On postural and non-postural activities of the mid-brain

In the course of experiments in which the cerebral cortex of the monkey is stimulated, it is peculiarly noticeable that the activity of the cortex varies from time to time. That such variation should occur is by no means strange, in view of the difficulty of maintaining a constant depth of narcosis. But there are other variations which seemingly are not conditioned by variation of depth of narcosis. Thus it not rarely happens that, when the depth of narcosis is certainly a constant one, the motor cortex becomes suddenly inexcitable. This occurs, for instance, after a cortical discharge, which is followed by “ epileptic ” after-discharge. But it also occurs without any apparent preceding cause. Thus suddenly the cortical excitability becomes abolished—at any rate, to practicable strengths of stimulation. This sudden loss of cortical excitability is a phenomenon of interest. It is accompanied by two marked states. Of these, the first is an anæmia of the cortex ; the second is a maintained postural contraction of certain of the muscles of the limbs. The anæmia seems to occur over the whole of the small area of cortex—pre-central and post-central—usually exposed in these experiments. It causes a sudden change in appearance from the “raw ham” look of the cortex when it is in the most favourable condition for electrical stimulation to a pale “ dead ” look. The cortex blanches; it may be surmised that it faints.

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Physiological properties of neurons projecting from area 3a to area 4 gamma of feline cerebral cortex

Journal of Neurophysiology ◽

10.1152/jn.1982.48.4.1048 ◽

1982 ◽

Vol 48 (4) ◽

pp. 1048-1057 ◽

Cited By ~ 19

Author(s):

H. Asanuma ◽

R. S. Waters ◽

H. Yumiya

Keyword(s):

Cerebral Cortex ◽

Motor Cortex ◽

Cortical Neurons ◽

Small Area ◽

Receptive Fields ◽

Projection Neurons ◽

Intracortical Microstimulation ◽

Projected Area ◽

Physiological Properties ◽

Area 3A

1. The corticocortical projection from area 3a to area 4 gamma was restudied using tranquilized cats. 2. Intracortical microstimulation (ICMS) of a given locus in area 3a produced effects on neurons in area 4 gamma that were located in a small area extending along the direction of the radial fibers constituting a columnar shape. 3. Cortical neurons in area 3a that projected to a particular neuron in area 4 gamma were located in a region that extended along the direction of the radial fibers and constituted a columnar shape. 4. Two-thirds of the projection neurons in area 3a had different receptive fields from those of neurons in the projected area in 4 gamma, thus suggesting that the 3a neurons are not simply transferring peripheral information to the 4 gamma neurons. 5. ICMS delivered to area 3a rarely excited 4 gamma neurons but rather facilitated their evoked discharges. 6. It is suggested that the activity of corticocortical projection from area 3a to 4 gamma can influence the activity of 4 gamma neurons only when combined with other inputs to the motor cortex.

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Effects of transcranial static magnetic stimulation over the primary motor cortex on local and network spontaneous electroencephalogram oscillations

Scientific Reports ◽

10.1038/s41598-021-87746-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Sumiya Shibata ◽

Tatsunori Watanabe ◽

Yoshihiro Yukawa ◽

Masatoshi Minakuchi ◽

Ryota Shimomura ◽

...

Keyword(s):

Motor Cortex ◽

Power Spectrum ◽

Magnetic Stimulation ◽

Primary Motor Cortex ◽

Cortical Excitability ◽

Controlled Study ◽

Functional Coupling ◽

Phase Lag ◽

Theta Band ◽

Double Blind

AbstractTranscranial static magnetic stimulation (tSMS) is a novel non-invasive brain stimulation technique that reduces cortical excitability at the stimulation site. We investigated the effects of tSMS over the left primary motor cortex (M1) for 20 min on the local electroencephalogram (EEG) power spectrum and interregional EEG coupling. Twelve right-handed healthy subjects participated in this crossover, double-blind, sham-controlled study. Resting-state EEG data were recorded for 3 min before the intervention and 17 min after the beginning of the intervention. The power spectrum at the left central electrode (C3) and the weighted phase lag index (wPLI) between C3 and the other electrodes was calculated for theta (4–8 Hz), alpha (8–12 Hz), and beta (12–30 Hz) frequencies. The tSMS significantly increased theta power at C3 and the functional coupling in the theta band between C3 and the parietal midline electrodes. The tSMS over the left M1 for 20 min exhibited modulatory effects on local cortical activity and interregional functional coupling in the theta band. The neural oscillations in the theta band may have an important role in the neurophysiological effects induced by tSMS over the frontal cortex.

