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Biomedical subjects

D Alway

Publications and source records attributed to D Alway.

6 recordsLinked to original sources
PubMed1996

Perceptual timing in cerebellar degeneration.

This study examined time perception in 12 patients with cerebellar degeneration (CD) and in 13 normal controls (NC). We used a time bisection procedure with four interval conditions (100-900 msec; 8-32 sec; 100-600 msec; 100-325 msec). Each subject's bisection point, discrimination ability (the Weber ratio) and precision (the inverse of the proportion of unexplained variance) was calculated for each condition. CD patients' performance on the 100-900 msec time bisection condition suggested a possible time discrimination deficit, which was confirmed with intervals in the range of 100-600 msec. Time discrimination was normal on the 100-325 msec condition and impaired on the 8-32 sec bisection task. However, when discriminating long intervals, CD patients also showed a precision deficit, which points to impaired sustained attention and/or decision processes. Our findings corroborate the view that cerebellar timing processes are not limited to the motor system but are also used in perceptual computations.

Adult↗
PubMed1996

Preserved cognitive processes in cerebellar degeneration.

Aspects of cognitive processing in patients with cerebellar degeneration (CD) were studied in order to examine the validity of recent findings that CD patients demonstrate deficits in visuospatial cognition and verbal-associative learning. Two groups of patients with CD were compared to stratified matched control groups on tests examining selective visual attention, visual spatial attention, mental rotation of geometric designs, and memory for the temporal order of words they were previously exposed to. CD patients performed similarly to their matched controls across all tasks. These results indicate that the reported cognitive deficits of CD patients are quite selective and need further specification in order to more fully describe their relationship to cerebellar dysfunction.

Atrophy↗
PubMed1994

Induction of a recall deficit by rapid-rate transcranial magnetic stimulation.

We used rapid-rate, repetitive transcranial magnetic stimulation (rTMS) for the noninvasive study of verbal recall. Five right-handed normal subjects were studied. Recall followed immediately after presentation of a 12-word list. Focal rTMS was applied with a figure eight coil in trains of 500 ms duration to F7, F8, T5, T6, P3, P4, or O1, O2 at latencies of 0, 250, 500, or 1000 ms during word list presentation. Recall was consistently significantly diminished only after left mid-temporal and bilateral dorsofrontal rTMS at both 0 and 250 ms latencies. We conclude that rTMS may be useful as a non-invasive tool for the study of verbal memory processes.

Adolescent↗
PubMed1994

Induction of visual extinction by rapid-rate transcranial magnetic stimulation of parietal lobe.

We used repetitive, rapid-rate transcranial magnetic stimulation (rTMS) for the noninvasive study of visual attention in humans. Six right-handed volunteers completed eight blocks of 20 single- and 10 double-visual-stimulus trials. The visual stimulus was a single asterisk on the right or left side of a computer screen or two asterisks presented simultaneously. The subject had to respond to the stimulus by pressing the right or left response key or both keys simultaneously. During six of the blocks, we applied focal rTMS in trains of five pulses at 25 Hz and 115% of the subject's motor threshold intensity to scalp positions O1, O2, P3, P4, T5, or T6. Occipital rTMS led to a large number of misses of the contralateral asterisk regardless of whether a single or double stimulus was presented. Parietal rTMS did not induce misses of single stimuli but led to a large number of misses of the contralateral asterisk in the double-stimulus condition. The effects of temporal rTMS were inconsistent. We conclude that rTMS to the occipital lobe causes a sensory detection block, whereas rTMS to the parietal lobe can induce selective extinction of contralateral visual stimuli during a simultaneous double stimulus.

Adolescent↗
PubMed1994

No specific effects of caloric stimulation on the visual-imagery processes of normal subjects.

Recent research indicates that neglect can be temporarily, but only partially, ameliorated by activating the contralateral hemisphere via caloric stimulation and other techniques. In this study, we evaluated whether caloric stimulation could be used to manipulate visual-imagery processes in normal subjects. 11 normal subjects participated in a quantitative visual-imagery task while undergoing caloric stimulation. Neither side of report nor ear of caloric stimulation affected performance. Possible reasons for this negative result are reviewed.

Adult↗