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Toshikatsu Fujii

Publications and source records attributed to Toshikatsu Fujii.

At least 19 recordsLinked to original sources
PubMed2006

Reactivation of medial temporal lobe and occipital lobe during the retrieval of color information: A positron emission tomography study.

It is widely accepted that memory traces of an event include various types of information about the content of the event and about the circumstances in which the individual experienced it. However, how these various types of information are stored and later retrieved is poorly understood. One hypothesis postulates that the retrieval of specific event information reactivates regions that were active during the encoding of this information, with the aid of binding functions of the medial temporal lobe (MTL) structures. We used positron emission tomography to identify the brain regions related to the encoding and retrieval of color information. Specifically, we assessed whether overlapping activity was found in both the MTL structures and color-related cortical regions during the encoding and retrieval of color information attached with meaningless shapes. During the study, subjects were asked to encode colored (red or green) and achromatic random shapes. At subsequent testing, subjects were presented with only achromatic shapes, which had been presented with or without colors during encoding, and were engaged in retrieval tasks of shapes and colors. Overlapping activity was found in the MTL and occipital lobe (the lingual and inferior occipital gyri) in the right hemisphere during the encoding and retrieval of meaningless shapes with color information compared with those without color information. Although there are some limitations to be considered, the present findings seem to support the view that the retrieval of specific event information is associated with reactivation of both the MTL structures and the regions involved during encoding of the information.

Adult↗
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↗
PubMed2005

Dissociable roles of the bilateral anterior temporal lobe in face-name associations: an event-related fMRI study.

Previous studies have suggested the importance of bilateral anterior temporal regions in face-name associations, but there is little evidence concerning their precise role. In this fMRI study, we investigated the effects of person-related semantics (PS) and repeated learning (R) on activations in these regions during the retrieval of face-name associations. For encoding stimuli, we prepared four lists of faces. To control the factor of PS, people's and occupation names were attached to the faces in lists A and B, whereas only people's names were attached to the faces in lists C and D. To control the factor of R, the stimuli in lists A and C were learned twice, whereas the stimuli in lists B and D were learned seven times during encoding before fMRI. During fMRI after the encoding, subjects participated in the retrieval task of people's names from faces or in the retrieval task of faces from people's names. The left anterior temporal lobe was significantly activated during the retrieval of people's names from faces encoded with, compared to without, PS; whereas the right anterior temporal lobe was activated during the retrieval of people's faces from names, compared to without, this encoding. Also, activation of the left (but not the right) anterior temporal lobe was significantly reduced after R of face-name associations. These findings suggest that the three components of faces, names, and PS may be mutually mediated by the bilateral anterior temporal lobe, whose activity may be dynamically changed by the level of consolidation of face-name associations.

Adult↗
PubMed2005

Dissociable roles of prefrontal and anterior cingulate cortices in deception.

Recent neuroimaging studies have shown the importance of the prefrontal and anterior cingulate cortices in deception. However, little is known about the role of each of these regions during deception. Using positron emission tomography (PET), we measured brain activation while participants told truths or lies about two types of real-world events: experienced and unexperienced. The imaging data revealed that activity of the dorsolateral, ventrolateral and medial prefrontal cortices was commonly associated with both types of deception (pretending to know and pretending not to know), whereas activity of the anterior cingulate cortex (ACC) was only associated with pretending not to know. Regional cerebral blood flow (rCBF) increase in the ACC was positively correlated with that in the dorsolateral prefrontal cortex only during pretending not to know. These results suggest that the lateral and medial prefrontal cortices have general roles in deception, whereas the ACC contributes specifically to pretending not to know.

Adolescent↗
PubMed2005

Recruitment of fusiform face area associated with listening to degraded speech sounds in auditory-visual speech perception: a PET study.

For the fast and accurate cognition of external information, the human brain seems to integrate information from multi-sensory modalities. We used positron emission tomography (PET) to identify the brain areas related to auditory-visual speech perception. We measured the regional cerebral blood flow (rCBF) of young, normal volunteers during the presentation of dynamic facial movement at vocalization and during a visual control condition (visual noise), both under the two different auditory conditions of normal and degraded speech sounds. The subjects were instructed to listen carefully to the presented speech sound while keeping their eyes open and to say what they heard. The PET data showed that elevation of rCBF in the right fusiform gyrus (known as the "face area") was not significant when the subjects listened to normal speech sound accompanied by a dynamic image of the speaker's face, but was significant when degraded speech sound (filtered with a 500 Hz low-pass filter) was presented with the facial image. The results of the present study confirm the possible involvement of the fusiform face area (FFA) in auditory-visual speech perception, especially when auditory information is degraded, and suggest that visual information is interactively recruited to make up for insufficient auditory information.

Acoustic Stimulation↗
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

The effect of encoding strategies on medial temporal lobe activations during the recognition of words: an event-related fMRI study.

It is known that manipulation of the encoding strategy affects behavioral and activation data during later retrieval. In the present fMRI study, we examined brain activity during the recognition of words encoded using three different strategies formed by the combination of two factors of relational and self-performed processes. The first encoding strategy involved subjects learning words using both relational and self-performed processes (R+S+). In the second, subjects learned words using only a relational process (R+S-). In the third, subjects learned words without using either process (R-S-). During fMRI after encoding, subjects were randomly presented with words encoded previously and with new words (New) and were required to judge whether or not the word presented had been previously encoded. The fMRI experiment was performed with the event-related design. Compared to New, activation of the left medial temporal lobe (MTL) occurred during the recognition of words encoded using R+S+ and R+S-, whereas right MTL activations only occurred with the R+S+ strategy. ROI analysis for the bilateral hippocampus and parahippocampal gyrus showed a linear increase in left MTL activity (hippocampus and parahippocampal gyrus) during the recognition of words encoded with the R-S-, R+S-, to R+S+, whereas right MTL activity (parahippocampal gyrus) was only increased with the R+S+ strategy. The findings suggest that the left and right MTL structures may contribute differentially to the processes involved in the recognition of stimuli and that these differential activities may depend on the encoding strategies formed by the two factors of relational and self-performed processes.

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

Changes in brain activation associated with use of a memory strategy: a functional MRI study.

It has been confirmed that some kinds of what are called memory strategies dramatically improve the performance of memory recall. However, there has been no direct research to examine changes in brain activity associated with the use of the method of loci within individuals. In the present study, using fMRI, we compared brain activations before and after instruction in the method of loci during both the encoding and recall phases. The resulting behavioral data showed that the use of the method of loci significantly increased scores for memory recall. The imaging data showed that encoding after instruction in the method of loci, relative to encoding before it, was associated with signal increases in the right inferior frontal gyrus, bilateral middle frontal gyrus, left fusiform gyrus, and bilateral lingual gyrus/posterior cingulate gyrus. Comparison of recall after instruction in the method of loci with that before it showed significant activation in the left parahippocampal gyrus/retrosplenial cortex/cingulate gyrus/lingual gyrus, left precuneus, left fusiform gyrus, and right lingual gyrus/cingulate gyrus. The present study demonstrated the changes in brain activation pattern associated with the use of the method of loci; left fusiform and lingual activity was associated with both the encoding and recall phases, bilateral prefrontal activity with the encoding phase, and activity of the posterior part of the parahippocampal gyrus, retrosplenial cortex, and precuneus with the recall phase. These findings suggest that brain networks mediating episodic encoding and retrieval vary with how individuals encode the same stimuli.

Adult↗
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

[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

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↗