A Review of Techniques for Detection of Movement Intention Using Movement-Related Cortical Potentials <s> Generator Sources of MRCP. <s> Abstract In order to clarify the significance of the various components of the movement-related cortical potentials, scalp-recorded potential changes associated with voluntary, self-paced middle finger flexion and extension were studied by an opisthochronic averaging program in 14 normal right-handed subjects. Topographical study, based on 14 simultaneously recorded and averaged EEG channels, enabled us to identify at least 8 components; 4 pre-motion and 4 post-motion. The pre-motion components are the Bereitschaftspotential (BP) (a symmetric early negative shift), NS′(−500 to −90) (a negative slope maximal over the contralateral precentral region and culminating in N −90 ipsilaterally), P −50 (corresponding to the pre-motion positivity, PMP), and N −10 (probably corresponding to the motor potential, MP). The post-motion components include N +50 (a sharp negative post-motion activity over the contralateral frontal region), P +90 , and N +160 (presumably representing sensory functions) and P +300 (a large positivity maximal over the contralateral precentral region but widely distributed). <s> BIB001 </s> A Review of Techniques for Detection of Movement Intention Using Movement-Related Cortical Potentials <s> Generator Sources of MRCP. <s> Movement-related cortical potentials (MRPs) were recorded from scalp electrodes in 8 normal volunteers and from chronically implanted subdural electrodes in 7 patients who were being evaluated for surgical treatment of epilepsy. From subdural electrodes, a clearly defined, extremely localized slow negative potential preceding the voluntary movement of the middle finger (Bereitschaftspotential, BP) was recorded in the contralateral and ipsilateral hand sensorimotor areas. The negative slope (NS') began approximately 250 to 400 ms before EMG onset and was recorded exclusively from the contralateral hand sensorimotor area. Both BP and NS' were maximum in the hand motor area. Although a negative slope was recorded also from the supplementary motor area, whether that particular slope corresponded to BP or NS', or both, could not be determined. Three kinds of progressively steeper negative potentials starting around the onset of the EMG were identified: (1) the 'hand motor potentials' which were seen in the contralateral hand motor area and started immediately before EMG onset and peaked 130 +/- 32 ms after EMG onset; (2) the 'hand somatosensory potentials' seen in the contralateral hand somatosensory area which started simultaneously or immediately after the EMG onset; and (3) the 'vicinity potentials' seen in the immediate surroundings of the contralateral hand area and which started after the EMG onset. The 'hand motor potentials' had the highest amplitude. From these findings, we concluded that bilateral hand sensorimotor areas and the supplementary motor area participate in the 'preparation' of movements, but that mainly the contralateral cortex generates the discharges necessary to produce the actual movement. <s> BIB002 </s> A Review of Techniques for Detection of Movement Intention Using Movement-Related Cortical Potentials <s> Generator Sources of MRCP. <s> Movement-related potentials (MRPs) were recorded from subdural electrodes chronically implanted in the interhemispheric fissure in two patients being evaluated for epilepsy surgery. Different types of movements (finger, foot, tongue and vocalization) were executed. Foot movements elicited a clearly defined, well-localized slow negativity or positivity (Bereitschaftspotential, BP) preceding electromyogram (EMG) onset These BPs were seen from the contralateral primary motor foot area and also from bilateral supplementary motor areas (SMAs) with equivalent amplitudes and temporal evolutions. A steeper potential [negative slope (NS')] occurred about 300 ms before EMG onset and the motor potential (MP) started 100 ms before EMG onset Negative slopes and MPs also arose from the contralateral primary motor area as well as from the bilateral SMAs. Finger movements elicited well-localized BPs and NS' which were generated from the bilateral SMAs, but were of higher amplitude on the contralateral SMA. Motor potentials started 50 ms prior to EMG onset and arose exclusively from the contralateral SMA. Tongue protrusions and vocalizations also elicited BP, NS' and MP which were seen in the bilateral SMAs. ::: ::: Movement-related potentials for different types of movements had a somatotopic distribution in the SMA, which was consistent with the SMA somatotopic organization defined by electrical simulation. Movement-related potentials for tongue movements and vocalization had a similar distribution and waveform. It was concluded that bilateral SMAs generate well-defined MRPs consistent with the assumption that the SMA plays a significant role in the organization of voluntary movements. However, the MRPs from the bilateral SMAs do not have characteristics which are different from those of the primary motor area. This suggests the hypothesis of ‘supplementary’ function for SMA, and does not support the hypothesis of ‘supramotor’ function. <s> BIB003 </s> A Review of Techniques for Detection of Movement Intention Using Movement-Related Cortical Potentials <s> Generator Sources of MRCP. <s> The 'Bereitschaftspotential' attributed to activation of the supplementary motor area (SMA) precedes the 'motor potential' of