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Atsushi Yamadori

Publications and source records attributed to Atsushi Yamadori.

At least 19 recordsLinked to original sources
PubMed2006

Differential involvement of regions of rostral prefrontal cortex (Brodmann area 10) in time- and event-based prospective memory.

Rostral prefrontal cortex (approximating Brodmann area 10) has been shown repeatedly to have a role in the maintenance and realization of delayed intentions that are triggered by event cues (i.e., event-based prospective memory). The cerebral organization of the processes associated with the use of time cues (time-based prospective memory) has however received less attention. In two positron emission tomography (PET) studies we therefore examined brain activity associated with time- and event-based prospective memory tasks. In the time-based condition of the first study, young healthy volunteers were asked to make a prospective response based on their self-estimation of the passage of time while engaged in an attention-demanding ongoing activity. In the time-based condition of the second study, participants had a clock available in the ongoing task display and did not need to estimate the time for the prospective response. In the event-based condition of both studies, participants were asked to make a prospective response when prospective cues were presented in ongoing trials. Both studies showed activation differences in rostral prefrontal cortex according to whether the task was time- or event-based. In study one, an area of left superior frontal gyrus was more active in the time-based condition. In study two, three rostral prefrontal regions were more active in the time-based condition: right superior frontal gyrus, anterior medial frontal lobe and anterior cingulate gyrus. A region in left superior frontal gyrus, different from the area found in the first study, was more active in the event-based condition. These results indicate involvement of multiple brain regions of rostral prefrontal cortex in time- and event-based prospective memory. The results are interpreted as reflecting the differing processing demands made by event- or time-based prospective memory tasks, and the differing demands of time-based tasks according to whether a clock is present as an aid.

Adult↗
PubMed2006

Non-verbal learning is impaired in very mild Alzheimer's disease (CDR 0.5): normative data from the learning version of the Rey-Osterrieth Complex Figure Test.

Mild cognitive impairment (MCI) is a transitional state between normal aging and dementia. Although there have been some studies on the role of verbal memory in learning ability, there have been no reports on the part played by visual memory. In the present study, the Rey-Osterrieth Complex Figure Test (RCFT) was given to healthy subjects and to those with MCI to determine if visual memory was maintained in these two groups. Additionally, normative data from the learning version of the RCFT for Japanese subjects were examined, for purpose of reference. The participants consisted of 381 clinical dementia rating (CDR) 0 subjects and 137 CDR 0.5 subjects who could perform the full set of RCFT tasks. The CDR 0 group had significantly higher scores than the CDR 0.5 group in all trials. The CDR 0 participants also showed a significant step-by-step learning effect, while the CDR 0.5 participants did not show a significant learning effect. These results suggest that the CDR 0 participants maintained intact learning abilities of encoding and retrieval, while the CDR 0.5 participants did not do so; but further studies will be needed to clarify these findings.

Aged↗
PubMed2005

Different MRI findings for normal elderly and very mild Alzheimer's disease in a community: implications for clinical practice the Tajiri Project.

To investigate magnetic resonance imaging (MRI) findings of very mild dementia, 485 participants were randomly selected in a community. Three hundred and forty participants were of Clinical Dementia Rating (CDR) 0 (healthy), 113 were of CDR 0.5 (questionable dementia), and 32 were of CDR 1 and 2 (including 20 Alzheimer's disease, AD). Cortical atrophy, white matter lesion, etc., were visually assessed. We found that each part of the brain showed atrophy in older adults for CDR 0. For CDR 0.5, the relationships between MRI findings and age were weaker, and for AD, there were no such relationship. Atrophy related with dementia severity was found to be limited to the lateral and medial temporal lobes. For CDR 0.5, amygdala atrophy was the only finding indicating CDR effect but no age effect. The amygdala or anterior entorhinal atrophy is important for discriminating very mild dementia from normal elderly.

Age Factors↗
PubMed2005

Dissociable brain activations during the retrieval of different kinds of spatial context memory.

