The Secondary Motor Cortex Encodes Aversive Signals and Exerts an Inhibitory Control of Motor Sequence Learning in...

Area of Science:

• Neuroscience
• Motor Control
• Behavioral Science

Background:

• The secondary motor cortex (M2) is crucial for planning and executing complex motor sequences.
• The specific nature of neuronal signals (reward vs. aversive) and their impact on motor learning by M2 neurons are not fully understood.

Purpose of the Study:

• To investigate the valence of neuronal signals in M2.
• To determine the behavioral effects of these signals on motor sequence learning.

Main Methods:

• Combined in vivo fiber photometry and optogenetics in mice.
• Recorded calcium signals from M2 subpopulations (general, PV+, VgluT2+) during exposure to reward and aversive stimuli.
• Optogenetically activated M2 neurons during reward delivery and assessed motor sequence learning, motivation (progressive ratio test), and general activity (open-field test).

Main Results:

• M2 neurons, including PV+ and VgluT2+ subpopulations, consistently encoded aversive signals, responding negatively to rewards and positively to aversive stimuli.
• Optogenetic activation of M2 neurons during reward delivery significantly suppressed motor sequence initiation and execution.
• Behavioral impairment was linked to reduced motivational vigor, evidenced by decreased lever pressing and a lower breakpoint in the progressive ratio test.

Conclusions:

• M2 neurons encode aversive signals that devalue rewards, reduce motivation, and inhibit motor sequence learning.
• M2 acts as a critical neural node that gates motor output based on negative motivational valence.