Remote memory after basal forebrain damage.
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Adult↗
Biomedical subjects
H J Markowitsch
Publications and source records attributed to H J Markowitsch.
Impaired episodic memory retrieval in a case of probable psychogenic amnesia.
A patient with severe, selective retrograde amnesia for personal material diagnosed as probable psychogenic amnesia, was investigated intensively neuropsychologically with cranial computed tomography (CCT), magnetic resonance imaging (MRI), and single photon emission tomography (SPECT). The patient was of average intelligence and memory with no anterograde amnesia. No evidence for structural brain damage was detected in CCT and MRI. SPECT, performed about 3 weeks after the onset of symptoms, demonstrated reduced perfusion in right temporal and frontal areas, that is, in areas which have been suggested as critical for episodic memory retrieval. To study episodic memory retrieval, positron-emission-tomography (PET) blood flow (rCBF) measurements were performed 6 months after the onset of symptoms. During episodic memory retrieval bilateral neuronal activations were observed in the precuneus, the lateral parietal and the right dorsolateral and polar prefrontal cortex. Compared to the results of previous functional imaging studies on episodic memory retrieval, our findings suggest an underlying functional disturbance of brain areas previously demonstrated to be involved in episodic memory retrieval.
Adult↗
Differential impairments in recalling people's names: a case study in search of neuroanatomical correlates.
The case of a patient with selective left hemispheric medial and lateral temporal lobe damage is described. The patient was of slightly supra-average intelligence and had no problems in normal memory functions, but was severely anomic with respect to people's names. One month post-onset, this deficit held for names of colleagues and friends she had gotten to know during the last 10 years prior to the infarct and for all names confronted with post-infarct. On the other hand, learning of face-name associations was preserved and was independent of the ability to generate context-specific information for the subjects whose names were requested. The results support the existence of category-specific naming impairments, and, moreover, indicate a deficit that has to be differentiated with regard to memory systems. A time-limited, but prolonged engagement of interconnected left medial and adjacent lateral temporal lobe structures in ecphory is stressed for context-restricted information such as proper names.
Anomia↗
The functional neuroanatomy of episodic memory retrieval.
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Brain↗
Memory beyond the hippocampus.
Improved neuroanatomical knowledge, technical and methodological innovations (such as PET), and more refined conceptualizations of memory have inspired a reappraisal of theoretical beliefs regarding the role of the hippocampus in memory. In the past few years, it has become apparent that the influence of the medial temporal lobe regions extends beyond memory and that memory processes (such as encoding, consolidation and retrieval) involve not only the hippocampus and the medial temporal and diencephalic regions, but also widely distributed neocortical and perhaps even cerebellar regions.
Animals↗
[Neuropsychological findings in obsessive-compulsive disorder].
The results of neuropsychological-cognitive investigations in patients with obsessive-compulsive disorder are presented in a meta-analysis. The analysis differentiates between intelligence, attention and concentration, memory executive functions, and visual-spatial and visuo-constructive performance. Changes in intelligence are only rarely manifest in obsessive-compulsive patients, and if so, principally in the visuo-constructive field, possibly including abstract-logical processes of thinking. Similarly, they are largely normal in functions of attention and verbal memory; only complex study designs reveal deficits in comparison to control subjects. Obtained deficits in visual memory should be interpreted as being likely due to deficient visuo-perceptive and visuo-constructive performance. Executive functions have not been studied in depth and are unimpaired in most investigations. Visuo-constructive problems are observed most frequently and might best be attributed to problems in Gestalt perception. It has to be pointed out that up to now techniques and designs of investigation are, in the majority of studies, imperfect and that it seems necessary to consider the existence of subgroups of obsessive-compulsive patients with differing degrees of impairment. Prognosis and evaluation of patients with obsessive-compulsive symptomatology depend considerably on their insight into the irrelevance of their behavioural patterns and on the contents of their predominant thoughts and actions. Transferring the deficit patterns to the brain level points to (a) right hemispheric damage and (b) damage in the frontostriatal system.
Attention↗
Massive and persistent anterograde amnesia in the absence of detectable brain damage: anterograde psychogenic amnesia or gross reduction in sustained effort?
