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H J Markowitsch

Publications and source records attributed to H J Markowitsch.

At least 55 records · Page 3Linked to original sources
PubMed1995

Which brain regions are critically involved in the retrieval of old episodic memory?

Memory is two-sided like the head of Janus: it looks into the past (retrograde memory) and the future (anterograde memory). While current opinion assumes a strong anatomical interdigitation in the processing of either kind of memory, recent single case reports and results obtained with the positron emission tomographic subtraction method indicate the likely existence of a dissociation: regions of the limbic system are primarily engaged in the encoding of autobiographical and semantic information, while cortical areas in the orbitofrontal and anterolateral temporo-polar regions are principally engaged in information retrieval. Within this retrieval system the right hemisphere may subserve episodic memory retrieval, and the left retrieval from the knowledge system (semantic memory).

Amnesia, Retrograde↗
PubMed1995

Fornix damage and memory. A case report.

The role of the fornix for episodic memory processing is still a matter of controversy. A juvenile patient of average post-surgical intelligence with fornical damage due to tumor removal is described. The fornix was damaged bilaterally at the level of the fornical columns. The patient thereafter suffered major anterograde amnesia which was most pronounced in tests using long delays (e.g., in the delayed recall index of the revised Wechsler Memory Scale). Amnesia was a prominent on the verbal as on the nonverbal level. Attention, concentration and short term memory abilities were preserved. Cognitive flexibility, procedural memory and priming were principally unimpaired. There was no evidence of retrograde amnesia. It is concluded that the fornix constitutes a major link between the three memory interfaces (medial diencephalon, medial temporal lobe, basal forebrain) and that its bilateral rupture anterior to the thalamic level may lead to lasting anterograde amnesia.

Adolescent↗
PubMed1995

[Neuropsychological aspects in idiopathic Parkinson disease].

Patients with Parkinson's disease can suffer from neuropsychological deficits which, in most cases, are already demonstrated at the very beginning (53). Primarily, they are characterized by impairments associated with frontal lobe function affecting psychomotor speed and mental flexibility. Furthermore they show circumscribed impairment of memory functions as well as deficits of visuospatial information processing. Sets of neuropsychological dysfunction of that kind are called subcortical dementia in the American literature. In addition, Parkinson's disease is quite often associated with depressive states which are independent of the neuropsychological deficits. Application of L-Dopa helps to improve the cognitive impairment.

Aged↗
PubMed1994

Novelty encoding networks in the human brain: positron emission tomography data.

Data from positron emission tomography (PET) studies showed novelty activations--higher regional cerebral blood flow associated with perceiving novel rather than familiar stimuli. Regions in the right 'expanded' limbic system--hippocampal formation, parahippocampal gyrus, retrosplenial cortex, thalamus, subcallosal area, the border between cortical areas 32 and 10, anterior and inferior cingulate cortex, putamen, and medial prefrontal cortex--showed such activations for complex pictures. Because novel information is usually encoded for storage in memory, these regions can be seen as constituting components of a visual/spatial novelty encoding network. Insular, opercular and temporal regions (e.g. area 37) showed novelty activations not only for visual pictures but also for auditorily presented sentences, and can be thought of as components of a transmodal novelty encoding network.

Auditory Pathways↗
PubMed1994

Cognitive processes and cerebral cortical fundi: findings from positron-emission tomography studies.

Positron-emission tomography (PET) studies of regional cerebral blood flow have provided evidence relevant to localization of cognitive functions. The critical loci identified in these studies are typically described in terms of macroanatomically labeled cortical and subcortical regions. We report the results of a meta-analysis of localization of changes in blood flow, based on nearly 1000 cerebral cortical peaks of activity obtained from groups of subjects in 30 PET studies. The results showed that, on average, 47% of these peaks were localized within the fundus regions of cortical sulci. This is an unexpectedly high proportion because fundal regions compose < 8% of the cortical mantle. Further analysis suggested a coarse correlation between the extent of fundal activation observed in different studies and the estimated cognitive complexity of the tasks used in the studies. These findings are potentially interesting because (i) the preponderance of fundal activation has implications for the interpretation of the PET data, (ii) they suggest that cortical sulcal and fundal regions may play a distinctive role in higher cognitive processing, or (iii) both of the above.

Attention↗
PubMed1994

The amygdala's contribution to memory--a study on two patients with Urbach-Wiethe disease.

