11/510. Sensorimotor skill learning in amnesia: additional evidence for the neural basis of nondeclarative memory. We investigated sensorimotor skill learning, a form of nondeclarative (implicit) memory, in 28 subjects with declarative (explicit) memory defects caused by either mesial temporal (n = 15) or basal forebrain (n = 13) damage and in 66 normal control subjects. All 28 amnesics had normal learning of a rotor pursuit task. We also studied in detail the sensorimotor skill learning of patient Boswell. As a result of bilateral damage to both mesial and lateral aspects of the temporal lobes and to the basal forebrain, Boswell has one of the most severe impairments ever reported for learning of all types of declarative knowledge. Compared to matched controls, Boswell acquired and retained normally the skills associated with performing motor tasks. We conducted a long-term (2-year) followup study of Boswell's retention of the rotor pursuit task, and we found that he retained the skill as well as normal controls. Our study builds on previous work in the following respects: (1) It provides evidence, for the first time, that skill learning is normal in basal forebrain amnesics; (2) it shows that patient Boswell has normal learning and long-term retention of sensorimotor skills, in spite of his extensive damage; and (3) it offers additional evidence that mesial temporal lobe damage spares skill learning. These findings demonstrate unequivocally that sensorimotor skill learning does not require structures in mesial and lateral temporal regions nor in basal forebrain. ( info) |
12/510. Naming people ignoring semantics in a patient with left frontal damage. Studies about proper name anomia generally assume that persons' names are harder to recall than other semantic information one knows about them and that name retrieval is not possible without biographical knowledge. We describe a patient, SB, who, after a left frontal haemorrhage, was unable to recall any biographical information about people she could name. Moreover, she had a normal score in an Object Picture Naming Test, but gave confabulatory answers in a Semantic Questionnaire involving the same items. The role of frontal function in producing this pattern of impairment is discussed, together with the possible existence of a direct route from visual perception to proper name retrieval. ( info) |
13/510. memory lost and regained following bilateral hippocampal damage. We present a longitudinal neuropsychological study (31 examinations over a period of 18 months) of patient DE DF demonstrated bilateral atrophy of the hippocampal formation and globus pallidus resulting from carbon monoxide poisoning. Eighteen months after the event, the volume of the hippocampal formation was reduced by 42% on the left side and 28% on the right. The patient initially presented with a severe global amnesia. Then, he showed a gradual, yet selective recovery of episodic memory function. Verbal free recall and spatial memory performance remained reduced, whereas immediate word recall and recognition memory, as well as picture learning and memory, improved to levels at the lower range of normal performance. Interestingly, nonspatial associative learning was never much impaired and recovered completely by the end of testing. These data are taken as evidence that the human hippocampal formation does not equally support different forms of episodic memory. ( info) |
14/510. Unreliable admissions to homicide. A case of misdiagnosis of amnesia and misuse of abreaction technique. BACKGROUND: The past decade has witnessed a recognition that unsafe criminal convictions may be occasioned by unreliable confessions. AIMS: To present a case which illustrates the dangers of using abreaction interview techniques in a legal context and demonstrate the relevance of the memory distrust syndrome to an unsafe confession to murder. METHOD: We under took a detailed assessment of a person appealing against his original murder conviction, 'the appellant', and a careful scrutiny of all the relevant papers in the case. RESULTS: The appellant served 25 years in prison before his conviction was quashed as 'unsafe' on the basis of fresh psychological and psychiatric evidence. CONCLUSIONS: amnesia for an offence had been misdiagnosed, and the use of repeated abreaction interviews had further confused both the appellant and the original court. At the Appeal Court, the advice was that the man had experienced a form of source amnesia which resulted in an unreliable confession. ( info) |
