Is disturbed transfer of learning in callosal agenesis due to a disconnection syndrome?

Disturbed intermanual transfer of tactile learning in callosal agenesis has been interpreted as a sign of disconnection syndrome. We observed this sign in one of four acallosal patients with a conventional form-board task, and tried to elucidate the nature of the deficit. The form-board performance of the patient with disturbed transfer of learning totally depended on motor skill, while the other acallosals and normal controls executed the task based on spatial and somesthetic information. All acallosals and normals, however, failed to show transfer of learning with another tactile task which needed motor skill but not spatial-somesthetic information. These findings suggest that the task-performing strategies in form-board learning change the state of interhemispheric transfer. Unimanual learning effect is transferred if spatial-somesthetic information is acquired in the process of learning, but is not transferred if motor skill is the exclusive content of learning. We conclude that disturbed "transfer" of learning in some acallosals is not a true disconnection sign. It should be attributed to a lack of appropriate strategy, as a result of ineffective problem solving in tactile tasks.

Prevalence and cognitive performances of vascular cognitive impairment no dementia in Japan: the Osaki?Tajiri Project

Prevalence, magnetic resonance imaging (MRI) findings, cognitive function and depression are four major aspects of vascular cognitive impairment no dementia (vascular CIND). We performed a community-based study to examine these using 497 community-residents aged 65 years or older. Vascular CIND was defined as a clinical dementia rating (CDR) 0.5 with cerebrovascular disease. Several neuropsychological tests were performed, including MMSE, Geriatric Depression Scale (GDS), and Trail Making Test (TMT). Cerebrovascular disease and white matter lesions were visually assessed using MRI. Prevalence of vascular CIND, localization of cerebrovascular disease, and the relationships amongst MRI findings, white matter lesions, cognitive impairment and depression were analyzed. The prevalence of vascular CIND was 8.5% amongst the total population, corresponding to the rate being 37.2% amongst the CDR 0.5 participants. Compared with the CDR 0, the CDR 0.5 group had more subjects with strategic cerebrovascular disease in the thalamus, etc. No effects of cerebrovascular disease on MMSE and GDS scores were found, but the CDR 0.5/strategic cerebrovascular disease group showed impaired TMT-B scores. In the CDR 0 group, only anterior periventricular hyperintensity was associated with TMT-A score independent of cerebrovascular disease. A vascular CIND population was identified, and executive dysfunction in this population is probably based on an impaired fronto-subcortical circuit.

Evolving atherosclerosis at carotid and intracranial arteries in Japanese patients with ischemic heart disease: a 5-year longitudinal study with MR angiography

Progression of atherosclerosis at extracranial carotid and intracranial arteries in patients with ischemic heart disease (IHD) is not well defined. We carried out a 5-year longitudinal study with magnetic resonance angiography (MRA) of patients with IHD to assess the incidence of progression of atherosclerosis at extracranial carotid and intracranial arteries and to determine predictors of the progression. We previously performed carotid and intracranial MRA on 67 patients who had received selective coronary angiography for the clinical diagnosis of IHD. Of these 67 subjects, 41 patients gave informed consent to undergo MRA reexaminations to evaluate changes of extra- and intracranial arteries over a 5-year period. The degree of stenosis was divided into five grades depending on the narrowness of the arteries, i.e. normal, mild, moderate, severe and occluded. The average of follow-up period with MRA examination was 58.8 months. The progression of atherosclerosis, as defined as an increase of one grade of the stenosis rating, including both the exacerbation of pre-existing stenosis and the appearance of new stenotic lesions, were found in five patients (12.2%) for the cervical carotid artery and in only one patient (2.4%) for the intracranial artery. A multiple logistic regression analysis revealed that baseline carotid artery stenosis (P = 0.008), age (P = 0.047), and coronary events during the follow-up period (P = 0.048) were significant and independent predictors of progression of carotid atherosclerosis. In conclusion, our findings suggest that follow-up evaluation of the carotid artery is indicated for patients with IHD in whom carotid artery stenosis was detected on an initial examination. Further study is needed with larger numbers of patients to confirm these findings.

Formant interaction as a cue to vowel perception: a case report

Accumulating evidence indicates that cerebral processing of consonants and vowels is separable. It has been shown that disordered temporal acuity leads to disturbed consonant perception in cases with pure word deafness. In contrast, there has been no clear explanation of how vowel perception is impaired. We examined a patient with auditory agnosia, who showed a differential ability to identify the five Japanese vowels after bilateral cerebral lesions. He correctly identified the vowel [a] in more than 70% of auditory presentations, whereas he identified [i] in only about 30% of presentations. The difference between the first and second formant frequencies "F2-F1" and an artificially defined value "F1-(F2-F1)" for each vowel correlated significantly with the percentage of correct identifications. These findings support the hypothesis that vowel perception is based on formant interactions.

Different spatial processing for stimulus-centered and body-centered representations

The authors describe a patient who experienced two successive strokes in the right hemisphere. After the first stroke, she showed stimulus-centered left neglect confined to right space on a circle discrimination task, which resolved. After the second stroke, she showed body-centered left neglect on the same task. These observations of two types of left neglect in the same patient suggest there are at least two distinct spatial attentional systems in the brain: global and focal attentional systems.

A case of frontal network amnesia

A 63 year old man developed an amnesic syndrome coupled with an array of "frontal lobe" signs after bilateral small subcortical infarcts. His amnesia was characterised by severe difficulty in voluntary recall of recently memorised verbal and non-verbal materials, while his recognition for the same materials was less affected. The symptoms remained unimproved at a follow up evaluation eight months after onset. Magnetic resonance imaging showed two small circumscribed lesions, one in the dorsomedial nucleus of the left thalamus and the other in a region of the right globus pallidus and anterior limb of the right internal capsule. The mammillothalamic tracts and anterior nuclei of the thalami were clearly spared bilaterally. The left dorsomedial nucleus lesion disrupted the thalamofrontal circuit, while the anterior limb lesion of the right internal capsule disconnected the same circuit by damaging part of the anterior thalamic radiation. Thus the amnesia in this patient may have been caused by disruption of the bilateral thalamofrontal circuits. This type of amnesic pathology should be separated from more conventional types of amnesia that are produced by disruption of the so called Papez circuit or the Delay-Brion memory system.

