Biomedical subjects

K M Heilman

Publications and source records attributed to K M Heilman.

At least 109 records · Page 6Linked to original sources

PubMed1997

Cognitive neuropsychological analysis and neuroanatomic correlates in a case of acute anomia.

We describe an analysis of lexical processing performed in a patient with the acute onset of an isolated anomia. Based on a model of lexical processing, we evaluated hypotheses as to the source of the naming deficit. We observed impairments in oral and written picture naming and oral naming to definition with relatively intact semantic processing across input modalities, suggesting that output from the semantic system was impaired. In contrast to previous reports, we propose that this pattern represents an impairment that arises late in semantic processing prior to accessing mode-specific verbal and graphemic output lexicons. These deficits were associated with a lesion in the posterior portion of the middle temporal gyrus or area 37, an area of supramodal association cortex that is uniquely suited as a substrate for the multimodal deficit in naming.

Aged↗

PubMed1997

The influence of center of mass effect on the distribution of spatial attention in the vertical and horizontal dimensions.

Normal subjects attend toward the middle of grouped items (center of mass effect). In order to learn if mass effect could influence performance on line bisection tasks and if the spatial orientation of the line (vertical vs. horizontal) could influence center of mass effect, we administered bisection tasks to 16 normal subjects using either lines composed of two unequal segments (one thick and one thin) or unsegmented lines. When the longer segment was to the right, left, up, or down, subjects erred by deviating their bisection toward the longer segment (center of mass effect). Our results demonstrate that the center of mass effect can be seen with bisection tasks and is greater in the vertical than in the horizontal dimension.

Adult↗

PubMed1997

The significance of body part as tool errors in limb apraxia.

When pantomiming to command, individuals with left hemisphere brain damage (LBD) often produce errors in which they use a body part as if it were the tool (BPT). Some clinicians question the significance of this type of error because subjects without brain damage at times also make BPT responses. We analyzed BPT errors in LBD and normal subjects who were reinstructed to modify the inappropriate BPT responses when they occurred. We also analyzed errors in normal subjects who were never reinstructed if a BPT occurred. Whereas LBD subjects who were reinstructed produced significantly more BPT errors than normals who were also reinstructed, LBD subjects were not different from normals who were not reinstructed. When reinstructed, normal control subjects correctly modified virtually all BPT errors, whereas LBD subjects did not modify BPT errors. These findings underscore the need for reinstruction when a BPT error occurs to determine whether it represents a true BPT error, a sign of limb apraxia.

Aged↗

PubMed1997

Adynamic aphasia: a transcortical motor aphasia with defective semantic strategy formation.

Adynamic aphasia is a form of transcortical motor aphasia characterized by sparse but otherwise normal spontaneous speech that may improve when concepts are introduced by external stimuli. Akinesia, impaired concept formation, inertia of concept generation, a defective semantic network, damage or impaired access to the verbal output lexicon, and defective semantic strategy formation have been proposed to account for this disorder. We studied a patient with adynamic aphasia and frontal lobe systems dysfunction due to bilateral striatocapsular infarctions. The patient was not akinetic but did demonstrate inertia of concept generation that could be overcome with prompting. However, prompting did not improve the number of concepts generated. He demonstrated a generally intact verbal lexicon and semantic network and normal lexical priming. However, his ability to sort closely related items into different classes without prior cuing regarding the nature of the classes was defective. Although his verbal memory was normal, he appeared to use a serial rather than a semantic strategy to recall items. Finally, despite normal lexical priming, he was impaired on a letter fluency task. These results most clearly demonstrate a defect in semantic strategy formation but indicate an additional and possibly related deficit in concept formation and a partial deficit in lexical strategy formation. All of these deficits appear to reflect impairment in the hierarchical organization of knowledge specific to the task at hand. This appears to be a key component of executive functions supported by frontal lobe systems.

Aphasia↗

PubMed1997

Tapping, talking and the thalamus: possible influence of the intralaminar nuclei on basal ganglia function.

A patient with a discrete lesion of the left, intralaminar thalamic, nuclei exhibited a paradoxical finding with regard to finger-tapping. Normal subjects typically reduce their tapping rate when performing simultaneous verbal activity. Tapping was impaired in our patient's contralesional hand on baseline trials; however, performing the controlled oral word association (COWA) task, while finger-tapping, normalized her deficit. Subsequent experiments showed that motoric tasks rather than cognitive aspects of the COWA task were critical in potentiating finger-tapping performance. A SPECT study performed at rest revealed focal perfusion asymmetries in motor and premotor cortices. Because the caudal intralaminar nuclei project heavily to the striatum, striatal deafferentiation may account for these asymmetries. These observations provide some insight into the influences of the caudal intralaminar thalamic nuclei on basal ganglia function and the basal ganglia's influence on motor gating.