Although memory for spatial information has often been regarded as unitary, it may be divided into two distinct types: memory for the place where an individual experienced an event and memory for the location of an experienced event within a specific reference object. We used functional magnetic resonance imaging (fMRI) to elucidate the distinctions between the retrieval of these two types of spatial context memory. During scanning, subjects judged the room (Place task) in which a photograph had been presented or the location of the photograph on the computer display (R-L task) during the encoding phase. In a control task, subjects were asked to judge whether the photograph had been presented or not. The left middle frontal gyrus, lateral parietal and occipital regions, and bilateral precunei were found to be active during both the Place task and the R-L task compared with the control task. Critically, the place task, compared with the R-L task, was associated with activations in the right lateral prefrontal gyri, the posterior part of the left parahippocampal gyrus, bilateral retrosplenial and lateral parieto-occipital areas, whereas the R-L task, relative to the place task, with activation only in the right lateral parietal cortex. These findings indicate that the retrieval processes of spatial context memory are not associated with a single network, but may vary and recruit different neural networks depending on the type of spatial information to be retrieved.

Adult↗
PubMed2005

Proper name anomia after left temporal subcortical hemorrhage.

We report here a patient with proper name anomia following subcortical hemorrhage in the left superior temporal gyrus. Despite the preserved ability to retrieve common names, the patient could not retrieve the names of people, countries, or racehorses, which he could recognize quite well. Semantic knowledge regarding people, countries, and racehorses was also preserved. In addition. the finding that phonological cueing was effective with preservation of the ability to point to photos corresponding to their names suggested that the lexicon of proper names was preserved in this patient. Thus, the output lexicon appeared to be partially disconnected from semantic knowledge. This rare and limited lesion suggested that the superior temporal gyrus plays an important role in connecting semantic knowledge and the output lexicon.

Anomia↗
PubMed2005

Anomic alexia of kanji in a patient with anomic aphasia.

The ability to read aloud kanji (logogram) words and to comprehend their meaning was systematically examined to clarify the underlying mechanism of kanji alexia in a patient with anomic aphasia. Confrontation naming, reading aloud and reading comprehension tasks were performed using 110 words from 11 semantic categories written in kanji or kana. Performance in oral reading of kanji words was significantly worse than oral reading of the same words transcribed into kana words. In addition, for kanji words reading aloud was much worse than reading comprehension. Oral reading of kanji words had a significant correlation with naming pictures corresponding to the words, but no correlation with comprehension of kanji words. Qualitative analyses demonstrated that errors in oral reading and naming tasks had many features in common. Our results indicated that some common mechanisms underlie both naming and oral reading of kanji words. We propose calling this type of alexia "anomic alexia of kanji", which should be distinguished from kanji alexia with difficulty in both reading aloud and comprehension. Lesions in our patient were located in the middle part of the left middle temporal gyrus and its subcortical area, which could be important for access to the phonological lexicon from semantics.

Aged↗
PubMed2005

[Amnesia following left medial frontal subcortical hemorrhage: a case report].

There has been a controversy as to the contribution of the frontal lobe to human memory function. We describe a 49-year-old right-handed patient with memory disturbance following a left medial frontal subcortical hematoma. Her amnesia was characterized by (1) predominant anterograde amnesia, (2) difficulty in both voluntary recall and recognition tasks, (3) a great number of false-alarm responses in a recognition task, and (4) no confabulation. An MRI demonstrated that her lesion was restricted to the left medial frontal area and anterior cingulate gyrus. This case represents a rare instance of amnesia following damage to the frontal lobe. We speculated that the unique feature of her memory impairment resulted from combined lesions in the medial frontal subcortical white matter and anterior cingulate gyrus. It seems that Papez's circuite participated in the development of these symptoms.

Amnesia↗
PubMed2004

Neural correlates of context memory with real-world events.

