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Biomedical subjects

J Grafman

Publications and source records attributed to J Grafman.

At least 37 records · Page 2Linked to original sources
PubMed2001

PET evaluation of bilingual language compensation following early childhood brain damage.

We report a positron emission tomography (PET) study in a 37-year-old, right handed, bilingual (English and American Sign Language) male with left frontal lobe damage, without evidence of language or general intellectual dysfunction. A brain MRI scan demonstrated an atrophic lesion of the left dorsolateral prefrontal, orbital, and opercular cortices extending from the frontal pole to precentral gyrus and including parts of anterior cingulate cortex, due to an probable infantile encephalitis. H(2) (15)O PET scans found evidence of increased right hemisphere activity compared to normal controls during spontaneous generation of narrative in both English and ASL. Neuropsychological data were within normal limits with the exception of visuospatial function. The results suggest the possibility that plasticity, unmasking of neural pathways, and or other adaptations of language function in the right hemisphere may have occurred, and are discussed with regard to the crowding hypothesis.

Adult↗
PubMed2001

Action planning in a virtual context after prefrontal cortex damage.

Patients with frontal lobe lesions are known to encounter severe problems in the organisation of their behaviour in everyday life. Script generation tasks assess the subject's conceptual ability to formulate and evaluate a coherent and structured plan of action. In the present study, we investigated to what extent neuropsychological deficits observed at the conceptual level of action knowledge lead to impairments in action execution. We examined seven patients with prefrontal cortex damage and sixteen normal subjects. Subjects were first asked to verbally formulate a plan of action and then to use this knowledge for 'executing' the actions in a virtual 3-dimensional interactive apartment presented on a computer screen. The results indicated that the presence of the realistic context improved patients' performance. However, specific impairments were observed in patients in the execution condition, namely actions slips, omissions, failure in initiating actions and purposeless displacements. Moreover, an analysis of planning time showed that, differently of the patients group, normal subjects spent more time during plan execution as compared to plan generation. These results suggest that after a frontal lobe lesion a defective formulation of a routine plan might affect the execution of the corresponding course of actions.

Adult↗
PubMed2001

Conjoint and extended neural networks for the computation of speech codes: the neural basis of selective impairment in reading words and pseudowords.

The computation of speech codes (i.e. phonology) is an important aspect of word reading. Understanding the neural systems and mech- anisms underlying phonological processes provides a foundation for the investigation of language in the brain. We used high-resolution three-dimensional positron emission tomography (PET) to investigate neural systems essential for phonological processes. The burden of neural activities on the computation of speech codes was maximized by three rhyming tasks (rhyming words, pseudowords and words printed in mixed letter cases). Brain activation patterns associated with these tasks were compared with those of two baseline tasks involving visual feature detection. Results suggest strong left lateralized epicenters of neural activity in rhyming irrespective of gender. Word rhyming activated the same brain regions engaged in pseudoword rhyming, suggesting conjoint neural networks for phonological processing of words and pseudowords. However, pseudoword rhyming induced the largest change in cerebral blood flow and activated more voxels in the left posterior prefrontal regions and the left inferior occipital-temporal junction. In addition, pseudoword rhyming activated the left supramarginal gyrus, which was not apparent in word rhyming. These results suggest that rhyming pseudowords requires active participation of extended neural systems and networks not observed for rhyming words. The implications of the results on theories and models of visual word reading and on selective reading dysfunctions after brain lesions are discussed.

Adult↗
PubMed2001

Divided attention deficits in patients with chronic fatigue syndrome.

Chronic fatigue syndrome (CFS) patients and controls were compared on a variety of mood state, personality, and neuropsychological measures, including memory, word finding, and attentional tasks that required participants to focus, sustain, or divide their attention, or to perform a combination of these functions. CFS patients demonstrated a selective deficit on 3 measures of divided attention. Their performance on the other neuropsychological tests of intelligence, fluency, and memory was no different than that of normal controls despite their reports of generally diminished cognitive capacity. There was an inverse relation between CFS patient fatigue severity and performance on 1 of the divided attention measures. Given these findings, it is probable that CFS patients will report more cognitive difficulties in real-life situations that cause them to divide their effort or rapidly reallocate cognitive resources between 2 response channels (vision and audition).

