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Biomedical subjects

Kenneth M Heilman

Publications and source records attributed to Kenneth M Heilman.

66 records · Page 4Linked to original sources
PubMed2002

Manual approach during hand gesture imitation.

BACKGROUND: Patients' tendency to draw near or into the target when copying figures, a phenomenon termed closing-in, has been previously described. That the closing-in could occur when copying hand gestures has also been noted. OBJECTIVES: To study a patient with corticobasal degeneration to quantify his manual approach behavior and to test a possible working memory hypothesis. METHODS: The subject of this study is a patient with severe ideomotor apraxia from probable corticobasal degeneration. Fluorine 18-labeled deoxyglucose-positron emission tomographic findings revealed a hypometabolism involving the bilateral parietotemporal and the right frontal lobes. When asked to copy an examiner's (J.C.K.) hand gesture, the patient approached, touched, or grasped the examiner's hand, a behavior mostly consistent with the closing-in behavior previously proposed. To investigate the frequency and severity of closing-in, the patient was asked to copy 20 meaningless hand gestures (10 simple and 10 complex). Copying the 20 hand gestures was performed with either the left or the right hand while the patient was seated opposite the examiner (across condition) or on the same side of the examiner (lateral condition). RESULTS: Of the 80 trials, closing-in occurred in 43 (53.8%) (35 with approaching, 6 with touching, and 2 with grasping). The closing-in was more frequent and more severe when gesturing with the left than the right hand, but it did not differ between the lateral and across conditions and between simple and complex gestures. CONCLUSIONS: Corticobasal degeneration might be associated with aberrant manual approach behavior. Although our results do not support the working memory hypothesis, frontal dysfunction might have led to a loss of voluntary control of ontologically primitive propensity to move the forelimb in the direction to which one attends.

Aged↗
PubMed2002

Far bias on the radial line bisection task: measuring perceptual-attentional and motor-intentional bias in normal subjects.

Normal subjects usually err distally when bisecting radial lines below eye level in midsagittal space (far bias). To learn if a radial line bisection bias may be characterized as primarily perceptual-attentional or primarily motor-intentional, we had subjects bisect lines while watching their hand and the line under two video monitoring conditions. In the DIRECT condition, proximal (near) and distal (far) on the video monitor corresponded with the workspace where subjects bisected lines. In the INDIRECT condition, we reversed proximal and distal as they appeared on the monitor. Thus, in the indirect condition, distal hand movement appeared proximal, and vice versa. In the DIRECT condition, subjects erred toward far space (mean 2.075 mm). In the INDIRECT condition, however, subjects erred proximally (mean 1.59 mm, near bias). Distal-proximal reversal of errors over the group of subjects is consistent with a primarily perceptual-attentional bias. In lower body space, normal visual-perceptual-attentional systems may be more biased toward far space than are kinesthetic-motor systems.

Adolescent↗
PubMed2002

Effect of background motion on line bisection performance in normal subjects.

Previous studies have demonstrated that optokinetic stimulation (OKS) influences line bisection (LB) performance in normal subjects and patients with hemispatial neglect. Since subjects were required to attend to stationary targets on a moving background, prior experimental designs might have induced an illusion of target motion or induced motion (IM) in a direction opposite the background. The current study tested whether the IM affects LB performance in normal subjects and how the speed of targets also influences LB. Thirty-two right-handed normal volunteers (aged 28.0 +/- 5.3 years) were asked to bisect stationary lines with a background of horizontal OKS. These stimuli were generated by computer displayed on a large screen via a beam projector. The OKS was varied according to direction (leftward or rightward) and speed (9.4 degrees/sec or 56.1 degrees/sec), producing 4 different experimental conditions. Mean bisection errors in all conditions were compared with a control condition with no background OKS. For each condition, subjects rated the degree of IM on a 5 point scale. With fast rate OKS, subjects reported minimal IM and LB errors were in the same direction as background motion, a finding that replicates previous studies. Conversely, the slow OKS rate caused subjects to report IM and resulted in deviation of the bisection mark in a direction opposite the background OKS. While this discrepancy between the slow and fast OKS conditions might be related to motion illusion, we did not find a direct correlation between the degree of IM and bisection errors and thus reasons for these results remain unexplained.

Adult↗
PubMed2002

Reading direction and spatial neglect.

