Disconnected Motor Intention and Spatial Attention in a Case of Probable Marchiafava-Bignami Disease

Marchiafava-Bignami disease (MBD) is a rare complication of chronic alcoholism that typically causes demyelination and necrosis of the corpus callosum. Here, we report a man with probable MBD with callosal and right medial paracentral lesions who presented with abnormal reaching behavior and ideomotor apraxia of the left hand. He exhibited difficulty in reaching with the left hand when a target object was placed on his right-hand side, and he exhibited rightward bias when using his right hand in a line bisection task. These disturbances in reaching suggest disruption of the top-down control of motor intention and spatial attention at the corpus callosum.

Perceptual uncertainty modulates auditory statistical learning: A magnetoencephalography study

Statistical learning allows comprehension of structured information, such as that in language and music. The brain computes a sequence's transition probability and predicts future states to minimise sensory reaction and derive entropy (uncertainty) from sequential information. Neurophysiological studies have revealed that early event-related neural responses (P1 and N1) reflect statistical learning - when the brain encodes transition probability in stimulus sequences, it predicts an upcoming stimulus with a high transition probability and suppresses the early event-related responses to a stimulus with a high transition probability. This amplitude difference between high and low transition probabilities reflects statistical learning effects. However, how a sequence's transition probability ratio affects neural responses contributing to statistical learning effects remains unknown. This study investigated how transition-probability ratios or conditional entropy (uncertainty) in auditory sequences modulate the early event-related neuromagnetic responses of P1m and N1m. Sequence uncertainties were manipulated using three different transition-probability ratios: 90:10%, 80:20%, and 67:33% (conditional entropy: 0.47, 0.72, and 0.92 bits, respectively). Neuromagnetic responses were recorded when participants listened to sequential sounds with these three transition probabilities. Amplitude differences between lower and higher probabilities were larger in sequences with transition-probability ratios of 90:10% and smaller in sequences with those of 67:33%, compared to sequences with those of 80:20%. This suggests that the transition-probability ratio finely tunes P1m and N1m. Our study also showed larger amplitude differences between frequent- and rare-transition stimuli in P1m than in N1m. This indicates that information about transition-probability differences may be calculated in earlier cognitive processes.

Bilateral asterixis in a patient with bilateral anterior cerebral artery infarction

A 83-year-old woman complained of muscular weakness in the left leg and trembling in all extremities. She was apathetic and had left leg paresis and asterixis in all extremities. Magnetic resonance imaging revealed acute cerebral infarctions in the bilateral frontal lobes perfused by the anterior cerebral artery (ACA). Anticoagulant treatments improved ischemia-induced damage of the frontal lobes, and then her neurological symptoms including asterixis gradually disappeared. A unique point of this case is that acute stroke in the bilateral ACA territory induced bilateral asterixis resembling metabolic encephalopathy. Occurrence of the bilateral ACA territory infarction is extremely rare, but it should be considered in patients presenting with bilateral asterixis.

[Hemichorea in a patient with acute cerebral infarction of the somatosensory cortex]

A 86-year-old woman with left hemiparesis was admitted to our hospital. When visiting to our hospital, hemichorea appeared on her left extremities in an ambulance. She also had mild disturbance of consciousness, spatial disorientation, and sensory disturbance. Blood biochemical studies revealed mild renal failure. DWI MRI showed hyperintensities in the postcentral gyrus and a posterior part of the insula in the right hemisphere, but no signal changes in FLAIR. No lesions were detected in the basal ganglia. The DWI-FLAIR mismatch suggested acute cerebral infarction, and we performed intravenous thrombolysis therapy. Her neurological symptoms including hemichorea gradually improved, and she was finally discharged on foot. Two conspicuous points of the present patient are the sensory cortical infarction and an association with renal failure. In this patient, the sensory cortical infarction must produce chorea even though sensory cortical lesions rarely caused chorea. The associated renal dysfunction may play some role in the production of chorea. The double-crash of cerebral infarction and metabolic abnormality (renal dysfunction) may cause hemichorea which is rarely seen in patients with cerebral infarction of the sensory cortex and insula with no metabolic abnormalities.

