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Biomedical subjects

S Handel

Publications and source records attributed to S Handel.

At least 19 recordsLinked to original sources
PubMed1992

The differentiation of rhythmic structure.

Listeners judged whether two five-tone nonmetric rhythms were the same or different. Each rhythm was presented one, two, or four times to study the process of perceptual differentiation. The results indicated that the listeners perceived these rhythms in terms of the grouping of the tones, and not in terms of the timing between the groups. Two rhythms that had the same perceptual grouping were judged as being identical, even if the timing between the groups was different. The perception of the groupings of tones developed gradually. If each rhythm was presented only once, then the listeners had only a global percept, focused on groups (runs) of three elements, and often judged two different rhythms as being identical. If the rhythms were presented two or four times, then the grouping of the tones became more differentiated and the listeners were less likely to judge different patterns as being identical. Thus, perception of auditory rhythmic structure appears to follow the same developmental process as the perception of visual spatial structure.

Adult↗
PubMed1991

The effect of amphetamine on regional cerebral blood flow during cognitive activation in schizophrenia.

To explore the role of monoamines on cerebral function during specific prefrontal cognitive activation, we conducted a double-blind placebo-controlled crossover study of the effects of 0.25 mg/kg oral dextroamphetamine on regional cerebral blood flow (rCBF) as determined by 133Xe dynamic single-photon emission-computed tomography (SPECT) during performance of the Wisconsin Card Sorting Test (WCST) and a sensorimotor control task. Ten patients with chronic schizophrenia who had been stabilized for at least 6 weeks on 0.4 mg/kg haloperidol participated. Amphetamine produced a modest, nonsignificant, task-independent, global reduction in rCBF. However, the effect of amphetamine on task-dependent activation of rCBF (i.e., WCST minus control task) was striking. Whereas on placebo no significant activation of rCBF was seen during the WCST compared with the control task, on amphetamine significant activation of the left dorsolateral prefrontal cortex (DLPFC) occurred (p = 0.0006). Both the mean number of correct responses and the mean conceptual level increased (p less than 0.05) with amphetamine relative to placebo. In addition, with amphetamine, but not with placebo, a significant correlation (p = -0.71; p less than 0.05) emerged between activation of DLPFC rCBF and performance of the WCST task. These findings are consistent with animal models in which mesocortical catecholaminergic activity modulates and enhances the signal-to-noise ratio of evoked cortical activity.

Adult↗
PubMed1988

Space is to time as vision is to audition: seductive but misleading.

Space and time serve two perceptual functions. First, space/time forms a framework for visual and auditory events. Second, spatial and temporal change defines the properties of events and objects. It is at this second level that correspondences (i.e., mappings) between visual and auditory qualities can be hypothesized. Due to the active nature of perceiving, all such mappings illustrate the possible relations between looking and listening.

Attention↗
PubMed1987

Neurobehavioral functioning and magnetic resonance imaging findings in young boxers.

In a prospective investigation of neurobehavioral functioning in young boxers, 13 pugilists and 13 matched control subjects underwent tests of attention, information-processing rate, memory, and visuomotor coordination and speed. The results disclosed more proficient verbal learning in the control subjects, whereas delayed recall and other measurements of memory did not differ between the two groups. Reaction time was faster in the boxers than in the control subjects, but no other differences were significant. Ten subjects in each group were retested 6 months later and exhibited improvement in their neuropsychological performance as compared to baseline measurements. However, there were no differences in scores between the boxers and the control subjects at the follow-up examination or in the magnitude of improvement from baseline values. Magnetic resonance imaging, which was performed in nine of the boxers, disclosed normal findings.

Adult↗
PubMed1983

Effect of rhythmic grouping on stream segregation.

Three experiments investigated the role of temporal grouping on auditory stream segregation. For sounds that formed frequency streams (e.g., 400 Hz, 500 Hz, 1600 Hz, and 2000 Hz), the effect of rhythm was minimal. Temporal grouping did not affect judgments of stream segregation and did not affect difficulty of sequence identification. In contrast, for sounds that tended to form one coherent sequence (e.g., 750 Hz, 1500 Hz, 3000 Hz, and 6000 Hz), temporal grouping affected judgments of stream segregation as well as difficulty of identification. The temporal grouping could space the three lower or three higher pitch tones equally in time and this induced isochronous stream segregation. Subjects could not interleave the resulting streams, and identification became far more difficult. The role of rhythmic grouping is therefore contextual, depending on the relationships between the elements as well as the order of the elements.

Auditory Perception↗
PubMed1982

Cranial computed tomography of breast carcinoma.

Cranial computed tomographic (CCT) manifestations of brain metastases were reviewed in 304 patients with carcinoma of the breast. Metastases were demonstrated in 103 patients; 13 had other significant abnormalities. Single lesions were found in 55 (54%) patients (cerebral hemisphere, 48; cerebellar hemisphere, 4; pineal, 1; pituitary and optic chiasm, 1; vermis, 1) and multiple metastases were found in 48 patients. Continuity with bony metastases was seen in 4 patients. Prior to contrast infusion, 13 (12.5%) patients with metastases had a normal CCT, and 13 (12.5%) showed lesions of increased attenuation. All metastases demonstrated enhancement following contrast infusion; 74 (72%) had a zone of surrounding "edema." Histopathologic-CCT correlation was available in 54 patients. Precontrast, increased attenuation of metastases was associated with hemorrhage or calcification, or both. Calcification accompanied by necrosis was the result of previous treatment. Following therapy, 3 patients demonstrated lesions that were impossible to differentiate from metastases by CCT, but proved histologically to have no viable tumor cells present.

