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Biomedical subjects

J Grafman

Publications and source records attributed to J Grafman.

At least 127 records · Page 7Linked to original sources
PubMed1994

Akinesia in Parkinson's disease. II. Effects of subthreshold repetitive transcranial motor cortex stimulation.

We studied the effects of repetitive transcranial stimulation of the motor cortex (rTMS) on choice reaction time (cRT), movement time (MT), and error rate (ER) in a serial reaction-time task in six medicated patients with Parkinson's disease (PD) and 10 age-matched normal controls. In normal subjects, subthreshold 5-Hz rTMS did not significantly change cRT, slightly shortened MT, but increased ER. In the patients, rTMS significantly shortened cRT and MT without affecting ER. These effects did not impair procedural learning. Performance on a grooved peg-board test was improved by rTMS in the same PD patients, especially when they were off medications, but worsened in the normal subjects. Repetitive, subthreshold motor cortex stimulation can improve performance in patients with PD and could be useful therapeutically.

Aged↗
PubMed1994

Number processing in deaf college students.

Magnitude comparison, calculation verification, and short-term memory span experiments were conducted as a means of investigating number processing in deaf college students. The level of accuracy shown by the deaf students did not differ from that shown by their hearing peers. However, mean response times for the deaf students were greater than those of the hearing students for all experimental tasks. The authors question the importance of development, working memory, and sign communication as factors that may contribute to explanations of the experimental results.

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↗
PubMed1993

Procedural learning in Parkinson's disease and cerebellar degeneration.

We compared procedural learning, translation of procedural knowledge into declarative knowledge, and use of declarative knowledge in age-matched normal volunteers (n = 30), patients with Parkinson's disease (n = 20), and patients with cerebellar degeneration (n = 15) by using a serial reaction time task. Patients with Parkinson's disease achieved procedural knowledge and used declarative knowledge of the task to improve performance, but they required a larger number of repetitions of the task to translate procedural knowledge into declarative knowledge. Patients with cerebellar degeneration did not show performance improvement due to procedural learning, failed to achieve declarative knowledge, and showed limited use of declarative knowledge of the task to improve their performance. Both basal ganglia and cerebellum are involved in procedural learning, but their roles are different. The normal influence of the basal ganglia on the prefrontal cortex may be required for timely access of information to and from the working memory buffer, while the cerebellum may index and order events in the time domain and be therefore essential for any cognitive functions involving sequences.

Adult↗
PubMed1993

Safety of rapid-rate transcranial magnetic stimulation in normal volunteers.

In 9 normal volunteers, we studied the safety of rapid-rate transcranial magnetic stimulation (rTMS) applied to different scalp positions at various frequencies and intensities. Pure tone threshold audiometry showed temporary threshold shifts in 3 subjects. In the subject stimulated at the highest intensity, rTMS induced a focal, secondarily generalized seizure despite the absence of definite risk factors for seizures. Rapid-rate TMS did not result in any important changes in the neurological examination findings, cognitive performance, electroencephalogram, electrocardiogram, and hormone levels (prolactin, adrenocorticotropic hormone, thyroid-stimulating hormone, luteinizing hormone, and follicle-stimulating hormone). In 10 additional subjects, the electromyographic activity in several contralateral muscles showed that trains of rTMS applied to the motor cortex induced a spread of cortical excitability. The spread of excitability depended on the intensity and frequency of the stimuli and probably constituted an early epileptogenic effect of rTMS. Guidelines for preventing the undesirable side effects of rTMS are offered.

Adult↗
PubMed1993

Precision and accuracy of subjective time estimation in different memory disorders.

The aim of this study was to evaluate how different memory disorders affect subjective time durations. For this purpose we studied prospective time estimations in 4 amnesic (A) and in 15 Alzheimer's disease (AD) patients, and compared their performance with that of 5 matched young normal controls (YC) and 15 elderly subjects (EC). For the short-time durations we asked the subject to repeatedly reproduce a standard interval of 1 s. To test how subjects evaluated longer time durations, we choose a verbal estimation procedure. The subjects' task was to read either 5, 10, 20, or 40 digits appearing one at a time, while concurrently keeping the rhythm of 1 key press per second. At the end of each sequence, subjects had to judge the elapsed time from the beginning of the trial. Results showed that amnesics can correctly reproduce 1-s intervals. However, their accuracy of verbal estimates of longer durations was severely impaired. AD patients showed increased variability on repeated reproduction of 1-s intervals and were both inaccurate and imprecise in their verbal estimate of longer durations. Using the framework of the Scalar Timing Model, we conclude that amnesic patients exhibit a deficit in encoding and storing the current time for intervals that exceed their short-term memory range, while AD patients show a pattern of deficit that is explained by a more widespread involvement of both the clock, the memory, and the decisional mechanisms.

Adult↗
PubMed1993

Analysis of neuropsychological functioning in patients with chronic fatigue syndrome.