Brain activation during the fist-edge-palm test: a functional MRI study

The purpose of our study is to clarify, using functional MRI, brain regions activated during the fist-edge-palm task (FEP) compared to relatively simple hand motor tasks using either the right or the left hand in right-handed normal volunteers. The FEP was introduced to detect a disorder of voluntary movement, and it is believed to be closely related to contralateral frontal lobe damage. However, this assumption still remains controversial. Ten subjects participated in this study. Hand motor tasks were as follows: (1) the FEP, in which the subjects were requested to place their hand in three different positions sequentially: a fist resting horizontally, a palm resting vertically, and a palm resting horizontally; (2) a fist-palm task (FP), in which the subjects were asked to clench and unclench their fist alternately; and (3) a control task requiring the subjects to knock lightly with their clenched fist. The contralateral sensomotor and premotor areas were activated in the FP with the right hand and the contralateral sensorimotor, premotor, and supplementary motor areas (SMA) were activated in the FP with the left hand. In the FEP with either hand, bilateral premotor and left parietal areas and ipsilateral cerebellum were also activated as well as contralateral sensorimotor area and SMA. Our results suggest that successful performance of the FEP requires the participation of more brain areas than FP, which may explain why some patients without frontal lobe damage failed to perform the FEP.

Five-year retrospective changes in hippocampal atrophy and cognitive screening test performances in very mild Alzheimer's disease: the Tajiri Project

The medial temporal lobe, especially the hippocampus, is important for normal cognitive function. especially for memory, and is the region with the earliest and most extensive pathological changes in Alzheimer's disease (AD). We investigated the atrophic changes of the hippocampus over a 5-year period and its relation to cognitive screening test performances in normal elderly subjects, those with very mild AD, and patients with AD. Fifty-seven elderly subjects without a moderate or greater degree of cerebrovascular disease as shown by MRI were randomly selected from the town of Tajiri. Thirty-three subjects with a clinical dementia rating (CDR) of 0 (normal), 18 CDR-0.5 (very mild AD) subjects, and six CDR-1&2 (AD) subjects underwent MRI and the Mini Mental State Examination (MMSE) twice during the period. Retrospective changes in the hippocampal width and the MMSE scores were evaluated. There were significant CDR group effects for the changes in the mean bilateral hippocampal widths and the MMSE scores. Normal subjects did not show cognitive decline, although there was a slight tendency for hippocampal atrophy. A significant and meaningful Spearman's correlation was noted between left hippocampal atrophy and the MMSE scores over the 5-year period for the CDR-0.5 group. These CDR-0.5 subjects met the MCI (mild cognitive impairment) criteria as proposed by the consensus paper. Findings suggested that normal elderly subjects maintain a high level of cognitive functions for at least 5 years, although hippocampal atrophy might occur. Atrophic change of the left hippocampus might be a good marker of the very early stage of AD.

Dissociation of body-centered and stimulus-centered representations in unilateral neglect

BACKGROUND

Previous studies on unilateral neglect have shown that there are at least two types of neglect-i.e., body-centered and stimulus-centered neglect. These symptoms suggest that the human brain has at least two different reference frames for processing external space. It is unknown, however, whether these two frames are represented independently in the brain and if so, which areas (or networks) of the brain are responsible for each frame of reference.

OBJECTIVE

To determine whether body-centered neglect and stimulus-centered neglect can be dissociated in patients with brain injury.

METHODS

New figure discriminative cancellation tasks were designed to simultaneously assess body-centered neglect and stimulus-centered neglect. Two neglect patients with lesions located in different anatomic regions were required to circle every complete figure and to cross out every figure with a missing portion on a sheet of white (29.7 x 42 cm) paper.

RESULTS

Patient 1 omitted leftward stimuli on the paper, but the stimuli he found were correctly circled or crossed out. On the other hand, Patient 2 marked stimuli across the paper although he mistakenly circled stimuli that were missing a portion of their left side. Neither patient manifested interaction between the two types of neglect.

CONCLUSION

The results of this study clearly showed double dissociation between the two types of neglect. Furthermore, it not only provides evidence that there are two distinct systems of reference frame for external space in the human brain, but also adds new knowledge indicating that these two systems function independently, at least in part.

Cognitive function and frontal lobe atrophy in normal elderly adults: Implications for dementia not as aging-related disorders and the reserve hypothesis

We examined the relations between cognitive function and age and education in the normal elderly population. As per the community-based stroke, dementia, and bed confinement prevention in the town of Tajiri, neuropsychological assessments, including the Cognitive Ability Screening Instrument (CASI), were performed for 99 randomly selected normal elderly subjects. We assessed the frontal function (working memory, word fluency, Trail-Making Tests, CASI subitems of list-generating fluency, attention, and concentration/mental manipulation), language function (proverbs, CASI subitem language), non-language function (the digit symbol test of the Wechsler Adult Intelligence Scale-Revised (WAIS-R), CASI subitem visual construction), memory (Alzheimer's Disease Assessment Scale recall/recognition, story recall, CASI subitems short and long-term memory, the Rey-Osterrieth Complex Figure Test), and the global function (CASI subitems orientation and abstraction and judgment). We found that the only test affected by age was the digit symbol test of the WAIS-R. The effects of education were distributed among various tests. There was a significant correlation between age and the frontal lobe atrophy in the lower educated group. The present findings suggest that cognitive function is spared by the aging process itself and dementia should be considered as age-related, not aging-related disorders, and that education might have a protective effect on cognitive change, supporting the reserve hypothesis.

[Qualitative features of confabulation in a case with basal forebrain amnesia]

We investigated qualitative features of confabulation in a case with basal forebrain amnesia. A 66-year-old, right-handed woman with a 8th-grade education, was admitted to the Rehabilitation Department of Tohoku University Hospital, Japan, for evaluation and therapy of amnesia. Her previous medical history included hypertension. Nine months before admission, she went to a hospital because of headache and blurred vision. She was diagnosed as suffering from a suprasellar arachnoid cyst and unruptured aneurysm at the anterior communicating artery. Five months later, resection of the cyst and clipping of the aneurysm was performed. After the operation, she became disoriented and amnesic with marked confabulation. On admission to our hospital 3 months later, she was alert and cooperative. Detailed neuropsychological assessment was performed during the next two months. She remained clinically stable throughout her hospitalization. Neurological examination showed no abnormalities. Brain magnetic resonance images revealed lesions in the bilateral orbito-frontal cortices and basal forebrain. Measurement of blood flow with 123I-IMP single photon emission computed tomography showed hypoperfusion in the bilateral frontotemporal regions. We performed systematic investigations to clarify the qualitative features of her confabulations. Her confabulations included many facts she had experienced before, but they were out of context. Each fact was recalled in isolation or associated with erroneous places, persons or times. Her confabulations were never fantastic or momentary in nature, but were consisted with isolated facts. Experimental investigation revealed that she could recognize individual facts (a person, a place, a task and time) in each episode. However, she could not integrate individual facts into an episode. We propose calling this type of confabulation "mosaic confabulation".

