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Biomedical subjects

Kenneth M Heilman

Publications and source records attributed to Kenneth M Heilman.

At least 37 records · Page 2Linked to original sources
PubMed2006

Radial character-line bisection.

BACKGROUND AND OBJECTIVES: With conventional solid radially oriented-line bisections (SLB), normal subjects tend to bisect distal to the true midpoint (distal bias). This bias is thought to reflect a distal attentional bias in the radial plane. Whereas the right hemisphere, which mediates distributed-global attention, has a distal bias, the left hemisphere, which mediates focal attention, has a proximal bias. When performing conventional radial-line bisections, participants might primarily use right hemisphere-mediated global-distributed attention and thus develop a distal bias. The character-line bisection (CLB) task consists of strings of target and nontarget characters (letters or symbols) that are linearly aligned, and subjects are required to bisect a character that is closest to the midline. Thus, when performing the CLB subjects must use focal attention and detect symbols and both these activities are mediated by their left hemisphere. This left hemisphere activation might either reduce or reverse the distal bias observed on the SLB. The purpose of this study is to test this hypothesis. METHODS: Fifteen normal subjects performed CLB (letter-line and symbol-line) and SLB tasks. RESULTS: Overall, the subjects revealed a distal bias in both tasks, but the attempted bisections in the CLB tasks were more proximal than those in the SLB tasks. CONCLUSIONS: These result are consistent with the hypothesis that the CLB task, which requires both focal attention and the detection of symbols, activates the left hemisphere that has a greater proximal bias than the right hemisphere, thus reducing the distal bias observed with the SLB task.

Adult↗
PubMed2006

The influence of vagus nerve stimulation on memory.

BACKGROUND: Vagus nerve stimulation (VNS) has been shown to improve memory. OBJECTIVE: The purpose of this study was to learn at which stage of memory formation this influence occurs. METHODS: Ten subjects who had been implanted with vagus nerve stimulators for the treatment of intractable seizures performed tasks that assessed learning and retention (Hopkins Verbal Learning Test) during actual and sham VNS. RESULTS: We found that VNS had no effect on learning but enhanced consolidation, which led to improved retention. CONCLUSIONS: The means by which VNS improves retention is probably related to the increased activity in the nucleus of the tractus solitarius and the locus coeruleus-central adrenergic system that activates the amygdala and increases long-term potentiation in the hippocampus.

Adult↗
PubMed2006

Finger agnosia in Alzheimer disease.

BACKGROUND AND OBJECTIVE: The purpose of this study was to learn if a deficit of finger naming (finger agnosia or anomia) is a sensitive test for Alzheimer disease (AD) and the best means of testing for finger agnosia. METHODS: The subjects were 38 patients with AD and 10 matched normal controls. All subjects were asked to name the thumb, index, and pinky fingers. RESULTS: No control subject had trouble naming any of these fingers, but 37% of the AD subjects did. When AD patients had difficulty with finger naming, they always had trouble naming the index finger. CONCLUSIONS: In the absence of stroke, the inability to name the index finger seems as an indicator of dementia. Although brief, this test is not extremely sensitive test for AD.

Agnosia↗
PubMed2006

Cognitive rehabilitation interventions for neglect and related disorders: moving from bench to bedside in stroke patients.

The spatial neglect syndrome, defined by asymmetric attention and action not attributed to primary motor or sensory dysfunction and accompanied by functional disability, is a major cause of post-stroke morbidity. In this review, we consider the challenges and obstacles facing scientific researches wishing to evaluate the mechanisms and effectiveness of rehabilitation interventions. Spatial neglect is a heterogeneous disorder, for which consensus research definitions are not currently available, and it is unclear which of the deficits associated with the syndrome causes subsequent disability. We review current opinion about methods of assessment, suggest a rational approach to selecting therapies which requires further study, and make systems-level and theoretical recommendations for building theory. We lastly review some creative questions for consideration in future research.

