Yutaka Kohno

An fMRI study of musicians with focal dystonia during tapping tasks.

Musician’s dystonia is a type of task specific dystonia for which the pathophysiology is not clear. In this study, we performed functional magnetic resonance imaging to investigate the motor-related brain activity associated with musician’s dystonia. We compared brain activities measured from subjects with focal hand dystonia and normal (control) musicians during right-hand, left-hand, and both-hands tapping tasks. We found activations in the thalamus and the basal ganglia during the tapping tasks in the control group but not in the dystonia group. For both groups, we detected significant activations in the contralateral sensorimotor areas, including the premotor area and cerebellum, during each tapping task. Moreover, direct comparison between the dystonia and control groups showed that the dystonia group had greater activity in the ipsilateral premotor area during the right-hand tapping task and less activity in the left cerebellum during the both-hands tapping task. Thus, the dystonic musicians showed irregular activation patterns in the motor-association system. We suggest that irregular neural activity patterns in dystonic subjects reflect dystonic neural malfunction and consequent compensatory activity to maintain appropriate voluntary movements.

The role of the dorsolateral prefrontal cortex in the inhibition of stereotyped responses

Stereotyped behaviors should be inhibited under some circumstances in order to encourage appropriate behavior. Psychiatrists have used the modified rock-paper-scissors (RPS) task to examine the inhibition of stereotyped behavior. When subjects are required to lose in response to a gesture, it is difficult for them to lose, and they have a tendency to win involuntarily. It is thought that the win response is the stereotyped response in the RPS task, and the difficulty in making positive attempts to lose is due to the requirement for inhibition of the stereotyped response. In this study, we investigated the brain regions related to inhibition of the stereotyped response using functional magnetic resonance imaging (fMRI). Subjects were assigned to one of two groups: the “win group” or the “lose group.” The lose group showed higher activation of the left dorsolateral prefrontal cortex (DLFPC) when compared to the win group. We also delivered transcranial magnetic stimulation (TMS) while the subjects performed the modified RPS task to investigate whether the left DLPFC (middle frontal gyrus, Brodmann area, BA 9) was directly involved in the inhibition of the stereotyped response. When TMS was delivered before onset of the visual stimulus, the subjects displayed increased response errors. In particular, the subjects had a tendency to win erroneously in a lose condition even though they were required to lose. These results indicate involvement of the left DLPFC in inhibition of the stereotyped responses, which suggests that this region is associated with inhibition of the preparatory setting for stereotyped responses rather than inhibition of ongoing processing to produce a stereotyped response.

TMS-induced artifacts on EEG can be reduced by rearrangement of the electrode’s lead wire before recording

OBJECTIVE Our purpose was to establish a technique to reduce residual artifacts after transcranial magnetic stimulation (TMS) from electroencephalographic (EEG) signals. METHODS We investigated the effects of coil direction and stimulus intensity on residual artifacts in an artificial circuit, and tested whether or not the size of the circuit area affects the residual artifact (the model study). Based on the results, the optimization by rearranging the electrodes lead wire was tested on the human scalp (the human study). RESULTS The residual artifact after TMS was dependent on the direction of the figure-of-eight coil, and on the artificial circuit area size. CONCLUSIONS In accordance with the model study, the scalp EEG shows that TMS-induced artifacts can be reduced dramatically before the amplifier input stages in TMS-EEG experiments by a step-wise procedure rearranging the lead wires relative to the fixed coil orientation. SIGNIFICANCE Our technique makes it possible to significantly reduce the residual artifacts from recordings of short-latency TMS-evoked potentials.

Clinicopathological features of adult-onset neuronal intranuclear inclusion disease

Neuronal intranuclear inclusion disease (NIID) has highly variable clinical manifestations. Sone et al. describe the clinical and pathological features of 57 adult-onset cases diagnosed by postmortem dissection/antemortem skin biopsy. They report ‘dementia dominant’ and ‘limb weakness’ subtypes, and recommend consideration of NIID in the differential diagnosis of leukoencephalopathy and neuropathy.

Walking activity in community-dwelling stroke survivors within 1 month after discharge from a rehabilitation setting

Abstract Objective: To characterize the pattern of activity accumulation in stroke survivors. Method: Nineteen stroke patients and 19 age–sex-matched healthy adults participated. Step counts were measured using a step activity monitor for 3 d. The steps per day, bouts per day, walking time per day, average steps per bout, and average walking time per bout were calculated in each walking-distance category (short, medium, and long-distance bout) and in total. Results: The total steps per day were 8446 and 11,749 steps in stroke survivors and control participants, respectively. The total steps per day and the total bouts per day for the stroke group were both significantly lower compared with the control group. Significant group differences were found in only the medium-distance range. No significant differences were found in average steps per bout. Conclusion: Fewer number of bouts is a characteristic pattern of walking activity in stroke survivors. In particular, a low number of medium-distance bouts in stroke survivors results in a low number of daily steps when compared with healthy adults. To facilitate physical activity in stroke survivors, not only the total number of bouts per day but the number of bouts of varying lengths must be considered. Implications for rehabilitation Fewer number of bouts is a characteristic pattern of walking activity in stroke survivors. Low number of bouts, especially medium-distance bouts, in stroke survivors, results in low number of daily steps when compared with healthy adults. The number of long-distance bouts is important for increasing total daily steps after stroke with mild disability. To facilitate physical activity in stroke survivors, not only the total number of bouts per day but the number of bouts of varying lengths must be considered.

11. Evoked brain potentials were changed by coil orientation of transcranial magnetic stimulation

(n = 10) received audible artifact. At 17 weeks old, field excitatory postsynaptic potential (fEPSP) and paired-pulse ratio (PPR) of population spike were recorded on hippocampal slices from two mice in each group. From 13 to 15 weeks old, seizure frequency was significantly (p < 0.05) decreased in rTMS-received mice comparing control. fEPSP and PPR showed no significant difference between two groups. Our results suggest low-frequency rTMS has the potential to modulate the development of ictogenesis without any significant changes of excitabilities of hippocampal slices in EL mouse.

Prefrontal cortex activities in the successful inhibition of habitual responses: An fMRI study

To analyze decision-making under risk of monkeys, 17 common marmosets were trained to select and remove one of two colored caps on vertically-arranged wells in front of them. Each well contained constant reward (3 grains of sugar-coated rice) or risky reward (0 or 6 grains; possibility, 50%:50%). For each marmoset, white or black color were determined randomly as symbols of constant or risky choice. Arrangement of white and black caps were determined randomly in each trial. After 200 trials (5 trials per day), the marmosets were classified according to the pattern of their selection. Seven of 17 marmosets (41.2%) were risk-aversive, while 5 marmosets (29.4%) were risk-prone. Remaining 5 marmosets (29.4%) became to select one side constantly (left n = 4, right n = 1). These results showed individual difference in decision-making of the marmoset. Expected value of the number of reward grains did not depend on selection strategy of marmosets in the present experiment. Thus, constant selection of one side was interpreted as reasonable way to reduce brain energy consumption.

Short latency TMS-evoked scalp-recorded potentials

Results We confirmed three components consisting of P25, N40 and P55 on the TMS-evoked scalp-recorded potentials. P25 and P55 components were positive deflections peaking at the latency of 25 ms and 55 ms post-stimulus, respectively. N40 component was negative deflection peaking at the latency of 40 ms post-stimulus. The scalp mappings revealed that P25 component had a potential distribution over the frontal areas on both sides, N40 component was spreading over the temporal and occipital areas on the right side. P55 component was localized in the central areas on both sides. These short latency components of TMS-evoked potentials tended to increase in amplitude as a function of TMS intensity.