Biomedical subjects

M Mennemeier

Publications and source records attributed to M Mennemeier.

4 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↗