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Biomedical subjects

Koji Inui

Publications and source records attributed to Koji Inui.

13 recordsLinked to original sources
PubMed2003

Central mechanisms for two-point discrimination in humans.

We studied the cognitive mechanisms for two-point discrimination (TPD) in 11 normal subjects, using electrical pulses. We used six ball-shaped electrodes placed in line on the dorsal surface of the left hand, and two-point was stimulated by two electrodes randomly selected. We measured the reaction time for TPD and calculated the percentage of correct responses for each two-point stimulation. The subjects' response was significantly affected by the preceding stimuli as well as the distance of the stimuli: for a two-point stimulus condition, subjects tended to feel the stimuli as two-point when the distance between the stimuli was longer than that of preceding stimuli, whereas they felt the stimuli as one-point when the distance was shorter than that of the preceding stimuli. The present results indicate that the TPD process involved evaluation of the distance between the stimuli relatively to that of the preceding stimuli, as well as evaluation of absolute distance between the stimuli.

Adult↗
PubMed2003

Effects of sleep on pain-related somatosensory evoked potentials in humans.

We investigated effects of sleep on pain-related somatosensory evoked potentials (SEP) following painful electrical stimulation of the left index finger. The biggest advantage of this method is that signals ascending through both A-beta fibers relating to touch and A-delta fibers relating to pain can be recorded simultaneously. While the subject was awake, non-painful stimulation evoked early- and middle latency components, N20, P30 and N60, at the C4 electrode, and painful stimulation evoked not only early- and middle latency components at the C4 but also later pain-specific components, N130 and P240, at the Cz electrode. During sleep, N20 and P30 did not show a significant change in amplitude, N60 showed a slight but significant amplitude reduction, and N130 and P240 significantly decreased in amplitude or disappeared, as compared with those while awake. Therefore, we speculate on the mechanisms generating each component as follows; (1) N20 and P30 are the primary components generated in SI ascending through A-beta fibers. (2) N60 is the secondary component generated in SI involving cognitive function to some degree. (3) N130-P240 are the pain-specific components ascending through A-delta fibers, and closely related to cognitive function, because they were much affected by consciousness, different from the components ascending through A-beta fibers.

Adult↗
PubMed2003

Cerebral responses following stimulation of unmyelinated C-fibers in humans: electro- and magneto-encephalographic study.

There are two kinds of pain, a sharp pain ascending through Adelta fibers (first pain) and a second burning pain ascending though C fibers (second pain). By using a novel method, the application of a low intensity CO(2) laser beam to a tiny area of skin using a very thin aluminum plate with numerous tiny holes as a spatial filter, we succeeded in selectively stimulating unmyelinated C fibers of the skin in humans, and could record consistent and clear brain responses using electroencephalography (EEG) and magnetoencephalography (MEG). The conduction velocity (CV) of the C fibers of the peripheral nerve and spinal cord, probably spinothalamic tract (STT), is approximately 1-4 m/s, which is significantly slower than that of Adelta (approximately 10-15 m/s) and Abeta fibers (approximately 50-70 m/s). This method should be very useful for clinical application. Following C fiber stimulation, primary and secondary somatosensory cortices (SI and SII) are simultaneously activated in the cerebral hemisphere contralateral to the stimulation, and then, SII in the hemisphere ipsilateral to the stimulation is activated. These early responses are easily detected by MEG. Then, probably limbic systems such as insula and cingulate cortex are activated, and those activities reflected in EEG components. Investigations of the cortical processing in pain perception including both first and second pain should provide a better understanding of pain perception and, therefore, contribute to pain relief in clinical medicine.

Animals↗
PubMed2003

Effects of sleep on pain-related somatosensory evoked magnetic fields in humans.

We investigated the effects of sleep on pain-related somatosensory evoked magnetic fields (SEFs) following painful electrical stimulation to identify the mechanisms generating them in both fast A-beta fibers relating to touch and slow A-delta fibers relating to pain. While the subjects were awake, non-painful and painful electrical stimulations were applied, and while asleep, painful stimulation was applied to the left index finger. During awake, five components (1M-5M) were identified following both non-painful and painful stimulation, but the 4M and 5M at around 70-100 ms and 140-180 ms, respectively, were significantly enhanced following painful stimulation. During sleep, 1M and 2M generated in the primary somatosensory cortex (SI) did not show a significant change, 3M in SI showed a slight but significant amplitude reduction, and 4M and 5M generated in both SI and the secondary somatosensory cortex (SII) were significantly decreased in amplitude or disappeared. The 4M and 5M are complicated components generated in SI and SII ascending through both A-beta fibers and A-delta fibers. They are specifically enhanced by painful stimulation due to an increase of signals ascending through A-delta fibers, and are markedly decreased during sleep, because they much involve cognitive function.