Adult↗

PubMed1997

Contributions of the left and right cerebral hemispheres to line bisection.

Thirty-one right-hemisphere lesioned (RHL) patients, 11 left-hemisphere lesioned patients (LHL) and 10 normal controls (NC) bisected lines in three spatial location and four directional cuing conditions. The error direction and error size were analyzed as separate and combined variables. Seventy-seven percent of RHL patients and 45% of LHL patients made abnormally large errors in line bisection. Right-hemisphere lesioned patients were more sensitive to spatial location and directional cuing than NC subjects. In contrast, LHL patients were less sensitive to either condition than NCs. The error direction and error size emerged as dissociable components of line bisection. Right-hemisphere lesioned patients and NC subjects bisected lines consistently to one side of the true center. Left-hemisphere lesioned patients bisected lines equally often on both sides of the true center. Both RHL and LHL patients made larger absolute bisection errors than NC subjects, but the RHL patient's errors were larger than those of the LHL patients. We propose that the greater sensitivity of RHL patients to spatial location and directional cues and the directional consistency of their bisection errors represent contributions of the intact left cerebral hemisphere to line bisection. In contrast, the LHL patient's unrestrained ability to orient to both ends of the line reflects a contribution of the intact right cerebral hemisphere to line bisection. The failure of both groups to accurately bisect lines reflects a common visuospatial processing deficit that is more pronounced following RHLs than LHLs.

Aged↗

PubMed1997

Visual-imitative dissociation apraxia.

Liepmann posited that, in right handers, the left parietal lobe contains movement formulas or representations. Therefore, performance failures may be induced by degraded representations, a failure of these representations to influence motor systems or a failure of stimuli to fully access these representations. Imitation may help the performance of subjects with degraded representations. However, patients who have impaired visual access to movement representations may perform more poorly with imitation than to verbal command. Trajectories of repetitive 'slicing' gestures made by a previously reported subject (Raymer et al.) with an infarction in the left visual association cortex (left occipital and inferior temporal lobe) that spared the parietal lobe were contrasted with those of three apraxic subjects with lesions that included the left parietal lobe and four non-brain-damaged control subjects. All subjects were asked to produce the gesture to verbal command and to imitation. Movements of the left hand, wrist, elbow and shoulder were digitized from neighboring views, reconstructed in three dimensions, and analysed graphically and numerically. The apraxic subjects with left parietal damage were unable to maintain the proper linearity and spatiotemporal attributes of their wrist motions and showed interjoint coordination deficits. Their deficits were most pronounced to verbal command, with their movements improving though remaining poorly performed when they imitated. The subject with the left occipital and inferior temporal lesion that spared parietal cortex, however, showed an opposite pattern. This subject exhibited close to normal performance when producing the movement to verbal command, but significant deficits when imitating.

Aged↗

PubMed1997

Diagonal neglect on cancellation.

Patients with right hemisphere injury frequently neglect to cancel targets primarily in the left part of the page nearest the body. Since this region is diagonally opposite the area from where such patients usually begin cancelling, near left ('diagonal') neglect may be consequent to stimulus order effects ('fatigue'). We evaluated the persistence of near left neglect in nine stroke patients when they had to cancel either the near or the far half of the page before proceeding to the other half. Our results showed that near left neglect on the page was largely unaffected by cancellation order. Furthermore, a near left gradient of omissions was established within both radial (near and far) halves of the page, as well as for the entire page. Our findings suggest that diagonal cancellation neglect is unrelated to fatigue and reflects a consistent, two-dimensional disorder of spatial attention. Such neglect may be related to the extent of the visible stimulus array, as well as to the array's location in egocentric space.

Attention↗

PubMed1997

Diencephalic temporal order amnesia.

OBJECTIVE: Amnesia for temporal relations may occur without amnesia for content memories. The aim was to determine whether a patient with mild memory loss due to a thalamic lesion had amnesia for temporal relations, and whether the amnesia was specific for particular material. METHODS: A male patient had an isolated right dorsomedial thalamic infarct and resolving amnesia. He was tested on tasks relating to content (what) and temporal (when) memories for both verbal and non-verbal material, three and seven months after his infarct. RESULTS: Three months after his infarct, the man had amnesia for temporal, but not content memories using non-verbal stimuli, and normal performance using verbal stimuli. Seven months after his infarct, he had a normal performance using verbal and non-verbal stimuli. CONCLUSIONS: Patients with thalamic lesions may have a material specific amnesia for temporal relations in the absence of amnesia for content.

