Re-thinking the role of motor cortex: Context-sensitive motor outputs?

Abstract

The standard account of motor control considers descending outputs from primary motor cortex (M1) as motor commands and efference copy. This account has been challenged recently by an alternative formulation in terms of active inference: M1 is considered as part of a sensorimotor hierarchy providing top–down proprioceptive predictions. The key difference between these accounts is that predictions are sensitive to the current proprioceptive context, whereas efference copy is not. Using functional electric stimulation to experimentally manipulate proprioception during voluntary movement in healthy human subjects, we assessed the evidence for context sensitive output from M1. Dynamic causal modeling of functional magnetic resonance imaging responses showed that FES altered proprioception increased the influence of M1 on primary somatosensory cortex (S1). These results disambiguate competing accounts of motor control, provide some insight into the synaptic mechanisms of sensory attenuation and may speak to potential mechanisms of action of FES in promoting motor learning in neurorehabilitation.

Oscillatory entrainment of the motor cortical network during motor imagery is modulated by the feedback modality

“…In this context, proprioceptive feedback may comprise feed-forward information important for motor skill learning (Gandolla et al, 2014;Hardwick et al, 2013). We intentionally increased the task difficulty in our study to keep participants in the deliberative phase of skill acquisition with high demands for activating distributed motor learning related cortical networks (Miller et al, 2010;Wander et al, 2013), thereby disentangling the underlying neural mechanisms.…”

Understanding the role of the primary somatosensory cortex: Opportunities for rehabilitation

“…According to this view, motor commands are context-dependent and modulate activity in S1. In other words, M1 activity has a direct effect on S1 activity both in terms of a facilitation of the M1-S1 connections and stronger S1 self-inhibition (in order to diminish sensitivity to unrelated information), which has been recently demonstrated in the human brain (Gandolla et al, 2014). …”

“…These cortico-cortical connections are considered to modulate the relationship between sensory and motor components of sensorimotor processes (Petreanu et al, 2009; Xu et al, 2012). Recent theorizations about the directionality of such an exchange between S1 and M1 emphasize the dominant (probably disinhibitory) role of M1 over S1, both in rodents (Lee et al, 2013) and humans (Gandolla et al, 2014). In accordance with this view, animal research showed that lesions of S1 are associated with increased excitability of M1 (Domenech et al, 2013; Harrison et al, 2013).…”

Network interactions underlying mirror feedback in stroke: A dynamic causal modeling study

“…Thus, we selected the subject-specific maxima in regions that were within 8 mm of the group maxima and in the same gyrus. This approach, in defining the center coordinates of each region of interest (ROI, 8 mm radius), has been shown to reduce the undesired effects of inter-subject variability in ROI location (Gandolla et al, 2014). These subject-specific ROI coordinates were averaged to obtain group level ROI center coordinates (see Table 2).…”