Memory impairment dominates the cognitive complaints of patients with chronic fatigue syndrome (CFS). Twenty CFS patients were available for studies with a clinical and experimental battery composed of memory and cognitive tests. The results on objective testing indicated that the CFS patients had some mild memory impairment, but only on tasks requiring conceptually driven encoding and retrieval processes. There were no associations between the nature of the precipitating illness, self ratings of fatigue, physical findings, or laboratory determination and objective memory performance or self report of memory functioning. These generally negative results indicate that memory impairment in CFS patients is typically mild and involves memory processes that participate in conceptualising information.

Adult↗
PubMed1993

Residual impairments and work status 15 years after penetrating head injury: report from the Vietnam Head Injury Study.

We investigated the relationship of neurologic, neuropsychological, and social interaction impairments to the work status of a large sample of penetrating head-injured patients wounded some 15 years earlier during combat in Vietnam. Extensive standardized testing of neurologic, neuropsychological, and social functioning was done at follow-up on each head-injured patient (N = 520), as well as on a sample of uninjured controls (N = 85). Fifty-six percent of the head-injured patients were working at follow-up compared with 82% of the uninjured controls. Seven systematically defined impairments proved to be most correlated with work status. These were post-traumatic epilepsy, paresis, visual field loss, verbal memory loss, visual memory loss, psychological problems, and violent behavior. These disabilities had a cumulative and nearly equipotent effect upon the likelihood of work. We suggest that a simple summed score of the number of these seven disabilities can yield a residual "disability score" which may prove to be a practical tool for assessing the likelihood of return to work for patients in this population and perhaps in other brain-injured populations. These findings may also help to focus rehabilitation efforts on those disabilities most likely to affect return to work.

Adult↗
PubMed1993

Memory in patients with cerebellar degeneration.

Eleven patients with relatively selective cerebellar degeneration and 11 normal control subjects underwent a comprehensive neurologic and neuropsychological examination. The neuropsychological tests assessed general intellectual ability, different aspects of memory (effortful, automatic, and implicit memory processes), speed of information processing, and verbal fluency (using both category and letter fluency tasks). The results indicated that cerebellar patients were significantly impaired only on tasks requiring the use of executive functions, such as the initiation/perseveration subtest of the Mattis Dementia Rating Scale or the fluency tests, and on memory measures requiring greater processing effort. They performed normally on automatic and implicit measures of memory. Performance on the effortful memory and executive measures was not associated with neurologic variables or mood state. After controlling for the initiation/perseveration deficit, the effortful memory scores of the cerebellar patients were no longer different from those of controls. The present study suggests that memory in patients with relatively pure cerebellar dysfunction is only partially compromised and that the impairment is secondary to a deficit in executive functions.

Adult↗
PubMed1992

Distinctions and similarities among working memory processes: an event-related potential study.

Working memory has been conceptualized as consisting of a number of components, such as an articulatory loop for rehearsing verbal material, a visuo-spatial sketch pad for maintaining visual images and a central executive that controls which information is made available for conscious processing. We recorded event-related brain potentials (ERPs) from normal human subjects while they maintained either visuo-spatial or phonological material in short-term memory for a 5-s interval. The results indicated that specialized brain systems for short-term storage of phonological and visuo-spatial information could be identified on the basis of marked differences between the topographies and morphologies of the ERP components elicited during these two types of short-term memory. The differences emerged during early encoding stages and continued through later retention stages.

Adult↗
PubMed1992

Saccadic dysmetria in a patient with a right frontoparietal lesion. The importance of corollary discharge for accurate spatial behaviour.

Double-step experiments have demonstrated that retinotopic coding is inadequate to explain the spatial performance of the saccadic system. In such experiments a subject is asked to make two successive saccades to fixate two sequentially flashed targets each of which disappears before the first saccade. Despite the dissonance thus created between the retinal location of the second target and the saccade necessary to acquire it, normal humans and monkeys perform the task perfectly well. Single unit recording in monkeys indicates that neurons in the superior colliculus, frontal eye fields and in parietal cortex generate a spatially accurate signal during the performance of double-step saccades, which is thought to be obtained by combining a retinotopic signal with a signal corollary to the previous saccadic eye movement. We studied saccadic eye movements in a patient with a right fronto-parietal lesion using single- and double-step tasks. Single saccades into the left (contralesional) hemifield had longer latency and were hypometric relative to those into the right (ipsilesional) hemifield. Varying the initial orbital position had no effect on the latency and accuracy of saccades to left and right retinal stimuli. When the patient was asked to do a double-step task with targets flashed first into the right field and then into the left field, she performed well. When she was asked to do the same task with a target flashed first into the left field and then into the right field she made the first saccade correctly but never acquired the second target, even though this required her to make a saccade in the normal direction to a stimulus that appeared in the normal field. Such a deficit therefore cannot be one of retinotopic or spatial coding, nor can it be one of generating a certain direction of saccade. We suggest that the deficit is a failure of corollary discharge, the inability to register the amplitude and direction of a saccade into the contralesional field, and use that information to update the representation of the location of the next saccade target.