Animals↗
PubMed2006

Distribution of attention in normal people as a function of spatial location: right-left, up-down.

The spatial allocation of attention influences estimates of stimulus magnitude, including line length and the line bisection task has been used to assess the asymmetrical allocation of spatial attention. The purpose of this study is to learn if normal subjects' allocation of attention changes as a function of the trunk-head centered spatial position of the line stimuli. Normal subjects were asked to bisect lines placed in five different head-trunk centered special positions (central, right up-distal, left up-distal, right down-proximal, left down-proximal). When compared with the central condition, deviations in the right or left lateral conditions were only significant in the down-proximal conditions, such that the bisection bias significantly shifted direction to the left of the objective midline in left hemispace and to the right of the objective midline in right hemispace, suggesting that stimuli presented in lateral hemispace primarily activate the contralateral hemisphere's attentional systems. The finding that the lines presented in down-proximal lateral hemispace induce a greater spatial bias than lines in up-distal lateral space suggests that the portion of the brain's dorsal visual system, which processes stimuli in down-proximal space, influences the horizontal (right-left) spatial allocation of attention more than does the brain's ventral visual system.

Adult↗
PubMed2005

Unawareness of cognitive deficit (cognitive anosognosia) in probable AD and control subjects.

OBJECTIVE: To develop a quantitative method of assessing cognitive anosognosia in six cognitive and two noncognitive domains. METHODS: Control (n = 32) and probable Alzheimer disease (pAD) (n = 14) subjects self-estimated memory, attention, generative behavior, naming, visuospatial skill, limb praxis, mood, and uncorrected vision, both before and after these abilities were assessed. Based on this estimate and their performance the authors calculated an anosognosia ratio (AR) by dividing the difference between estimated and actual performance by an estimated and actual performance sum. With perfect awareness, AR = 0. Overestimating abilities would yield a positive AR (< or =1); underestimation would yield a negative AR (> or =-1). RESULTS: Relative to controls, pAD subjects demonstrated anosognosia. Pre-testing (off-line), pAD subjects overestimated their visuospatial skill; post-testing (on-line), pAD subjects overestimated their memory. Control subjects also made self-rating errors, underestimating their attention pre-testing and overestimating limb praxis and vision post-testing. CONCLUSIONS: This anosognosia assessment method may allow more detailed examination of distorted self-awareness. These results suggest that screening for anosognosia in probable Alzheimer disease (pAD) should include self-estimates of visuospatial function, and that, in pAD, it may be useful to assess anosognosia for amnesia both before and after memory testing.

Aged↗
PubMed2005

The effects of focal and global attentional systems on spatial biases.

The background page on which a stimulus is presented can influence the allocation of attention to that stimulus. The purpose of this study was to learn if there are hemispheric asymmetries in how background distraction affects attentional processing. Asymmetries were investigated by having right eye dominant subjects perform line bisections and manipulating the side of background distraction (right versus left), the eye of regard (right versus left), and the type of attention allocated (focal versus global). Overall subjects bisected lines to the left of center (pseudoneglect) and when viewing with the right eye (versus left) deviated more to the left. Subjects had more background distraction when viewing symbol than solid lines. Although overall, bias did not differ with the side of background distraction or the line being on one side or the other, when subjects viewed symbol, but not solid lines, this leftward bias was increased when the line was displaced to the right, thereby increasing the size of the left sided background. These findings suggest that when engaging the left hemisphere by using focused attention and placing the line on the right side, there is more distraction than when the right hemisphere is engaged.

Adult↗
PubMed2005

Affective facial and lexical expression in aprosodic versus aphasic stroke patients.

