Fine grain temporal analysis in aphasia: evidence from auditory gap detection.

Auditory temporal processing was investigated in individuals with acquired aphasia using a task in which they were asked to detect brief silent gaps inserted between noise segments modeled after formants in speech. To examine within-channel gap detection, gaps of 10, 20, 40, and 80ms duration were inserted between an initial segment (IS) and a trailing segment (TS) centered at the same frequency (1kHz). In a between-channel gap detection condition, gaps of 20, 40, 80, and 100ms duration were inserted between an IS that differed in frequency (4kHz) from the TS (1kHz). The effect of gap onset timing was examined in both conditions by systematically varying the duration of the IS by 10, 20, or 40ms. A combined analysis revealed that for both conditions and all gap and IS durations, individuals with aphasia produced fewer correct responses than age-matched neurologically intact controls. Separate condition analyses revealed that when noise segments were centered at the same frequency, individuals with aphasia demonstrated poorer accuracy in detecting 40 and 80ms gaps relative to normal controls (p<0.001). When gaps were inserted between noise segments differing in frequency, on average, aphasic subjects performed less accurately at durations of 40, 80 and 100ms (p<0.025). Detection in both groups decreased with smaller IS durations. The difficulties with gap detection observed in the aphasic group suggest the existence of fundamental problems in processing the temporal form or microstructure of sounds characterized by rapidly changing onset dynamics.

Androgen-responsive aspects of cognition in girls with Turner syndrome.

Turner syndrome (TS) represents a unique, sex hormone-deficient model in which to study the biological effects of androgen treatment (replacement) on cognition in females because TS girls have gonadal dysgenesis and absent ovarian androgen and estrogen production. We investigated the effects of androgen replacement therapy in TS girls, ages 10-14 yr, on cognitive function. A total of 64 TS girls were randomized to receive oxandrolone or placebo for 2 yr. They had a cognitive evaluation of four domains (verbal abilities, spatial cognition, executive function, and working memory) at baseline, 1, and 2 yr of the study. In addition, all subjects were examined for study safety every 6 months. Three of the four domains studied did not change significantly in response to oxandrolone treatment (verbal abilities, spatial cognition, and executive function). In contrast, the working memory summary score had a significant group by time interaction. The oxandrolone-treated group demonstrated improved performance after 2 yr, compared with the placebo group (P < 0.03). Minimal or no side effects were observed. In conclusion, oxandrolone treatment for 2 yr improves working memory in adolescent girls with TS. What this degree of improvement will mean in real life terms for TS girls remains to be determined.

Persistent cognitive deficits in adult women with Turner syndrome.

BACKGROUND: Turner syndrome (TS) has a characteristic neurocognitive profile. Verbal abilities are, in general, normal; however, women with TS, as a group, have specific deficits in visual-spatial abilities, visual-perceptual abilities, motor function, nonverbal memory, executive function, and attentional abilities. Observed deficits could be caused by genetic or endocrine factors. OBJECTIVE: To evaluate the specific cognitive deficits that appear to persist in adulthood, are not estrogen-responsive, and may be genetically determined. METHODS: The cognitive performance of adult women with TS (n = 71) who were estrogen repleted was compared with verbal IQ- and socioeconomic status-matched female controls (n = 50). Sixty-one women with TS had ovarian failure and received estrogen replacement and 10 had preserved endogenous ovarian function and were not receiving estrogen replacement at the time of evaluation. RESULTS: Similar to children and adolescents with TS, adults with TS have normal verbal IQ but have relative difficulty on measures of spatial/perceptual skills, visual-motor integration, affect recognition, visual memory, attention, and executive function despite estrogen replacement. These deficits are apparent in women with TS despite apparently adequate estrogen effect, either endogenous or by hormone replacement. CONCLUSION: The cognitive phenotypes of adults with TS, with or without ovarian failure, are similar, indicating that estrogen replacement does not have a major impact on the cognitive deficits of adults with TS.

Attention deficit/hyperactivity disorder as a right hemisphere syndrome. Selective literature review and detailed neuropsychological case studies.

Recent studies of ADHD implicate well-defined neuroanatomical networks and neurochemical pathways in its pathophysiological basis. Considerable attention has focused on the role of anterior and superior frontal regions and portions of the basal ganglia, including the caudate nucleus and globus pallidus. This paper reviews a growing literature suggesting differential involvement of right hemisphere mechanisms specialized for behavioral regulation and attention. Supportive data are drawn from neuropsychology, neuroanatomy, and neurochemistry. In addition, three cases are presented that illustrate the complex role of right hemisphere dysfunction in adult manifestations of ADHD. We suggest that the pleomorphic presentations of ADHD can be understood in terms of a spectrum of disturbances in overlapping neural regions, especially involving frontal and parietal areas of the right hemisphere and their connections to subcortical structures (including the striatum, limbic system and diencephalic nuclei).

