Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0002622 (amnesia)
 5,520 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

To date, positron emission tomography (PET) has been the only technology for the quantitative imaging of the changes of regional cerebral glucose (rCMRGl) or oxygen metabolism and blood flow (rCBF) associated with psychophysical stimulation and with the performance of mental tasks. So far, the majority of studies performed in healthy subjects demonstrated activation patterns involving not only certain limbic structures, most of all hippocampus, amygdala, parahippocampus, and cingulate, but also temporal, parietal, and occipital association cortex, depending on the applied paradigm. Indeed, the closest correlation between regional metabolism and memory test scores was found in mesiotemporal structures during the performance of memory tasks. Metabolic or CBF studies also seem to indicate that memorizing strategies may differ among individuals. PET was repeatedly used to investigate metabolic and/or blood flow abnormalities in patients with various amnestic syndromes. In cases with uni- or bilateral lesions of mesiotemporal structures, caused by surgery, herpes simplex encephalitis, or permanent ischemic, anoxic, or toxic damage, disturbances of metabolism and blood flow typically extended far beyond the morphological defects detected by computed tomography or magnetic resonance. In acute transient global amnesia, CBF and metabolism were decreased bilaterally in the mesiotemporal lobes, where hypometabolism persisted for some time, while higher values were observed in thalamus and some cortical areas. Diencephalic lesions causing Korsakoff's syndrome were associated with decreased rCMRGl in the hippocampal formation, upper brainstem, cingulate, and thalamus. Discrete thalamic infarcts caused amnesia and metabolic depression in the morphologically intact ipsilateral thalamus and in various projection areas of the infarcted nuclei. In ischemic forebrain lesions, amnestic deficits could be related to involvement of the anterior cingulate and of basal cholinergic nuclei. A large number of pathologies are diffusely spread out in the brain and affect partially or predominantly structures in memory processing. This holds true especially in the various dementias where memory disturbances are a consistent and often leading feature. Notably, Alzheimer's disease can be distinguished from other dementias by its characteristic pattern of metabolic dysfunction, with the most prominent changes occurring in parietotemporal and frontal association cortex whose residual metabolism is related to the severity of the disease. Therefore, activation studies using paradigms involving memory functions enhance that typical pattern. Only in the activated state is metabolism of mesiotemporal structures significantly correlated with the performance in memory tests. Other dementias also affect some of the distributed memory networks, with Huntington's disease suggesting a role of the striatum in memory processing.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:PET correlates of normal and impaired memory functions. 156 50

Normal volunteers underwent three successive scans of regional cerebral blood flow (rCBF) using the 133Xe inhalation technique during visual stimulation, a recognition memory task and a resting state defined by high EEG alpha content. Since the stimulation was virtually identical in both non-rest conditions, we were able to separate the CBF pattern resulting from simple stimulation and that resulting from the cognitive (recognition memory) component alone. These turned out to have very nearly opposite effects on the normal anterior-to-posterior resting state gradient: the sensory component diminished the gradient, while the cognitive component exaggerated it. It is suggested that these normative data can be of clinical value in the study of cerebral recovery/reorganization following post-traumatic amnesia.
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PMID:CBF gradient changes elicited by visual stimulation and visual memory tasks. 371 34

In order to further understand the pathology of Alzheimer's disease (AD), we have utilized image analysis in diagnosing the early stages of AD in patients with cognitive disorders. CT and MRI, however, have not been feasible since only atrophy is seen and it is difficult to differentiate the changes in AD from age associated changes. In this study we tried to determine whether regional cerebral blood flow (rCBF) measurements using single photon emission CT (SPECT) are feasible for the early diagnosis of AD. Regional CBF (rCBF) was measured using SPECT in three subject groups: Age-associated memory impairment (AAMI. n = 9), mild AD (n = 16), and normal aged patients (mean age = 68.3; n = 20). The subjects were then observed for three years. The region of interest (ROI) for the medial temporal lobe was set at OM-30 degrees to cover the maximum area of the hippocampus. The absolute values of rCBF in the frontal, temporal, and parietal lobes and the cerebellum were significantly lower in the mild AD subjects than in the normal aged subjects. A significant decrease in rCBF was also seen in the medial temporal lobe in both the AD and the AAMI subjects compared to the normal controls. During the three years of follow up, no cases of dementia were seen in the AAMI subjects. However, there were two patients who appeared to have difficulty in adapting to daily life due to amnesia, one with a decrease in rCBF of the medial temporal lobe on the second SPECT, and the other showing a low rCBF the first time. This study suggests that AAMI subjects may comprise both AD and normal subjects. Therefore a more prospective study is needed.
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PMID:[Cerebral blood flow of patients with age-associated memory impairment and the early stage of Alzheimer's disease. A study by SPECT using the ARG method]. 959 49

Transient amnesia caused by minor head injury is commonly encountered in daily neurosurgical practice, but the mechanism of such amnesia has not been extensively studied. We measured the regional cerebral blood flow (rCBF) of patients with postconcussive amnesia with Xe/CT CBF to examine whether a focal disturbance of CBF exists. The Xe/CT CBF study was performed in eight patients with closed head injury without organic cerebral lesion while they were suffering from posttraumatic amnesia (concussion group). The time interval between accident and CBF measurement was less than 2 h in three patients, 5-6 h in two, 8-9 h in two, and 18 in one. The results were compared with those of nine normal volunteers and eight other age-matched patients who recovered without any neurological deficit despite the presence of hemorrhagic regions (mild hemorrhage group). The rCBF of the concussion group was significantly elevated in the bilateral mesial temporal cortex in comparison to the normal group. The rCBF in the mild hemorrhage group was lower than that of normal controls in all regions. The analysis of right-left difference in CBF indicated that there was significant asymmetry (right > left) in the frontal and temporal cortex in the concussion group, but not in the normal and mild hemorrhage group. This Xe/CT CBF study in acute stages of cerebral concussion, in which patients were amnestic, detected focal cerebral hyperemia. Such hyperemia in regions closely related to human memory function may be the result of vasoparalysis or the compensatory activation of memory circuits after denervation injury.
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PMID:Focal cerebral hyperemia in postconcussive amnesia. 1178 Aug 63