the primary motor cortex (Ml) about 500-1000 ms during self-initiated movements. A measurement procedure is reported to evaluate the sequence of hemodynamic activation within both motor areas by functional magnetic resonance imaging (fMRI). The fMRI-data were averaged across multiple trials of single voluntary finger movements and analyzed with respect to the onset-time of signal increase. All participants showed a sequential hemodynamic response with SMA preceding M1 activation. The mean latency between hemodynamic activation of SMA and M1 amounted to 0.8 s. These findings suggest that the vascular response parallels the electrical events and that a sufficient temporal resolution can be achieved by fMRI to detect sequential hemodynamic activation of functionally connected cortical areas. <s> BIB004 </s> A Review of Techniques for Detection of Movement Intention Using Movement-Related Cortical Potentials <s> Generator Sources of MRCP. <s> Abstract To clarify the precise location and timing of the motor cortical activation in voluntary movement, dipole source analysis integrating multiple constraints was conducted for the movement-related cortical potential (MRCP). Six healthy subjects performed single self-paced extensions of the right index finger at about 15-s intervals during EEG and event-related fMRI acquisitions. EEG was recorded from 58 scalp electrodes, and fMRI of the entire brain was obtained every 2.6 s. Coordinates of the two methods were coregistered using anatomical landmarks. During dipole source modeling, a realistic three-layer head model was used as a volume conductor. To identify the number of uncorrelated sources in the MRCP, principal component (PC) analysis was performed, which was consistent with the existence of six sources in the left (Lt SM1) and right (Rt SM1) sensorimotor and medial frontocentral (MFC) areas. After dipoles were seeded at the activated spots revealed by fMRI, dipole orientations were fixed based on the interpretation of the topography of distribution of the PC. The strength of the six dipoles (three dipoles in Lt SM1, two in Rt SM1, and one in MFC) was then computed over time. Within the bilateral SM1, activation of the precentral gyrus occurs bilaterally with similar strength from −1.2 s, followed by that of the precentral bank from −0.5 s with contralateral preponderance. Subsequently, the postcentral bank becomes active only on the contralateral side at 0.1 s after movement. Activation of the MFC shows timing similar to that of the bilateral precentral gyri. These deduced patterns of activation are consistent with previous studies of electrocorticography in humans. <s> BIB005 </s> A Review of Techniques for Detection of Movement Intention Using Movement-Related Cortical Potentials <s> Generator Sources of MRCP. <s> Abstract Since discovery of the slow negative electroencephalographic (EEG) activity preceding self-initiated movement by Kornhuber and Deecke [Kornhuber HH, Deecke L. Hirnpotentialanderungen bei Willkurbewegungen und passiven Bewegungen des Menschen: Bereitschaftspotential und reafferente Potentiale. Pflugers Archiv 1965;284:1–17], various source localization techniques in normal subjects and epicortical recording in epilepsy patients have disclosed the generator mechanisms of each identifiable component of movement-related cortical potentials (MRCPs) to some extent. The initial slow segment of BP, called ‘early BP’ in this article, begins about 2 s before the movement onset in the pre-supplementary motor area (pre-SMA) with no site-specificity and in the SMA proper according to the somatotopic organization, and shortly thereafter in the lateral premotor cortex bilaterally with relatively clear somatotopy. About 400 ms before the movement onset, the steeper negative slope, called ‘late BP’ in this article (also referred to as NS′), occurs in the contralateral primary motor cortex (M1) and lateral premotor cortex with precise somatotopy. These two phases of BP are differentially influenced by various factors, especially by complexity of the movement which enhances only the late BP. Event-related desynchronization (ERD) of beta frequency EEG band before self-initiated movements shows a different temporospatial pattern from that of the BP, suggesting different neuronal mechanisms for the two. BP has been applied for investigating pathophysiology of various movement disorders. Volitional motor inhibition or muscle relaxation is preceded by BP quite similar to that preceding voluntary muscle contraction. Since BP of typical waveforms and temporospatial pattern does not occur before organic involuntary movements, BP is used for detecting the participation of the ‘voluntary motor system’ in the generation of apparently involuntary movements in patients with psychogenic movement disorders. In view of Libet et al.’s report [Libet B, Gleason CA, Wright EW, Pearl DK. Time of conscious intention to act in relation to onset of cerebral activity (readiness-potential). The unconscious initiation of a freely voluntary act. Brain 1983;106:623–642] that the awareness of intention to move occurred much later than the onset of BP, the early BP might reflect, physiologically, slowly increasing cortical excitability and, behaviorally, subconscious readiness for the forthcoming movement. Whether the late BP reflects conscious preparation for intended movement or not remains to be clarified. <s> BIB006 </s> A Review of Techniques for Detection of Movement Intention Using