The consequences of primary amygdaloid damage on memory performance are described in terms of neuropsychological, CT, MRI and PET results of two patients, a brother and a sister. Both had circumscribed, bilaterally symmetrical damage confined to the amygdaloid region, while the hippocampal formation and other brain structures were intact. PET-imaging furthermore revealed an overall decrease in glucose metabolism which was particularly apparent at the cingular and thalamic levels. Although neither patient was amnesic, both showed memory impairments in selective tests. In one patient these impairments were more pronounced and they were accompanied by marked affective-emotional fluctuations. Our results suggest that the amygdaloid region is a bottle-neck structure that confers an affective flavour to memories, thereby enhancing the probability of their long term storage.

Adult↗
PubMed1994

Neuroanatomical correlates of retrieval in episodic memory: auditory sentence recognition.

This study used positron emission tomography (PET) to investigate the neuroanatomical correlates of remembering previously experienced events. Twelve young healthy adults listened to "old" meaningful sentences which they had studied 24 hr previously. As a control task the subjects listened to comparable "new" sentences that they had never heard before. Regional cerebral blood flow associated with each task was measured by PET scans using 15O-labeled water. Comparison (old-sentence task minus new-sentence task) of the PET images revealed an extended strip of increased blood flow in the right dorsolateral prefrontal cortex (Brodmann's areas 10, 46, and 9) and the anterior portion of area 6. Other principal regions of increased blood flow were situated around the left anterior cingulate sulcus and bilaterally in the parietal lobes (areas 7 and 40). Major decreases in blood flow were situated bilaterally in the temporal lobes (areas 21, 22, 41, and 42). A high proportion of activity changes seemed to be located in the depths of cortical sulci. Increases in blood flow are seen as reflecting the operations of a widely distributed neuronal network involving prefrontal and parietal cortical regions that subserves the conscious recollection of previously experienced events. Decreases in blood flow in the temporal auditory areas are interpreted as reflecting auditory priming. The prevalence of sulcal blood-flow changes may reflect extensive cortical gyrification; it may also indicate that memory-related processes rely on the densely packed neuropil of sulcal regions.

Adult↗
PubMed1994

Left hemispheric neuronal heterotopia: a PET, MRI, EEG, and neuropsychological investigation of a university student.

A 21-year-old left-handed medical student had a prominent unilateral cerebral cortical malformation due to an ontogenetic migration disorder. We performed neuropsychological studies, EEG, T1- and T2-weighted and proton-density MRI, and positron emission tomography (PET) (under both the resting condition and neuropsychological activation). Neuropsychological testing revealed normal intelligence and generally normal memory functioning but selective deficits in tests of verbal fluency and spatial-figural relationships. Proton-density and T2-weighted MRI revealed extensive left cortical heterotopia that included parts of the Wernicke area. PET under the resting condition revealed a small interhemispheric difference with slightly reduced glucose metabolism in the left temporoparietal cortical zone. An activation PET (with the patient performing a verbal fluency test) resulted in a normal overall increase in metabolism but marked deviations in cortical areas. The highest activity changes were in the Broca and Wernicke areas of the right hemisphere, and there was very little activation in those regions of the left hemisphere that were expected to respond well to the activation--the temporal, parietal, and temporo-occipital cortical zones. We conclude that there can be large compensations for unilateral heterotopia.

Adult↗
PubMed1994

Subliminal perception of words and faces.

The aims of this study were to determine whether stimuli which cannot be detected consciously may nevertheless influence subjects' choices, and whether such an effect is dependent upon stimulus quality and the cerebral hemisphere involved in processing. We subliminally presented words (associated with left hemisphere processing) and faces (associated with right hemisphere processing) to each visual half-field. Subsequently, subjects had to choose among six items. The performance of subjects was compared to that of controls to whom only blank stimuli were presented. Subjects chose the correct word or face significantly more often than controls. For words this effect was significant only when they were subliminally presented to the left hemisphere, whereas subliminal face processing was done by both hemispheres. Our results demonstrate that (i) subliminally presented stimuli influence subjects' choices and thus must have been perceived, and (ii) that cerebral dominance seems to play a role in subliminal perception.

Adult↗
PubMed1994

[The structure of mnestic problems in multiple sclerosis: everyday memory performance and neuroradiologic findings].

35 multiple sclerosis patients and 30 matched healthy controls were investigated for mnestic problems using a German everyday memory test. The objects were both the description of structural characteristics of disturbances and "ecological validity" to meet rehabilitative issues prospectively. In the MS group, impairments were found mainly in the memory domain under delayed recall conditions of complex material. The processing of these tasks may be especially sensitive against fiber tract lesions. While discrete lesions, mostly found in patients with relapsing-remitting courses, inconsistently lead to partial memory disturbances, global mnestic deficits are to be expected in confluent lesion patterns exceeding a critical "threshold of cerebral tolerance." The latter characterises mostly patients with chronic progressive disease courses.

