Biomedical subjects

K M Heilman

Publications and source records attributed to K M Heilman.

At least 19 recordsLinked to original sources

PubMed1992

Contributions of the left intralaminar and medial thalamic nuclei to memory. Comparisons and report of a case.

A patient complained of memory disturbance after a small left thalamic infarction. Neuropsychological testing revealed her memory to be normal provided that she was allowed to rehearse or use semantic encoding strategies. When these strategies were prevented, her performance was impaired. Mapping of the lesion demonstrated involvement of the caudal intralaminar nuclei (centre médian and parafascicular nuclei), and portions of the medial nuclei (medioventral [reuniens], centromedial, and the most inferior aspect of the mediodorsal nucleus). The majority of mediodorsal nucleus, the mammillary bodies, the mammillothalamic tract, and the anterior thalamic nuclei, were spared. A comparison among our patient's performances and those of alcoholic Korsakoff patients, patient NA, and amnestic patients with circumscribed diencephalic lesions suggests that there are two distinct behavioral and anatomic types of memory impairment associated with diencephalic lesions. The severe amnesia associated with damage to the mammillary bodies, midline nuclei, mammillothalamic tract, and/or dorsomedial nucleus of the thalamus (eg, Korsakoff and NA) is characterized by encoding deficits that never approximate normal performance. The memory disturbance associated with damage to the intralaminar and medial nuclei of the thalamus is milder and is characterized by severe distractibility.

Adult↗

PubMed1992

Search patterns and neglect: a case study.

An irregular and unsystematic search pattern may contribute to unilateral neglect. We examined the sequence of cancellations performed by a patient with unilateral neglect and found that she followed a systematic and stereotypic vertical search pattern. To overcome this vertical search pattern, foils were placed in rows. These foils induced slightly more horizontal movements, but did not alter her neglect. In another attempt to overcome her vertical search and tendency to cancel on the right, she was explicitly instructed to cancel targets alternating to and from the right and left sides of the array. This strategy overcame her vertical search, but, instead of modifying the severity of her neglect, this task only changed its spatial distribution. The altered spatial distribution of neglect is difficult to reconcile with current theories of neglect. We suggest that this patient demonstrates a limited capacity to sequentially be aware of or act upon stimuli.

Aged↗

PubMed1992

A stimulus-response relationship in unilateral neglect: the power function.

We have previously suggested that patients with unilateral neglect may be limited in their ability to sequentially attend or act upon stimuli. To assess the nature of this capacity limitation, we examined the relationship between number of stimuli presented on cancellation arrays and how many targets a patient with neglect cancelled. This relationship was systematic and described by a power function: targets cancelled = K (targets presented)B, in which the constant and exponent were derived empirically. Density of targets and time taken to cancel targets did not account for the relationship. Improvement on subsequent testing was reflected in an increase in the constant. However, the exponent of the power function did not change, suggesting that some critical aspect of her dysfunction remained the same. These data also imply that she had implicit knowledge of quantity of stimuli presented, and that this knowledge systematically influenced her explicit behavior.

Aged↗

PubMed1992

Neglect of near peripersonal space. Evidence for multidirectional attentional systems in humans.

Neglect is most commonly observed and studied in the horizontal spatial dimension. Vertical neglect has been described in a few studies. We now report on a patient with near radial space neglect following bilateral posterior parietal lobe lesions. Our patient also had neglect of inferior vertical and left horizontal space. These spatial deficits appear primarily attentional. Our findings compliment other studies that demonstrate neglect may occur in multiple spatial dimensions and provide evidence for a three-dimensional attentional system in humans. Whereas neglect of inferior vertical space may be associated with bilateral parietal lobe lesions, neglect of superior vertical and far radial space has been associated with bilateral inferior temporo-occipital lesions.

Adult↗

PubMed1992

Conceptual apraxia in Alzheimer's disease.