Adult↗

PubMed1997

Gaze related enhancement of hemispheric blood flow in a stroke patient.

OBJECTIVE: A patient with a right posterior cerebral artery territory infarction and a left superior quadrantanopia exhibited improvement on various visual tasks including Goldmann perimetry during extreme right gaze. The phenomenon was investigated by functional imaging of cerebral blood flow. METHODS: [(99m)Tc]HMPAO SPECT was carried out while the patient gazed to the right and to the left at an 8 Hz flash stimulus. RESULTS: When compared with left gaze, photic stimulation during right gaze was associated with an up to 39.8% increase in regional cerebral blood flow in the damaged right hemisphere, including Brodmann's areas 3-1-2, 7, 21, 22, 39, and 40. CONCLUSIONS: These gaze related alterations in function and synaptic activity suggest the engagement of a novel arousal-like mechanism that may account in part for comparable findings in patients with neglect and other disorders, and may have relevance to rehabilitation.

Brain↗

PubMed1997

Anosognosia: examining the disconnection hypothesis.

OBJECTIVE: To test the hypothesis that anosognosia for hemiparesis results from intrahemispheric disconnection. METHODS: Using right carotid barbiturate injection as a model for anosognosia for hemiparesis, systematic attempts were made to modify deficit awareness by providing the left hemisphere with explicit information regarding left upper extremity function. RESULTS: Experimental interventions failed to modify deficit awareness in 19 of 32 patients. In those patients who discovered their weakness, attempted movement of the weak limb seems more important than explicit observation of the extremity by the left hemisphere. CONCLUSIONS: The results fail to support Geschwind's disconnection hypothesis for anosognosia for hemiparesis.

Adult↗

PubMed1997

The neurobiology of emotional experience.

The author discusses a neurological model of a modular network that mediates emotional experience. According to this theory, emotional experience has three components: valence (positive and negative), arousal, and motor activation (approach, avoid, neither). In this model, the cortex is critical in regulating activities of the limbic system, basal ganglia, and reticular system. The frontal lobes are important for valence: the left mediates positive emotions, the right negative emotions. The right hemisphere, especially the parietal lobe, is important in activating arousal systems, and the left hemisphere modulates inhibition of these systems. The right hemisphere is also critical in motor activation. The frontal lobes, especially the orbitofrontal portions, mediate avoidance behaviors, and the parietal lobes mediate approach behaviors. The cortical areas discussed have rich interconnections and are also closely connected with the limbic system, basal ganglia, and reticular systems. Emotional experience may depend on the patterns of neural activation in this modular network.

Animals↗

PubMed1997

Spatial bias: attentional and intentional influence in normal subjects.

Normal subjects often demonstrate a spatial bias on line bisection (LB) and cancellation (CA) tasks. We wanted to learn if horizontal spatial bias found in normal subjects may be dissociable into sensory-attentional (ATT) and motor-intentional (INT) subgroups similar to those described in brain-injured patients with spatial neglect. We studied the influence of ATT and INT factors on the spatial bias observed in normal subjects using a new technique that uncouples the direction of action from the direction of attention. This technique also allowed us to test both LB and CA tasks on the same individuals. Our results show that ATT bias significantly influenced performance on an LB task, whereas performance on a CA task was influenced by biases in both the ATT and INT systems. In addition, the overall bias on these two tasks reflects an interaction between the biases induced by the ATT and INT systems that may be in the same or different directions.

Adult↗

PubMed1997

Conceptual apraxia from lateralized lesions.

Models of praxis have posited two major components, production and conceptual. Conceptual praxis disorders may occur in two domains: associative knowledge (tool-action associations such as hammer pound; tool-object associations such as hammer nail) and mechanical knowledge such as knowing the advantage that tools afford. Patients with Alzheimer's disease not only have conceptual apraxia (CA) but can dissociate CA from language deficits and from praxis production deficits (ideomotor apraxia). These findings suggests that knowledge about tools (action semantics) is independent of verbal semantics as well as movement representations. To learn if conceptual praxis knowledge is stored in one hemisphere (right or left) and if associative and mechanical conceptual praxis knowledge can be dissociated, we studied 29 right-handed subjects with unilateral strokes. Ten had left-hemisphere damage with no ideomotor apraxia. Eleven had left-hemisphere damage with ideomotor apraxia. There were eight right-hemisphere-damaged controls and 10 normal controls. These subjects were given tests for conceptual apraxia. There was a significant difference between groups, the left-hemisphere group with ideomotor apraxia being most impaired on both the associative and mechanical CA tests. There was a trend for associative and mechanical knowledge to be dissociated. Although conceptual praxis representations are stored in the left hemisphere, analysis of lesion sites did not reveal where in the left hemisphere they may be stored.