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Pre-motor versus motor cerebral cortex neuromodulation for chronic neuropathic pain

Scientific Reports ◽

10.1038/s41598-021-91872-2 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Igor Lavrov ◽

Timur Latypov ◽

Elvira Mukhametova ◽

Brian Lundstrom ◽

Paola Sandroni ◽

...

Keyword(s):

Neuropathic Pain ◽

Cerebral Cortex ◽

Motor Cortex ◽

Initial Assessment ◽

Motor Cortex Stimulation ◽

Chronic Neuropathic Pain ◽

Long Term Effect ◽

Stimulation Of

AbstractElectrical stimulation of the cerebral cortex (ESCC) has been used to treat intractable neuropathic pain for nearly two decades, however, no standardized approach for this technique has been developed. In order to optimize targeting and validate the effect of ESCC before placing the permanent grid, we introduced initial assessment with trial stimulation, using a temporary grid of subdural electrodes. In this retrospective study we evaluate the role of electrode location on cerebral cortex in control of neuropathic pain and the role of trial stimulation in target-optimization for ESCC. Location of the temporary grid electrodes and location of permanent electrodes were evaluated in correlation with the long-term efficacy of ESCC. The results of this study demonstrate that the long-term effect of subdural pre-motor cortex stimulation is at least the same or higher compare to effect of subdural motor or combined pre-motor and motor cortex stimulation. These results also demonstrate that the initial trial stimulation helps to optimize permanent electrode positions in relation to the optimal functional target that is critical in cases when brain shift is expected. Proposed methodology and novel results open a new direction for development of neuromodulation techniques to control chronic neuropathic pain.

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Cortical Excitability across the ALS Clinical Motor Phenotypes

Brain Sciences ◽

10.3390/brainsci11060715 ◽

2021 ◽

Vol 11 (6) ◽

pp. 715

Author(s):

Thanuja Dharmadasa

Keyword(s):

Motor Cortex ◽

Cortical Excitability ◽

Phenotypic Variability ◽

Specific Treatment ◽

Underlying Disease ◽

Selective Vulnerability ◽

Clinical Feature ◽

Cortical Hyperexcitability ◽

Wide Range

Amyotrophic lateral sclerosis (ALS) is characterized by its marked clinical heterogeneity. Although the coexistence of upper and lower motor neuron signs is a common clinical feature for most patients, there is a wide range of atypical motor presentations and clinical trajectories, implying a heterogeneity of underlying pathogenic mechanisms. Corticomotoneuronal dysfunction is increasingly postulated as the harbinger of clinical disease, and neurophysiological exploration of the motor cortex in vivo using transcranial magnetic stimulation (TMS) has suggested that motor cortical hyperexcitability may be a critical pathogenic factor linked to clinical features and survival. Region-specific selective vulnerability at the level of the motor cortex may drive the observed differences of clinical presentation across the ALS motor phenotypes, and thus, further understanding of phenotypic variability in relation to cortical dysfunction may serve as an important guide to underlying disease mechanisms. This review article analyses the cortical excitability profiles across the clinical motor phenotypes, as assessed using TMS, and explores this relationship to clinical patterns and survival. This understanding will remain essential to unravelling central disease pathophysiology and for the development of specific treatment targets across the ALS clinical motor phenotypes.

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Cerebellar rTMS and PAS effectively induce cerebellar plasticity

Scientific Reports ◽

10.1038/s41598-021-82496-7 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Martje G. Pauly ◽

Annika Steinmeier ◽

Christina Bolte ◽

Feline Hamami ◽

Elinor Tzvi ◽

...

Keyword(s):

Motor Cortex ◽

Healthy Subjects ◽

Primary Motor Cortex ◽

Cortical Excitability ◽

Motor Evoked Potentials ◽

Repetitive Transcranial Magnetic Stimulation ◽

Premotor Cortex ◽

Motor Pathways ◽

Non Invasive ◽

Cerebellar Plasticity

AbstractNon-invasive brain stimulation techniques including repetitive transcranial magnetic stimulation (rTMS), continuous theta-burst stimulation (cTBS), paired associative stimulation (PAS), and transcranial direct current stimulation (tDCS) have been applied over the cerebellum to induce plasticity and gain insights into the interaction of the cerebellum with neo-cortical structures including the motor cortex. We compared the effects of 1 Hz rTMS, cTBS, PAS and tDCS given over the cerebellum on motor cortical excitability and interactions between the cerebellum and dorsal premotor cortex / primary motor cortex in two within subject designs in healthy controls. In experiment 1, rTMS, cTBS, PAS, and tDCS were applied over the cerebellum in 20 healthy subjects. In experiment 2, rTMS and PAS were compared to sham conditions in another group of 20 healthy subjects. In experiment 1, PAS reduced cortical excitability determined by motor evoked potentials (MEP) amplitudes, whereas rTMS increased motor thresholds and facilitated dorsal premotor-motor and cerebellum-motor cortex interactions. TDCS and cTBS had no significant effects. In experiment 2, MEP amplitudes increased after rTMS and motor thresholds following PAS. Analysis of all participants who received rTMS and PAS showed that MEP amplitudes were reduced after PAS and increased following rTMS. rTMS also caused facilitation of dorsal premotor-motor cortex and cerebellum-motor cortex interactions. In summary, cerebellar 1 Hz rTMS and PAS can effectively induce plasticity in cerebello-(premotor)-motor pathways provided larger samples are studied.