Event-Related Potentials During Decision-Making in a Mixed-Strategy Game

The decisions we make are sometimes influenced by interactions with other agents. Previous studies have suggested that the prefrontal cortex plays an important role in decision-making and that the dopamine system underlies processes of motivation, motor preparation, and reinforcement learning. However, the physiological mechanisms underlying how the prefrontal cortex and the dopaminergic system are involved in decision-making remain largely unclear. The present study aimed to determine how decision strategies influence event-related potentials (ERPs). We also tested the effect of levodopa, a dopamine precursor, on decision-making and ERPs in a randomized double-blind placebo-controlled investigation. The subjects performed a matching-pennies task against an opposing virtual computer player by choosing between right and left targets while their ERPs were recorded. According to the rules of the matching-pennies task, the subject won the trial when they chose the same side as the opponent, and lost otherwise. We set three different task rules: (1) with the alternation (ALT) rule, the computer opponent made alternating choices of right and left in sequential trials; (2) with the random (RAND) rule, the opponent randomly chose between right and left; and (3) with the GAME rule, the opponent analyzed the subject's past choices to predict the subject's next choice, and then chose the opposite side. A sustained medial ERP became more negative toward the time of the subject's target choice. A biphasic potential appeared when the opponent's choice was revealed after the subject's response. The ERPs around the subject's choice were greater in RAND and GAME than in ALT, and the negative peak was enhanced by levodopa. In addition to these medial ERPs, we observed lateral frontal ERPs tuned to the choice direction. The signals emerged around the choice period selectively in RAND and GAME when levodopa was administered. These results suggest that decision processes are modulated by the dopamine system when a complex and strategic decision is required, which may reflect decision updating with dopaminergic prediction error signals.

Time Distortion in Parkinsonism

Although animal studies and studies on Parkinson’s disease (PD) suggest that dopamine deficiency slows the pace of the internal clock, which is corrected by dopaminergic medication, timing deficits in parkinsonism remain to be characterized with diverse findings. Here we studied patients with PD and progressive supranuclear palsy (PSP), 3–4 h after drug intake, and normal age-matched subjects. We contrasted perceptual (temporal bisection, duration comparison) and motor timing tasks (time production/reproduction) in supra- and sub-second time domains, and automatic versus cognitive/short-term memory–related tasks. Subjects were allowed to count during supra-second production and reproduction tasks. In the time production task, linearly correlating the produced time with the instructed time showed that the “subjective sense” of 1 s is slightly longer in PD and shorter in PSP than in normals. This was superposed on a prominent trend of underestimation of longer (supra-second) durations, common to all groups, suggesting that the pace of the internal clock changed from fast to slow as time went by. In the time reproduction task, PD and, more prominently, PSP patients over-reproduced shorter durations and under-reproduced longer durations at extremes of the time range studied, with intermediate durations reproduced veridically, with a shallower slope of linear correlation between the presented and produced time. In the duration comparison task, PD patients overestimated the second presented duration relative to the first with shorter but not longer standard durations. In the bisection task, PD and PSP patients estimated the bisection point (BP50) between the two supra-second but not sub-second standards to be longer than normal subjects. Thus, perceptual timing tasks showed changes in opposite directions to motor timing tasks: underestimating shorter durations and overestimating longer durations. In PD, correlation of the mini-mental state examination score with supra-second BP50 and the slope of linear correlation in the reproduction task suggested involvement of short-term memory in these tasks. Dopamine deficiency didn’t correlate significantly with timing performances, suggesting that the slowed clock hypothesis cannot explain the entire results. Timing performance in PD may be determined by complex interactions among time scales on the motor and sensory sides, and by their distortion in memory.

Prominent Prolongation of Cortical Silent Period Induced by Transcranial Magnetic Stimulation in Creutzfeldt-Jakob Disease

The cortical silent period (CSP) induced by transcranial magnetic stimulation (TMS) has been reported to be prolonged in 2 Creutzfeldt-Jakob disease (CJD) patients who presented with periodic myoclonus. Herein, we will show a prominent prolongation of TMS-induced CSP in a patient with CJD who did not have periodic myoclonus. The patient was a 66-year-old woman who developed rapidly progressive dementia. No myoclonic jerks were observed. Brain magnetic resonance imaging showed high-intensity lesions in the cerebral cortex, basal ganglia, and thalamus on diffusion-weighted images. Electroencephalography (EEG) showed diffuse and continuous slow waves, but no periodic synchronous discharges (PSDs). A TMS study revealed that the duration of CSP was prominently prolonged: the duration of CSP (370 ms) equaled that of the mean + 6.5 SD of the normal value. One month after admission, the patient exhibited akinetic mutism and developed periodic myoclonus in her limbs. The clinical course was compatible with CJD. To date, CSP has been measured in only 2 CJD patients. The common findings in both cases were marked prolongation of CSP, periodic myoclonus, and PSD on EEG. In short, we demonstrated that TMS-induced CSP was prominently prolonged even at the early stage of CJD without periodic myoclonus or PSD. In other disorders, the CSP has not been reported to be comparably prolonged to that of CJD patients. Therefore, we conclude that TMS-induced CSP could be prominently prolonged even in the early stage of CJD. The marked prolongation of the CSP might be an early biomarker of CJD.