Theoretical models of praxis have two major components, a praxis conceptual system that includes knowledge of tool use and mechanical knowledge and a praxis production system that includes the information needed to program skilled motor acts. Because patients with Alzheimer's disease may have an impairment of the central conceptual system, we wanted to learn if they had a conceptual apraxia by testing their knowledge of the type of actions associated with tool use, their ability to associate tools with objects that receive their action, their ability to understand the mechanical nature of problems and the mechanical advantages tools may afford. We studied 32 subjects with probable Alzheimer's disease and 32 controls by examining tool-action relationships and tool-object associations. We tested mechanical knowledge by having subjects select alternative tools and solve mechanical puzzles by developing new tools. The Alzheimer's group was subdivided into four groups based on the presence or absence of ideomotor apraxia and a lexical-semantic deficit. Results indicated that each of the four Alzheimer's groups differed from normal controls on at least some measures of conceptual apraxia, suggesting that Alzheimer's patients do have a disturbance of the praxis conceptual system and that impairment of this system is not directly related to language impairment or ideomotor apraxia.

Aged↗

PubMed1992

Amnesia following a discrete basal forebrain lesion.

Destructive lesions of the basal forebrain are associated with memory impairment in both humans and experimental animals. The basal forebrain is thought to contribute to memory function by providing cholinergic innervation to critical memory structures such as the hippocampus and amygdala. In previously reported clinical cases of basal forebrain amnesia, multiple neuroanatomical regions have been damaged, preventing identification of the minimal critical lesion necessary to produce an amnestic syndrome. We describe a patient who developed persistent, global anterograde and retrograde amnesia following resection of a low-grade glioma. Post-surgical magnetic resonance imaging studies revealed a small discrete lesion, centred in the right diagonal band of Broca, that included the preoptic area, the anterior hypothalamus, the lamina terminalis and the paraterminal gyrus. The septal nuclei and the cell bodies of the nucleus basalis of Meynert appeared to have been spared, as were other structures in the medial temporal lobe and diencephalon. Our case provides critical support for the independent contribution of the basal forebrain, in particular the diagonal band nuclei, in memory function. We propose that our patient's amnesia resulted from disconnection of pathways between the diagonal band nuclei and the hippocampal region, depriving the hippocampus of cholinergic innervation.

Amnesia↗

PubMed1992

Anosognosia during Wada testing.

Anosognosia, the verbally explicit denial of hemiplegia, is more often reported after right- than left-hemisphere lesions. However, this asymmetric incidence of anosognosia may be artifactual and related to the aphasia that often accompanies left-hemisphere lesions. Anosognosia has been attributed to psychological denial and the emotional changes associated with hemispheric dysfunction. Eight consecutive patients undergoing intracarotid barbiturate (methohexital) injections as part of their presurgical evaluations for intractable epilepsy were assessed for anosognosia after their hemiplegia and aphasia had cleared. After their left-hemisphere anesthesia, all subjects recalled both their motor and language deficits. However, after right-hemisphere anesthesia, none of the eight patients recalled their hemiplegia. These results suggest that anosognosia is more often associated with right- rather than left-hemisphere dysfunction and that it cannot be attributed to either psychological denial or the emotional changes associated with hemispheric dysfunction.

Agnosia↗

PubMed1991

Frontal verbal amnesia. Phonological amnesia.

Although aphasic patients with frontal lobe damage may demonstrate impaired retention of verbal material, significant anterograde memory disturbances have not, to our knowledge, been reported with a minor Broca's aphasia. We describe a patient with minor Broca's aphasia who exhibited an unusual and profound anterograde memory disturbance, especially for phonologically specified stimuli. We suggest that this disturbance is attributable to an impairment in the volitional, controlled search of stored phonological information.

Amnesia↗

PubMed1991

The relationship between buccofacial and limb apraxia.

There are at least two possible models depicting the relationship between buccofacial and limb apraxia. First, apraxia can be viewed as a unitary motor disorder which transcends the output modalities of both buccofacial and limb output. A high degree of similarity between the two types of apraxia would support this model. Alternatively, the relationship between buccofacial and limb apraxia may not include a unitary mechanism. The presence of quantitative and qualitative differences between buccofacial and limb performance would support this nonunitary model. The results of the present study support the nonunitary model.