Adult↗
PubMed2003

Mechanisms of differences in gating effects on short-and long-latency somatosensory evoked potentials relating to movement.

We investigated the mechanisms underlying the differences in gating effects on short- and long-latency somatosensory evoked potentials (SEPs) relating to movement. SEPs were recorded in normal subjects for 6 different tasks in Experiment 1: Control, Movement, Distraction, Attention, Movement during Distraction and Movement during Attention, and for 4 different tasks in Experiment 2: Control, Passive Movement, Contralateral Movement and Movement Imagery. The amplitudes of short-latency SEPs were significantly reduced by active and passive movement of the stimulated hand, but long-latency SEPs (N140-P200) were significantly enhanced by active movement of the stimulated hand. Attention, Distraction, Contralateral Movement and Movement Imagery did not affect the amplitudes of SEPs. The degree of enhancement of long-latency SEPs by active Movement was greater than that by active movement with Attention or Distraction. Gating effects on long-latency SEPs were different from those on short-latency SEPs. Since this effect was not related to Attention/Distraction, Passive Movement, Movement Imagery or Movement of another site, it is probably due to specific centrifugal effects, which are different from more direct gating effects on short-latency components. This study showed the difference in gating effects on somatosensory perception depending on time periods following stimulation, which may indicate an interaction between motor and somatosensory cortex.

Adult↗
PubMed2002

Late-onset depression: can EEG abnormalities help in clinical sub-typing?

BACKGROUND: The purpose of this study was to determine the frequency of EEG abnormalities indicative of mild cerebrovascular dysfunction in patients with late-onset depression and to correlate these abnormalities with clinical features. METHODS: The subjects, aged > or = 50 years, were 51 outpatients with major depression diagnosed according to DSM-IV criteria. They were living in the community and prospectively selected at their initial consultation for mostly mild-moderate depression. We also included 32 normal age-matched controls. We examined basic rhythms and temporal slow waves on EEG and determined the Hamilton Rating Scale for Depression (HAMD) as a scale for the severity of psychiatric symptoms. RESULTS: Temporal slow waves were more common in depressed patients (47%) than in normal controls (22%). Depressed patients with temporal slow waves had significantly lower frequency of family history of mood disorders (P<0.05). There was no difference in the total score of HAMD between patients with and without temporal slow waves, however, each score of HAMD in patients with temporal slow waves showed a significantly lower score for "feeling of guilt" (P<0.01) and a significantly higher score for "general somatic symptoms" (P<0.01) and "hypochondriasis" (P<0.01). CONCLUSIONS: Our EEG study suggested that temporal slow waves, which were probably associated with subtle cerebrovascular lesions, might reflect vulnerability to late-onset depression. In addition, depressed patients with temporal slow waves could be classified as a subgroup of heterogeneous late-onset depression based on the clinical findings. These results must be interpreted within the limitations of the sample selection procedure.

Age of Onset↗
PubMed2002

Conduction velocity of the spinothalamic tract following CO2 laser stimulation of C-fibers in humans.

Pain-related somatosensory-evoked potential following CO(2) laser stimulation (laser-evoked potential (LEP)) is now used not only for research objectives, but also for clinical applications. Estimating the conduction velocity (CV) of the spinothalamic tract (STT) by analyzing LEP following activation of Adelta-fibers (Adelta-CVSTT) by CO(2) laser stimulation has been performed previously, but estimating the CV of STT following activation of C-fibers (C-CVSTT) has not. This is the first report to estimate the C-CVSTT in humans; by using the novel method of CO(2) laser stimulation applied to tiny skin areas. The calculation method was based on that of Kakigi and Shibasaki (Electroenceph clin Neurophysiol 80 (1991) 39) who measured Adelta-CVSTT by conventional CO(2) laser stimulation. The C-CVSTT ranged between 1.4 and 4.0 m/s, and its mean+/-SD was 2.9+/-0.8 m/s. This C-CVSTT was significantly slower than the Adelta-CVSTT, which ranged approximately from 10 to 21 m/s. The nociceptive signal of the C-fibers in STT is probably conveyed by unmyelinated axons of projection neurons to reach the thalamus. Our findings provide the first physiological evidence of the signals ascending through unmyelinated axons in the spinal cord in humans. In addition, estimating C-CVSTT and Adelta-CVSTT combined with conventional methods to measure the CV of the posterior column using electrical stimulation should be useful and have important clinical applications, particularly in patients with spinal cord lesions showing various kinds of sensory disturbances.

Adult↗
PubMed2002

Preferential stimulation of Adelta fibers by intra-epidermal needle electrode in humans.