Aged↗
PubMed1992

Viscosity and social cohesion in temporal lobe epilepsy.

Clinical case reports suggest that viscosity, the behavioural tendency to talk repetitively and circumstantially about a restricted range of topics, is common in patients with temporal lobe epilepsy (TLE). Such patients are also reported to exhibit heightened levels of social cohesion, the tendency to become interpersonally "clingy". This "sticky" interpersonal style may be particularly common in TLE patients with a left sided temporal lobe seizure focus. To test this hypothesis, self-report and observer rating scales were developed to assess both viscosity and social cohesion. Subjects consisted of patients with right, left, or bilateral temporal lobe seizure foci, absence or primary generalised tonic-clonic seizures, psychiatric controls (panic disorder patients), and normal controls. Elevations on the viscosity scale were observed primarily in TLE patients with left or bilateral seizure foci. Viscosity scores also correlated with seizure duration and left handedness. No group differences were observed on the social cohesion scale. These findings are consistent with the hypothesis that viscosity results from subtle interictal language disturbances, although other pathogenetic mechanisms are discussed.

Anomia↗
PubMed1992

Cognitive planning deficit in patients with cerebellar atrophy.

We compared the performance of 12 patients with cerebellar atrophy (CA) and 12 normal controls matched for age and education on the Tower of Hanoi, a nine-problem task that requires cognitive planning. CA patients performed significantly worse than controls on this task despite no difference in planning and between-move pause times. A reanalysis of the data using just the subgroup of patients with pure cerebellar cortical atrophy (CCA) (N = 9) replicated the above results and also showed that CCA patients had significantly increased planning times compared with controls. Neither age, sex, education level, severity of dementia, word fluency, response time, memory, nor visuomotor procedural learning predicted CA or CCA performance. This deficit in cognitive planning suggests a functional link between the cerebellum, basal ganglia, and the frontal lobe concerning specific cognitive processes. However, the exact role of the cerebellum in cognitive planning remains undetermined.

Adult↗
PubMed1992

Attention and short-term memory in chronic fatigue syndrome patients: an event-related potential analysis.

We recorded event-related brain potentials (ERPs) from 13 patients with chronic fatigue syndrome (CFS) and 13 matched normal controls. To assess attentional and memory deficits in CFS patients, we used a short-term memory task in which events occurred in different spatial locations and the patients made a rapid-response (RT) when a letter in a relevant location matched a letter in the prememorized set (Attention paradigm). Time-on-task effects on the ERP and behavioral measures were assessed over the 2 1/4-hour duration of this task. Both groups also performed a visual Oddball paradigm, with an RT, before and after the Attention paradigm. The patients' RTs were much more variable and, in nine of 13 cases, slower than the mean RT of the controls in both paradigms. The patients' memory performance was not significantly different from that of the controls and there were no group differences in the overall amplitude, latency, or scalp distribution of the N1, P2, N2, or P300 components of the ERP in either paradigm. The ERP and performance data from both paradigms suggest that perceptual, attentional, and short-term memory processes were unaffected in CFS patients and that the differences were limited to response-related processes.

Adult↗
PubMed1991

Automatic memory processes in patients with multiple sclerosis.

To better understand the nature of the memory deficit in patients with multiple sclerosis, we designed a study to compare automatic vs effortful memory processes. Forty-one patients with definite multiple sclerosis and 45 demographically matched normal control subjects were administered two tasks designed to assess both automatic (monitoring frequency and modality) and effortful (free and cued-recall) processing. Results indicated that patients with multiple sclerosis, as expected, were significantly impaired on memory measures requiring effort, but performed normally on automatic measures. Performance on the memory indexes did not correlate with self-reported depression. The implications of these findings for delineating the locus of the memory impairment in multiple sclerosis is discussed.

Adult↗
PubMed1991

Is focal hand dystonia associated with psychopathology?

The purpose of this study was to determine if patients with focal hand dystonia have any significant psychopathology. We studied 20 patients with hand cramps who were participating in a therapeutic trial of botulinum toxin injections. Patients were interviewed and administered the Minnesota Multiphasic Personality Inventory (MMPI). Beck Depression Inventory, Spielberger State-Trait Anxiety Scale, a finger tapping test, and a choice serial reaction time test. Behavioral ratings were also obtained. Group statistics indicated that all personality scale scores and performances on motor tasks were within normal limits. Four out of 20 patients demonstrated mild depression. Trait anxiety scores were higher than state anxiety scores, suggesting that receiving medical treatment had a beneficial effect on mood. The number of depressive symptoms endorsed on the MMPI was correlated with reaction time speed but not finger dexterity. None of the 20 patients reported a remarkable psychiatric history. These results indicate that hand cramps are not associated with serious psychopathology.

Adult↗