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K M Heilman

Publications and source records attributed to K M Heilman.

At least 145 records · Page 8Linked to original sources
PubMed1995

Ecological implications of limb apraxia: evidence from mealtime behavior.

Humans learn skilled acts in order to effectively interact with their environment. A loss of the ability to perform skilled acts is termed apraxia. Apraxia has been thought to be of theoretical interest, but the ecological implications of apraxia are controversial and have not been fully studied. We examined ten patients with unilateral left hemisphere cerebral infarctions (eight of whom were apraxic) and compared their mealtime eating behavior to a group of neurologically normal, age-matched controls. The stroke patients were less efficient in completing the meal. They made more action errors and were less organized in the sequencing of mealtime activities. Because the patients made more errors while using tools than when performing nontool actions, their deficit could not be accounted for by an elemental motor deficit. A positive relationship was found between mealtime action errors and the severity of apraxia. These findings suggest that limb apraxia may adversely influence activities of daily living.

Activities of Daily Living↗
PubMed1995

Joint coordination deficits in limb apraxia.

Competing models of the basis of limb apraxia were tested through analysis of joint coordination deficits in three apraxic subjects with lesions that included the left parietal lobe. Three-dimensional shoulder, elbow, wrist and hand trajectories were recorded for repetitive 'slicing' gestures made in a series of conditions in which contextual cues were introduced in a graded fashion. The apraxic subjects showed marked deficits in joint coordination across context conditions. Even when actually manipulating a tool and object, the apraxic subjects failed to show proper joint synchronization, failed to apportion their relative joint amplitudes properly, and failed to produce the correct phase relationships among pairs of arm angles. Thus, apraxic subjects not only have deficits in the spatial plan for the movement, but they also have deficits in translating those plans into the details of the angular motions at the joints, even when actually manipulating a tool and object. These data support a model of apraxia in which apraxia can result from either the destruction of visuo-kinaesthetic motor representations of learned movement, stored in posterior association cortex, or from a separation of these representations from premotor or motor areas.

Aged↗
PubMed1995

Neglect of radial and vertical space: importance of the retinotopic reference frame.

Neglect from bilateral brain injury can disrupt responses along space defined by the vertical and radial axes. The spatial reference frames for vertical and radial neglect remain largely undefined, however. The viewer centred system, for example, consists of retinocentric and cephalocentric/corporacentric frames. In the present study, different viewer centred reference frames were dissociated in a patient with combined far radial superior vertical neglect through performance of radial line bisections above and below eye level. To separate reference frames for vertical space, bisections were performed while the patient was lying sideways. Results suggest that this patient's neglect respected a retinotopic viewer centred reference frame.

Adult↗
PubMed1995

Dissociation of anosognosia for hemiplegia and aphasia during left-hemisphere anesthesia.

The stroke literature indicates that the explicit denial of hemiplegia, a form of anosognosia, is associated more commonly with right- than left-hemisphere lesions. Some investigators have suggested that this asymmetry may be an artifact and that the aphasia that often accompanies left-hemisphere dysfunction may mask some instances of anosognosia. Mechanisms suggested for anosognosia have been either "global" or "modular" in nature. Mechanisms posited in global explanations include psychological denial and general mental deterioration; modular explanations include feedback and feedforward theories. Videotapes of 54 patients with medically intractable seizures who had selective barbiturate anesthesia (Wada test) as part of their evaluation for seizure surgery were assessed for anosognosia of hemiplegia and aphasia after hemispheric anesthesia had worn off. The results suggest that, although aphasia may confound the reported rate of anosognosia for hemiplegia following left-hemisphere dysfunction, the frequency of anosognosia for hemiplegia is still higher with right- than left-side dysfunction. Anosognosia for hemiplegia and aphasia were dissociable, providing support for the postulate that awareness of dysfunction is mediated by a modular system.

Adult↗
PubMed1995

Anosognosia for hemiplegia: test of the personal neglect hypothesis.

OBJECTIVE: To test the personal neglect hypothesis of anosognosia for hemiplegia (AHP) using selective anesthesia of the right hemisphere. BACKGROUND: Although AHP most commonly follows right-hemisphere injury, the mechanism responsible for this hemispheric asymmetry has not been entirely elucidated. Because denial of ownership of parts on the contralesional side of one's body (personal neglect) also more commonly follows right-hemisphere damage, personal neglect might account for AHP. DESIGN/METHODS: AHP and personal neglect were assessed in 20 patients during right intracarotid barbiturate infusion. With vision restricted to the central field, patients were randomly presented with either their own hands or those of examiners matched for size, gender, and race. Patients were asked to read numbers placed on the hands to establish that hemianopia did not confound hand recognition. RESULTS: All subjects correctly read the numbers on all trials. Only 4 of 20 subjects misidentified their hands and denied awareness of left hemiplegia. All errors occurred for the left hand, indicating personal neglect. However, the 16 subjects without personal neglect also demonstrated AHP. CONCLUSION: Because AHP and personal neglect are dissociable, personal neglect cannot completely account for AHP.