Pure anarthria with predominantly sequencing errors in phoneme articulation: a case report

A 77-year-old left-handed man presented with pure anarthria following cerebral infarction. The lesion was restricted to the right precentral gyrus extending to the immediately underlying subcortical white matter and the frontal part of the insular cortex. Qualitative analysis of anarthria revealed that half of the phonemic-articulatory errors in spontaneous speech were sequencing ones. Sequential errors were detected at the phoneme level in both consonants and vowels, and at the syllable level. Most of the sequential errors were pre-positioning. Sequential errors were observed both within and across words. In clear contrast with anarthria, writing and comprehension was preserved, which suggested the problem was limited to oral expression. Our findings provide further support that the precentral gyrus and/or the insular cortex of the language dominant hemisphere is responsible for the temporal sequencing of the articulatory programming.

Global intellectual deterioration in Alzheimer's disease and a reverse model of intellectual development: an applicability of the Binet scale

Since intellectual deterioration in Alzheimer's disease (AD) might be considered to demonstrate a reverse of the intellectual development of children, we herein investigated the applicability of the Tanaka-Binet Intelligence scale (TB scale). This scale can assess the mental age (MA) and the lower-limit age (LLAge) values, and was reported to be correlated with the tasks determining Piaget's developmental stages of intelligence. Thirty AD patients and 30 age-matched normal control subjects were examined with the scale. We found that the mean MA values of the AD patients and controls were 97.4 and 150.3 months, respectively. In the control group, there were significant correlations between the MA and chronological age, and between the MA and years of education. In the AD patients, there was a significant correlation between the MA and the MMSE score. Regarding the LLAge for the AD patients, similar to the theory of Piaget, there was a tendency that they could be classified into three LLAge groups. We consider that the TB scale is useful in assessing the intellectual function in AD patients.

Hemispatial visual-searching impairment correlated with decreased contralateral parietal blood flow in Alzheimer disease

BACKGROUND

Impairment of visuospatial attention in Alzheimer disease (AD) has not been fully investigated. Mendez et al reported that patients with AD showed hemispatial biases on visual search tasks. Parietal lobe involvement might be related to such impairment. The Picture Description Task is one of the most sensitive tests for detecting language disorders and might be also useful in assessing visual search.

OBJECTIVE

The applicability of the Picture Description Task for evaluating hemispatial visual search impairment of AD was investigated, as well as whether the hemispheric difference in parietal blood flow is related to such impairment.

METHODS

Thirty-four patients with AD and age-matched 16 normal subjects performed the Picture Description Task. The elements of the picture were divided into three portions: the right portions (five elements), the central portions (two elements), and the left portions (five elements), so as to assess the patients' hemispatial visual searching ability. Using single photon emission CT, the absolute regional cerebral blood flow (CBF) values at resting condition were calculated by the method of Kuhl et al.

RESULTS

Fourteen patients with AD showed a decreased number of elements pointed out in the left portion of the picture, whereas 12 patients had decreased attention in the right portion. The remaining eight pointed only to the central portion. None of them showed hemispatial neglect on the figure copying tasks. The patients with decreased left spatial attention had lower CBF in the right parietal lobe, and vice versa. A significant negative (biologically meaningful) Spearman correlation was found between the right-left indices of the elements pointed out in the picture and the CBF values.

CONCLUSIONS

The results suggest that the Picture Description Task is useful for assessing visual search, and impaired hemispatial visual search in AD is related to decreased contralateral parietal blood flow. The right-left asymmetry of the parietal CBF might be associated with hemispatial visual attention impairments in AD.

A 5-year retrospective examination of cognitive screening test stages in normal older adults and patients with Alzheimer's disease: the Tajiri project

One conception of aging and cognitive deterioration is that cognitive decline becomes common with age, and dementia may be regarded as one extreme of the continuum. An alternative conception is that the cognitive process is spared by the aging process itself and that cognitive functioning of normal older adults and those with slight cognitive impairment, a CDR (Clinical Dementia Rating) score of 0.5 (suspected dementia), should be different. We examined changes in the screening test performances of 170 older adults over a 5-year period and found the following: (a) The CDR 0 (normal) participants did not show remarkable changes even in the older groups and (b) the subitems of orientation, memory, and so forth were useful for distinguishing normal older adults from early Alzheimer's disease patients. The results support the idea that dementia is better conceptualized as an age-related than as an "aging-related" disorder and that a CDR score of 0.5 should be considered very mild Alzheimer's disease.

Elderly Japanese emigrants to Brazil before World War II: I. Clinical profiles based on specific historical background

OBJECTIVE

To research the demographic and clinical profiles of elderly Japanese emigrants, who arrived in Brazil before World War II, in order to give them appropriate psychogeriatric care.

DESIGN

Elderly Japanese immigrants aged 65 years and over, belonging to the Miyagi Association in the São Paulo Metropolitan Area, were targeted. They emigrated from Miyagi Prefecture to Brazil and are now living in the area. We were able to interview 166 respondents. All data were gathered using standardized interview methods covering (a) free interview about the immigration history, (b) demographics, and (c) physical status.

RESULTS

Through the free interview, we found their immigration histories, which affected their clinical profiles. The mean age and educational level were 77.5 years and 6.3 years, respectively. Sixty per cent of them immigrated when they were younger than 14. Ninety-four per cent of them still keep Japanese nationality. Fifty-seven per cent of them usually use Japanese, while 10% of them use Portuguese. Although their emigration histories were hard, 76% of them perceived their health as being excellent or relatively good. The percentages of subjects with histories of disease were hypertension, 52.5%; cardiac disease, 20.8%; diabetes mellitus, 24.2%; and hyperlipidemia, 25.0%, which were affected by the Brazilian environment.

CONCLUSION

The elderly Japanese who emigrated to Brazil before World War II have a unique historical and demographic background. Their clinical profiles cannot be fully understood without knowing their histories. They definitely need high quality international psychogeriatric care.

Elderly Japanese emigrants to Brazil before World War II: II. Prevalence of senile dementia

BACKGROUND

We previously showed the prevalence of dementia in the town of Tajiri (Miyagi Prefecture, Japan), and found it to be 8.0%. The first population-based study on dementia in Brazil (Catanduva) disclosed the prevalence as being 7.1%. To evaluate the effects of environment on development of dementia, elderly Japanese immigrants living in Brazil were examined. Brazil is the country with the largest number of Japanese immigrants.