Training in the practice of noninvasive brain stimulation: Recommendations from an IFCN committee

As the field of noninvasive brain stimulation (NIBS) expands, there is a growing need for comprehensive guidelines on training practitioners in the safe and effective administration of NIBS techniques in their various research and clinical applications. This article provides recommendations on the structure and content of this training. Three different types of practitioners are considered (Technicians, Clinicians, and Scientists), to attempt to cover the range of education and responsibilities of practitioners in NIBS from the laboratory to the clinic. Basic or core competencies and more advanced knowledge and skills are discussed, and recommendations offered regarding didactic and practical curricular components. We encourage individual licensing and governing bodies to implement these guidelines.

Premature saccades: A detailed physiological analysis

OBJECTIVE

Premature saccades (PSs) are those made with latencies too short for the direction and amplitude to be specifically programmed. We sought to determine the minimum latency needed to establish accurate direction and amplitude, and observed what occurs when saccades are launched before this minimum latency.

METHODS

In Experiment 1, 249 normal subjects performed the gap saccade task with horizontal targets. In Experiment 2, 28 normal subjects performed the gap saccade task with the targets placed in eight directions. In Experiment 3, 38 normal subjects, 49 patients with Parkinson's disease (PD), and 10 patients with spinocerebellar degeneration (SCD) performed the gap saccade task with horizontal targets.

RESULTS

In Experiment 1, it took 100 ms to accurately establish saccade amplitudes and directions. In Experiment 2, however, the latencies needed for accurate amplitude and direction establishment were both approximately 150 ms. In Experiment 3, the frequencies of PSs in patients with PD and SCD were lower than those of normal subjects.

CONCLUSIONS

The saccade amplitudes and directions are determined simultaneously, 100-150 ms after target presentation. PSs may result from prediction of the oncoming target direction or latent saccade activities in the superior colliculus.

SIGNIFICANCE

Saccade direction and amplitude are determined simultaneously.

Direct comparison of efficacy of the motor cortical plasticity induction and the interindividual variability between TBS and QPS

BACKGROUND

Theta burst stimulation (TBS) and quadripulse stimulation (QPS) are known to induce synaptic plasticity in humans. There have been no head-to-head comparisons of the efficacy and variability between TBS and QPS.

OBJECTIVE

To compare the efficacy and interindividual variability between the original TBS and QPS protocols. We hypothesized that QPS would be more effective and less variable than TBS.

METHODS

Forty-six healthy subjects participated in this study. Thirty subjects participated in the main comparison experiment, and the other sixteen subjects participated in the experiment to obtain natural variation in motor-evoked potentials. The facilitatory effects were compared between intermittent TBS (iTBS) and QPS5, and the inhibitory effects were compared between continuous TBS (cTBS) and QPS50. The motor-evoked potential amplitudes elicited by transcranial magnetic stimulation over the primary motor cortex were measured before the intervention and every 5 min after the intervention for 1 h. To investigate the interindividual variability, the responder/nonresponder/opposite-responder rates were also analyzed.

RESULTS

The facilitatory effects of QPS5 were greater than those of iTBS, and the inhibitory effects of QPS50 were much stronger than those of cTBS. The responder rate of QPS was significantly higher than that of TBS. QPS had a smaller number of opposite responders than TBS.

CONCLUSION

QPS is more effective and stable for synaptic plasticity induction than TBS.

[Triad TMS of Human Motor Cortex]

To study cortical excitability changes induced by external stimulation with a certain rhythm, we developed a new method using motor evoked potentials (MEPs) elicited by transcranial magnetic stimulation (TMS) over the primary motor cortex. In this method, three conditioning TMS with the intensity below the motor threshold are given prior to the supra-threshold test stimulus with the four TMSs were separated by a certain interval (triad-conditioning stimulation: TCS). In healthy volunteers, MEP facilitation was elicited at an interval of 25ms, whereas TCSs with other intervals induced no facilitation. This frequency-dependent facilitation may reflect some intrinsic rhythm of M1 (25ms, i.e. 40Hz). In cortical myoclonus, the facilitation at 25ms was gone whereas facilitation was elicited by triad-conditioning stimulus at 40ms (25Hz), which is consistent with a previously reported abnormal beta rhythm in cortical myoclonus reported previously. Facilitation at 25ms was evoked in neither Parkinson's disease nor in amyotrophic lateral sclerosis. With TCS, we were able to investigate the intrinsic rhythmic activity of M1 and its changes in neurological disorders.