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Online and offline effects of transcranial alternating current stimulation of the primary motor cortex

Scientific Reports ◽

10.1038/s41598-021-83449-w ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Ivan Pozdniakov ◽

Alicia Nunez Vorobiova ◽

Giulia Galli ◽

Simone Rossi ◽

Matteo Feurra

Keyword(s):

Motor Cortex ◽

Primary Motor Cortex ◽

Cortical Excitability ◽

Motor Evoked Potentials ◽

Random Noise ◽

Single Pulse ◽

Alternating Current ◽

Online Application ◽

Transcranial Random Noise Stimulation ◽

Transcranial Alternating Current Stimulation

AbstractTranscranial alternating current stimulation (tACS) is a non-invasive brain stimulation technique that allows interaction with endogenous cortical oscillatory rhythms by means of external sinusoidal potentials. The physiological mechanisms underlying tACS effects are still under debate. Whereas online (e.g., ongoing) tACS over the motor cortex induces robust state-, phase- and frequency-dependent effects on cortical excitability, the offline effects (i.e. after-effects) of tACS are less clear. Here, we explored online and offline effects of tACS in two single-blind, sham-controlled experiments. In both experiments we used neuronavigated transcranial magnetic stimulation (TMS) of the primary motor cortex (M1) as a probe to index changes of cortical excitability and delivered M1 tACS at 10 Hz (alpha), 20 Hz (beta) and sham (30 s of low-frequency transcranial random noise stimulation; tRNS). Corticospinal excitability was measured by single pulse TMS-induced motor evoked potentials (MEPs). tACS was delivered online in Experiment 1 and offline in Experiment 2. In Experiment 1, the increase of MEPs size was maximal with the 20 Hz stimulation, however in Experiment 2 neither the 10 Hz nor the 20 Hz stimulation induced tACS offline effects. These findings support the idea that tACS affects cortical excitability only during online application, at least when delivered on the scalp overlying M1, thereby contributing to the development of effective protocols that can be applied to clinical populations.

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Transcranial Magnetic Stimulation as a Tool to Investigate Motor Cortex Excitability in Sport

Brain Sciences ◽

10.3390/brainsci11040432 ◽

2021 ◽

Vol 11 (4) ◽

pp. 432

Author(s):

Fiorenzo Moscatelli ◽

Antonietta Messina ◽

Anna Valenzano ◽

Vincenzo Monda ◽

Monica Salerno ◽

...

Keyword(s):

Transcranial Magnetic Stimulation ◽

Motor Cortex ◽

Magnetic Stimulation ◽

Motor Coordination ◽

Cortical Excitability ◽

Non Invasive ◽

Motor Cortex Excitability ◽

Invasive Method ◽

And Control ◽

The Impact

Transcranial magnetic stimulation, since its introduction in 1985, has brought important innovations to the study of cortical excitability as it is a non-invasive method and, therefore, can be used both in healthy and sick subjects. Since the introduction of this cortical stimulation technique, it has been possible to deepen the neurophysiological aspects of motor activation and control. In this narrative review, we want to provide a brief overview regarding TMS as a tool to investigate changes in cortex excitability in athletes and highlight how this tool can be used to investigate the acute and chronic responses of the motor cortex in sport science. The parameters that could be used for the evaluation of cortical excitability and the relative relationship with motor coordination and muscle fatigue, will be also analyzed. Repetitive physical training is generally considered as a principal strategy for acquiring a motor skill, and this process can elicit cortical motor representational changes referred to as use-dependent plasticity. In training settings, physical practice combined with the observation of target movements can enhance cortical excitability and facilitate the process of learning. The data to date suggest that TMS is a valid technique to investigate the changes in motor cortex excitability in trained and untrained subjects. Recently, interest in the possible ergogenic effect of non-invasive brain stimulation in sport is growing and therefore in the future it could be useful to conduct new experiments to evaluate the impact on learning and motor performance of these techniques.

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