms obtained by subtracting the non-discrimination ERP from those obtained during semantic discrimination exhibited a negative potential with similar onset timing. We concluded that the early negative potential indexed acoustic processes necessary for stimulus identification. To identify potentials associated with determination of a word's meaning, we subtracted the verbal discrimination from the semantic discrimination ERPs. This difference waveform exhibited a later negativity beginning at 150 msec and lasting about 250 msec. This potential may be related to the semantic processing of speech.

An electrophysiologic indication of auditory processing defects in autism.

Averaged evoked potentials (EPs) to clicks, random pitch changes (signals), and random deletions of stimuli within a regular train of tones were examined in five autistic and five normal children. Brainstem auditory EPs were abnormal in one of the autistic patients. The early cortical EP components P60 and N100 showed no differences across groups, whereas the P200 component of the cortical responses to clicks, as well as the late positive component (P300) to the pitch changes and deleted stimuli, were significantly smaller in the autistic subjects as a group. Furthermore, when P200 and P300 amplitudes were averaged across conditions for the individual subjects, these components were smaller in every autistic subject than in any of the normal subjects. These results are consistent with the view that there are auditory defects in autism that may sometimes involve lower levels of neural transmission as manifested by abnormalities in the brainstem and auditory EP, but are more consistently manifest in higher aspects of processing that involve the registration and storage of stimulus information. It is suggested that the severe language disorder in childhood autism may be secondary to the basic deficits in higher auditory processing.

An electrophysiologic indication of defective information storage in childhood autism.

We used a combined behavioral and electrophysiological technique to test the hypothesis that storage of information is impaired in childhood autism. Endogenous event-related potentials associated with the random deletion of stimuli within a regular train of auditory or visual stimuli were examined in three autistic and three normal children. We found that all subjects were able to detect the stimulus deletions, but cortical potentials associated with stimulus omissions were smaller or absent in the autistic subjects. These results are consistent with dysfunction within the system that includes posterior parietal cortex and its connections with the mesolimbic temporal cortex and hippocampus.