Biomedical subjects

Manabu Honda

Publications and source records attributed to Manabu Honda.

23 records · Page 2Linked to original sources

PubMed2002

Cognitive slowing in Parkinson's disease: a behavioral evaluation independent of motor slowing.

Parkinson's disease (PD) is attributable primarily to depletion of dopamine in the basal ganglia, but the full effects of this depletion are unknown. It is well known that PD involves motor slowing, and although it is not easy to distinguish between the motor and cognitive components of behavior, clinical observations suggest that cognitive processing may also be compromised. However, it remains unclear whether such cognitive involvement exists, and if so, to what extent. Previous studies of cognitive slowing in PD have yielded conflicting results. This may be attributable to variations in experimental procedures, because most of the experiments used reaction-time tasks, which are inevitably confounded by motor components. In the present study, we evaluated the speed of cognitive processing in patients with PD without bradykinesia as a variable. We developed a mental-operation task that required serial updating of mental representations in response to a series of visual stimuli. By changing the speed of visual presentation and evaluating performance accuracy, the speed of cognitive processing was assessed independently of motor slowing. Cognitive impairment in PD became evident when higher speeds of cognitive processing (verbal more so than spatial) were required. In addition, cognitive slowing and motor slowing were significantly correlated. The results of the present study suggest that slowing in PD is not restricted to the motor domain but can be generally observed in other domains of behavior, including cognitive mental operations.

Behavior↗

PubMed2002

Modulation of the visual word retrieval system in writing: a functional MRI study on the Japanese orthographies.

We used functional magnetic resonance imaging (fMRI) to examine whether the act of writing involves different neuropsychological mechanisms between the two script systems of the Japanese language: kanji (ideogram) and kana (phonogram). The main experiments employed a 2 x 2 factorial design that comprised writing-to-dictation and visual mental recall for kanji and kana. For both scripts, the actual writing produced a widespread fronto-parietal activation in the left hemisphere. Especially, writing of kanji activated the left posteroinferior temporal cortex (lPITC), whereas that of kana also yielded a trend of activation in the same area. Mental recall for both scripts activated similarly the left parietotemporal regions including the lPITC. The writing versus mental recall comparison revealed greater activations in the left sensorimotor areas and right cerebellum. The kanji versus kana comparison showed increased responses in the left prefrontal and anterior cingulate areas. Especially, the lPITC showed a significant task-by-script interaction. Two additional control tasks, repetition (REP) and semantic judgment (SJ), activated the bilateral perisylvian areas, but enhanced the lPITC response only weakly. These results suggest that writing of the ideographic and phonographic scripts, although using the largely same cortical regions, each modulates the visual word-retrieval system according to their graphic features. Furthermore, comparisons with two additional tasks indicate that the activity of the lPITC increases especially in expressive language operations regardless of sensory modalities of the input stimulus.

Acoustic Stimulation↗

PubMed2002

Critical period for cross-modal plasticity in blind humans: a functional MRI study.

The primary visual cortex (V1) in congenitally blind humans has been shown to be involved in tactile discrimination tasks, indicating that there is a shift in function of this area of cortex, but the age dependency of the reorganization is not fully known. To investigate the reorganized network, we measured the change of regional cerebral blood flow using 3.0 Tesla functional MRI during passive tactile tasks performed by 15 blind and 8 sighted subjects. There was increased activity in the postcentral gyrus to posterior parietal cortex and decreased activity in the secondary somatosensory area in blind compared with sighted subjects during a tactile discrimination task. This suggests that there is a greater demand for shape discrimination processing in blind subjects. Blind subjects, irrespective of the age at onset of blindness, exhibited higher activity in the visual association cortex than did sighted subjects. V1 was activated in blind subjects who lost their sight before 16 years of age, whereas it was suppressed in blind subjects who lost their sight after 16 years of age during a tactile discrimination task. This suggests that the first 16 years of life represent a critical period for a functional shift of V1 from processing visual stimuli to processing tactile stimuli. Because of the age-dependency, V1 is unlikely to be the "entry node" of the cortex for the redirection of tactile signals into visual cortices after blinding. Instead, the visual association cortex may mediate the circuitry by which V1 is activated during tactile stimulation.

Adult↗

PubMed2002

Electroencephalographic measurement of possession trance in the field.

OBJECTIVES: To verify the utility of a portable electroencephalogram (EEG) measurement system developed for investigating spontaneous EEG from vigorously moving healthy subjects in a possession trance under a natural condition. METHODS: A portable multi-channel EEG telemetry system was developed to record the EEGs of 3 healthy male Balinese while they were performing a ritual dedicatory drama in the field. After reducing extraneous artifacts using a digital filter, the EEGs and their power spectra were analyzed in terms of evolution from one state to another. RESULTS: During the drama, one of the subjects became possessed while the others did not. The EEG of the possessed subject did not show any pathological findings including epileptic discharges, but indicated enhanced power in the theta and alpha frequency bands during the trance. This finding was not observed in the other two subjects, who did not go into trances, with no pathological EEG findings. CONCLUSIONS: The measurement system and data analysis methods we developed have allowed us, for the first time, to obtain an EEG from healthy subjects who are vigorously moving while in a possession trance. The present technique enables us to use a spontaneous EEG as a marker of the underlying physiology of a state of possession trance.

Adult↗

PubMed2002

The role of rostral Brodmann area 6 in mental-operation tasks: an integrative neuroimaging approach.

Recent evidence indicates that classical 'motor' areas may also have cognitive functions. We performed three neuroimaging experiments to investigate the functional neuroanatomy underlying three types of nonmotor mental-operation tasks: numerical, verbal, and spatial. (i) Positron emission tomography showed that parts of the posterior frontal cortex, which are consistent with the pre-supplementary motor area (pre-SMA) and the rostral part of the dorsolateral premotor cortex (PMdr), were active during all three tasks. We also observed activity in the posterior parietal cortex and cerebellar hemispheres during all three tasks. Electrophysiological monitoring confirmed that there were no skeletomotor, oculomotor or articulatory movements during task performance. (ii) Functional magnetic resonance imaging (fMRI) showed that PMdr activity during the mental-operation tasks was localized in the depths of the superior precentral sulcus, which substantially overlapped the region active during complex finger movements and was located dorsomedial to the presumptive frontal eye fields. (iii) Single-trial fMRI showed a transient increase in activity time-locked to the performance of mental operations in the pre-SMA and PMdr. The results of the present study suggest that the PMdr is important in the rule-based association of symbolic cues and responses in both motor and nonmotor behaviors.

Adult↗