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Biomedical subjects

J Grafman

Publications and source records attributed to J Grafman.

At least 91 records · Page 5Linked to original sources
PubMed1996

The role of the dorsolateral prefrontal cortex in implicit procedural learning.

We studied the role of the dorsolateral prefrontal cortex in procedural learning. Normal subjects completed several blocks of a serial reaction time task using only one hand without or with concurrent non-invasive repetitive transcranial magnetic stimulation. To disrupt their function transiently, stimulation was applied at low intensity over the supplementary motor area or over the dorsolateral prefrontal cortex contralateral or ipsilateral to the hand used for the test. Stimulation to the contralateral dorsolateral prefrontal cortex markedly impaired procedural implicit learning, as documented by the lack of significant change in response times during the task. Stimulation over the other areas did not interfere with learning. These results support the notion of a critical role of contralateral dorsolateral prefrontal structures in learning of motor sequences.

Adult↗
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

Sustained attention deficits in patients with right frontal lesions.

Patients with frontal lobe lesions were compared to controls matched for age and education on several tests of sustained attention. One was a simple reaction time task requiring subjects to respond whenever they saw an "X', one was a Continuous Performance Test that required subjects to respond to an "X' but refrain from responding to other letters, and one involved reading a story and responding to a specified target. Patients with right frontal lesions showed longer RTs and missed more targets than control subjects for all three tests. In addition, right frontal patients got worse with time on the CPT. These results suggest a special role for the right frontal lobe in sustaining attention over time.

Arousal↗
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↗
PubMed1996

Selective impairments within episodic memories.

We report the case of a patient (T.R.) who developed a severe and selective amnesia for names and dates associated with events. His amnesia was temporally limited, affecting only the last two to three decades of his life. When recalling an event he was able to evoke both its content and place, while he could not provide any information about people (names or their physical features) and the time (date/period) of its occurrence. His performance on event-memory tests was consistent across the type of material used (personal and public events) or the period of life investigated. These results suggest that knowledge of an episode is specified across multiple representations.

Amnesia↗
PubMed1996

Encoding of sequence and boundaries of scripts following prefrontal lesions.

Script analysis was investigated in patients with lesions in the prefrontal (n = 10) and posterior (n = 8) cortical regions, and in normal subjects (n = 15). The selection and temporal organization of relevant actions belonging to different pre-established sequences were studied in three different situations: (A) script with headers, (B) script with headers and distractors, and (C) scripts without headers. Contrarily to Normals and Posterior patients, Frontal patients committed sequence and boundary errors, and failed to eliminate distractors elements. The analysis of errors suggests two different cognitive modes of representing actions: (1) One using temporal contiguity between actions, that would be mainly under the control of the posterior associative areas; (2) the other, using the goal of the action and its consequences as a binding element between script and context, that would require the intervention of prefrontal cortex.

Adolescent↗
PubMed1996

The effects of frontal lobe damage on everyday problem solving.

The prefrontal cortex plays an especially important role in human social-cognitive behavior. It has been difficult to quantify deficits in this domain in patients with frontal lobe lesions using standardized psychological instruments. We administered the Everyday Problem Solving Inventory (EPSI), which is composed of a range of scenarios depicting everyday social problems and their possible solutions, to a group of patients with frontal lobe lesions who were required to rate each of 4 possible solutions to each problem for their effectiveness. Our sample consisted of 27 normal controls (NCs), 33 patients with focal frontal lobe lesions (FLL), and 3 patients with frontal lobe dementia (FLD). The performance of the FLL patients on the EPSI instrument was also compared with their performance on traditional neuropsychological tests. The results indicated that the FLD patients' EPSI rank ordering of social problem solutions was uncorrelated with the performance of NCs and about half of the FLL patients EPSI rank orderings of solutions also varied substantially from those of the NCs. These same FLL patients also had the lowest scores, compared to FLL patients whose judgements on the EPSI were similar to that of the NCs, on a set of neuropsychological tasks sensitive to frontal lobe dysfunction. There was no obvious relationship between locus of lesion within the frontal lobes and performance on the EPSI. These results suggest that some patients with prefrontal lobe lesions may have impaired social judgement that can be directly revealed through the use of a conventional psychological inventory such as the EPSI.

Adult↗
PubMed1996

Frontal lobe injuries, violence, and aggression: a report of the Vietnam Head Injury Study.

Knowledge stored in the human prefrontal cortex may exert control over more primitive behavioral reactions to environmental provocation. Therefore, following frontal lobe lesions, patients are more likely to use physical intimidation or verbal threats in potential or actual confrontational situations. To test this hypothesis, we examined the relationship between frontal lobe lesions and the presence of aggressive and violent behavior. Fifty-seven normal controls and 279 veterans, matched for age, education, and time in Vietnam, who had suffered penetrating head injuries during their service in Vietnam, were studied. Family observations and self-reports were collected using scales and questionnaires that assessed a range of aggressive and violent attitudes and behavior. Two Aggression/Violence Scale scores, based on observer ratings, were constructed. The results indicated that patients with frontal ventromedial lesions consistently demonstrated Aggression/Violence Scale scores significantly higher than controls and patients with lesions in other brain areas. Higher Aggression/Violence Scale scores were generally associated with verbal confrontations rather than physical assaults, which were less frequently reported. The presence of aggressive and violent behaviors was not associated with the total size of the lesion nor whether the patient had seizures, but was associated with a disruption of family activities. These findings support the hypothesis that ventromedial frontal lobe lesions increase the risk of aggressive and violent behavior.