Many American and European investigators have reported that hemispatial neglect is more frequent and more severe after right than left hemisphere lesions. This hemispheric asymmetry may be due to biological asymmetries, learned behavior, or both. Readers of European languages, unlike readers of Semitic languages, scan from left to right. Learned rightward scanning may increase the unilateral neglect associated with right hemisphere lesions and reduce the severity of neglect associated with left hemisphere lesions. To learn if hemispheric asymmetries of neglect are influenced by learned scanning behavior, we used line bisection and cancellation tasks to study patients with unilateral stroke who read only a Semitic or European language before the age of fifteen. We found that independent of reading direction, unilateral neglect was more commonly associated with right than left hemisphere lesions. After right hemisphere damage right to left readers bisected lines closer to center than left to right readers, but on the cancellation test readers of European languages did not perform differently than readers of Semitic languages. These findings suggest that whereas learned scan direction may influence the severity of neglect when measured by line bisection, these learned directional scans cannot fully account for the observed hemisphere asymmetries of neglect. They also suggest that the line bisection test is more influenced by the direction of scanning than is the cancellation test.

Aged↗
PubMed2002

Spatial bias: effects of early reading direction on Korean subjects.

Spatial bias may occur in subjects performing a number of cognitive and visual-motor tasks. These include coordinate visuospatial computations (e.g. bisecting a line) and categorical representations of syntactic information (e.g. drawing a picture depicting the action of a sentence). Readers of European languages scan from left-to-right and this learned visual scanning may contribute to leftward spatial bias. In 30 subjects who first learned to read in a top-to-bottom, right-to-left direction (right-left vertical readers, RL), we tested spatial-syntactic bias by reading sentences to subjects, who drew pictures depicting the actions. We noted whether the subject of the sentence was located leftward or rightward of the object. We assessed visual-spatial bias by measuring subjects' accuracy at bisecting lines, and by measuring how closely their drawings on the house-tree-person test were centered on the page. On the spatial-syntactic task, the RL were not right- or left-biased (P=0.581). Korean controls (left-right horizontal readers, LR) also showed no significant spatial-syntactic bias. RL only tended to bisect lines leftward, but displaced house-tree-person drawings left of page center (P<0.001). LR erred leftward on line bisection, and had a smaller magnitude leftward bias on drawing tasks. We conclude that a leftward spatial-syntactic bias may not be innate and does not appear to be influenced by learned reading direction. In contrast, the leftward visual-spatial bias may occur in subjects whose cultural and reading background is neither western nor left-to-right.

Adult↗
PubMed2002

Category-specific naming deficits for objects and actions: semantic attribute and grammatical role hypotheses.

Research on category-specific naming deficits and on noun and verb naming has raised questions about how organization of knowledge in the brain impacts word retrieval. The semantic attribute hypothesis posits that lexical access is mediated by brain systems that process the most definitive attributes of specific concepts. For example, it has been suggested that the most definitive attribute of living things is their visual form, whereas the most definitive attribute of non-living things is their function. The competing grammatical role hypothesis posits that access to a word depends on the grammatical role it plays in a sentence. Since nouns and verbs have different roles, it is assumed that the brain uses different systems to process them. These two hypotheses were tested in experimental subjects who had undergone left anterior temporal lobectomy (LATL) or right anterior temporal lobectomy (RATL) by assessing confrontation naming of living things, tools/implements, non-human actions, and human actions. The names of living things and implements are nouns and the names of actions are verbs. Within each grammatical class, items were characterized either predominantly by visual attributes (living things and non-human actions) or by attributes related to human activity (implements and human actions). Our results support the semantic attribute hypothesis. Patients with LATL were worse at naming tools/implements and human actions than RATL patients. Dysfunction in or removal of the left anterior temporal lobe disrupts fronto-temporal connections from the uncinate fasciculus. These connections may mediate activation of action-related information (i.e. movement plan and/or motor use) that facilitates the retrieval of names for tools/implements and human actions.

Adult↗
PubMed2002

Postural knowledge of transitive pantomimes and intransitive gestures.

Patients with apraxia are more impaired when performing transitive pantomimes than intransitive gestures. This dissociation might be related to the differences in movement complexity. Alternatively, the programs for intransitive gestures might be better defined, more widely distributed, or easier to activate than are those for transitive pantomimes. The purpose of this study was to test the complexity versus representational hypotheses. Twenty right-handed normal subjects both performed and discriminated correct from incorrect transitive pantomimes and intransitive gestures. The discrimination was performed by having subjects point at illustrations of hand postures. The subjects performed better when discriminating postures than when performing gestures or pantomimes. On both the production and discrimination tests, subjects performed better with intransitive gestures than transitive pantomimes. Although the finding that even normal subjects had more difficulty performing transitive pantomimes than intransitive gestures might appear to support the complexity hypothesis, that subjects also had more difficulty discriminating transitive than intransitive postures supports the representational activation hypothesis.

Adult↗
PubMed2002

Effects of monocular viewing and eye dominance on spatial attention.