There has been little evidence for the difference in the retrieval processes of when and where something happened, one of the important factors in understanding episodic memory. We used positron emission tomography (PET) to identify the neural networks associated with temporal and spatial context memory of events experienced under experimental conditions similar to those of everyday life. Before PET, subjects experienced 36 events. The events were divided into four groups of nine each. The subjects experienced the first two groups of events before a 15-min recess and the other two after the recess; they experienced the first and last groups of events in one room, took a recess in another room, and experienced the second and third groups in a different room. During PET, the subjects were scanned under three different retrieval tasks: a time-retrieval task, a place-retrieval task, and a simple recognition task. The results showed that the retrieval of time and space, compared with the simple recognition, was associated with activity in substantially different regions as well as a common region: time retrieval with the posterior part of the right orbitofrontal cortex and left inferior parietal lobule, place retrieval with two regions in right parietal association cortex, right posterior cingulate gyrus, left precentral gyrus, and right cerebellum, and both with the right inferior frontal gyrus. These findings indicate that there are unique areas, in addition to a common area, for retrieving temporal and spatial context.

Adult↗
PubMed2004

[Visual search training for a case of homonymous field defect with multiple visual dysfunctions].

A 72-year-old right handed man developed right homonymous hemianopia without macular sparing, left homonymous lower quadranopia with macular sparing, cerebral amblyopia, cerebral achromatopsia, impaired form vision, and mild right hemispatial neglect, after multiple cerebral infarctions, involving bilateral occipital cortices. His intelligence and memory were deteriorated moderately. He failed to notice objects located in the affected visual field, because of his severely impaired visual search. When ordinary lighting was used, he showed severe right-sided omissions on the line cancellation test. However, omissions were less marked under the brighter lighting. By using a modified method of Kerkhoff and Vianen (1994), he was trained to make saccadic eye movements toward affected regions to find a target and to search and point at targets arranged randomly. As the sensitivity for contrast of isoluminante red and green stimuli was preserved well at high spatial frequencies despite the decreaced contrast sensitivity for brightness, we used green targets as the training stimuli. After the training, search field and pointing range that could be covered by the patient increased in size for both green and white targets, and daily activities improved. Moreover, after the training, he no longer showed discrepancy in line cancellation performances between ordinary and brighter lighting conditions. In the follow up period, the search field and the performance on the line cancellation test were maintained, while the performance of pointing targets array declined. The family members complained of mild re-deterioration of daily activities. Then, the training for searching and pointing re-introduced at home. After the training, his pointing performance and daily activities, evaluated by questionnaires to his family members, improved again. In conclusion, it was suggested that disordered visual search after a homonymous field defect can be treated effectively, even if multiple visual dysfunctions were associated.

Aged↗
PubMed2004

[Normative data on tests for frontal lobe functions: Trail Making Test, Verbal fluency, Wisconsin Card Sorting Test (Keio version)].

Trail Making Test (TMT Part A, B), Verbal fluency test (phonemic, semantic) and Wisconsin Card Sorting Test (Keio version : KWCST) are useful to evaluate frontal lobe functions and are commonly used in clinical settings. However, few normative data for aged Japanese have been reported. We collected normative data on these tests in elderly population, and examined the effects of age and education on the performance of these tests. Seventy-six healthy adults, aged 45 to 74 years, participated in this study. Subjects were classified into three groups by age (45-54, 55-64, 65-74). Fifty-five subjects repeated the same tests after 6 months to examine the test-retest reliability. Performance of the TMT Part A was correlated with age (r= 0.530) and that of Part B was correlated with age (r=0.500) and education (r=-0.340). Performance on both phonemic and semantic fluency was correlated with education (phonemic: r=0.357, semantic: r=0.279). Number of Categories Achieved (CA) of KWCST was correlated with education (r=0.376). The test-retest reliability of all these tests except for semantic verbal fluency and difficulty maintaining set (DMS) of KWCST was good enough for longitudinal studies.

Aged↗
PubMed2004

[Broca aphasia with neologisms].