Movement-Related Cortical Potentials <s> Generator Sources of MRCP. <s> The dorsal premotor cortex (PMd) is thought to play a significant role in movement preparation cued by sensory information rather than in self-initiated movements. The evidence in humans for this contention is still circumstantial. Here we explored the effects of modulation of PMd by excitability decreasing 1 Hz repetitive transcranial magnetic stimulation (rTMS) versus excitability increasing 5 Hz rTMS on two forms of movement related cortical potentials: contingent negative variation (CNV) versus Bereitschaftspotential (BP) reflecting externally cued versus self-triggered movement preparation. Ten healthy right-handed subjects performed visually cued or self-triggered simple sequential finger movements with their right hand. CNV and BP were recorded by 25 EEG electrodes covering the fronto-centro-parietal cortex and divided into an early (1500–500 ms before a go-signal or movement onset) and a late potential (500–0 ms). MRI-navigated 1 Hz rTMS of the left PMd resulted in significant increase of the late CNV over the left central region predominantly contralateral to the prepared right hand movement, while 5 Hz rTMS had no effect on CNV. In contrast, 1 and 5 Hz rTMS did not modify BP. Control experiments of 1 Hz rTMS of the supplementary motor area (SMA) and of low-intensity 1 Hz rTMS of the left primary motor cortex did not change CNV, but 1 Hz SMA-rTMS increased late BP. This double dissociation of effects of PMd-rTMS versus SMA-rTMS on CNV versus BP provides direct evidence that the left PMd in humans is more involved in preparatory processes of externally cued rather than self-initiated movements, contrasting with an opposite role of the SMA. Hum Brain Mapp 2012. © 2011 Wiley Periodicals, Inc. <s> BIB007
Several studies reported that the BP might be recorded from subcortical structures such as basal ganglia and thalamus BIB006 . The work BIB002 deduced that the early BP was produced by both sensorimotor areas. The work BIB003 verified that both the ipsilateral and contralateral supplementary motor areas (SMAs) generated potentials consistent with the early BP. In order to elucidate the exact area and timing of the motor cortical activation in voluntary movement, dipole source analysis incorporating multiple constraints was applied for MRCP. The work BIB005 suggested that medial frontocentral (MFC) and sensorimotor areas (SM1) were probable generators of MRCP. The strength of the six dipoles, seeded at the activated spots (three dipoles in left SM1, two in right SM1, and one in MFC) revealed by fMRI, was measured over time. Inside the bilateral SM1, activation of the precentral gyrus happens bilaterally with comparable strength from −1.2 s, taken after by that of the precentral bank from −0.5 s with contralateral dominance through movement execution BIB005 . Consequently, the postcentral bank gets active just on the contralateral side at 0.1 s after movement. Activation of the MFC shows timing similar to bilateral precentral gyri. The strength and timing of arousal in the ipsilateral precentral gyrus were like those in the contralateral precentral gyrus and the MFC. But the ipsilateral precentral bank demonstrated much lesser strength than the contralateral precentral bank BIB005 . To a certain degree, automatic movements such as blinking of eyelids, spontaneous eye movements, swallowing, chewing, and respiration are also controlled by volitional factors; therefore, BP is recorded when these movements are reiterated at a self-paced rate BIB006 . Self-paced finger movements were related with activation of the anterior SMA, both contralateral sensorimotor cortex and the lateral premotor cortices, but without substantial activation of the ipsilateral sensorimotor cortex  . For externally triggered movement, a premovement potential preceding the stimulus was present  . Similarly, there were few distinctions in the areas of activation between externally triggered activations and self-paced activation. For a self-paced finger movement, BIB004 reported SMA activation anteceded that of the motor cortex by 800 ms. The dorsal premotor cortex (PMd) is believed to play substantial role in cued movement preparation rather than in self-initiated movements BIB007 . The terminal CNV is generated in the prefrontal cortex including PMd, while the late BP is generated in the primary motor cortex, SMA, and primary somatosensory cortex BIB007 . This study discovered the effects of variation of PMd on BP and CNV reflecting selfinitiated versus cued movement preparation by increasing and decreasing the excitability of brain using 5 Hz and 1 Hz repetitive transcranial magnetic stimulations (rTMS), respectively. They found that rTMS of the left PMd resulted in variation of terminal CNV but not late BP while rTMS of the SMA proper resulted in a modification of late BP but not terminal CNV. This provided evidence that neuronal activity of the left PMd in humans is favorably included in the preparation of externally cued movements as compared to self-initiated movements, contrasting with an opposite role of the SMA proper. Comparing the MRCP for a foot movement with hand movement showed interesting differences across some movement components BIB001 . For the hand movement, the late BP is highest over the contralateral central area (approximately C1 or C2 of the International 10-20 System) and for the foot movement, late BP is maximal at the midline (approximately Cz) BIB001 .