[TMS Intervention of Human Neuronal Network]

I describe quadripulse stimulation (QPS) briefly, and show several examples of its applications, such as rTMS treatment of Parkinson's disease, gait induction by lumbar rTMS, and roles of presupplementary motor area (pre-SMA) and SMA in visuo-motor sequence learning, role of SMA in negative compatibility effect, and role of dendritic back propagation potential in I-wave generation.

Differential effects of thyrotropin releasing hormone (TRH) on motor execution and motor adaptation process in patients with spinocerebellar degeneration

BACKGROUND

The cerebellum is known to play a crucial role in sensori-motor adaptation, which includes the prism adaptation. TRH has been widely used as a treatment for cerebellar ataxia in Japan, however effects of TRH on cerebellar adaptation process have not been studied. Here, we studied effects of TRH treatment on the prism adaptation task.

METHODS

Eighteen spinocerebellar degeneration (SCD) patients participated in this study. The participants received intravenous injection of 2 mg/day protirelin tartrate once a day for 14 days. In the prism adaptation task, the participants reached to the target on the screen wearing wedge prisms. We compared the Scale for Assessment and Rating of Ataxia (SARA), baseline errors and the aftereffect (AE) of the prism adaptation task between before and after TRH therapy.

RESULTS

TRH therapy improved SARA significantly (p = .005). Multiple regression analysis revealed that improvement of SARA score was mainly due to improvement of "Stance" category score. TRH decreased baseline errors of the prism adaptation task (p = .021), while unaffected AEs (p = .252).

CONCLUSION

TRH differentially affected clinical cerebellar ataxia including baseline reaching performance in the prism adaptation task, whereas TRH did not affect the learning process of prism adaptation. Different cerebellar functional aspects may underlie the learning process of sensori-motor adaptation and simple motor execution (clinically evaluated cerebellar ataxia).

Central motor conduction time reveals upper motor neuron involvement masked by lower motor neuron impairment in a significant portion of patients with amyotrophic lateral sclerosis

OBJECTIVE

We retrospectively investigated the utility of the central motor conduction time (CMCT) in detecting upper motor neuron (UMN) involvements in patients with amyotrophic lateral sclerosis (ALS).

METHODS

Fifty-two ALS patients and 12 disease control patients participated in this study. Surface electromyograms were recorded from the first dorsal interosseous (FDI) and tibialis anterior (TA) muscles. We stimulated the motor cortex, brainstem, and spinal nerve using transcranial magnetic stimulation (TMS) in order to measure the cortical, brainstem, and spinal latencies. We divided the ALS patients into 2 subgroups (with UMN impairment vs. without UMN impairment) and calculated the rates of abnormal CMCT prolongation judged by their comparison with the normal ranges obtained by the measurement in the control patients.

RESULTS

The CMCTs in the FDI and TA were abnormally prolonged in over 40% of the ALS patients with UMN impairment and in nearly 30% of those without UMN impairment.

CONCLUSIONS

CMCT shows UMN dysfunction in ALS patients without clinical UMN impairment.

SIGNIFICANCE

TMS still has diagnostic utility in a significant portion of ALS patients.

Effects of electromagnetic fields from long-term evolution on awake electroencephalogram in healthy humans

Mobile phones are indispensable for daily life, and the adverse effects of the electromagnetic field (EMF) emitted by mobile phones have been a great concern. We studied the effects of long-term evolution (LTE) -like EMF for 30 min on an awake electroencephalogram (EEG). Thirty-eight healthy volunteers, aged 20-36 years old, participated in this study. The maximum local SAR (specific absorption rate) averaged over 10-g mass was 2.0 W/kg. The EEG was recorded before and after real or sham exposures. The effects of exposure conditions (real or sham) and the recording time (before, during, and after exposure) on each EEG power spectrum of θ, α, and β frequency ranges were analyzed. The θ and α band waves were enhanced after both exposure conditions. These results may be explained by the participants' drowsiness during the EEG recording in both exposures. We conclude that an LTE-like exposure for 30 min in this study showed no detectable harmful effects on awake EEGs in healthy humans.