Patients with jargon aphasia generally have fluent speech with poor comprehension. However, outstanding jargons may appear in non-fluent aphasics. We report a 69-year-old left-handed woman with non-fluent jargon aphasia due to lesions in the right frontoparietal area. Features of her speech included non-fluent meaningless sequences of syllables, i. e., phonetic jargon, which was obvious in all the tasks including spontaneous speech, repetition, naming and reading. Her utterance was sparse, but not effortful or anarthric. She understood most of spoken single words, but was confused by complex sentences. Brain CTs revealed acute lesions affecting the inferior and middle frontal gyri, insular cortex, precentral and postcentral gyri, and a part of the angular gyrus in the right hemisphere. Old infarcts were also noted in the right frontal pole and prefrontal area. The unique feature of her language impairment suggested somewhat deviated lateralization and localization of her language function.

Aged↗
PubMed2003

Decreased striatal D2 receptor density associated with severe behavioral abnormality in Alzheimer's disease.

OBJECTIVES: Since patients manifesting behavioral and psychological symptoms of dementia (BPSD) are a burden for their families and caregivers, the underlying neurobiological mechanism of this condition should be clarified. Using positron emission tomography (PET), we previously reported that wandering behavior in dementia was associated with a disturbed dopaminergic neuron system. We herein investigated the relationship between the severity of BPSD and the striatal D2 receptor density in Alzheimer's disease (AD). METHODS: Ten patients with probable AD as per the National Institute of Neurological and Communicative Disorders and Stroke (NINCDS) and the AD and Related Disorders Association (ADRDA) criteria and five normal subjects were examined with PET. The tracer used was [11C]raclopride (D2 antagonist). The uptake of [11C] raclopride was calculated as the estimation of binding potential (BP) of the striatum to the cerebellum. The AD patients were institutionalized in multiple nursing homes, and their BPSD were evaluated by the Behavioral Pathology in AD Frequency Weighted Severity Scale (BEHAVE-AD-FW) scale (Reisberg). RESULTS: There was a significant inverse Spearman's correlation between BEHAVE-AD-FW score and the BP, especially between the score of the behavioral domain and the BP values. The BP was found to be lower in severer BPSD patients. CONCLUSIONS: Patients with AD who manifest severe BPSD may have some dysfunction of striatal dopamine metabolism compared with those without BPSD.

Aged↗
PubMed2003

Visuospatial deficits due to impaired visual attention: investigation of two cases of slowly progressive visuospatial impairment.

Two patients with slowly progressive visuospatial impairment demonstrated a peculiar type of visuoconstructive deficit. The most prominent manifestation appeared when handling kanji (logogram) characters and other figurative patterns. The patients showed pure agraphia for complex kanji but not for kana (syllabogram) or Arabic numerals. Their abilities to read and understand kanji characters and to orally describe the structure of a kanji character were preserved. They could not draw or copy figures or symbols except for single lines or simple symbols, although they could identify and name the targets easily. They also performed poorly in such visuoconstructive tasks as the block design subtest and matching to sample tests that require the ability to simultaneously attend to multiple saliencies. When asked to copy multiple kana characters scattered on a sheet of paper, they could correctly describe the location of a particular character in relation to the others, but actually wrote each character in grossly mislocated positions. These findings suggest that when the patients start particular tasks, which require detailed visual analysis, their range of visual attention becomes extremely narrow. This task-dependent narrowing and fixation of visual attention might explain some of the visuoconstructive symptoms described in patients with slowly progressive visuospatial impairment.

Agnosia↗
PubMed2003

Preserved ability to recognize keywords related to remote events in the absence of retrieval of relevant knowledge: a case of postencephalitic amnesia.

We describe a case of severe anterograde and retrograde amnesia resulting from herpes simplex encephalitis. Magnetic resonance imaging revealed pathological changes in the bilateral hippocampi, parahippocampal gyri, fusiform gyri, medial temporal poles, posterior part of the cingulate gyri, and insula. The patient showed severe amnesia for autobiographical episodic memory in relation to events that had occurred throughout her life, but temporally graded amnesia for autobiographical semantic memory, and severe amnesia without a temporal gradient for public events and famous people. However, using a multiple-choice method, she showed a high level of accuracy when choosing keywords related to public or personal events, although this did not prompt her recollection of the events. An important indication of these results is that, even with severe retrograde amnesia, memories of past events are not completely lost. We propose that an event may be stored in a fragmented form, consisting of many components, and that normal recall of an event may require recombination or reconstruction of these components.

