Breathing-Driven Modulation of Reticulospinal Tract Activity

Abstract The reticulospinal tract (RST) plays a pivotal role in motor control, especially during recovery after neurological injuries such as stroke and spinal cord injury (SCI). Understanding how RST activity is modulated offers valuable insights into improving motor function recovery. Recent studies have demonstrated that breathing rhythms influence brain activity. This study explores how respiratory rhythms modulate RST excitability during motor tasks, using the StartReact paradigm to examine reaction times (RTs) across visual (VRT), visual-auditory (VART), and visual-auditory startling (VSRT) conditions. We measured RTs in three muscles (first dorsal interosseous, flexor digitorum superficialis, and biceps) in healthy adult participants (n=13, both sexes) performing multi-joint movements. RTs were longest in the VRT condition and significantly decreased when auditory stimuli were added (VART), with further reductions observed in the VSRT condition. Additionally, respiratory phase transitions, particularly from inspiration to expiration (IE), significantly influenced RTs, with the shortest RTs observed during these transitions in the VSRT condition. These findings suggest that RST excitability is dynamically modulated by respiratory rhythms. This modulation of the RST by respiratory phase transitions could inform future neurorehabilitation strategies, such as respiratory-phase-aligned stimulation, to enhance motor recovery following corticospinal lesions. Ultimately, this approach may optimize the timing of interventions, improving outcomes in conditions such as stroke and SCI. Significance Statement Brainstem pathways play a crucial role in motor recovery after stroke, and understanding how these pathways change during recovery is key to optimizing their participation in rehabilitation. This study demonstrates how respiratory rhythms influence these brainstem pathways. Using the StartReact paradigm, we show that muscle response times are faster when transitioning from inspiration to expiration. These findings suggest that the body’s natural breathing rhythms can enhance motor output by activating these pathways. This could inform innovative rehabilitation strategies, such as aligning interventions with specific respiratory phases, to improve motor recovery in stroke and spinal cord injury. Our research highlights the potential for personalized therapies that harness the body’s intrinsic rhythms to optimize recovery. Competing Interest Statement The authors have declared no competing interest. Footnotes Conflict of interest: The authors declare no competing financial interests.