Preclinical Testing of Hypotheses from Human Studies on Reactive Stopping
Jordi ter Horst, Morgane Boillot, Michael Cohen, and Bernhard Englitz
(see article e0463242024)
From quickly stopping in crowded places when people walk in front of you unexpectedly to slamming on your brakes in a car because a deer abruptly runs in front of it, reactive stopping is important in our day-to-day lives. Clinical research has pointed to what is called the hyperdirect pathway as the neural circuit involved in reactive stopping, but preclinical studies have yet to assess how the brain regions in this pathway work together or separately to drive this behavior. In this issue, ter Horst et al. used multielectrode recordings in male rats to measure activity from two regions in the hyperdirect pathway, the orbitofrontal cortex (OFC) and subthalamic nucleus (STN), as rats performed in a task where they responded to go and stop signals. During reactive stopping, both OFC and STN showed reductions in beta power as compared to beta power during movement or preceding the go signal. The decrease in beta power occurred ∼200 ms prior to movement change, and phase synchronization between the two areas was reduced. The use of an experimental approach and subsequent analyses that were modeled off human data to test hypotheses from human studies mark this study as a major advancement. The authors also make suggestions for future experiments that will take our understanding of the neural underpinnings of reactive stopping even further.
This diagram shows how OFC–STN connectivity changed relative to the baseline during stopping. Black spots correspond to electrode position in the array. See ter Horst et al. for more details.
Validating the Somatosensory Cortex’s Pivotal Role in Motor Memory
Shahryar Ebrahimi, Bram van der Voort, and David Ostry
(see article e0629242024)
Learning new movements requires retaining memories of the movements so that we can continue to do them. Continuous transcranial magnetic brain stimulation (cTBS) has shed light on the distinct roles brain regions play in motor memory retention. A recent study from David Ostry’s lab used cTBS to discover that the primary somatosensory cortex may be involved, but not the motor cortex. This finding was surprising, and, herein, his lab probed the theory further by investigating a follow-up question: does plasticity in sensory systems and not the motor cortex underlie motor memory retention? Ebrahimi et al. trained human participants in a visuomotor adaptation task and used cTBS to target either the primary motor cortex, primary sensory cortex, or a control brain region (the occipital cortex). A day later, retention for the motor memory was tested. Only after disrupting the somatosensory cortex with cTBS was motor memory disrupted. This long-term motor memory impairment from somatosensory disruption supports the theory that motor learning requires plasticity in the somatosensory system and not in the primary motor cortex.
Footnotes
This Week in The Journal was written by Paige McKeon