Mental rotation: a task for the assessment of visuospatial skills of children.

7 girls and 5 boys, ranging in age from 7 to 12 years, participated in the pilot testing of a mental rotation task developed for use in a comprehensive test battery of visuoperceptual abilities. Two asymmetric, three-dimensional objects were constructed from wood strips such that one object was the mirror-image of the other. Black and white photographs were taken of these objects in various spatial orientations along a horizontal plane. 16 photographs depicted the object right-side-up and in 16 the object was upside-down (rotated 180 degrees in the vertical plane). These photographs were presented to the children who were asked to match each with the corresponding object. Analysis indicated correct judgements of the right-side-up images occurred more frequently than the upside-down images (t11 = 4.73, p < .001). Using these data, adjustments were made to the task instructions to provide greater clarity for the young participants.

Steady-state auditory evoked responses to pulsed frequency modulations in children.

This study investigated steady-state auditory evoked responses to pulsed frequency modulations (FM) of a continuous tone in normal children ranging in age from 6 to 12 years. We examined variations in response amplitude and phase as a function of age, recording site, and FM pulse duration. The surface topography of these evoked potentials suggested a relatively broad distribution with maximal responses observed at frontal electrode sites, smaller responses from parietal leads and the smallest responses were evident at the temporal lobe placements. Response parameters varied significantly as a function of pulse duration. Fifty milliseconds pulses elicited responses that were on average 20% larger than 100 ms FM pulses. Mean phase differences suggested that responses to the 100 ms pulses also lagged behind responses to the 50 ms pulses by the equivalent of 20 ms. There were no significant age-related variations in response amplitude. Phase varied with age only in response to the 50 ms FM pulses. The findings indicated that steady-state responses are sensitive to temporal parameters of frequency change present in pulsed modulations. The possibility is raised that this paradigm may be clinically useful in detecting dysfunction of specialized auditory mechanisms involved in frequency modulation analysis.

Case study: corticosteroid treatment of language regression in pervasive developmental disorder.

The authors describe a child whose language and behavior regressed at 22 months and in whom pervasive developmental disorder was later diagnosed. At 6 years, he displayed a profound receptive-expressive aphasia accompanied by behavioral disturbances characterized by hyperactivity, impaired social interactions, tantrums, gestural stereotypies, and echolalia. A single-photon emission computed tomography scan and steady-state auditory evoked potentials suggested bitemporal and left frontal pathophysiology. The overall profile resembled Landau-Kleffner syndrome, but no electroencephalographic disturbance was evident. Corticosteroid treatment resulted in amelioration of language abilities and behavior. These findings suggest that the factors underlying language regression in pervasive developmental disorder can, in special circumstances, be amenable to pharmacological treatment.

Specific neurocognitive deficits in Cornelia de Lange syndrome.

Cornelia de Lange Syndrome (DLS) is a dysmorphogenic disorder typically associated with severe mental retardation. This report describes a rare case with normal-range verbal intelligence and specific cognitive deficits suggestive of a developmental visuospatial disorder. This was apparent in selective deficits in the ability to integrate visual percepts, copy spatial configurations, and manipulate representations of objects in space. Visual memory and psychomotor skills were also impaired. These deficits occurred within the context of normal language abilities and language-related academic achievement. The observed pattern of neuropsychologic impairment, in addition to aspects of socioemotional development, was similar to that seen in children with developmental right-hemisphere dysfunction. These findings suggest that the factors underlying DLS can be associated with fairly specific aberrations of cortical functioning.

Neurophysiological evidence of auditory channel anomalies in developmental dysphasia.

Steady-state auditory evoked responses to frequency-modulated tones were obtained from normal children and two groups of children with developmental language disorders (developmental dysphasia). Children with predominantly expressive language impairment produced responses not different from normal children, while children with primary receptive language impairment produced responses that were markedly diminished, even absent. This occurred in recordings from either cerebral hemisphere and at mean frequency-modulation depths ranging from +/- 20 to +/- 100 Hz. Pathophysiology of auditory mechanisms concerned with frequency-modulation analysis are particularly associated with receptive developmental language impairment and may underlie associated difficulties in speech perception.