METHODS

All immigrants aged 65 years and over from Miyagi Prefecture, living in the four cities of the São Paulo Metropolitan area were targeted (n = 192). We were able to examine 166 subjects (86.5%). The diagnosis of dementia was based on the DSM-IV with the severity assessed by the CDR (clinical dementia rating) scales. The cognitive ability screening instrument (CASI) was used for neuropsychological assessment.

RESULTS

Thirteen subjects were diagnosed with dementia, CDR 1-3, the prevalence being 7.8%. Older subjects suffered more from dementia, and, paradoxically, the more highly educated subjects also suffered more. All the CASI items, except for long-term memory and visual construction, significantly deteriorated in the CDR 0.5 group compared with the CDR 0 group.

COMMENTS

The prevalence of dementia was not thought to be affected by environmental factors. A paradoxically higher rate of dementia in the more educated subjects was probably due to the historical problems of the immigrants. Intact CASI item long-term memory in the CDR 0.5 group indicated that suspected dementia patients could maintain this function. This is the first epidemiological study on dementia in elderly Japanese immigrants in Brazil.

Depressive symptoms and associated factors in a cognitively normal elderly population: the Tajiri Project

BACKGROUND AND OBJECTIVE

Since depression is one of the main problems of elderly subjects, it is important to examine the prevalence of this condition and to identify associated factors.

METHODS

A total of 1525 cognitively normal subjects aged 65 years and over in the town of Tajiri, a typical agricultural town in Japan, were analysed. Their MMSE (mini-mental state examination) scores were 24 or over. Depressive state was assessed by Zung's SDS (self-rating depression scale) with a comprehensive interview to examine ADL, demographics and symptoms associated with illness, etc. The prevalence of depression was calculated. To determine the factors associated with depression, the t-test and the Chi-square test were used. To examine the relative strength of each factor, logistic regression analysis was performed.

RESULTS

The ratio of the depressive subjects was 6.4%, lower than those of previous reports, probably due to the effect of excluding dementia subjects. The ratio for older females aged 80 years and over was 14.3%, which was significantly higher than that of the males. Among socio-demographic factors, sex, age, number of children and perception of economic status, were significantly related. For health status and ADL, such factors as perception of health and medical history of heart disease and rheumatism were related. For familial and social status, factors such as daily activity and several conversation abilities were related. The logistic regression analysis indicated that perception of health and daily activity were associated.

CONCLUSIONS

In this study, we isolated some factors related to depression in a cognitively normal population. Knowledge of such factors is important for appropriate mental care of aged subjects.

Pure Kana agraphia as a manifestation of graphemic buffer impairment

We report a left-handed man who demonstrated a pure agraphia limited to words written in Kana characters (syllabograms) following a right putaminal hemorrhage. Writing words in Kanji characters (logograms) was well preserved. His performance in Kana writing was characterized by intact ability to write single syllables, error increase in the second half of words directly proportional to the word length and correct but slow writing of words using kana blocks. Errors were more prominent in Hiragana words than Katakana words which are usually used to transcribe foreign words. Acoustic-grapheme sequencing per se was not impaired as shown by his correct performance in arranging character blocks. These findings suggest selective damage to the graphemic buffer, a module that temporarily maintains the graphemic representation elaborated in previous stages before it is sent to the peripheral systems for its motor realization.

The influence of misnaming on object recognition: a case of multimodal agnosia

We present a case of multimodal agnosia in the visual and tactile modality due to an infarction in the territory of the left posterior cerebral artery. The patient's ability to recognize objects fluctuated depending on his verbal activity. When he misnamed presented objects, he tended to use them and to draw them in keeping with the wrong name. We submit that the mechanism causing associative agnosia is more dynamic than it was hitherto considered. It originates from the rivalry between top-down central regulation and bottom-up peripheral flow.

Neuroanatomical discrimination between manipulating and maintaining processes involved in verbal working memory; a functional MRI study

We used functional magnetic resonance imaging (fMRI) to investigate neural correlates of processes concerning store and manipulation in verbal working memory. We prepared a revised lag 1 digit span, digit span and a simple number detection task. Specific activities in association with manipulating process were identified in the right middle (BA 9/46) and left precentral gyrus (BA 6). Activated areas specific to maintaining process were detected in the right middle (right BA 11/10) and medial (BA 6) frontal gyri, the right inferior parietal lobule (BA 40), and the left middle (BA 9) and inferior frontal gyri (BA 44). The process-nonspecific activated areas common to two processes were identified in the right inferior frontal gyrus (BA 47) and the left superior parietal lobule (BA 7). Using the signal percent change of each subject, we calculated the correlation coefficients among each activated area. The results of this analysis showed that two processes of verbal working memory were clearly discriminated. The two essential processes of manipulation and maintenance in working memory seem to activate process-specific and overlapping (process-nonspecific) areas, but the patterns of combination were definitely different.

[A case of crossed aphasia with echolalia after the resection of tumor in the right medial frontal lobe]

We report a right-handed woman, who developed a non-fluent aphasia after resection of astrocytoma (grade III) in the right medial frontal lobe. On admission to the rehabilitation department, neurological examination revealed mild left hemiparesis, hyperreflexia on the left side and grasp reflex on the left hand. Neuropsychologically she showed general inattention, non-fluent aphasia, acalculia, constructional disability, and mild buccofacial apraxia. No other apraxia, unilateral spatial neglect or extinction phenomena were observed. An MRI demonstrated resected areas in the right superior frontal gyrus, subcortical region in the right middle frontal gyrus, anterior part of the cingulate gyrus, a part of supplementary motor area. Surrounding area in the right frontal lobe showed diffuse signal change. She demonstrated non-fluent aprosodic speech with word finding difficulty. No phonemic paraphasia, or anarthria was observed. Auditory comprehension was fair with some difficulty in comprehending complex commands. Naming was good, but verbal fluency tests for a category or phonemic cuing was severely impaired. She could repeat words but not sentences. Reading comprehension was disturbed by semantic paralexia and writing words was poor for both Kana (syllabogram) and Kanji(logogram) characters. A significant feature of her speech was mitigated echolalia. In both free conversation and examination setting, she often repeated phrases spoken to her which she used to start her speech. In addition, she repeated words spoken to others which were totally irrelevant to her conversation. She was aware of her echoing, which always embarrassed her. She described her echolalic tendency as a great nuisance. However, once echoing being forbidden, she could not initiate her speech and made incorrect responses after long delay. Thus, her compulsive echolalia helped to start her speech. Only four patients with crossed aphasia demonstrated echolalia in the literature. They showed severe aphasia with markedly decreased speech and severe comprehension deficit. A patient with a similar lesion in the right medial frontal lobe had aspontaneity in general and language function per se could not be examined properly. Echolalia related to the medial frontal lesion in the language dominant hemisphere was described as a compulsive speech response, because some other 'echoing' phenomena or compulsive behavior were also observed in these patients. On the other hand, some patients with a large lesion in the right hemisphere tended to respond to stimuli directed to other patients, so called 'response-to-next-patient-stimulation'. This behavior was explained by disinhibited shift of attention or perseveration of the set. Both compulsive speech responses and 'response-to-next-patient-stimulation' like phenomena may have contributed to the echolalia phenomena of the present case.