We recorded evoked potentials (EPs) induced by conventional transcutaneous electrical stimulation (TS), laser stimulation (LS) and epidermal electrical stimulation (ES) using a specially made needle electrode. We evaluated the activated fibers by epidermal stimulation by assessing the conduction velocity (CV) of the peripheral nerves. The EPs were recorded from Cz electrode (vertex) of the International 10-20 system in 12 healthy subjects. For the ES, the tip of a stainless steel needle electrode was inserted in the epidermis of the skin (0.2 mm in depth). Distal and proximal sites of the upper limb were stimulated by the LS and ES with an intensity which induced a definite pain sensation. Similar sites were stimulated by TS with an intensity of two times the sensory threshold. A major EP positive response (P1) was obtained by stimulation by all three types of stimuli. The P1 latency for the TS (245+/-22 ms) was significantly shorter than that for the ES (302+/-17 ms, P<0.0001) and LS (341+/-21 ms, P<0.0001) and the peak latency P1 by the LS was also significantly longer, approximately 40 ms, than that by the ES (P<0.0001). The CVs were 15.1, 15.3 and 44.1 m/s obtained by ES, LS and TS, respectively. The CV indicated that the fibers activated by the ES were mainly A fibers, which corresponded to the fibers stimulated by the LS. We considered that the ES with our newly developed needle electrode was a very convenient method for the selective stimulation of the A fibers, since it was very simple, not requiring any special apparatus, did not cause bleeding or burns and caused minimum uncomfortable feeling.

Adult↗
PubMed2002

A point mutation of mitochondrial ATPase 6 gene in Leigh syndrome.

A T-to-G transition at nucleotide 9176 (T9176G) in the mitochondrial adenosine triphosphate 6 gene (MTATP6) was detected in two siblings with Leigh syndrome. Heteroplasmy was observed in the mother's leukocytes. The T9176G mutation changes a highly conserved leucine residue to an arginine in subunit 6 of ATPase and is maternally inherited like mutations in the other mitochondrial genes. Another mutation in the same codon (T9176C) has been previously reported in Leigh syndrome. This gives strong support to the relevance of MTATP6 dysfunction in Leigh syndrome and the importance of leucine at that position.

Child↗
PubMed2002

Pain-related magnetic fields evoked by intra-epidermal electrical stimulation in humans.

OBJECTIVES: We recently developed a new method for the preferential stimulation of Adelta fibers in humans. The aim of the present study was to examine whether this method can serve as an appropriate stimulus in a magnetoencephalographic study. METHODS: We recorded somatosensory-evoked magnetic fields (SEFs) following intra-epidermal electrical stimulation applied to the hand and elbow. Superficial parts of the skin were electrically stimulated through a needle electrode whose tip was inserted in the epidermis. RESULTS: In all 13 subjects, the equivalent current dipole was estimated in the secondary somatosensory cortices (SII). In 5 out of 13 subjects, simultaneous activation of the primary somatosensory cortex (SI) in the hemisphere contralateral to the stimulation was identified. The mean peak latencies of magnetic fields corresponding to contralateral SI, SII and ipsilateral SII activation following hand stimulation were 162, 158 and 171 ms, respectively. The respective latency following elbow stimulation was 137, 139 and 157 ms, respectively. Estimated peripheral conduction velocity was 15.6m/s. CONCLUSIONS: All the results were consistent with previous findings in pain SEF studies. We concluded that our novel intra-epidermal electrical stimulation is useful for pain SEF studies since it does not need special equipment and is easy to control.

Adult↗
PubMed2002

Effects of attention, distraction and sleep on CO(2) laser evoked potentials related to C-fibers in humans.

OBJECTIVES: The objective of this study is to evaluate the effects of attention, distraction and sleep on CO(2) laser-evoked potentials (LEP) relating to C-fibers (ultra-late LEP). METHODS: Non-painful CO(2) laser pulses were delivered to a tiny skin area of the dorsum of the right hand. Ultra-late LEP were recorded from 10 normal subjects in 5 different conditions: control (wakefulness), attention, distraction, drowsiness and sleep (stage 2). RESULTS: The amplitude of ultra-late LEP was slightly increased during attention and significantly decreased during distraction, relative to the control. The ultra-late LEP decreased much in amplitude or almost disappeared during sleep. However, significant differences in latency among the conditions were not found. CONCLUSIONS: We confirmed that the brain responses relating to signals ascending through C-fibers were much affected by the level of consciousness, being consistent with the findings of late LEP relating to Adelta-fibers. This is the first study to indicate the important characteristics of ultra-late LEP relating to consciousness, suggesting that they include cognitive function and also that one has to be careful of the change in alertness when recording.

Adult↗