Adult↗
PubMed1995

Anosognosia during intracarotid barbiturate anesthesia: unawareness or amnesia for weakness.

Previous studies have demonstrated asymmetric hemispheric contributions to deficit awareness during hemisphere inactivation with intracarotid barbiturate infusion (Wada studies). These observations provide insight into the neuropsychological basis of anosognosia for hemiparesis (AHP), arguing against earlier explanations based upon psychological denial, global cognitive disturbance, or emotional indifference. Although prior Wada studies equated AHP after the procedure with AHP during the period of deficit, a selective memory failure could also account for these findings. We, therefore, assessed the occurrence of AHP during and after right-hemisphere inactivation in a group of epilepsy patients undergoing preoperative Wada testing. Because aphasia obscures assessment of deficit awareness during left carotid studies, we compared the frequency of AHP between right- and left-hemisphere inactivation only after recovery. As noted in earlier reports, AHP was present significantly more often after right- than left-hemisphere inactivation. The proportions of subjects with AHP during right-hemisphere anesthesia compared with the proportion of subjects with AHP after the procedure were statistically equivalent, suggesting that the AHP observed after right-hemisphere anesthesia results from true failure of deficit awareness rather than inability to recall the deficit.

Amnesia↗
PubMed1995

Attention and anosognosia: the case of a jargonaphasic patient with unawareness of language deficit.

Some patients with aphasia lack awareness of the language errors they make. We describe a man with undifferentiated jargonaphasia and preserved auditory comprehension who was unaware of his speech production errors when he had to both speak and listen simultaneously. However, when listening to a recording of his speech, he could detect the speech errors he had made. We attribute this patient's unawareness of his speech production errors to a reduced attentional capacity for simultaneous linguistic tasks.

Aged↗
PubMed1995

Frontal lobe neglect in monkeys.

Using a crossed-response task, monkeys with neglect induced by frontal lesions appear to have motor rather than sensory neglect. However, the crossed-response task may not reveal sensory neglect (inattention) if no perceptual discrimination is required. We therefore trained two monkeys in a perceptually complex crossed-response task. Following unilateral frontal (arcuate gyrus) ablation, we found no contralateral perceptual disorders or sensory neglect in either monkey but did find a failure to respond with the contralateral arm (motor neglect) in both monkeys. We also found that the monkeys made more incorrect responses with the arm ipsilateral to the lesion than they did with the contralateral arm. The errors made by the ipsilateral arm could be a compensatory strategy or a disinhibition phenomenon. Because these incorrect responses were not rewarded and became more frequent as motor neglect improved, the incorrect responses of the ipsilateral arm are not a compensatory strategy, but rather a defect we term "disinhibition hyperkinesia" or "allokinesia."

Animals↗
PubMed1995

Impaired perception of facial identity and facial affect in Huntington's disease.

We tested five patients with Huntington's disease on tasks of facial discrimination and facial affect discrimination and matching. Four patients were impaired on a task or tasks of face discrimination, and all patients were impaired on at least one task of facial affect discrimination. We suggest that these findings reflect the role of the basal ganglia or its connections in visual processing.

Adolescent↗
PubMed1995

Apraxia during Wada testing.

Apraxia is the loss of the ability to perform learned skilled movements correctly. In right-handers, apraxia and aphasia are most frequently associated with left-hemisphere lesions. When they are dissociated, however, aphasia is more common in the absence of apraxia than vice versa. There are two hypotheses that can account for this discrepancy: (1) in right-handers, praxis is more likely than language to be mediated by the right hemisphere, or (2) the left-hemisphere network that mediates language is either more widely distributed than the network that mediates praxis or is more likely to be in the middle cerebral artery distribution. We studied apraxia in a group of right-handers undergoing selective hemispheric anesthesia, or Wada testing. All nine subjects had language lateralized to the left hemisphere, and seven of the nine had praxis lateralized to the left hemisphere. Two of the subjects had praxis bilaterally represented. Although our data suggest that speech and praxis functions tend to be lateralized to the left hemisphere in most right-handers, praxis appears to be more distributed between the hemispheres than speech-language functions. Furthermore, an analysis of the types of errors made during praxis testing suggests differential roles of the hemispheres in praxis functions.