Past research has shown that lesions in the left cerebral hemisphere often result in aphasia, while lesions in the right hemisphere frequently impair the production of emotional prosody and facial expression. At least 3 processing deficits might account for these affective symptoms: (1) failure to understand the conditions that evoke emotional response; (2) inability to experience emotions; (3) disruption in the capacity to encode non-verbal signals. To better understand these disorders and their underlying mechanisms, we investigated spontaneous affective communication in right hemisphere damaged (RHD) stroke patients with aprosody and left hemisphere damaged (LHD) stroke patients with aphasia. Nine aprosodic RHD patients and 14 aphasic LHD patients participated in a videotaped interview within a larger treatment protocol. Two naïve raters viewed segments of videotape and rated facial expressivity. Verbal affect production was tabulated using specialized software. Results indicated that RHD patients smiled and laughed significantly less than LHD patients. In contrast, RHD patients produced a greater percentage of emotion words relative to total words than did LHD patients. These findings suggest that impairments in emotional prosodic production and facial expressivity associated with RHD are not induced by affective-conceptual deficits or an inability to experience emotions. Rather, they likely represent channel-specific nonverbal encoding abnormalities.

Affect↗
PubMed2005

The influence of illusory motion on line bisection performance in normal subjects.

The present study examines whether illusory movement (IM) of a horizontal line, induced by a moving background (MB), influences line-bisection performance in normal subjects. The first experiment attempted to identify the speeds of MB that induce IM. We found that when speed is increased from 1.53 degrees to 13.3 degrees/sec, IM increases, but that with further speed increases, IM decreases. Leftward MB induces rightward IM, and vice versa. In the second experiment, we had subjects bisect lines at MB speeds that had been shown to induce IM in the first experiment. We found that leftward MB induced a rightward bias, and vice versa. We also found that there was a relationship between the magnitude of IM and the degree of bias. In the third experiment, by making the target line larger than the MB, we made the conditions where IM was presumably absent. Unlike the results of bisection performed with IM, subjects showed a bias in the direction of the MB. Overall, these experiments demonstrated that the perception of motion induces subjects to attend in the direction of movement.

Adult↗
PubMed2005

Left hemispatial visual neglect associated with a combined right occipital and splenial lesion: another disconnection syndrome.

Damage to the left occipital lobe and the splenium or forceps major is often associated with pure alexia, thought to be an occipital-temporoparietal disconnection syndrome. A patient with the parallel lesion, a combined right occipital and splenial lesion, showed severe left-sided visual spatial neglect, but no significant neglect in other sensory modalities. This visual neglect might be related to a disconnection between the visual information processed by the left occipital lobe and the right posterior temporal-inferior parietal areas that mediate attention in the left hemispace.

Aged↗
PubMed2004

Spatial cognition.

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Brain Mapping↗
PubMed2004

Intentional neglect.

The neglect syndrome has been defined as a failure to report, respond or orient to novel or meaningful stimuli presented to the side opposite of a brain lesion when this failure can not be attributed to elemental sensory (e.g., hemianopia) or motor (hemiplegia) deficits. This failure to report, respond or orient can be induced by attentional, representation-memory, and intentional deficits. The four major intentional deficits that can be associated with neglect include, akinesia (body part, directional and hemispatial), impersistence, defective response inhibition and motor perseveration. In this article we define and discuss each of these intentional disorders, describe how to test patients for these disorders and the neuropsychological and pathophysiological mechanisms that might be associated with these disorders.

Animals↗
PubMed2004

Eye patching biases spatial attention after thalamic hemorrhage in a patient without spatial neglect: a case report.

Monocular patching has been advocated as a treatment for spatial neglect. Eye patching, however, is also reported to increase spatial bias. Thus, patching brain injury patients for ocular conditions may also impair their attention. To learn if an eye patch may induce asymmetric attention in a patient without spatial neglect, we tested a woman with diplopia after a left thalamic-intraventricular hemorrhage. She had no spatial neglect on bedside attention tasks. Using a laser pointer, she bisected a blank space at near (279 mm) and far (914 mm) distances under 3 conditions: unpatched and wearing a right or left eye patch. Unpatched, she showed no bias. She erred further leftward with right patching at both distances. Right eye patching appeared to induce neglect of right space when the patient performed this task. With left patching, leftward error tended to increase in near space only. Clinicians prescribing eye patches to patients with brain injury even for purely ocular indications, should evaluate them for spatial neglect once the patch is in place.

