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Volga Neuroscience School 2016 Astroglial control of rhythm genesis in the brain
Whether the Motor Cortex Excitability Changes during Control of Phantom Hand within P300-Based BCI Contour
N.V.Syrov1,3 *, D.D.Zhigulskaya1, D.A.Kirjanov1,3, S.V.Borisov1,2, A.Ya.Kaplan1,2,3
1 Lomonosov Moscow State University, Moscow, Russian Federation;
2 Pirogov Russian National Research Medical University, Moscow, Russian Federation;
3 Lobachevsky State University of Nizhni Novgorod, Nizhni Novgorod, Russian Federation. * Presenting e-mail: [email protected]
Introduction
Motor imagery (MI) activates brain regions participating in motor control, such as primary motor cortex (Brodmann area 4). Transcranial magnetic stimulation (TMS) studies demonstrated increased amplitudes of motor evoked potentials (MEPs) from this area what suggests increasing of cortical excitability during MI. In addition to the MI, an observation of movement also leads to motor cortex excitability increasing and this activation overlaps significantly with activation taking place during actual movement. These facts suggest that MI based brain computer interfaces (BCI) with robotic hand or exoskeleton movement can be proposed as potentially useful tools in rehabilitation from stroke and other brain injuries. However, the ability of a patient to form vivid motor images can be impaired. Even after many training sessions, such patients cannot achieve acceptable accuracy of BCI control.
In such a case, using T300 BCI' based on visual evoked potentials and commonly used in BCI spellers could be more promising.
The aim of our experiment was to study the motor cortex excitability changes during control movements of phantom hand fingers within P300-based BCI contour.
Methods
20 healthy right-handed volunteers (mean age, 36 years; age range, 24-68 years; 7 males and 4 females) were included into the study.
The electromyogram was recorded by standard EMG cup electrodes placed on the target muscles of the right hand [extensor digitorum communis (EDC) and flexor digitorum suprficialis (FDS)] and positioned according to the belly-tendon principle. The ground electrode was placed on the left processus styloideus ulnae. We then determined the stimulation intensity and "intermediate" hot-spot i.e. point on the scalp where TMS evokes MEPs of EDC higher than 1 mV and FDC higher than 0,5 mV peak to peak amplitude in 5/10 trials in subjects during rest condition (EDC has the lower threshold).
EEG activity was recorded at the CPz, Pz, Po3, Po4, Po7, Po8, O1, O2 electrode sites placed according to the interna-tional10-20 system and referenced to the linked earlobe electrodes. A ground electrode was attached to the forehead. Event related potentials were recorded during oddball visual stimulus presentation. In this study, blinks of light-emitting diodes (LEDs) on fingers of phantom hand were used as visual stimulus. Significant components of ERP were extracted from EEG by linear discriminate analysis (LDA). One finger of phantom hand was flexed when the particular features of ERD were detected. Simultaneously (several ms after start of movement of finger), single TMS pulse was applied to the above mentioned "intermediate" hot-spot. In addition, when participants were fully relaxed and looked at the inactive phantom hand MEPs were also recorded (correspond to baseline). MEPs of all subjects were normalized by baseline and separated corresponding to type of feedback (flexing of target finger, flexing of non target finger and absence of any movements of fingers). Kruskal-Wallis and Mann-Whitney tests were used to test whether MEPs amplitude differs between the conditions. P-values were adjusted by Dunn's test.
Results
Amplitude (peak-to-peak) of MEPs recorded during flexion of non-target finger decreased significantly compared to the other conditions (Fig.1.).
Moreover, post-hoc tests revealed that MEPs amplitude during baseline condition was significantly lower than during the BCI condition (control of finger flexion)(Fig.2). These results suggest the increases in corticospinal excitability during BCI condition, especially during wrong finger movement observation. The latter fact can be related to the most emotional reactions of participants during observation of unexpected finger flexion.
Our results suggest that motor cortex excitability changes may occur within 'P300- BCI' experiments with phantom hand fingers movements as a feedback
OM&P
OM&P
Volga Neuroscience School 2016 Astroglial control of rhythm genesis in the brain
Fig.1. Motor-evoked potential (MEP) for FDS data of all subjects regarding to different types of feedback. 'Correct' and 'wrong' correspond to MEPs which were recorded during movement of target and non-target finger respectively. "Without feedback" corresponds to the cases when participants watched flashes of LEDs but no any finger flexed. Amplitude of responses is presented as a percentage of the baseline condition mean MEPs . Columns and error bars are median and interquartile range of distribution of each group of MEPs. Note: **p <0,01; *p<0,05
#
Fig.2. Motor-evoked potential (MEP) for FDS data of all subjects regarding to to different types of feedback. Amplitude of responses is shown as a percentage of the baseline condition mean MEPs . Columns and error bars are median and interquartile range of distribution of each group of MEPs. Note: #p <0,0001
Acknowledgements
This study was partially supported by funding from the Skolkovo Foundation (project 1110034) and from the Russian Science Foundation (15-19-20053).
References
1. Williams J. et al. The relationship between corticospinal excitability during motor imagery and motor imagery ability // Behav. Brain Res. Elsevier B.V., 2012. Vol. 226, № 2. P. 369-375.
2. Burns A., Adeli H., Buford J. a. Brain-Computer Interface after Nervous System Injury // Neurosci. 2014. Vol. 20, № September. P. 639-651.