Judging semantic and episodic incongruity: a magnetoencephalographic study

Evoked magnetic fields over the entire head were measured during a semantic judgment task, in which conditions of the pre-test learning session were manipulated. Subjects learnt related and unrelated category-noun pairs, and were then asked to judge the relationship between category and noun. Unrelated pairs evoked activation around 400 ms in the left temporal area. In addition, newly presented related pairs, of which the categories were used to learn unrelated pairs, also evoked similar activities. Our findings suggest that these activities are not only related to the semantic incongruity between a pair of words as in previous studies, but also to the episodic incongruity between the learning and measurement sessions.

Isolated and focal retrograde amnesia: a hiatus in the past

Two cases of isolated retrograde amnesia were reported. Both showed the same clinical pattern in development and resolution of amnesia despite of different etiologies. Sudden insult to the brain (trauma in Case 1 and viral encephalitis in Case 2) caused concurrent antero- and retrograde amnesia. Fortunately both recovered from the anterograde amnesia completely. However, both were left with a period of postictal amnesia of a few months and retrograde amnesia of up to 14 months' duration. The analysis of their pattern of temporal evolution and dissolution of amnesia support the hypothesis that recently acquired episodic information requires a certain amount of constant activation for a certain period of time in order to be organized into a durable memory. The nature of this activation as well as its origin remains to be solved.

Ideomotor apraxia in patients with Alzheimer disease: why do they use their body parts as objects?

OBJECTIVE

Difficulty in pantomiming the use of tools is observed in patients with Alzheimer disease. Patients with Alzheimer disease tend to use their body parts as objects when they try to pantomime the use of tools. The body-parts-as-objects phenomenon was thought to consist of appropriate gross movement of patients' arms despite inappropriate patterns of handling tools with their hands. However, the mechanism has not been investigated fully.

METHODS

The authors examined 11 healthy individuals and 24 patients with Alzheimer disease for ability to recognize tools, to pantomime the use of tools, to use actual tools, and to select an appropriate photograph of a handling pattern of the tool.

RESULTS

In comparison with the patients with Alzheimer disease, the healthy individuals had higher scores for all tasks. The authors classified the patients into group A (patients with higher pantomime scores), group B (patients with middle level scores), and group C (patients with lower scores). Frequency of use of body parts as objects for patients in group B was higher than that of patients in group A and in group C. The mean Mini-Mental State Examination score for patients in group A was higher than that of patients in group B and in group C. In comparison with patients in group A, patients in group B showed lower scores on the hand-posture discrimination task without a tool, even after controlling the Mini-Mental State Examination score.

CONCLUSIONS

The authors conclude that body-parts-as-objects responses in patients with Alzheimer disease occur because general cognition is lowered or because retrieval ability of the appropriate holding posture for tools is impaired.

[A dynamic neuropsychological approach]

There are at least two approaches in evaluating neuropsychological patients. One is to analyze negative symptoms and find a correlation between a damaged brain lesion and a lost function. The other is to focus on the nature of positive symptoms and find a principle ruling a behavioral change caused by a lesion. Although both approaches are equally important, I focused on the latter approach in this symposium. Two syndromes, i.e. forced manipulation of tools and hyperlexia are interpreted in terms of the rivalry between the top-down process of inhibition and bottom-up process of stimulus processing, resulting in the predominance of the latter. Two other symptoms, i.e. misperception in a case of associative visual agnosia and habitual behavior in a frontal damaged-dementia are interpreted in the same terms, but resulting in the predominance of the top-down process. These syndromes clearly illustrate that the behavior is organized on the dynamic balance between the information generated internally and the one coming in from the environment.

Intact verbal description of letters with diminished awareness of their forms

Visual processing and its conscious awareness can be dissociated. To examine the extent of dissociation between ability to read characters or words and to be consciously aware of their forms, reading ability and conscious awareness for characters were examined using a tachistoscope in an alexic patient. A right handed woman with 14 years of education presented with incomplete right hemianopia, alexia with kanji (ideogram) agraphia, anomia, and amnesia. Brain MRI disclosed cerebral infarction limited to the left lower bank of the calcarine fissure, lingual and parahippocampal gyri, and an old infarction in the right medial frontal lobe. Tachistoscopic examination disclosed that she could read characters aloud in the right lower hemifield when she was not clearly aware of their forms and only noted their presence vaguely. Although her performance in reading kanji was better in the left than the right field, she could read kana (phonogram) characters and Arabic numerals equally well in both fields. By contrast, she claimed that she saw only a flash of light in 61% of trials and noticed vague forms of stimuli in 36% of trials. She never recognised a form of a letter in the right lower field precisely. She performed judgment tasks better in the left than right lower hemifield where she had to judge whether two kana characters were the same or different. Although dissociation between performance of visual recognition tasks and conscious awareness of the visual experience was found in patients with blindsight or residual vision, reading (verbal identification) of characters without clear awareness of their forms has not been reported in clinical cases. Diminished awareness of forms in our patient may reflect incomplete input to the extrastriate cortex.