Adult↗

PubMed1991

Autobiographical memory: influence of right hemisphere damage on emotionality and specificity.

This study investigated the ability of right hemisphere damaged (RHD) patients to recall autobiographical material in response to emotional versus nonemotional cues. A modified Crovitz paradigm was used in which patients were asked to recall a specific episode from their own life that related to a cue word. These episodes were rated for emotionality and specificity by independent raters. Patients also rated the emotionality of their own episodes. Independent raters judged the reports of the RHD patients as less specific and less emotional than those of matched nonneurologic control subjects. This was true for episodes in response to emotional as well as nonemotional cue words. RHD patients' own ratings of these episodes, however, did not differ from those of controls. These findings are discussed in terms of RHD patients' overall difficulties in processing emotional material and in terms of the nature of autobiographical memory.

Aged↗

PubMed1991

Auricular myoclonus.

We describe a young man with a two and a half year history of idiopathic irregular contractions of an antitragicus muscle in the absence of a more generalized movement disorder. These contractions persisted in sleep and could not be replicated voluntarily. Because proximal nerve block temporarily eliminated the movements and complex hand movements reduced their amplitude and frequency, we suspect a central generator. However, these movements were not associated with any known pathologic condition.

Adult↗

PubMed1991

The role of the right hemisphere in emotional communication.

Previous research has established that patients with right hemisphere damage (RHD) are impaired in the comprehension of emotional prosody and facial expression. There are several explanations for this impairment. It may reflect defective acoustic and visuospatial analysis, disruption of nonverbal communicative representations, or a disturbance in the comprehension of emotional meaning. In order to examine these hypotheses, we asked RHD patients, left hemisphere damaged patients (LHD) and normal controls (NC) to judge the emotional content of sentences describing nonverbal expressions, and sentences describing emotional situations. We found that RHD subjects performed normally in their ability to infer the emotion conveyed by sentences describing situations. However, RHD patients were impaired in relation to both LHD and NC in the capacity to judge the emotional content of sentences depicting facial, prosodic, and gestural expressions, suggesting a disruption of nonverbal communicative representations.

Cerebrovascular Disorders↗

PubMed1991

Phonolexical agraphia. Superimposition of acquired lexical agraphia on developmental phonological dysgraphia.

Study of neuropsychological sequelae of a focal acquired brain lesion may bring out and help delineate the features of a compensated developmental language disorder and its anatomical substrate. A left-handed man with a history of phonological developmental dyslexia and dysgraphia learned in early adulthood to read and write using a lexical system. Following a small posterior right parietal infarct when aged 56 yrs he developed a severe agraphia displaying features of phonological dysgraphia with impaired segmentation and features of lexical agraphia. Writing was severely impaired for all classes of word and nonword stimuli but his errors did not resemble those attributable to a deficit in the system responsible for the short-term storage of the graphemic representation of a word (graphemic output buffer). These observations imply that an acquired lexical agraphia has been superimposed on his developmental phonological dysgraphia, resulting in a combined or 'phonolexical' agraphia.

Agraphia↗

PubMed1991

Differential impact of right and left hemisphere lesions on facial emotion and object imagery.

Thirty-six patients with unilateral hemispheric lesions of the right hemisphere (RHD), left hemisphere (LHD), or no neurologic disease were evaluated on two tasks of visual imagery: one involved imagery for facial emotions and the other involved imagery for common objects. As a group, the RHD patients were more impaired on the emotional than the object imagery task, whereas the LHD patients showed the opposite pattern. Individual case analyses suggested that the RHD group consisted of different behavioural subtypes. One patient with a right inferior occipito-temporal lesion had a facial emotion imagery generation defect, other RHD patients displayed a facial affect agnosia (being impaired on emotional imagery and emotional perceptual tasks), while other RHD patients had perceptual defects with sparing of imagery performance. A final RHD group was globally impaired across all imagery and perceptual tasks. These findings support the hypothesis that the right hemisphere may contain a 'lexicon' of facial emotions. Furthermore, these findings argue against current views that it is exclusively the left or right hemisphere that mediates visual imagery. Rather, hemispheric asymmetries in imagery performance are to some extent material-representation specific and may arise when (a) the representations of objects/events to be imaged are differentially represented in the hemispheres, and/or (b) when the operations acting on these imaged events are differentially lateralized.