The case of a young patient with severe and persistent anterograde amnesia of no known cause is reported. Anterograde amnesia arose within a 1-month period and has persisted for more than 1 year. Although a wide variety of neurological and neuroradiological assessments were completed (EEG, evoked potential recordings, Doppler sonography, MRI, PET), no evidence of brain damage was detected. Neuropsychologically, the patient was of high intelligence, had average to above-average short-term memory, and normal retrograde memory abilities, but severe and persistent anterograde amnesia in both verbal and nonverbal domains. Furthermore, he demonstrated grossly reduced long-term concentration. It is likely that a complex chain of interacting variables can produce a syndrome that appears phenomenologically as anterograde amnesia without organically measurable correlates.
Adult↗
Prefrontal asymmetric interictal glucose hypometabolism and cognitive impairment in patients with temporal lobe epilepsy.
Depressions of regional cerebral metabolism beyond the epileptogenic zone have been demonstrated in patients with intractable temporal lobe epilepsy. However, their clinical relevance, and the causes of prefrontal metabolic asymmetries are less well understood. We investigated 96 temporal lobe epilepsy patients by FDG-PET and neuropsychological assessment who had a corresponding unilateral temporal hypometabolism, left hemisphere speech dominance, full scale IQ of > 70 and no extratemporal lesion in MRIs. The regional glucose metabolism was determined in each patient in homologous regions including prefrontal cortex, and normalized to whole brain metabolism. Regional differences of > 10% were regarded as asymmetrical. Prefrontal metabolic asymmetries were more frequent in patients with left temporal lobe epilepsy (21 left, six right) and a history of secondarily generalized seizures. A multivariate analysis of variance revealed a main effect for prefrontal metabolic asymmetry on neuropsychological 'frontal lobe measures', including verbal and performance intelligence measures. Prefrontal metabolic asymmetry was not related to 'measures of episodic memory', presence of psychiatric symptoms or frontal interictal epileptiform discharges. We conclude that prefrontal metabolic asymmetry is associated with cognitive impairment. Patients with temporal lobe epilepsy of the left speech dominant hemisphere and a history of secondarily generalized seizures are at considerable risk of developing prefrontal metabolic asymmetry.
Adult↗
Retrieval of old memories: the temporofrontal hypothesis.
Extensive neuropsychological testing is reported on two chronic patients with combined temporopolar and prefrontal damage, dominantly left-hemispheric, and, as control, one chronic patient with bi-hemispheric prefrontal damage. The principal finding is that combined temporofrontal damage, but not substantial prefrontal damage alone, results in marked retrograde memory deficits while leaving intelligence and new learning relatively unimpaired. Although their general world knowledge was good, the temporopolar patients demonstrated retrograde memory impairments on several tests of past events and faces of previously famous people. With respect to retrograde autobiographical memory, one of the temporopolar patients was severely impaired and the other was judged to be moderately impaired. The control patient appeared to be normal. These results, together with corresponding data from related single case and dynamic imaging studies, strongly support a crucial role of the temporofrontal junction area in the ecphory of old memories.
Adult↗
Individual prediction of change in delayed recall of prose passages after left-sided anterior temporal lobectomy.
Prognostic variables for individual memory outcome after left anterior temporal lobectomy (ATL) were studied in 27 patients with refractory temporal lobe epilepsy. The difference between pre- and postoperative performance in the delayed recall of two prose passages (Story A and B) from the Wechsler Memory Scale served as measure of postoperative memory change. Fifteen independent clinical, neuropsychological, and electrophysiological variables were submitted to a multiple linear regression analysis. Preoperative immediate and delayed recall of story content and right hemisphere Wada memory performance for pictorial and verbal items explained very well postoperative memory changes in recall of Story B. Delayed recall of Story B, but not of Story A, had high concurrent validity to other measures of memory. Patients who became seizure-free did not differ in memory change from patients who continued to have seizures after ATL. The variables age at epilepsy onset and probable age at temporal lobe damage provided complementary information for individual prediction but with less effectiveness than Wada test data. Our model confirmed that good preoperative memory functioning and impaired right hemispheric Wada memory performance for pictorial items predict a high risk of memory loss after left ATL. The analyses demonstrate that the combination of independent measures delivers more information than Wada test performance or any other variable alone. The suggested function can be used routinely to estimate the individual severity of verbal episodic memory impairment that might occur after left-sided ATL and offers a rational basis for the counseling of patients.
