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.
To determine whether body-centered neglect and stimulus-centered neglect can be dissociated in patients with brain injury.
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.
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.
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.
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.
To determine the effect of intravenous recombinant tissue plasminogen activator (rt-PA) on vascular and neurologic outcomes, we enrolled 31 patients with acute carotid artery-territory ischemic ...stroke within 6 hours from symptom onset in a randomized, double-blind, placebo-controlled study. We gave either rt-PA (duteplase at the dose of 20 or 30 mega-international units MIU) or placebo intravenously for 60 minutes in patients randomly assigned to the three groups. A comparison between the baseline and postinfusion angiograms showed that complete or partial reperfusion occurred in 50% (5/10) of patients treated with 30 MIU rt-PA, 44% (4/9) of those treated with 20 MIU rt-PA, and 17% (2/12) in the control group. In patients with middle cerebral artery occlusions, reperfusion occurred in 71% (5/7) of the 30-MIU group, in 67% (4/6) of the 20-MIU group, and in 13% (1/8) of the control group. Patients treated with 30 MIU rt-PA showed a significantly early and better clinical improvement, as measured by the neurologic scale, than did those treated with placebo. Parenchymal hemorrhage occurred in one patient in each group, and frequency of clinically insignificant hemorrhagic infarction was comparable among the treatment groups. No major systemic complications occurred in any group. These results support the efficacy of intravenous infusion of rt-PA soon after the onset of stroke in producing rapid thrombolysis and neurologic recovery; it may be of particular value in patients with thromboembolic occlusion in the middle cerebral artery.
OBJECTIVES Memory impairment is not only the earliest clinical symptom but a central and prominent feature throughout the course of Alzheimer’s disease. Alzheimer related pathological alterations in ...the medial temporal structures may account for the memory impairments in patients with Alzheimer’s disease. The aim of this study was to elucidate the role of the medial temporal structures in memory impairment caused by Alzheimer’s disease. METHODS Using high resolution MRI and a semiautomated image analysis technique, volumes of the medial temporal structures (amygdaloid complex, hippocampal formation, subiculum, and parahippocampal gyrus) were measured, and correlations between atrophy of each structure and memory dysfunction in patients with Alzheimer’s disease were examined. RESULTS Patients with Alzheimer’s disease showed poor performance on verbal and non-verbal memory tests, and MRI volumetry showed a significant volume reduction of the medial temporal lobe structures. Volumes of the amygdaloid complex and of the subiculum correlated with memory performance. Stepwise regression analyses disclosed that the volume of the right amygdaloid complex specifically predicted visual memory function and to some extent verbal memory function, and that the volume of the left subiculum specifically predicted verbal memory function. Atrophy of the hippocampus did not predict severity of memory impairment. CONCLUSIONS The presence of perihippocampal damage involving the amygdala proper, its surrounding cortex, and the subiculum further increased the severity of memory impairment attributable to hippocampal damage in Alzheimer’s disease.
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.
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.
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.
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.
Thepurpose 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 sensorimotor 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.
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.
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