15/510. neuroimaging and behavioral correlates of recovery from mnestic block syndrome and other cognitive deteriorations. OBJECTIVE: We conducted a follow-up study on a patient with enduring psychic shock-induced cognitive impairment to study by neuropsychological and functional imaging methods the degree of his recovery process on the brain and cognitive levels. BACKGROUND: Based on the assumption that trauma and stress conditions can alter the functions of the nervous systems, we report on a patient whom we studied 2 and 12 months after he suffered "mnestic block syndrome" and additional cognitive deterioration symptoms. methods: We report on a patient studied 2 and 12 months after he suffered "mnestic block syndrome" and additional cognitive deterioration symptoms. magnetic resonance imaging and fluorodeoxyglucose positron emission tomography were used for neural and detailed neuropsychological testing for cognitive deficits. RESULTS: The patient initially manifested severe intellectual decline, including severe anterograde and retrograde amnesia. His symptoms were correlated with major, although selective, reductions in his brain metabolism (2-3 SD below those of controls). Presently, he shows a normal brain metabolism and has regained parts of his memory and many of his other intellectual capabilities. Nevertheless, he still has long-term memory impairments. CONCLUSIONS: This case demonstrates a close relation between brain metabolism and cognitive performance, with major deficits of both at 2 months and major recovery of both at 12 months after a shocking event. It can serve as an example for possible stress-related deteriorations in certain brain regions, which can be partly corrected by psychotherapeutic interventions, passing time, and favorable environmental conditions. ( info) |
16/510. Amnesic syndrome with bilateral mesial temporal lobe involvement in Hashimoto's encephalopathy. A 25-year-old woman presented with a subacute confusional state, headaches, unsteadiness, myoclonus, seizures, and an amnesic syndrome as a manifestation of Hashimoto's encephalopathy. Investigations showed biochemical hypothyroidism, raised thyroid microsomal antibodies, and weakly positive antineuronal antibodies. A T2-weighted MRI of the brain showed bilateral symmetric areas of increased signal in the mesial temporal lobes and hippocampi that had a low signal intensity on T1-weighted imaging. Despite clinical and radiologic improvement after steroid and thyroid hormone replacement therapy, a severe amnesic syndrome with associated localized MRI abnormalities persists. ( info) |
17/510. Acquisition of novel semantic information in amnesia: effects of lesion location. Two patients with severe global amnesia are described who differ in the extent to which they have acquired new semantic information. Patient SS, who has extensive medial temporal lobe damage including the hippocampus as well as surrounding cortical areas, has failed to acquire virtually any new information regarding vocabulary or famous faces that entered the public domain since the onset of his amnesia. In contrast, patient PS, who has a selective lesion of the hippocampus proper, has gained a sense of familiarity of novel vocabulary and famous people, even though her effortful retrieval of this new semantic knowledge remains impaired. These findings extend to amnesia of adult onset, the proposal of Vargha-Khadem and colleagues that in patients with selective hippocampal injury, cortical areas surrounding the hippocampus may play an important role in new semantic learning [Vargha-Khadem, F., Gadian, D.G., Watkins, K. E., Connelly, A., Van Paesschen, W. and Mishkin, M., regarding the importance of the subhippocampal cortices in the mediation of new semantic learning in children with hippocampal lesions, science, 1997, 277, 376-380]. ( info) |
18/510. Amnesic confabulatory syndrome after focal basal forebrain damage. A 73-year-old woman developed amnesic confabulatory syndrome after a right focal basal forebrain hemorrhage. The confabulation, despite persistent antegrade amnesia, gradually subsided with improvement of the frontal executive function. The lesion appeared to disrupt connections of the medial and lateral limbic circuits important for memory. Simultaneous dysfunctioning of the two circuits involving the medial temporal and frontal lobes may be necessary for the development of this syndrome. ( info) |
19/510. Electronic memory aids for outpatient brain injury: follow-up findings. The introduction of highly portable computers extends the range of tools potentially useful to persons with functional impairments of prospective memory resulting from brain injury. This study reviews the experience of 12 patients with brain injury undergoing outpatient treatment using palmtop computers to assist with memory dependent activities in their everyday lives. During the initial supervised trial period, each was provided a palmtop computer based memory aid capable of generating audible and visible reminder cues. Subsequently, patients were contacted for follow-up between 2 months and 4 years after initial trial usage, and surveyed as to the utility of the computer. Nine patients found palmtop computers were useful during supervised trials. Seven of nine patients actually continued to use such devices after the usage trials had ended. Experience with this technology has shown it to be useful in a high proportion of patients for assisting with memory dependent functions. ( info) |
20/510. occupational exposure to methyl isobutyl ketone causes lasting impairment in working memory. The authors describe serial evaluations of a 44-year-old man who became cognitively impaired during a 6-year period of repeated exposure to high levels of methyl isobutyl ketone (MIBK). neuropsychological tests administered six times over 10 years demonstrated a stable pattern of cognitive impairment. Dynamic imaging studies suggested persistent CNS dysfunction. The authors conclude that chronic, high-level, occupational MIBK exposure can cause a persistent cognitive syndrome best explained by impaired working memory. ( info) |