Atrophy of the corpus callosum correlates with white matter lesions in patients with cerebral ischaemia

Many studies of white matter high signal (WMHS) on T2-weighted MRI have disclosed that it is related to cerebral ischaemia and to brain atrophy. Atrophy of the corpus callosum (CC) has also been studied in relation to ischaemia. Our objective was to test the hypothesis that CC atrophy could be due to ischaemia. We therefore assessed CC, WMHS and brain atrophy in patients with risk factors without strokes (the risk factor group) and in those with infarcts (the infarct group), to investigate the relationships between these factors. We studied 30 patients in the infarct group, 14 in the risk factor group, and 29 normal subjects. Using axial T1-weighted MRI, cortical atrophy and ventricular enlargement (brain atrophy) were visually rated. Using axial T2-weighted MRI, WMHS was assessed in three categories: periventricular symmetrical, periventricular asymmetrical and subcortical. Using the mid-sagittal T1-weighted image, the CC was measured in its anterior, posterior, mid-anterior and mid-posterior portions. In the normal group, no correlations were noted between parameters. In the infarct group, there were significant correlations between CC and brain atrophy, and between CC atrophy and WMHS. After removing the effects of age, gender and brain atrophy, significant correlations were noted between some CC measures and subcortical WMHS. In the risk factor group, there were significant correlations between CC and brain atrophy and between CC atrophy and WMHS. After allowance for age, gender and brain atrophy, significant correlations between some CC measures and periventricular WMHS remained. The hypothesis that CC atrophy could be due to cerebral ischaemia was supported by other analyses. Namely, for correlations between the extent of infarcts and partial CC atrophy in patients with anterior middle cerebral artery (MCA) and with posterior MCA infarcts, there were significant correlations between the extent of infarct and mid-anterior CC atrophy in the former, and posterior CC atrophy in the latter. Our findings could indicate that CC atrophy is associated with cerebral ischaemia.

The nature of age-related decline on the reading span task

We examined the effect of age on working memory with a reading span task (RST) together with other verbal span tasks. Sixty-two participants were divided into three subgroups (young, middle-aged, and elderly). The RST performances were significantly different among all the subgroups. To elucidate which component of the working memory system is affected by age, we performed an analysis of covariance with the scores of simple and complex verbal span tasks as covariates. From the results, we conclude that the difference of the RST performance between the middle-aged and elderly groups reflects a decline in the capacity of the phonological loop, and the difference between the young and middle-aged groups reflects malfunctioning of the central executive system.

[The left central gyral lesion and pure anarthria]

We report a very rare case of pure anarthria with lesion analysis. A 44-year-old right-handed man suffered from a cerebral infarction with a mild right hemiparesis and speech disturbance. An MRI of the brain 1.5 months post onset revealed a lesion confined to the left central gyrus. One month after the onset, his spontaneous speech was dysprosodic and laborious. It was contaminated with dysarthria and phonological paraphasias. However, language comprehension, repetition and naming abilities were normal. Most remarkably he showed no impairment in writing with his left hand. Over the following months, his difficulties in verbal output showed general amelioration, but the isolated impairment in the domain of articulation characterized by dysprosody, dysarthria, and phonological paraphasia persisted. As for the symptomatology of pure anarthria resulting from precentral gyral lesions, there have been controversies about its pureness. Some argue that the so called pure anarthria always shows some degree of writing disturbances, albeit mild in degree. Others maintain there certainly exists the pure type without any signs of agraphia. In the present case lesions were limited to the central gyrus but spared the lowest opercular portion. The previous reports of pure anarthria that had mild agraphia all had lesions involving the opercular portion. We conclude the sparing of this area is most likely related with sparing of writing capacity in pure anarthria.

Apraxia of single tool Use

We report a 72-year-old right-handed man who showed an 'apraxia of tool use' after a cerebral infarct in the territory of the left middle cerebral artery. His apraxia of tool use was characterized by a clear dissociation between the inability to use a single tool and the ability to use plural tools. Most of the errors occurred in selecting an appropriate target where a tool is expected to be applied. Detailed examinations confirmed that his conceptual knowledge of tool use was well preserved. Furthermore, when a target of a tool was provided as a cue, he used a single tool correctly. These results suggest that his inability to use a single tool originated from his inability to evoke a target image from an actual tool.

[Hyperlexia in an adult patient with lesions in the left medial frontal lobe]

A 69-year-old right-handed woman developed a transcortical motor aphasia with hyperlexia following resection of a glioma in the left medial frontal lobe. Neurological examination revealed grasp reflex in the right hand and underutilization of the right upper extremity. An MRI demonstrated lesions in the left medial frontal lobe including the supplementary motor area and the anterior part of the cingulate gyrus, which extended to the anterior part of the body of corpus callosum. Neuropsychologically she was alert and cooperative. She demonstrated transcortical motor aphasia. Her verbal output began with echolalia. Furthermore hyperlexia was observed in daily activities and during examinations. During conversation she suddenly read words written on objects around her which were totally irrelevant to the talk. When she was walking in the ward with an examiner she read words written on a trash bag that passed by and signboards which indicated a name of a room. Her conversation while walking was intermingled with reading words, which was irrelevant to the conversation. She also read time on analog clocks, which were hung on a wall in a watch store. In a naming task, she read words written on objects first and named them upon repeated question about their names. When an examiner opened a newspaper in front of her without any instructions she began reading until the examiner prohibited it. Then she began reading again when an examiner turned the page, although she remembered that she should not read it aloud. She showed mild ideomotor apraxia of a left hand. Utilization behavior, imitation behavior, hypergraphia, or compulsive use of objects was not observed throughout the course. Hyperlexic tendency is a prominent feature of this patient's language output. Hyperlexia was often reported in children with pervasive developmental disorders including autism. There are only a few reports about hyperlexia in adults and some of them were related to diffuse brain dysfunction. Hyperlexia of our patient was associated with echolalia but not with the other "echo" phenomena, which may be because the lesion was unilateral on the left side. Dysfunction of the left supplementary motor area could lead to disinhibition of regulatory mechanism of verbal output in response to auditory and visual stimuli.

Retention of words in long-term memory: a functional neuroanatomical study with PET

We used PET to identify brain regions associated with retention of verbal materials in long-term memory. During a PET scan, subjects repeated many sets of words one after another. In a retention condition, they were simultaneously required to retain 10 key words that were irrelevant to the repetition task. Significant increases in regional cerebral blood flow during the retention condition were found in bilateral parahippocampal regions, the left prefrontal and parietal association cortices, the supplementary motor area, the neostriatum and the cerebellum. We clearly demonstrated that retention of verbal materials was accompanied by neural activities in the medial temporal lobes. We also showed that, in the early phase, retention of words in long-term memory recruited left cortical areas surrounding those relevant to verbal short-term memory.