Amnesia↗
PubMed2003

Thinking of the future and past: the roles of the frontal pole and the medial temporal lobes.

Human lesion data have indicated that the frontal polar area might be critically involved in having an insight into one's future. Retrospective memory mediated by medial temporal lobes and related structures, on the other hand, could be used to extract one's future prospects efficiently. In the present study, we investigated the roles of these two brain structures in thinking of the future and past by using positron emission tomography (PET) and a naturalistic task setting. We measured regional cerebral blood flow (rCBF) in healthy subjects while they were talking about their future prospects or past experiences, with regard to two different temporal windows (in years or days). Many areas in the frontal and the medial temporal lobes were activated during the future and past tasks compared with a control task requiring semantic retrieval. Among these, areas in anteromedial frontal pole showed greater activation during the future tasks than during the past tasks, showing significant effect of temporal distance from the present. Most areas in the medial temporal lobes showed greater or equivalent level of activations during the future tasks compared with the past tasks. The present results suggest that thinking of the future is closely related to retrospective memory, but that specific areas in the frontal pole and the medial temporal lobes are more involved with thinking of the future than that of the past.

Adult↗
PubMed2003

Changes in brain activation patterns associated with learning of Korean words by Japanese: an fMRI study.

We used functional magnetic resonance imaging (fMRI) to explore the change in brain activation associated with the learning of Korean words written in Han-gul characters (K-words) by young Japanese at two stages. Subjects were 12 right-handed native Japanese without previous knowledge of Korean words and characters. On the first day they were taught the pronunciation and meaning of 20 K-words. Then, after the first fMRI session (on day 2), they were given a set of 20 cards with the words and corresponding photographs. They also received a tape and were instructed to memorize the 20 K-words by studying them every day until the day of the second fMRI session (day 16). During the fMRI sessions, 20 Japanese words written in kana syllabograms (J-words) and the 20 previously presented K-words, as well as 20 new K-words (Kn-words) were presented visually for silent reading. The first J-word reading, relative to the first K-word reading, showed activation in the left angular gyrus. K-word reading relative to J-word reading during both sessions showed activation in occipital regions. Within these activated areas, session by condition interaction was found only in the left angular gyrus. The interaction between session and condition resulted from the fact that the differences in blood oxygenation-level-dependent signals between K-words and J-words and between Kn-words and J-words were significantly greater in the first session than in the second session. From the results, we concluded that patterns of brain activation changed as the memory of the 20 K-words became fixed through daily practice and that reading of both Korean words and Japanese syllabograms engaged the left angular gyrus.

Adult↗
PubMed2003

[Hippocampo-parahippocampal area and its role on human memory].

The hippocampo-parahippocampal area (medial temporal lobe system: MTL) plays an important role on human memory. Its bilateral damage may produce selective and severe impairment of anterograde and retrograde episodic memory. Our MRI volumetric study of 5 cases of pure MTL amnesia secondary to herpes simplex encephalitis showed that degree of amnesia and recovery was significantly correlated with the volume of the remaining or functioning MTL. It has to be kept in mind that MTL is a part of a widely distributed memory system. Our functional imaging studies on verbal memory showed that one of the major participants in this system is the frontal lobe. The most interesting finding in our studies is that the area and pattern of frontal activation changed according to the questions asked. For instance, in short term memory of verbal materials classical speech areas such as Broca's area was activated in conjunction with MTL. In long term verbal memory, activated areas shifted to areas anterior as well as superior to Broca's area. These data suggest that strategy of storing changes over time. Damage to bilateral MTL at an early life seems to impair acquisition of semantic memories such as language, and mathematics, as well as more general knowledge necessary for social life. However, detailed information on this important topic remains scanty.

Adult↗