Neural Signals in Red Nucleus during Reactive and Proactive Adjustments in Behavior.

The ability to adjust behavior is an essential component of cognitive control. Much is known about frontal and striatal processes that support cognitive control, but few studies have investigated how motor signals change during reactive and proactive adjustments in motor output. To address this, we characterized neural signals in red nucleus (RN), a brain region linked to motor control, as male and female rats performed a novel variant of the stop-signal task. We found that activity in RN represented the direction of movement and was strongly correlated with movement speed. Additionally, we found that directional movement signals were amplified on STOP trials before completion of the response and that the strength of RN signals was modulated when rats exhibited cognitive control. These results provide the first evidence that neural signals in RN integrate cognitive control signals to reshape motor outcomes reactively within trials and proactivity across them.SIGNIFICANCE STATEMENT Healthy human behavior requires the suppression or inhibition of errant or maladaptive motor responses, often called cognitive control. While much is known about how frontal brain regions facilitate cognitive control, less is known about how motor regions respond to rapid and unexpected changes in action selection. To address this, we recorded from neurons in the red nucleus, a motor region thought to be important for initiating movement in rats performing a cognitive control task. We show that red nucleus tracks motor plans and that selectivity was modulated on trials that required shifting from one motor response to another. Collectively, these findings suggest that red nucleus contributes to modulating motor behavior during cognitive control.

Firing of Putative Dopamine Neurons in Ventral Tegmental Area Is Modulated by Probability of Success during Performance of a Stop-Change Task.

Response inhibition, the ability to refrain from unwanted actions, is an essential component of complex behavior and is often impaired across numerous neuropsychiatric disorders such as addiction, attention-deficit hyperactivity disorder (ADHD), schizophrenia, and obsessive-compulsive disorder. Accordingly, much research has been devoted to characterizing brain regions responsible for the regulation of response inhibition. The stop-signal task, a task in which animals are required to inhibit a prepotent response in the presence of a STOP cue, is one of the most well-studied tasks of response inhibition. While pharmacological evidence suggests that dopamine (DA) contributes to the regulation of response inhibition, what is exactly encoded by DA neurons during performance of response inhibition tasks is unknown. To address this issue, we recorded from single units in the ventral tegmental area (VTA), while rats performed a stop-change task. We found that putative DA neurons fired less and higher to cues and reward on STOP trials relative to GO trials, respectively, and that firing was reduced during errors. These results suggest that DA neurons in VTA encode the uncertainty associated with the probability of obtaining reward on difficult trials instead of the saliency associated with STOP cues or the need to resolve conflict between competing responses during response inhibition.