Adult↗
PubMed2001

Frontotemporal dementia: report of a familial case.

The authors describe a 49-year-old woman (R.K.) who presented with one year of progressive frontal lobe dysfunction, including signs of expressive aphasia. Signs of parkinsonism were absent until late in the clinical course. Neuropsychologic testing and neuroimaging studies are described. The patient died at age 55, after 7 years of symptoms. Family history was remarkable for a mother who died at the age of 45, after experiencing 7 years of progressive aphasia. R.K.'s brain showed asymmetric frontotemporal atrophy, which was more severe on the left side. Histopathologic analysis was remarkable for numerous tau-positive neurons with some classic-appearing Pick bodies and many ballooned neurons. Tau-positive glial cells were also present. The authors suggest that the abnormal tau aggregates are related to the symptoms experienced by affected members of this family.

Aphasia↗
PubMed2001

The Word Completion Memory Test (WCMT): a new test to detect malingered memory deficits.

In recent years, much research has focused on developing tests to detect malingering. A drawback of existing tests is their poor ability to detect malingerers possessing more "sophisticated" knowledge of neuropsychological deficits. The current study presents preliminary validation data on a new measure, the Word Completion Memory Test (WCMT), which is the first malingering test to utilize a sophisticated coaching methodology in its development. The WCMT was administered to control participants, memory-impaired patients, and coached simulators. The coached simulators were provided with specific information about and examples of memory deficits commonly experienced following closed head injury (CHI; e.g., anterograde vs. retrograde amnesia). They also read a detailed scenario describing the lifestyle and motivations likely experienced by CHI litigants, and then practiced their roles by taking a quiz about their deficits. Results showed that 93% of coached simulators and 100% of control and memory-impaired participants were correctly classified by the WCMT.

Journal Article↗
PubMed2000

Dissociating the role of the medial and lateral anterior prefrontal cortex in human planning.

The anterior prefrontal cortex is known to subserve higher cognitive functions such as task management and planning. Less is known, however, about the functional specialization of this cortical region in humans. Using functional MRI, we report a double dissociation: the medial anterior prefrontal cortex, in association with the ventral striatum, was engaged preferentially when subjects executed tasks in sequences that were expected, whereas the polar prefrontal cortex, in association with the dorsolateral striatum, was involved preferentially when subjects performed tasks in sequences that were contingent on unpredictable events. These results parallel the functional segregation previously described between the medial and lateral premotor cortex underlying planned and contingent motor control and extend this division to the anterior prefrontal cortex, when task management and planning are required. Thus, our findings support the assumption that common frontal organizational principles underlie motor and higher executive functions in humans.

Humans↗
PubMed2000

Language disturbances in corticobasal degeneration.

To characterize the language deficits in corticobasal degeneration (CBD) and their relation to neuroradiologic findings, the authors administered a standardized battery of neurobehavioral tests and performed MRI studies on 15 patients with CBD. Eight patients (53%) had classifiable aphasias, including anomic, Broca's and transcortical motor aphasias. The aphasias were associated primarily with left frontal and parietal cortical damage and subcortical white matter and corpus callosum abnormalities. Our findings demonstrate that language disturbances in CBD are more frequent than previously considered.

Aged↗
PubMed2000

Toward neuroanatomical models of analogy: a positron emission tomography study of analogical mapping.

Several brain regions associated with analogical mapping were identified using (15)O-positron emission tomography with 12 normal, high intelligence adults. Each trial presented during scanning consisted of a source picture of colored geometric shapes, a brief delay, and a target picture of colored geometric shapes. Analogous pictures did not share similar geometric shapes but did share the same system of abstract visuospatial relations. Participants judged whether each source-target pairing was analogous (analogy condition) or identical (literal condition). The results of the analogy-literal comparison showed activation in the dorsomedial frontal cortex and in the left hemisphere; the inferior, middle, and medial frontal cortices; the parietal cortex; and the superior occipital cortex. Based on these results as well as evidence from relevant cognitive neuroscience studies of reasoning and of executive working memory, we hypothesize that analogical mapping is mediated by the left prefrontal and inferior parietal cortices.

