Dissociating motor cortex from the motor

Abstract

During closed-loop control of a brain-computer interface, neurons in the primary motor cortex can be intensely active even though the subject may be making no detectable movement or muscle contraction. How can neural activity in the primary motor cortex become dissociated from the movements and muscles of the native limb that it normally controls? Here we examine circumstances in which motor cortex activity is known to dissociate from movement -including mental imagery, visuo-motor dissociation and instructed delay. Many such motor cortex neurons may be related to muscle activity only indirectly. Furthermore, the integration of thousands of synaptic inputs by individual α-motoneurons means that under certain circumstances even cortico-motoneuronal cells, which make monosynaptic connections to α-motoneurons, can become dissociated from muscle activity. The natural ability of motor cortex neurons under voluntarily control to become dissociated from bodily movement may underlie the utility of this cortical area for controlling brain-computer interfaces.

Activity in the brain network for dynamic manipulation of unstable objects is robust to acute tactile nerve block: An fMRI study

“…According to a hierarchical view of motor control (Kawato et al, 1987;Loeb et al, 1999;Konen and Kastner, 2008) dexterous manipulation capabilities, such as the compression of an unstable spring prone to buckling, are likely not exclusively controlled Q7 by the neo-and somatosensory cortices (Lawrence et al, 2014;Lemon, 1993;Schieber, 2011) but involve also subcortical and spinal structures (Lawrence et al, 2014). Even if we presume a limited role of the spinal cord in movement generation in humans, the spinal cord can certainly shape the motor commands coming from supraspinal structures by gating, inhibiting, or disinhibiting the behavior of spinal circuitry (Pierrot-Deseilligny and Burke, 2005).…”

Does dysfunction of the mirror neuron system contribute to symptoms in amyotrophic lateral sclerosis?

“…However, a large fraction of the mirror PTNS in M1 showed suppression of discharge during action observation (Kraskov et al , 2014); some cortico-motoneuronal PTNs also showed this suppression. One suggested role for these suppression mirror neurons relates to involvement in withholding unwanted movement during action observation, and that such a braking mechanism would avoid unintended overflow of activity (Schieber, 2011).…”

Joint cross-correlation analysis reveals complex, time-dependent functional relationship between cortical neurons and arm electromyograms

“…Davidson et al (2007) and Schieber (2011) called a similar disparity between activity of M1 neurons and EMGs, "dissociating motor cortex from the motor." In their experiments, monkeys were rewarded for synchronous activation of specific motor neurons and arbitrary muscles.…”

“…The now classic STA approach, which effectively represents cross-correlation between single neurons and EMGs, was introduced to assess functional connectivity of spinal motoneurons Jackson et al 2006;Mantel and Lemon 1987;McKiernan et al 2000;Miller et al 1993;Morrow and Miller 2003;Schieber and Rivlis 2007). This and similar methods have been used to analyze the inputs to the spinal cord from the cortex (Carmena et al 2003;Davidson et al 2007;Fuglevand 2011;McKiernan et al 2000;Morrow et al 2007;Schaefer et al 2009;Schieber 2011), red nucleus (Miller et al 1993) and reticular formation (Stuphorn et al 1999). The analytic approach employed in the present study, JCC, is very similar to the JPSTH method introduced in the late 1960s for the analysis of time-dependent correlations between neurons (Aertsen et al 1989;Cardoso de Oliveira et al 2001;Gerstein and Perkel 1969;Vaadia et al 1995).…”

“…DESPITE MANY DECADES OF research, the way that cortical signals control voluntary muscle contractions is not well understood (Kalaska 2009;Levine et al 2012;Rothwell 2012;Schieber 2011). Particularly, it is still controversial (Hirasaki et al 2004) whether motor cortical neurons encode muscle force Kalaska 2009;Levine et al 2012;Rothwell 2012), limb kinematics (Georgopoulos et al 1982;Moran and Schwartz 1999;Oby et al 2013) or higher-order representations of movements Wessberg et al 2000;).…”