Cortical activity in the null space: permitting preparation without movement

Abstract

Neural circuits must perform computations and then selectively output the results to other circuits. Yet synapses do not change radically at millisecond timescales. A key question then is: how is communication between neural circuits controlled? In motor control, brain areas directly involved in driving movement are active well before movement begins. Muscle activity is some readout of neural activity, yet remains largely unchanged during preparation. Here we find that during preparation, while the monkey holds still, changes in motor cortical activity cancel out at the level of these population readouts. Motor cortex can thereby prepare the movement without prematurely causing it. Further, we found evidence that this mechanism also operates in dorsal premotor cortex (PMd), largely accounting for how preparatory activity is attenuated in primary motor cortex (M1). Selective use of “output-null” vs. “output-potent” patterns of activity may thus help control communication to the muscles and between these brain areas.

Distinct Roles for Alpha- and Beta-Band Oscillations during Mental Simulation of Goal-Directed Actions

“…This interpretation is in line with the notion that alpha-band oscillations implement "gating by inhibition" (Jensen and Mazaheri, 2010). Within this framework, stronger oscillations in the alpha-band are a mechanism for inhibiting neuronal processing in task-irrelevant cortical regions.…”

“…Within this framework, stronger oscillations in the alpha-band are a mechanism for inhibiting neuronal processing in task-irrelevant cortical regions. This framework has been developed on the basis of lateralized power changes observed during selective spatial processing of sensory material, first in occipital and parietal regions (Worden et al, 2000;Thut et al, 2006;Tan et al, 2013), and then in the somatosensory system (Haegens et al, 2010(Haegens et al, , 2011(Haegens et al, , 2012Jones et al, 2010;Anderson and Ding, 2011). This study generalizes this framework to sensorimotor processing, showing that during motor imagery the alpha-band power is selectively increased in the ipsilateral sensorimotor cortex.…”

Robust neuronal dynamics in premotor cortex during motor planning

“…ALM responses to perturbations resembles robust systems, where critical state variables are particularly stiff 26 . Selective stability of neural dynamics supports the idea that behaviorrelated activity comprises only a low-dimensional subspace of neural activity space 33,40 , constrained by the structure of neural circuits 43 . Our findings place constraints on the circuit architectures that underlie memory-related cortical activity and suggest general principles of robust system control in the brain.…”

“…Circuit dynamics are actively restored along behavior-related directions in the activity space, but not along certain non-informative directions 33,40 .…”

Flow of Information Underlying a Tactile Decision in Mice

“…Contra-lateral population activity in PT neurons arose late during the delay Weak activation of the PT neurons during movement planning could "write-in" specific motor plans that resulted in contra-lateral licking movements. These results suggest that, during movement planning, distributed preparatory activity in IT neuron networks is converted into a movement command in PT neurons ('outputpotent' activity; Kaufman et al 2014), which ultimately triggers directional movements (Li et al 2015).…”