Adult↗
PubMed2000

How patients with Parkinson's disease retrieve and manage cognitive event knowledge.

Several studies have pointed out that basal ganglia are involved in adaptive control of action at both motor and cognitive level. This study aimed to investigate how basal ganglia retrieve and manage script event knowledge required in planning behavior. Script event knowledge was investigated in patients with Parkinson's Disease using three kinds of activity that differed in familiarity. Unlike patients with prefrontal lesions, patients with Parkinson's Disease were able to order events in a typical sequence and obeyed the boundaries and hierarchies between events. In contrast, patients with Parkinson's Disease were impaired in evaluating how important each script event was within the context of goal-oriented planning activity. Our findings indicate that the prefrontal cortex and the basal ganglia are differentially involved in planning. The role of the basal ganglia might consist in providing a feedback about the goodness of each action while building up meaningful sequences of events during learning.

Adult↗
PubMed2000

A case of prosopagnosia following moderate closed head injury with left hemisphere focal lesion.

This study describes a left handed woman with prosopagnosia following traumatic brain injury with a focal lesion confined to the left-posterior hemisphere. Few cases of prosopagnosia following unilateral left hemisphere lesions have previously been reported in the literature. Corrected visual acuity was 20/70 (binocular), color vision was intact on screening, and shape detection was borderline. Impairments in higher order visual perception were evident to varying degrees on nonfacial tasks. Matching of unfamiliar faces was very slow but accurate. A marked impairment in the ability to recognize familiar faces and learn new face-name associations was evident on experimental tasks relative to the performance of healthy control subjects. In contrast, identification of characteristics of faces (gender, age) and identification and matching of facial expressions were relatively preserved. We discuss the cognitive processing stages that appear to be disrupted using Bruce and Young's (1986) model of facial recognition and perception as a framework.

Adult↗
PubMed2000

The calculating brain: an fMRI study.

To explore brain areas involved in basic numerical computation, functional magnetic imaging (fMRI) scanning was performed on college students during performance of three tasks; simple arithmetic, numerical magnitude judgment, and a perceptual-motor control task. For the arithmetic relative to the other tasks, results for all eight subjects revealed bilateral activation in Brodmann's area 44, in dorsolateral prefrontal cortex (areas 9 and 10), in inferior and superior parietal areas, and in lingual and fusiform gyri. Activation was stronger on the left for all subjects, but only at Brodmann's area 44 and the parietal cortices. No activation was observed in the arithmetic task in several other areas previously implicated for arithmetic, including the angular and supramarginal gyri and the basal ganglia. In fact, angular and supramarginal gyri were significantly deactivated by the verification task relative to both the magnitude judgment and control tasks for every subject. Areas activated by the magnitude task relative to the control were more variable, but in five subjects included bilateral inferior parietal cortex. These results confirm some existing hypotheses regarding the neural basis of numerical processes, invite revision of others, and suggest productive lines for future investigation.

Adult↗
PubMed2000

Planning impairments in frontal lobe dementia and frontal lobe lesion patients.

Patients with frontal lobe brain damage are reportedly impaired on tasks that require plan development and execution. In this study, we examined the performance of 15 patients diagnosed with frontal lobe dementia and 14 patients with focal frontal lobe lesions on the Tower of London planning task. Patients with frontal lobe dementia committed a significantly higher number of rule violations, made more moves, and demonstrated longer solution time latencies compared to their matched controls. Patients with frontal lobe lesions demonstrated significantly delayed solution times and also made more moves compared to their matched controls. Frontal lobe lesion patient performance suggests an impairment in execution-related processes, while frontal lobe dementia patients appear to be impaired in both plan development and execution. Despite these findings, the identification of a specific cognitive impairment that induces these planning problems remains elusive.