Aged↗

PubMed1997

Selective deficit of praxis imagery in ideomotor apraxia.

We studied imagery for learned, skilled movements (praxis imagery) in a patient with severe ideomotor apraxia and intact language abilities. This patient, who made predominantly spatial and movement errors when performing transitive movements demonstrating the use of tools (transitive gestures), was also impaired in her ability to answer imagery questions about joint movement or the spatial position of the hands during action. However, visual object imagery was spared. The finding of parallel praxis production and praxis imagery deficits in this patient suggests that the same representations used for gesture production are also activated during imagery of motor acts. Our findings also suggest that certain aspects of motor imagery may be dissociable from general object imagery.

Apraxias↗

PubMed1997

Search patterns using the line bisection test for neglect.

BACKGROUND/OBJECTIVE: Neglect has been attributed to sensory-attentional, motor-intentional, and representational disorders. Although patients with neglect may have defective visual exploration, the nature of this exploration deficit has not been entirely elucidated. The purpose of this study is to learn how, compared with control subjects, a patient with neglect performs visual exploration. METHODS: The line bisection test is commonly used to detect and evaluate the performance of patients with unilateral or hemispatial spatial neglect. We tested an experimental subject with left premotor-intentional neglect using an infrared eye monitoring instrument. Thirteen right-handed healthy volunteers served as control subjects. From different starting ocular positions, we assessed the direction of eye movements when the subjects initially oriented to the line, scanned the line, and then attempted to look at the center of the line. RESULTS: Independent of starting ocular position, normal subjects most often initially orient to the left end of the line, scan rightward, then look leftward to the center. However, the eye movements in our experimental subject with neglect were directed to the right end of the line without any scanning or leftward eye movement back to the center of the line. CONCLUSION: Our subject with neglect had defective line exploration that may be attributed to a directional ocular motor intentional deficit.

Adult↗

PubMed1997

Anosognosia and confabulation during the Wada test.

Feinberg et al. proposed that right-hemisphere-damaged stroke patients with anosognosia for hemiplegia (AHP) confabulate seeing stimuli on the left side but those without AHP admit to having inadequate visual information. This study examines the relationship between AHP and confabulation using selective anesthesia of the cerebral hemispheres. Seventeen patients with intractable epilepsy were tested during intracarotid methohexital infusion. For half of the trials, subjects were stimulated on their paretic hand with a material (sandpaper, metal, or cloth), and for the remaining trials they were not stimulated. The subjects were trained to use a pointing response to indicate if they been stimulated and the type of material they had felt. Admission of uncertainty was defined as pointing to a question mark. Confabulation was defined as any material response to a no-touch trial. During anesthesia of either hemisphere, subjects with and without AHP confabulated responses. The AHP and non-AHP groups did not differ in admission of uncertainty. Our results support the postulate that confabulation and AHP are independent disorders, and therefore confabulation cannot fully account for AHP.

Adolescent↗

PubMed1997

Atrophy of the hippocampus, parietal cortex, and insula in Alzheimer's disease: a volumetric magnetic resonance imaging study.

The hippocampus, parietal cortex, and insula were measured on volumetric magnetic resonance imaging to determine whether patients with early Alzheimer's disease had significantly more atrophy than healthy controls. To determine whether the atrophy is limited to certain cortical regions, the striate cortex was measured because this area is not usually neuropathologically involved early in Alzheimer's disease. Eight mildly to moderately impaired patients who met National Institute of Neurological Disorders and Stroke-Alzheimer's Disease and Related Disorders Association criteria for probable Alzheimer's disease and eight controls who matched for age, gender, and educational level were studied. Atrophy was quantified in the following regions: hippocampus, parietal cortex, insular cortex, and striate cortex. The authors found significantly more atrophy of the hippocampus (p < 0.0001), parietal cortex (p < 0.025), and insula (p < 0.003) in the Alzheimer's patients. Measures of the striate cortex did not differ between the groups. There were no significant left-right differences in any of the regions measured. Their findings show that mildly to moderately impaired Alzheimer's patients have significantly more atrophy of the hippocampus, parietal cortex, and insula than healthy age-matched controls. Furthermore, this atrophy is probably discrete because the groups did not differ on measures of the striate cortex. Selective atrophy of the parietal and insular cortices has not previously been reported using the authors' methodology on volumetric magnetic resonance imaging. Their data suggest that the insula may be involved early in Alzheimer's disease and that atrophy of the insular cortex may contribute to the cognitive deficits typical of early Alzheimer's disease.

Aged↗