Observations in primates and patients with unilateral spatial neglect have suggested that patching of the eye ipsilateral to the injury and contralateral to the neglected space can sometimes improve attention to the neglected space. Investigators have generally attributed the effects of monocular eye patching to activation of subcortical centers that interact with cortical attentional systems. Eye patching is thought to produce preferential activation of attentional systems contralateral to the viewing eye. In this study we examined the effect of monocular eye patching on attentional biases in normal subjects. When normal subjects bisect vertical (radial) lines using both eyes, they demonstrate a far attentional bias, misbisecting lines away from their body. In a monocular viewing experiment, we found that the majority of subjects, who were right eye dominant, had relatively nearer bisections and a diminished far bias when they used their right eye (left eye covered) compared with when they used their left eye (right eye covered). The smaller group of subjects who were left eye dominant had relatively nearer bisections and a diminished far bias when they used their left eye compared with when they used their right eye. In the hemispatial placement experiment, we directly manipulated hemispheric engagement by having subjects perform the same task in right and left hemispace. We found that right eye dominant subjects had a diminished far bias in right hemispace relative to left hemispace. Left eye dominant subjects showed the opposite pattern and had a diminished far bias in left hemispace. For both groups, spatial presentation affected performance more for the non-dominant eye. The results suggest that monocular viewing is associated with preferential activation of attentional systems in the contralateral hemisphere, and that the right hemisphere (at least in right eye dominant subjects) is biased towards far space. Finally, the results suggest that the poorly understood phenomenon of eye dominance may be related to hemispheric specialization for visual attention.

Adult↗
PubMed2002

Emotional experience and perception in the absence of facial feedback.

The facial feedback hypothesis suggests that facial expressions are either necessary or sufficient to produce emotional experience. Researchers have noted that the ideal test of the necessity aspect of this hypothesis would be an evaluation of emotional experience in a patient suffering from a bilateral facial paralysis; however, this condition is rare and no such report has been documented. We examined the role of facial expressions in the determination of emotion by studying a patient (F.P.) suffering from a bilateral facial paralysis. Despite her inability to convey emotions through facial expressions, F.P. reported normal emotional experience. When F.P. viewed emotionally evocative slides her reactions were not dampened relative to the normative sample. F.P. retained her ability to detect, discriminate, and image emotional expressions. These findings are not consistent with theories stating that feedback from an active face is necessary to experience emotion, or to process emotional facial expressions.

Adult↗
PubMed2002

Cerebral blood flow changes in depressed patients after treatment with repetitive transcranial magnetic stimulation: evidence of individual variability.

OBJECTIVE: To elucidate the neural mechanisms of depression. BACKGROUND: Despite extensive study, the neurophysiology of the brain's state(s) corresponding to depression remains uncertain. METHODS: HMPAO single photon emission computed tomographic (SPECT) scans were obtained from eight adults diagnosed with major depression resistant to medication (average age 51 years; 4 men) before and immediately after 10 days of 20 Hz repetitive transcranial magnetic stimulation (rTMS) (2000 stimuli/daily 30' treatment). To maximize the likelihood that SPECT scans reflected the state of depression, rather than uncontrolled responses of patients to poorly constrained environments, HMPAO was administered while subjects performed a simple task involving continuous monitoring of the direction of a large arrow on a computer screen and continuously tapping with the left or right index finger according to the direction of the arrow. Mean baseline Beck Depression Inventory (BDI) score was 27.4 (SD = 8.3) and mean posttreatment BDI score was 17.5 (SD = 8.5). RESULTS: Treatment responders (defined by reduction in BDI score of > or = 30%) had significantly less pretreatment blood flow in the left amygdala compared with nonresponders. Responders demonstrated two patterns of change in regional blood flow with treatment: a reduction in orbitofrontal blood flow and/or a reduction in anterior cingulate blood flow. Nonresponders did not demonstrate any regional changes in blood flow with treatment. CONCLUSIONS: These results suggest that there may be either more than one state of depression, or that depression may be associated with more than one pattern of psychologic activity, which in turn defines the depressive experience for individual patients.

Adult↗
PubMedDate not supplied

Effects of two treatments for aprosodia secondary to acquired brain injury.

Expressive aprosodia is an impaired ability to change one's voice to express common emotions such as joy, anger, and sadness. Individuals with aprosodia speak in a flat, unemotional voice that often results in miscommunicated emotional messages. This study investigated two conceptually based treatments for expressive aprosodia: imitative treatment and cognitive-linguistic treatment. Five women and nine men with expressive aprosodia following right-hemisphere brain damage received the treatments in two phases 1 month apart in random order. Treatment was received 3 to 4 days a week for a total of 20 sessions each phase. As the outcome measure, sentences that elicited treated (happy, angry, sad, neutral) and untreated (fear) emotional tones of voice were administered during baseline, prior to treatment sessions, following treatment termination, and at 1- and 3-month follow-ups. Effect sizes indicated that treatment effects were modest to substantial and that 12 participants responded to at least one treatment. Four responsive participants who were available for follow-up showed benefit at 1 and 3 months posttreatment. Most visual and statistical analyses were congruent.

Adult↗