Adult↗
PubMed1993

The possible contribution of the septal region to memory.

A particularly well-documented, intelligent patient (H.I.) with very selective, minute, but most likely bilateral damage of the basal forebrain including the septal region is presented. Though behavioral progress was found for a number of areas, she remained deficient, especially in long-term memory. The severest and largely modality-nonspecific deficits were observed in recall (as opposed to recognition) situations. As a peculiar finding which we would attribute to septal damage, H.I. was mainly affected in tests containing emotional (especially emotionally negative) stimuli, or certain flavours. While this involvement might have helped her in memorizing material judged as positive, it was of negative influence under other circumstances. The septal area may serve as an interface contributing a specific combination of emotional flavour and evaluating (feedback) judgement to a larger (septo-hippocampal-amygdalar) memory and learning processing network.

Affective Symptoms↗
PubMed1993

Mnestic performance profile of a bilateral diencephalic infarct patient with preserved intelligence and severe amnesic disturbances.

The case of a patient with above-average intelligence and educational background, high motivation, and an approximate IQ-MQ difference of 40 points is documented. The patient has been examined repeatedly for nearly a decade. Extensive neuroradiological material of his focal bilateral brain damage in the dorsal diencephalon is available. A widespread range of cognitive tests was used to investigate his actual performance on all relevant aspects of intelligence, attention, subjective memory, immediate retention, learning, skill and problem solving abilities, concept formation, cognitive flexibility, priming, constructional ability, retrograde memory, and long-term retention. The total of more than 50 tests included German-language forms of the revised Wechsler Memory Scale and of the Rivermead Behavioural Memory Test. The patient's short-term memory and attention were, in spite of his advanced years, average or well above average. He gave a number of examples of still intact skills and implicit memory abilities, though there was no uniformity in his performance on implicit memory tests (e.g., with respect to stored vs. new implicit information). He had no awareness of his severe anterograde and retrograde amnesia, documented over a large range of verbal and figural tests. Taken together, the results from our patient confirm the principal dichotomy between declarative and nondeclarative mnestic functions, but give evidence for some restrictions as well. They furthermore demonstrate that focal diencephalic damage may result in profound anterograde and selective retrograde amnesia, especially with respect to data-based material, and that disconnecting portions of the medial and basolateral limbic circuits has devastating consequences on memory.

Aged↗
PubMed1993

Searching for the anatomical basis of retrograde amnesia.

The case of a patient with profound retrograde and minor anterograde amnesia is described and used to discuss the kind of brain damage which will most likely result in persistent retrograde amnesia as the principal symptom. The patient was an industrial manager who had fallen off a horse four years prior to the present neuropsychological and neuroradiological investigation. MRI examination revealed an injury to both temporal poles and to the latero-ventral portion of the right prefrontal cortex. The prefrontal and temporal cortical damage on the right side deeply invaded the white matter while the temporal cortical damage on the left side was much smaller; here, however, portions of the temporo-parietal transition zone were affected as well. The patient was of average intelligence. His attention, short-term memory, and learning ability were average or somewhat below average. His old memories were severely affected in the personal-episodic domain, and much less so in that of semantic remote memory. We conclude from this case that the necessary anatomical substrate for the retrieval of old episodic memories lies within the anterior temporal regions (including deeper situated fiber projections) and possibly involves an interaction with the prefrontal cortex, and that this damage is dissociable from the medial temporal-lobe damage leading to anterograde amnesia.

Amnesia, Retrograde↗
PubMed1993

Retrograde amnesia after traumatic injury of the fronto-temporal cortex.

An industrial manager had severe retrograde and variable but usually mild anterograde amnesia four years after a head injury. MRI showed damage of both temporal poles and the lateral portion of the right prefrontal cortex. The prefrontal and temporal cortical damage on the right side extended deeply into the white matter while the temporal cortical damage on the left side was much smaller. There was an additional left temporo-parietal lesion. The patient was of average intelligence. His attention, short term memory and learning ability were average or somewhat below average. His old memories were severely affected for the personal-episodic domain and less so for semantic remote memory abilities. Therefore an anatomical dissociation between anterograde and retrograde amnesia is possible at the anterior temporal regions, possibly interacting with the prefrontal cortex; these regions seem necessary for the retrieval of old episodic memories.

Amnesia, Retrograde↗