Adult↗
PubMed2004

Affective aprosodia from a medial frontal stroke.

BACKGROUND AND OBJECTIVES: Whereas injury to the left hemisphere induces aphasia, injury to the right hemisphere's perisylvian region induces an impairment of emotional speech prosody (affective aprosodia). Left-sided medial frontal lesions are associated with reduced verbal fluency with relatively intact comprehension and repetition (transcortical motor aphasia), but persistent affective prosodic defects associated with right medial frontal lesions have not been described. METHODS: We assessed the prosody of a man who sustained a right medial frontal cerebral infarction seven years prior. RESULTS: While propositional speech expression was normal including syntactic prosody, the patient was impaired at expressing emotions using prosody. His comprehension and repetition of prosody were also impaired but less so than expression. CONCLUSIONS: Right medial frontal lesions can induce an affective aprosodia that primarily impairs expression.

Aged↗
PubMed2004

Length perception and production of normal subjects in proximal versus distal peripersonal space.

We investigated whether the perception or production of a given line length in normal subjects varies according to where in peripersonal space the line is perceived or produced. We also investigated the influence of the direction of movement used to make the line. In Experiment 1, blindfolded normal subjects were asked to estimate distances while the examiner moved the subject's hand in proximal (medial) or distal (lateral) space, moving centripetally or centrifugally. The subjects showed a spatial effect, perceiving the same length as shorter in proximal space than distal space. This result could be related to either a proximal spatial attentional bias or an anisometric representation of spatial distances. In Experiment 2, we attempted to dissociate these hypotheses by studying blindfolded normal subjects, who were requested to produce horizontal lines of a given length (100 or 200 mm) in proximal versus distal peripersonal space using centripetal or centrifugal movements. Centrifugal movements in proximal space were the longest; centrifugal movements in distal space were the shortest: in between were the proximal centripetal and distal centripetal movements which did not differ from each other. These results suggest that in peripersonal space the perception of length in normal subjects is most consistent with anisometric mental representation where the size of mental representations of length units decreases as a function of the distance from the subject's midsagittal plane. Length production, however, may depend on an interaction of the anisometric mental representation and the premotor/intentional factors.

Adult↗
PubMed2004

What's in a "smile?" Intra-operative observations of contralateral smiles induced by deep brain stimulation.

OBJECTIVE: To describe smiling and euphoria induced by deep brain stimulation (DBS). BACKGROUND AND SIGNIFICANCE: The brain systems inducing emotional experiences and displays are not entirely known, but the ventral striatum including the nucleus accumbens has been posited to play a critical role in mediating emotions with positive valence. DBS has been successfully employed for the treatment of movement disorders, and most recently obsessive compulsive disorder (OCD). The purpose of this report is to describe the emotional changes associated with stimulation of the ventral striatum. METHODS: A single patient with intractable OCD had electrode arrays placed in the right and left anterior limbs of the internal capsule and region of the nucleus accumbens. Changes in facial movement during stimulation were quantified by video recording. Ten video segments, time locked to the onset of stimulation, were digitized and changes in pixel intensity that occurred over both sides of the lower face, on a frame by frame basis, following stimulation onset were computed. These summed changes in pixel intensity represented the dependent variable of "entropy" and directly corresponded to changes in light reflectance that occur during facial movement. RESULTS: During stimulation on both the right and left side, the patient consistently developed a half smile on the side of the face contralateral to the stimulating electrode, and also became euphoric. The effect ceased when DBS was discontinued. CONCLUSIONS: DBS in the region of the nucleus accumbens produced smile and euphoria suggesting that alterations in the ventral striatum may result in emotional experience and displays. We hypothesize the existence of a limbic-motor network responsible for such changes. This observation suggests that DBS may be useful as a therapy for mood disorders.

Adult↗