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Neurologic Diagnosis
Published in Philip B. Gorelick, Fernando D. Testai, Graeme J. Hankey, Joanna M. Wardlaw, Hankey's Clinical Neurology, 2020
This readiness potential indicates preparation for self-paced voluntary movements. It has components arising from the presupplementary motor area, supplementary motor area, and the premotor cortex. The potential comprises a slowly increasing negative potential beginning 1–2 seconds before the movement, and then a steeper increasing negativity (the NS′) about 400 ms before the movement (Figure 1.59). It can be recorded from the scalp EEG, triggering the acquisition with EMG electrodes placed over a muscle involved in the movement and then back-averaging the EEG preceding the movement. Jerk-locked back-averaging of an EEG requires a bandwidth to include low frequencies. In patients with suspected functional jerky movements, the presence of a Bereitschaftspotential (BP) strongly supports voluntary movement and a psychogenic origin. Limitations include continuous and pleomorphic movements preventing discrete triggering for back-averaging, and the BP is not always seen with voluntary movements in normal subjects.
The Nucleus Accumbens Core and Shell: Accumbal Compartments and Their Functional Attributes
Published in Peter W. Kalivas, Charles D. Barnes, Limbic Motor Circuits and Neuropsychiatry, 2019
Ariel Y. Deutch, Andrea J. Bourdelais, Daniel S. Zahm
How does this affective drive gain access to the motor circuitry? The core may be the substrate through which motoric acts are derived. The core has direct projections to classic extrapyramidal structures, including the entopeduncular nucleus, subthalamic nucleus, and pars reticulata of the SN. The anatomical organization of afferents to the core also offers support for the contention that the NAScore may be intimately involved in the execution of voluntary motoric acts. The core, in contrast to the shell, receives afferents from the dorsal part of the PFC of the rat, including the medial precentral (shoulder) cortex. Behavioral data have led to the suggestion that the shoulder cortex in the rat represents the homologue to the premotor cortex, supplementary motor area (SMA), and frontal eye field in primates.174 The SMA in man appears to be the site at which the Bereitschaftspotential is generated.222 This DC negative wave precedes the execution of voluntary movements and is markedly diminished in Parkinsonian patients,222,223 presumably because of the loss of DA in this region.224 If the organization of afferents to the core in the primate is similar to that observed in rodents (i.e., the core receives SMA projections), the functional link between the SMA and core would suggest that the NAS core is the motoric locus within the accumbal complex.
Movement Disorders
Published in John W. Scadding, Nicholas A. Losseff, Clinical Neurology, 2011
Specific PMDs may have additional features that support the diagnosis. In psychogenic tremor, these include distractibility and entrainability of tremor to the frequency of contralateral hand movements. In psychogenic myoclonus, the presence of a Bereitschaftspotential (premovement potential) preceding myoclonic movements, of prolonged or variable duration EMG bursts, and of long latency and variable recruitment in stimulus-sensitive myoclonus, all support the diagnosis.
Preserved critical ability and free will in deep hypnosis during oral surgery
Published in American Journal of Clinical Hypnosis, 2021
Enrico Facco, Christian Bacci, Edoardo Casiglia, Gastone Zanette
The debate on free will come about caused by Libet ’s work reflects the inclination to separate and reify conscious and unconscious processes as two distinct components of the human mind-brain (a tendency rooted in the dualistic ego-centered stance of Western metaphysics). Instead, these processes engage in a ceaseless reciprocal exchange, necessarily making the experience of agency that results from their dynamic interactions incomplete and fallible (Gomes, 2007). The Bereitschaftspotential (readiness potential) observed by Libet and colleagues – which appears on the EEG before any volitional movement or awareness of intending to make it – also exists in post-hypnotic voluntary movements unaccompanied by any sense of agency and will (Schlegel et al., 2015); in other words, they share the same physiological pattern. Terhune and Hedman (2017) reported finding that the sense of agency of highly hypnotizable individuals is less sensitive to manipulations of their perceived control. This would suggest an altered meta-awareness of agency, a feature observed outside hypnosis, and belonging more to their personality when in a state of ordinary consciousness than to the state of hypnosis.
The Cognitive Demands of Gait Retraining in Runners: An EEG Study
Published in Journal of Motor Behavior, 2020
Tyler Whittier, Richard W. Willy, Gustavo Sandri Heidner, Samantha Niland, Caitlin Melton, J. C. Mizelle, Nicholas P. Murray
No significant differences in spectral power were observed in the primary motor cortices. These findings contradict one of our initial hypotheses that both beta and mu frequency bands spectral power would decrease, and lower gamma spectral power would increase in the primary motor cortices as participants transitioned into their new gait, with higher stride rate. This was not expected and contradicted other findings in similar conditions (Presacco et al., 2011; Severens, Nienhuis, Desain, & Duysens, 2012; Wagner et al., 2012). It is possible that an increase in cognitive effort might set the motor system into a suppressed state that results in an increase in mu frequency power over the motor areas compared to a low cognitive effort (Freeman, Itthipuripat, & Aron, 2016). In addition, previous gait manipulation studies often include an external cue to modify SR (e.g., Wagner, et al., 2016). Smith and Staines (2012) demonstrated that cued movements and self-paced movements modulate different brain regions and differing cortical activations. Using the Bereitschaftspotential (pre-motor potential), the self-paced motor task elicited cortical activity over the supplementary motor area whereas the cued task resulted in activation, specifically the movement- related potential, within the premotor and motor cortex.