Aged↗

PubMed1991

A possible pathophysiologic substrate of attention deficit hyperactivity disorder.

The attention deficit hyperactivity disorder (ADHD) is associated with defective attention and response inhibition and motor restlessness. Inattention, defective response inhibition, and impersistence are more commonly seen in adults with right than with left hemisphere dysfunction. In light of this fact and because children with ADHD not only appear to demonstrate these symptoms but also neglect the left side and have decreased activation of their right neostriatum, we propose that these children have a right hemisphere dysfunction. In addition, because both inattention and defective response inhibition can be seen in children with ADHD and in patients and animals who have frontal lobe and striatal dysfunction, we propose that children with ADHD have dysfunction in a right-sided frontal-striatal system. Motor restlessness may reflect frontal lobe dysfunction due to impairment of the mesocortical dopamine system.

Adolescent↗

PubMed1991

Ipsilateral neglect in a patient following a unilateral frontal lesion.

Using a crossed-response task, it has been demonstrated that as a patient with unilateral frontal lesion recovers from visual inattention, he or she may inappropriately saccade to contralateral stimuli (visual grasp). We report a patient with a right frontal lesion who showed a similar phenomenon on sequential line bisection tasks. On day 1, he showed left-sided neglect on line bisections that enhanced with sequential trials. On day 5, he exhibited right-sided neglect (ipsilateral neglect) on line bisection tasks that also enhanced with repeated trials.

Aged↗

PubMed1991

Gaze-dependent hemianopia without hemispatial neglect.

A hemispheric field is the space defined by the midsagittal plane of the body. Hemianopia, in the absence of hemispheric spatial neglect, has been thought to be purely retinotopic. Confrontation testing of visual fields in eccentric positions of gaze in hemianopic patients permits the discrimination of hemispheric from retinotopic deficits. In the primary position of gaze, a patient with an ischemic lesion of the right occipital and temporal lobes, who was without unilateral spatial neglect, was unable to detect finger movement, name objects, or identify shapes or colors in the left retinotopic hemifield, but when gazing 30 degrees to the right (so that the left retinotopic field was in the right hemispheric field), he performed nearly as well in the left retinotopic field as in the right. The mechanism of this gaze-dependent hemifield visual impairment is unknown, but we discuss four possibilities: (1) eccentric gaze enhances an alternative visual system; (2) the lesion led to modality-specific hemispheric inattention that was corrected by directing intention (plan to act) and gazing to the right; (3) the lesion led to modality specific inattention that was corrected by compensatory mechanisms that may normally enhance attentive vigilance in central space during eccentric gaze; and (4) the neuronal substrate for hemispheric vision was destroyed, whereas that for retinotopic vision was preserved.

Attention↗

PubMed1990

Frontal hypermetabolism and thalamic hypometabolism in a patient with abnormal orienting and retrosplenial amnesia.

A patient with verbal amnesia and a propensity to direct his attention to the right following a retrosplenial area lesion was studied with positron emission tomography using [F-18] fluorodeoxyglucose. These studies showed that the left thalamus was hypometabolic, and the anterior 2/3 of the left hemisphere was hypermetabolic when compared with the right. There were no significant differences seen in the medial temporal lobes. Based on this study, it is posited that interruption of hippocampal input into the anterior thalamus was responsible for the amnesia, and the left frontal hyperactivity was associated with the propensity to attend contralaterally.

Adult↗