Human cerebellum plays an important role in memory-timed finger movement: an fMRI study

The purpose of this study was to determine, by using functional magnetic resonance imaging, the areas of the brain activated during a memory-timed finger movement task and compare these with those activated during a visually cued movement task. Because it is likely that subjects engage in subvocalization associated with chronometric counting to achieve accurate timing during memory-timed movements, the authors sought to determine the areas of the brain activated during a silent articulation task in which the subjects were instructed to reproduce the same timing as for the memory-timed movement task without any lip movements or vocalization. The memory-timed finger movement task induced activation of the anterior lobe of the cerebellum (lobules IV and V) bilaterally, the contralateral primary motor area, the supplementary motor area (SMA), the premotor area (PMA), the prefrontal cortex, and the posterior parietal cortex bilaterally, compared with the resting condition. The same areas in the SMA and left prefrontal cortex were activated during the silent articulation task compared with the resting condition. The anterior lobe of the cerebellum on both sides was also activated during the silent articulation task compared with the resting condition, but these activations did not reach statistical significance (P < 0.05 corrected). In addition, the anterior cerebellum on both sides showed significant activation during the memory-timed movement task when compared with the visually cued finger movement task. The visually cued finger movement task specifically activated the ipsilateral PMA and the intraparietal cortex bilaterally. The results indicate that the anterior lobe of the cerebellum of both sides, the SMA, and the left prefrontal cortex were probably involved in the generation of accurate timing, functioning as a clock within the CNS, and that the dorsal visual pathway may be involved in the generation of visually cued movements.

Prevalence of senile dementia in a rural community in Japan: the Tajiri project

Knowledge of the prevalence of dementia in different age groups is needed for the planning of a health policy. This study shows the prevalence of dementia and magnetic resonance imaging (MRI) findings in elderly people aged 65 years and over, living in the town of Tajiri in the northern part of Japan. They were shown by two cognitive screening tests, the Mini-Mental State examination (MMS) and the Dementia Screening Test (DST) and medical diagnosis. Two subject groups were assessed, those who completed both tests (Subjects I, n=2066) and those from among the 200 'MRI-administered subjects' who were interviewed and diagnosed (Subjects II, n=170). For Subjects I, there were 6.3 and 10.2% 'dementia range' according to the severe and mild criteria, respectively. As for Subjects II, 9.4% were clinically diagnosed as having dementia. They met the National Institute of Neurological and Communicative Disorders and Stroke and the Alzheimer's Disease and Related Disorders Association (NINCDS-ADRDA) criteria of probable Alzheimer's disease (AD) or possible AD with cerebrovascular disease. The estimated prevalence rate of dementia was 8.0%. Visual ratings of brain atrophy using MRI disclosed two distribution patterns. The 'continuous' pattern of the frontal and temporal lobes atrophy suggest that both are affected by the aging process, while a 'discontinuous' pattern of the hippocampal atrophy could indicate a pathologic background such as early changes of AD.

[Effect of number of syllables in word repetition]

We report a case of non-fluent conduction aphasia. The patient was a 59-year-old right-handed male. He suffered from aphasia after a left internal carotid artery occlusion. MRI study revealed subcortical lesions in the left inferior frontal gyrus and cortical lesion in the anterior part of the left insular gyrus and the left postcentral gyrus. The patient showed good comprehension of words and daily conversation but had a common difficulty in the following tasks; naming of pictures, repetition of words, reading of kanji and kana letters. In these tasks, the phonological output of the patient contained many literal paraphasias and there was a tendency that errors appeared more in the posterior portion of a target word. We analyzed the position of errors in the target word on word repetition tasks. The result confirmed the above observation. We speculate that the length of a target word may have played a critical rote in this patient's repetition capability.

Disproportionate retrograde amnesia in a patient with herpes simplex encephalitis

We describe a patient who developed a severe but temporally limited retrograde amnesia coupled with a relatively mild anterograde amnesia following herpes simplex encephalitis. The patient showed a profound retrograde amnesia for autobiographical events extending for about 10 years prior to the disease onset. Her knowledge about public events and famous persons was also impaired for this period. An MRI and SPECT demonstrated bilateral medial temporal pathology. This case represents a further instance of a relatively focal retrograde amnesia following brain damage. We review other reported cases with focal retrograde amnesia and consider theoretical and neuroanatomical accounts for the present case. Two factors may account for her amnesic patterns: a partial disruption of the store for premorbid binding codes (i.e., information that multimodal feature representations occurred synchronously); along with a relative preservation of the encoding process required to develop new synchronous codes.

[Episodic and semantic memory after traumatic brain injury in a child]

In an early-life, a memory disturbance affects the learning and school record directly. Furthermore, it may cause the problem of maltreatment or adaptation difficulty for school life. We report a child amnesia caused by a traumatic brain injury when she was 9 years old. We examined her episodic and semantic memory. We developed 3-steps tasks of recognition and recall for the post-accident episodic memory. First, the examiner presented the patient with four words orally including a label of her episode, and asked her to choose one that she felt familiar with (the recognition of the episodic label). Second, if the word she selected was correct, she was required to recall the episode related to the word (the recall of the episode). Third, if she could not recall the episode herself correctly, she was required to choose a correct sentence about the episode (the recognition of the episode). She could not recall episodes correctly, but produced confabulation instead. She showed, however, good recognition of each episode. Furthermore, we performed recognition tests of time, person, and place about the same post-accident episodes, which were poor especially for time. In semantic memory tasks, we examined about kanji characters (ideogram) learned from the first grade to the sixth grade and mathematical knowledge learned from the second grade to the sixth grade at elementary school ("What centimeters is equal to one meter?" or "Tell me the formula of the size of a circle." etc). We found that she showed a retrograde impairment for about one year. For both episodic and semantic memory, she showed an anterograde impairment. Because of the anterograde amnesia she could not acquire new facts, and also showed para-amnesia or confabulation. In a child with brain damage, neuropsychological assessment is important in predicting effect of rehabilitation and recovery of school performance.

[Two cases of fluent aphasia with selective difficulty of syllable identification]

We report two aphasic patients who could discriminate Japanese syllables but could not identify them. Case 1 was a 51-year-old right handed woman with 12-year education. Case 2 was a 50-year-old right handed man with 9-year education. They developed fluent aphasia after a cerebral infarction. Brain MRI of case 1 revealed widely distributed lesions including inferior frontal, superior temporal, angular and supramarginal gyri. Lesions revealed by Brain CT in case 2 included the left superior and middle temporal, angular and supramarginal gyri. Both showed severe impairment of repetition and confrontation naming. No difference of performance was present between repetition of single syllables and polysyllabic words. On the contrary, oral reading of Kana characters were preserved. We examined their ability to perceive syllables in detail. In the discrimination task, they judged whether a pair of heard syllables was same or different. Case 1 was correct in 85% of the tasks and case 2 in 98%. In an identification task, they heard a syllable and chose a corresponding Kana, Kanji, or picture out of 10 respective candidates. Case 1 was correct only in 30% and case 2 in 50% of these tasks. On the other hand, selection of a correct target in response to a polysyllabic word was much better, i.e. 70% in case 1 and 90% in case 2. Based on these data we concluded that (1) syllabic identification is a different process from syllabic discrimination, and (2) comprehension of a polysyllabic word can be achieved even when the precise phonological analysis of continuent syllables are impaired.