Adolescent↗
Clinical case report: memory functions after anterior communicating artery aneurysm rupture.
The case of a patient suffering from rupture of an aneurysm of the anterior communicating artery is reported. The hematoma was located in the basal forebrain, one of the anatomical regions associated with mnestic functions. Memory and other cognitive functions were studied. The patient performed well on all non-mnestic tests, but showed significant memory impairment. Anterograde memory was deficient not only in recall, but also in recognition. Performance on remote memory tests showed some differentiation. The patient remembered autobiographical material and famous faces correctly, but presented deficits on a Famous Events Test. This dissociation represents a difference in emotional content or familiarity of the material; the performance in tests using material with a higher emotional content was unremarkable. Lesions within the basal forebrain seem to deteriorate anterograde and remote memory, but performance may be inconspicuous if test material of high emotional content or familiarity is used.
Acute Disease↗
Reorganization of memory functions after human temporal lobe damage.
Hemispheric (re-)organization of episodic memory functions after temporal lobe damage (TLD) was investigated by the intracarotid amobarbital procedure in patients suffering temporal lobe epilepsy. Memory of the speech-dominant left hemisphere was intact after right-sided TLD independent of the age at manifestation. In contrast, the right hemisphere mediated memory well only after early left-sided TLD. These findings suggest a predisposition of the speech-dominant left hemisphere for the encoding of episodic memory, and indicate that for left-sided TLD the right hemisphere may compensate memory encoding sufficiently only if the damage occurred within a critical period in childhood.
Brain Damage, Chronic↗
Cerebral representation of one's own past: neural networks involved in autobiographical memory.
We studied the functional anatomy of affect-laden autobiographical memory in normal volunteers. Using H2 15O positron emission tomography (PET), we measured changes in relative regional cerebral blood flow (rCBF). Four rCBF measurements were obtained during three conditions: REST, i.e.,, subjects lay at rest (for control); IMPERSONAL, i.e., subjects listened to sentences containing episodic information taken from an autobiography of a person they did not know, but which had been presented to them before PET scanning (nonautobiographical episodic memory ecphory); and PERSONAL, i.e., subjects listened to sentences containing information taken from their own past (autobiographical episodic memory ecphory). Comparing IMPERSONAL with REST (nonautobiographical episodic memory ecphory) resulted in relative rCBF increases symmetrically in both temporal lobes including the temporal poles and medial and superior temporal gyri. The same loci, however, with a stronger lateralization to the right hemisphere were activated in the comparison PERSONAL to REST (autobiographical episodic memory ecphory). In addition, the right temporomesial, right dorsal prefrontal, right posterior cingulate areas, and the left cerebellum were activated. A comparison of PERSONAL and IMPERSONAL (autobiographical vs nonautobiographical episodic memory ecphory) demonstrated a preponderantly right hemispheric activation including primarily right temporomesial and temporolateral cortex, right posterior cingulate areas, right insula, and right prefrontal areas. The right temporomesial activation included hippocampus, parahippocampus, and amygdala. These results suggest that a right hemispheric network of temporal, together with posterior, cingulate, and prefrontal, areas is engaged in the ecphory of affect-laden autobiographical information.
Adult↗
Right temporofrontal cortex as critical locus for the ecphory of old episodic memories.
A 54 year old patient of average intelligence with a severe and enduring loss of old autobiographical memories after herpes simplex type 1 infection is described. She was tested with a comprehensive neuropsychological battery two years after the infection. Special emphasis was laid on examining different aspects of retrograde memory. The neurological examination involved MRI and SPECT. Brain damage was found mainly in the right temporofrontal region, but minor left sided damage to this region seems possible. The patient was in the normal or slightly subnormal range for all tested anterograde memory functions, but manifested severe retrograde memory deficits with respect to episodic old memories and more moderate deficits in tests of general knowledge (semantic old memories). It is concluded that the ecphory of old autobiographical memories relies heavily on an activation of the right lateral temporofrontal junction area, but that probably only some complementary left hemispheric damage to these regions will lead to major and persistent retrograde amnesia. Alternatively, the disconnection between major prefrontal and posterior cortical regions may provide a basis for retrograde amnesia.
