Encoding of speed and direction of movement in the human supplementary motor area: Laboratory investigation

ArticleinJournal of Neurosurgery 110(6):1304-16 · March 2009with11 Reads
DOI: 10.3171/2008.10.JNS08466 · Source: PubMed
Abstract
The supplementary motor area (SMA) plays an important role in planning, initiation, and execution of motor acts. Patients with SMA lesions are impaired in various kinematic parameters, such as velocity and duration of movement. However, the relationships between neuronal activity and these parameters in the human brain have not been fully characterized. This is a study of single-neuron activity during a continuous volitional motor task, with the goal of clarifying these relationships for SMA neurons and other frontal lobe regions in humans. The participants were 7 patients undergoing evaluation for epilepsy surgery requiring implantation of intracranial depth electrodes. Single-unit recordings were conducted while the patients played a computer game involving movement of a cursor in a simple maze. In the SMA proper, most of the recorded units exhibited a monotonic relationship between the unit firing rate and hand motion speed. The vast majority of SMA proper units with this property showed an inverse relation, that is, firing rate decrease with speed increase. In addition, most of the SMA proper units were selective to the direction of hand motion. These relationships were far less frequent in the pre-SMA, anterior cingulate gyrus, and orbitofrontal cortex. The findings suggest that the SMA proper takes part in the control of kinematic parameters of endeffector motion, and thus lend support to the idea of connecting neuroprosthetic devices to the human SMA.
    • "Participation of patients with epilepsy, implanted with microelectrodes for clinical reasons, in single-neuron studies has yielded important novel understandings in multiple fields of neuroscience [4,5] . These include , for example, speech encoding [6,7], memory [8][9][10], auditory encoding [11,12], face identity [13], vision [14], visuomotor coordination [15], motor representation [16], and sleep [17,18]. The same setup can also serve for studying mechanisms of human epilepsy, ictogenesis, at the single-cell level. "
    [Show abstract] [Hide abstract] ABSTRACT: Today, localization of the seizure focus heavily relies on EEG monitoring (scalp or intracranial). However, current technology enables much finer resolutions. The activity of hundreds of single neurons in the human brain can now be simultaneously explored before, during, and after a seizure or in association with an interictal discharge. This technology opens up new horizons to understanding epilepsy at a completely new level. This review therefore begins with a brief description of the basis of the technology, the microelectrodes, and the setup for their implantation in patients with epilepsy. Using these electrodes, recent studies provide novel insights into both the time domain and firing patterns of epileptic activity of single neurons. In the time domain, seizure-related activity may occur even minutes before seizure onset (in its current, EEG-based definition). Seizure-related neuronal interactions exhibit complex heterogeneous dynamics. In the seizure-onset zone, changes in firing patterns correlate with cell loss; in the penumbra, neurons maintain their spike stereotypy during a seizure. Hence, investigation of the extracellular electrical activity is expected to provide a better understanding of the mechanisms underlying the disease; it may, in the future, serve for a more accurate localization of the seizure focus; and it may also be employed to predict the occurrence of seizures prior to their behavioral manifestation in order to administer automatic therapeutic interventions.
    Article · May 2016
    • "The only positive correlation for valence ratings found in our study concerned the right SMA. As this region is a key component of motor initiation and sequence planning (Tankus et al., 2009 ), our finding might indicate that musically induced pleasantness engenders motor action tendencies like the urge to dance or move with the music (Zatorre and Halpern, 2005). Moreover, induced mirth and smiling have been associated with activity in the SMA (Iwase et al., 2002). "
    [Show abstract] [Hide abstract] ABSTRACT: To study emotional reactions to music, it is important to consider the temporal dynamics of both affective responses and underlying brain activity. Here we investigated emotions induced by music using functional magnetic resonance imaging (fMRI) with a data-driven approach based on inter-subject correlations (ISC). This method allowed us to identify moments in the music that produced similar brain activity (i.e. synchrony) among listeners under relatively natural listening conditions. Continuous ratings of subjective pleasantness and arousal elicited by the music were also obtained for the music outside of the scanner. Our results reveal synchronous activations in left amygdala, left insula, and right caudate nucleus that were associated with higher arousal, whereas positive valence ratings correlated with decreases in amygdala and caudate activity. Additional analyses showed that synchronous amygdala responses were driven by energy-related features in the music such as rms and dissonance, while synchrony in insula was additionally sensitive to acoustic event density. Inter-subject synchrony also occurred in the left nucleus accumbens, a region critically implicated in reward processing. Our study demonstrates the feasibility and usefulness of an approach based on ISC to explore the temporal dynamics of music perception and emotion in naturalistic conditions. © The Author (2015). Published by Oxford University Press. For Permissions, please email: journals.permissions@oup.com.
    Full-text · Article · May 2015
    • "The only positive correlation for valence ratings found in our study concerned the right SMA. As this region is a key component of motor initiation and sequence planning (Tankus et al., 2009 ), our finding might indicate that musically induced pleasantness engenders motor action tendencies like the urge to dance or move with the music (Zatorre and Halpern, 2005). Moreover, induced mirth and smiling have been associated with activity in the SMA (Iwase et al., 2002). "
    [Show abstract] [Hide abstract] ABSTRACT: To study emotional reactions to music, it is important to consider the temporal dynamics of both affective responses and underlying brain activity. Here, we investigated emotions induced by music using functional magnetic resonance imaging (fMRI) with a data-driven approach based on intersubject correlations (ISC). This method allowed us to identify moments in the music that produced similar brain activity (i.e. synchrony) among listeners under relatively natural listening conditions. Continuous ratings of subjective pleasantness and arousal elicited by the music were also obtained for the music outside of the scanner. Our results reveal synchronous activations in left amygdala, left insula and right caudate nucleus that were associated with higher arousal, whereas positive valence ratings correlated with decreases in amygdala and caudate activity. Additional analyses showed that synchronous amygdala responses were driven by energy-related features in the music such as root mean square and dissonance, while synchrony in insula was additionally sensitive to acoustic event density. Intersubject synchrony also occurred in the left nucleus accumbens, a region critically implicated in reward processing. Our study demonstrates the feasibility and usefulness of an approach based on ISC to explore the temporal dynamics of music perception and emotion in naturalistic conditions.
    Full-text · Article · May 2015
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