Hemispheric asymmetry in a perceptual priming task: evidence from patients with unilateral brain damage

The present study examined the relationship between unilateral brain damage and the effect of nonverbal perceptual priming using a picture-fragment completion task. Subjects consisted of 11 left brain-damaged patients, 8 right brain-damaged patients, and 10 healthy normal controls. The mean score of normal controls was significantly higher than those of left and right brain-damaged patients. Although there were significant effects of priming in all the groups, a significant difference in amplitude of priming effects was found only between right brain-damaged patients and normal controls. The correlation between amount of fragmentation at which there was identification and priming effect was not significant. We conclude that the right hemisphere is more involved in perceptual priming of form than is the left hemisphere, and form-dependent processing in the perceptual priming task has an asymmetrical distribution in the right and left hemispheres.

Proper name anomia after left temporal lobectomy: a patient study

A patient with a selective deficit in retrieving proper names after left temporal lobectomy is reported. He showed proper name anomia in conversation, in response to photographs, and in verbal descriptions, despite being able to provide semantic information about the people he was unable to name. This report provides evidence that the rostral part of the left temporal lobe plays a crucial role in processing proper names without involvement of other verbal functions.

[Reassessment of the Luria's fist-edge-palm test]

In clinical practice, we often use the Luria's fist edge-palm test (FEP) to detect frontal lobe dysfunction. However, we have sometimes encountered patients with failure in this test following posterior lesions. The aim of our study is to evaluate the sensitivity of this test to frontal lobe damage and to clarify the relationship between the FEP performance and other neuropsychological findings. Forty brain-damaged patients (mean age: 61.7 years) were studied. Thirty-four patients were right-handed and 6 non right-handed. Their lesions were confirmed by CT or MRI scan. Following six tests were performed; 1) imitation of single hand posture, 2) imitation of a sequence of two hand postures (fist-edge), 3) imitation of a sequence of three and postures (FEP), 4) copying a cube, 5) serial drawing, and 6) verbal and non-verbal short-term memory span. Imitation of hand postures were performed with non-paralytic hand. Twenty-four patients, i.e., 60% of the patients tested, failed to perform the FEP sequence. The failure was significantly correlated with the presence of constructional disability, perseveration and short-term memory impairment. There was significant relationship between the failure the FEP and frontal lobe damage. However, we found five patients without frontal lesion who failed in performing the FEP. We conclude that we should be careful in associating the failure in the FEP with frontal lobe damage, although this test is sensitive to brain dysfunction.

A normative, community-based study of Mini-Mental State in elderly adults: the effect of age and educational level

We investigated community-based data of the Mini-Mental State Examination (MMSE) scores of elderly residents along with the effects of age and educational level. MMSE was planned for all residents over 65 years of age in a town in northern Japan. The number of elders who took the MMSE was 2,266 (90%). The score significantly declined with age and lower educational level, although no effect of sex was apparent. For the MMSE subitems, all the values except for that of naming showed effects of both age and educational level. Those screened by MMSE who fell in the range of cognitive impairment (< 24) accounted for 21.8% and those with severe cognitive impairment (< 18) constituted 6.0%. Despite the differences in language and culture, the mean scores are remarkably similar between Japan and other countries. This is the first normative, community-based study of MMSE among elderly adults in Japan.

Dissociation of letter and picture naming resulting from callosal disconnection

BACKGROUND

Detailed mapping of the corpus callosum for functional fractionation in humans remains incomplete.

OBJECTIVE

To examine separable interhemispheric transfer of visual information by callosal fibers, especially in the splenium.

METHODS

We examined callosal disconnection signs in a 14-year-old boy with a lesion confined to the posterior part of the splenium and reviewed reported cases with callosal lesions.

RESULTS AND CONCLUSION

The patient presented with left hemialexia as the only manifestation of callosal disconnection syndrome. The only difficulty demonstrated was in reading aloud or copying letters, which were presented tachistoscopically to the left visual field, with his right hand. He could copy letters presented to his left visual field with his left hand, however. Therefore, left hemialexia was not due to hemiamblyopia or hemineglect. There was no anomia for pictures and colors in the left visual field. MRI revealed that the lesion was limited to the ventroposterior end of the splenium. Review of 40 reported patients with callosal lesions suggests that the anterior to middle part of the splenium is involved in transferring picture information from the language-nondominant hemisphere to the language-dominant hemisphere and that the ventroposterior part is involved in transferring letter information.

Participation of the prefrontal cortices in prospective memory: evidence from a PET study in humans

Prospective memory is a memory feature in humans which involves activities for remembering to do something in the future. The present study provides functional neuroanatomy of prospective memory for the first time. We used positron emission tomography (PET) and found several localized brain activations in relation to a prospective memory task required to retain and remember a planned action while performing an ongoing routine activity. Activations were identified in the right dorsolateral and ventrolateral prefrontal cortices, the left frontal pole and anterior cingulate gyrus, the left parahippocampal gyrus, and midline medial frontal lobe. We attributed these activations to several cognitive processes involved in prospective memory, such as holding an intention toward future behavior, checking target items within presented stimuli, and dividing attention between the planned action and the routine activity.

Pure topographical disorientation related to dysfunction of the viewpoint dependent visual system

A 70-year-old woman presented with pure topographical disorientation following haemorrhage in the right medial parietal lobe. She could not navigate in the real world despite good ability to draw maps, describe routes, and identify objects and buildings. Her performance on mental rotation, visual memory, and spatial learning tests also was normal. In contrast, she failed totally in a locomotor map test and in a task in which she was requested to judge viewpoints of buildings. Her highly selective topographical disorientation was probably caused by the inability to identify a viewpoint of a particular building. The lesion may have disconnected the association between the spatial information processed in the lateral parietal lobe and the visual memory mediated by the limbic system, which seems to be important for viewpoint dependent analysis.