Amnesia, Retrograde↗
Interdependence of priming performance and brain-damage.
Basically, two hospitalized patient groups were a variety of different learning situations which are subdividable into conventional and experimental tests and which covered so-called implicit and explicit memory tests. Furthermore, data from other cases were used for comparison and for support of the proposed hypotheses. The main sample consisted of 15 focal brain-damaged patients (group N) and 15 patients after surgical interventions outside the nervous system (group O). Aside from affective behavior and intelligence, memory tests were used. These included the WMS-r, picture and face recognition tests, the Tower of Hanoi, the Wisconsin Card Sorting Test (WCST), a Concept Comprehensive Test, and word and picture priming tests. A number of significant differences were obtained between the two age, sex, and education matched groups. Above all, intelligence and memory were reduced in parallel in the cortically damaged compared to the well-matched orthopedic group, while attention and concentration did not differ. Even performance in tests such as the Tower of Hanoi and the WCST differed, perhaps explainable by the proportion of frontal lobe damaged patients and the overall decrease in intelligence in group N. Verbal priming was found to a similar degree in both groups. On the other hand, priming of incomplete pictures was significantly poorer in group N than in group O; furthermore, results from MQ- and IQ-based group splitting (independent of their previous N or O affiliations) suggested a direct relation between mnemonic and other cognitive abilities and success in priming. As perceptual, but not verbal priming differed between groups, and explanation of group N results, based primarily on explicit memory processing, is unlikely. It is concluded that non-brain damaged patients in general are able to use a wider repertoire of information encoding strategies which at least in part is memory and intelligence correlated.
Adult↗
The amygdala and emotional memory.
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Amygdala↗
Cognitive processes and cerebral cortical fundi.
Human brain evolution has resulted in a large increase in cortical folding as a result of which 60% of the cerebral cortical mantle is buried within sulci. Cortical regions within the sulci, and especially in the fundal zones (fundi) at the bottom of sulci, differ from the rest of the cortex in a number of ways with respect to anatomical and histological morphology. Although physiological implications of the fundal morphology have been discussed from time to time, and although scattered evidence hints at a special functional role for fundi, until recently there have been few empirical facts to guide the inquiry into a possibly special physiological function of fundal zones. In this article we review findings yielded by positron emission tomography studies showing that the peaks of changes in neuronal activity are frequently observed in and near fundi. We discuss, but do not accept, the possibility that these findings reflect either the partial volume effect or the course of cerebral blood vessels. Instead, because of a coarse correlation observed between fundal fraction (the proportion of fundally related activity peaks) and the apparent cognitive complexity of the tasks probed, and in light of the anatomical evidence reviewed, we propose the hypothesis that cortical sulcal and fundal regions play a distinctive role in higher cognitive processing.
Brain Mapping↗
Cerebral bases of consciousness: a historical view.
Attempts of modern brain research, starting at the end of the nineteenth century, to define and hierarchically order consciousness are reviewed. It is emphasized that roots from philosophy, biology, and psychology influenced brain research in its search for possible physical bases of consciousness. Among the mainstreams of research were approaches which defined consciousness by selecting numerous attributes of it and ordering these hierarchically. Similarly, there was widespread speculation on whether all kinds of animals or only some of them are conscious or manifest some of the hierarchically defined attributes of consciousness. On the brain side, the cerebral cortex and in particular its frontal aspects, the prefrontal cortex, was regarded as the principal anatomical basis of consciousness. The dependence of consciousness on memory and the ability to order processes in time were widely acknowledged and case descriptions from Korsakoff patients and epileptics were considered especially to demonstrate the interdependence between consciousness and the brain.
Alcohol Amnestic Disorder↗