Adult↗
PubMed2000

Differential amygdala responses to winning and losing: a functional magnetic resonance imaging study in humans.

The amygdala has been shown to respond to many distinct types of affective stimuli, including reward and punishment feedback in animals. In humans, winning and losing situations can be considered as reward and punishment experiences, respectively. In this study, we used functional magnetic resonance imaging (fMRI) to measure regional brain activity when human subjects were given feedback on their performance during a simple response time task in a fictitious competitive tournament. Lexical stimuli were used to convey positive 'win' or negative 'lose' feedback. The frequency of positive and negative trials was parametrically varied by the experimenters independently from the subjects' actual performance and unbeknownst to them. The results showed that the parametric increase of winning was associated with left amygdala activation whereas the parametric increase of losing was associated with right amygdala activation. These findings provide functional evidence that the human amygdala differentially responds to changes in magnitude of positive or negative reinforcement conveyed by lexical stimuli.

Adult↗
PubMed2000

Neural correlates of imaginal aggressive behavior assessed by positron emission tomography in healthy subjects.

OBJECTIVE: Neurodegenerative or traumatic lesions of the frontal lobes often lead to abnormally aggressive behavior. The authors hypothesized that the imaginal evoking of scenarios involving aggressive behavior would be associated with a modulation of the functional activity in the human frontal cortex. METHOD: Regional cerebral blood flow (rCBF) determinations by positron emission tomography and psychophysiological measures of emotional responsivity were obtained in a group of 15 young healthy volunteers with good visual imagery abilities and no history of abnormal behavior while they imagined the same scenario with four variations involving emotionally neutral behavior and aggressive behavior. RESULTS: Compared to the imagined neutral scenario, the imagined scenarios involving aggressive behavior were associated with significant emotional reactivity and rCBF reductions in the ventromedial prefrontal cortex, suggesting that a functional deactivation of this cortical area occurs when individuals respond to the eliciting of imagined aggressive behavior. CONCLUSIONS: These results in healthy subjects further expand previous findings from animal and human studies by providing an in vivo functional demonstration of the involvement of the orbitofrontal cortex in the expression of aggressive behavior. They are also consistent with the hypothesis that a functional alteration of this cortical region may be present in individuals with pathological aggressive behavior.

Adult↗
PubMed2000

Cognitive effects of 1- and 20-hertz repetitive transcranial magnetic stimulation in depression: preliminary report.

OBJECTIVE: To determine the cognitive effects of daily repetitive transcranial magnetic stimulation (rTMS) administered under the conditions of a treatment trial for major depression. BACKGROUND: Although daily left dorsal prefrontal rTMS has improved mood in some patients with treatment-refractory depression, potential cognitive side effects of extended daily treatment have not been systematically studied. METHOD: In a randomized double-blind treatment study, 10 subjects (mean age, 42 +/- 15 years) with an episode of major depression received either 2 weeks of low-frequency (1 Hz) or high-frequency (20 Hz) rTMS (800 pulses, 20 trains over 20 minutes, 80% of motor threshold, 5 days per week) to the left dorsolateral prefrontal cortex and then were crossed over to the other treatment condition. Patients received cognitive testing at baseline and after the first and second weeks of low- or high-frequency rTMS, which was examined by repeated-measures ANOVA. RESULTS: Of 16 cognitive measures tested after 1 or 2 weeks of rTMS compared with baseline status, none showed deterioration, and the only significant main treatment effect indicated improvement on a list-recall test from pre- to post-rTMS after 1 week (p <0.05). CONCLUSIONS: These preliminary data suggest no gross deleterious cognitive effects of 2 weeks of 1- or 20-Hz rTMS at 80% of motor threshold over the left prefrontal cortex. Further cognitive studies of the effects of rTMS at other parameters used in clinical trials for mood disorders remain to be undertaken.

Adult↗