Date of Degree
In this study, we assessed the corticospinal integration in healthy people while seated. Corticospinal integration was assessed by establishing the latency and amplitude of motor evoked potentials (MEPs) evoked following transcranial magnetic stimulation (TMS) of the primary motor cortex area representing the leg muscles, and the latency and amplitude of spinally-mediated reflex responses. Further, the modulation pattern of the spinally-mediated reflex responses were determined following subthreshold and suprathreshold TMS. All compound muscle action potentials, descending motor or spinally-mediated reflexes were recorded from the leg muscles through surface electromyography. Both subthreshold and suprathreshold TMS induced a similar modulation pattern on the TA short-latency (~75 ms) flexor reflex. The conditioned flexor reflex was facilitated when test and conditioning stimuli interacted at subcortical/cortical levels, and depressed when interaction occurred at spinal level. Similarly, TA MEPs were facilitated upon foot stimulation at sensory and at reflex threshold intensities, when test and conditioning stimuli interacted at subcortical/cortical levels. No effects were observed on the conditioned TA MEPs when interaction occurred at spinal level. Descending and somatosensory inputs increase corticospinal and spinal reflex excitability when integration occurs at supraspinal levels. In neurological disorders, corticospinal excitability can be strengthened through paired cortical and peripheral stimulation paradigms when neuronal integration occurs at cortical levels.
Krivis, Lisa; Mackey, Ann; McDonough, Maureen; and Uttaro, Denise, "Interactions Between Descending and Somatosensory Inputs in Humans" (2015). CUNY Academic Works.