Adult↗
PubMed1982

A phase I study of intracarotid artery infusion of cis-Diamminedichloroplatinum(II) in patients with recurrent malignant intracerebral tumors.

A phase I study of intracarotid cis-diamminedichloroplatinum was performed in 11 patients with intracerebral tumors (five glioblastoma, four melanoma, one meningeal sarcoma, and one lung carcinoma) progressing after radiation +/- chemotherapy. The internal carotid artery was temporarily cannulated by a percutaneous transfemoral approach. All patients received i.v. heparin, mannitol, and fluids; seven received dexamethasone, 50 mg i.v., twice the day before and the day of treatment. Intracarotid cis-diamminedichloroplatinum, 60 to 100 mg/sq m in 175 to 250 ml 0.45% NaCl solution with 1000 units heparin, was infused over 1 hr. Six patients received two or more courses (maximum of 6) at 2- to 8-week intervals. Gastrointestinal toxicity was mild to moderate. Ototoxicity was minor. Central nervous system (CNS) toxicity was focal, severe, permanent, and possibly due to embolus in one patient at 75 mg/sq m; focal and reversible in one patient at 100 mg/sq m; and generalized but reversible in one patient at 75 mg/sq m. Possible CNS toxicity was noted in two additional patients. Two patients with CNS toxicity developed permanent ipsilateral retinal toxicity, and one patients without CNS toxicity developed bilateral decreased visual and auditory acuity 2 weeks after his sixth treatment. Renal and hematological toxicity and orbital pain were mild. Response status included: early death, one; probable responses, six (2+ 4+, 6, 6+, 8, and 8+ months); stabilization, two (3+ and 4 months); and failure, two. We recommend cis-diamminedichloroplatinum (60 mg/sq m) every 2 to 4 weeks for Phase II studies. Severe CNS and retinal toxicity are possible.

Adult↗
PubMed1981

Cranial computed tomography of malignant melanoma.

Two hundred seventy-five cranial computed tomography (CT) scans performed on 179 patients with malignant melanoma were reviewed. Of the 101 patients with confirmed cerebral metastases, CT demonstrated lesions in 93. In 72% of these, areas of increased attenuation were present in the precontrast scan. These lesions also enhanced after contrast infusion. There was a direct correlation between the extent of bleeding in the neoplasm and the density of the metastasis, at least 20% red blood cells per high power field were consistently present within lesions of increased attenuation. Cerebral metastases were occasionally associated with subdural or intracranial hemorrhage. Meningeal melanomatosis was recognized by CT only when associated with adjacent parenchymal metastases. In nine (11%) of 74 patients without clinical evidence of brain involvement, CT revealed cerebral metastases; this suggests that a staging CT scan might be useful on patients with diffuse or advanced local extracranial disease prior to definitive therapy.

Adolescent↗
PubMed1979

The sella turcica in primary end organ failure.

Pituitary hyperplasia, or adenoma, may result from end or target organ failure as seen in primary hypothyroidism and hypogonadism. Associated enlargement of the sella turcica and contour alterations without significant increase in volume may be seen. A review was made of 12 patients with end organ failure demonstrating the spectrum of radiologic changes within the sella turcica. Recognition of pituitary enlargement resulting from end organ failure may eliminate unnecessary surgery.

Adenoma↗
PubMed1977

Changing venous pattern in a hemangioblastoma resembling an arteriovenous malformation.

A patient with cerebellar hemangioblastoma underwent two successive cerebral arteriograms within a 48-hour period. The first arteriogram suggested an arteriovenous malformation. The second angiogram showed a dramatic change with nearly total absence of the earlier dilated draining veins. This change was found on examination of the surgical specimen to be caused by venous thrombosis.

Adult↗
PubMed1976

The role of pattern goodness in the reproduction of backward masked patterns.

Four experiments investigated the role of pattern goodness in backward masking using five- and four-dot patterns constructed by placing dots in the cells of a 3 x 3 matrix. In Experiment 1, subjects rated the goodness of these patterns and the results replicated previous work showing that good patterns had few alternatives. In Experiment 2, the dot patterns were the target stimuli in a backward masking task using a variety of masking stimuli. For all masking, good patterns were reproduced more accurately than poor patterns. In Experiment 3, the goodness of the masking stimulus was varied. The results indicated that good patterns were reproduced more accurately (replicating Experiment 2) and that good patterns were less effective as stimulus than were poor patterns. In Experiment 4, a long interstimulus interval which precluded masking was used to determine whether goodness affected encoding or memory. At these intervals, there were no differences among patterns, suggesting that the effect of pattern goodness was on rate of encoding. These results demonstrate the importance of configural properties in pattern perception.

Discrimination, Psychological↗