Adolescent↗
PubMed1995

Emotional facial imagery, perception, and expression in Parkinson's disease.

Patients with Parkinson's disease (PD) may be impaired at expressing emotional faces and perceiving emotional facial affect. We tested the hypothesis that patients with PD may be impaired at imaging emotional faces. We first compared 12 patients with PD and 30 control subjects on perceptual and imagery tasks. Patients were significantly impaired on a task of emotional facial imagery but not on a control task of object imagery. Patients were also impaired on a task of perceiving emotional faces. Subsequently, we found that PD patients were impaired relative to controls on making emotional faces. Performance on both the perceptual and motor tasks of facial expression significantly correlated with performance on the emotional facial imagery task. We suggest that the basal ganglia, together with the right hemisphere, are part of a neural network subserving emotional facial tasks.

Aged↗
PubMed1994

Posterior neocortical systems subserving awareness and neglect. Neglect associated with superior temporal sulcus but not area 7 lesions.

OBJECTIVE: In humans and monkeys, the intraparietal sulcus separates the superior parietal lobule from the inferior parietal lobule (IPL). Whereas in humans Brodmann's area 7 is above this sulcus, in monkeys it is below and therefore part of the IPL. In humans, the IPL consists of Brodmann's areas 39 and 40. Some investigators contend that the monkey homologue of the human IPL (areas 39 and 40) is the monkey's IPL (area 7). Others contend that it is, at least in part, in the monkey's superior temporal sulcus (STS). In humans, IPL lesions induce neglect. Although IPL lesions in monkeys also have been reported to induce neglect, the STS was involved in these lesions. We sought to learn which of these two areas, when ablated, produces neglect. DESIGN: Study of five adult stump-tailed macaque monkeys by making five isolated STS and six IPL lesions. RESULTS: Inferior parietal lobule lesions were associated with misreaching but not with unilateral neglect. Neglect was observed in association with five of the six STS lesions. CONCLUSIONS: With regard to neglect, STS may be the monkey homologue of the human IPL. Animals with STS lesions and humans with IPL lesions may manifest unilateral neglect because these areas are necessary for normal awareness of external stimuli. This awareness may result from the integration of the areas important in stimulus localization (the "where is it?" system) and stimulus identification (the "what is it?" system), as well as the areas important in defining the biologic importance of stimuli, such as the frontal lobes and limbic areas.

Animals↗
PubMed1994

Apperceptive visual agnosia: a case study.

A man with an infarction of his inferior temporal and occipital association cortex bilaterally, which spared primary visual cortex, had impaired visual recognition of objects, faces, colors, words, and gestures. Analysis of visual function indicated that the recognition failures resulted from an agnosia, rather than elemental visual impairment. Whereas his impairment of gesture recognition appeared to be related to an associative agnosia, his inability to recognize objects was related to an apperceptive agnosia. There may be four subtypes of apperceptive agnosia: one where the internal object representations or structural descriptions are impaired, another where an adequate percept cannot be derived, a third where the internal referent and percept are dissociated, and a fourth where both levels are impaired. Our patient demonstrated a failure to relate individual elements to the whole, a failure to integrate multiple elements, and a reliance on global perception. He had normal object imagery. These results suggest that, whereas internal representations were intact, he was unable to form adequate perceptual representations.

Aged↗
PubMed1994

The psychophysical power law and unilateral spatial neglect.

The relationship between objective measures and subjective experiences of sensory stimuli is described by a power law, psi = K phi beta, in which psi represents the psychological value and phi the physical value. The constant (K) and the exponent (beta) are empirically derived. This relationship is often assumed to correspond to properties of peripheral receptor sensory transduction. Patients with left-sided spatial neglect tend to bisect lines to the right of the objective midline. Line bisection bias was used as the dependent variable in how a patient with neglect and five normal subjects bisected lines of varying lengths. Analyzing these data as a power function accounted for over 99% of the variance in five different experimental conditions. The normal exponent matched the value expected from traditional psychophysical experiments of line length estimation, whereas the patient's exponent was diminished. The patient's data provide evidence for central nervous system participation in computations underlying psychophysical relationships. The notion that attentional and perceptual processes are closely linked was supported by the influence of attentional cuing on the power functions obtained in normal subjects. The descriptive precision of the power function uncovered qualitative variability in how normal subjects allocate attention across different spatial reference frames and demonstrated that this patient had a quantitative defect in directing attention across an allosteric reference frame, but a qualitative defect in directing attention across a viewer/environment reference frame.

Aged↗