Adult↗
PubMed1996

Clinical research criteria for the diagnosis of progressive supranuclear palsy (Steele-Richardson-Olszewski syndrome): report of the NINDS-SPSP international workshop.

To improve the specificity and sensitivity of the clinical diagnosis of progressive supranuclear palsy (PSP, Steele-Richardson-Olszewski syndrome), the National Institute of Neurological Disorders and Stroke (NINDS) and the Society for PSP, Inc. (SPSP) sponsored an international workshop to develop an accurate and universally accepted set of criteria for this disorder. The NINDS-SPSP criteria, which were formulated from an extensive review of the literature, comparison with other previously published sets of criteria, and the consensus of experts, were validated on a clinical data set from autopsy-confirmed cases of PSP. The criteria specify three degrees of diagnostic certainty: possible PSP, probable PSP, and definite PSP. Possible PSP requires the presence of a gradually progressive disorder with onset at age 40 or later, either vertical supranuclear gaze palsy or both slowing of vertical saccades and prominent postural instability with falls in the first year of onset, as well as no evidence of other diseases that could explain these features. Probable PSP requires vertical supranuclear gaze palsy, prominent postural instability, and falls in the first year of onset, as well as the other features of possible PSP. Definite PSP requires a history of probable or possible PSP and histopathologic evidence of typical PSP. Criteria that support the diagnosis of PSP, and that exclude diseases often confused with PSP, are presented. The criteria for probable PSP are highly specific, making them suitable for therapeutic, analytic epidemiologic, and biologic studies, but not very sensitive. The criteria for possible PSP are substantially sensitive, making them suitable for descriptive epidemiologic studies, but less specific. An appendix provides guidelines for diagnosing and monitoring clinical disability in PSP.

Humans↗
PubMed1996

Use and safety of a new repetitive transcranial magnetic stimulator.

In order to test a new repetitive transcranial magnetic stimulator, the Dantec MagPro, we administered transcranial magnetic stimulation (TMS) at 1 Hz and 125% of motor threshold for an average of 204 s (until the coil temperature reached 40 degrees C) and 20 Hz stimulation at 100% of motor threshold for 2 s every minute for 10 min, on different days to 10 healthy volunteers. We stimulated 6 scalp positions (primary motor area (M1) and sites 5 cm anterior and posterior on each hemisphere) with an 8-shaped coil. We tested immediate and delayed memory, verbal fluency, prolactin levels and EEG at the beginning of the study and after stimulation on each day. No abnormalities were found. Motor evoked potentials evoked with 1 Hz stimulation diminished progressively in amplitude, and 1 Hz stimulation of M1 caused inhibition lasting at least 1 min in 3 of 4 subjects who were tested with 0.1 Hz stimulation before and after the 1 Hz stimulation period. This did not occur with 20 Hz stimulation. Finger tapping frequency was tested at the beginning of the study and after TMS at each scalp site. Finger tapping rate data from 6 additional subjects who were stimulated in an identical fashion with a different stimulator were also analyzed. There was an increase in tapping rate after TMS which was independent of scalp site. This was most pronounced with 1 Hz stimulation at 125% of threshold and reached statistical significance in the hand contralateral to the stimulation. The results of this study indicate that rTMS with the MagPro stimulator is safe at specific combinations of intensity, frequency and train duration.

Adult↗
PubMed1995

Where the brain appreciates the moral of a story.

To identify the distributed brain regions used for appreciating the grammatical, semantic and thematic aspects of a story, regional cerebral blood flow was measured with positron emission tomography in nine normal volunteers during the reading of Aesop's fables. In four conditions, subjects had to monitor the fables for font changes, grammatical errors, a semantic feature associated with a fable character, and the moral of the fable. Both right and left prefrontal cortices were consistently, but selectively, activated across the grammatical, semantic, and moral conditions. In particular, appreciating the moral of a story required activating a distributed set of brain regions in the right hemisphere which included the temporal and prefrontal cortices. These findings emphasize that story processing engages a widely distributed network of brain regions, a subset of which become preferentially active during the processing of a specific aspect of the text.

Attention↗
PubMed1995

Modeling other minds.

Nine normal volunteers performed a 'theory of mind' task while their regional brain blood flow pattern was recorded using the PET [15O]H2O technique. Control conditions induced subjects to attend to the visual and semantic attributes of known objects. In a third condition, subjects had to infer the function of an unfamiliar object from its form. In the 'theory of mind' condition, subjects had to infer function based on the form of both familiar and unfamiliar objects and in addition, model the knowledge and rationality of another mind about the function of these objects. Performance during the 'theory of mind' condition evoked the activation of a distributed set of neural networks with prominent activation of the left medial frontal lobe (Brodmann area 9) and left temporal lobe (Brodmann areas 21, 39/19, 38). This result suggests that when inferential reasoning depends on constructing a mental model about the beliefs and intentions of others, the participation of the prefrontal cortex is required. When access to such knowledge is affected by central nervous system dysfunction, such as that found in autism, modeling other minds may prove difficult.

Adolescent↗