RESUMEN
Changes in somatosensory input can remodel human cortical motor organization, yet the input characteristics that promote reorganization and their functional significance have not been explored. Here we show with transcranial magnetic stimulation that sensory-driven reorganization of human motor cortex is highly dependent upon the frequency, intensity, and duration of stimulus applied. Those patterns of input associated with enhanced excitability (5 Hz, 75% maximal tolerated intensity for 10 min) induce stronger cortical activation to fMRI. When applied to acutely dysphagic stroke patients, swallowing corticobulbar excitability is increased mainly in the undamaged hemisphere, being strongly correlated with an improvement in swallowing function. Thus, input to the human adult brain can be programmed to promote beneficial changes in neuroplasticity and function after cerebral injury.
Asunto(s)
Lesiones Encefálicas/rehabilitación , Terapia por Estimulación Eléctrica/métodos , Magnetismo/uso terapéutico , Corteza Motora/lesiones , Trastornos del Movimiento/rehabilitación , Plasticidad Neuronal/fisiología , Recuperación de la Función/fisiología , Adulto , Vías Aferentes/fisiología , Anciano , Anciano de 80 o más Años , Lesiones Encefálicas/patología , Lesiones Encefálicas/fisiopatología , Mapeo Encefálico , Tronco Encefálico/fisiología , Deglución/fisiología , Trastornos de Deglución/etiología , Trastornos de Deglución/fisiopatología , Trastornos de Deglución/rehabilitación , Femenino , Humanos , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Corteza Motora/patología , Corteza Motora/fisiopatología , Trastornos del Movimiento/etiología , Trastornos del Movimiento/fisiopatología , Faringe/inervación , Faringe/fisiopatología , Estimulación Física , Tractos Piramidales/fisiología , Accidente Cerebrovascular/patología , Accidente Cerebrovascular/fisiopatología , Rehabilitación de Accidente CerebrovascularRESUMEN
The rectum has a unique physiological role as a sensory organ and differs in its afferent innervation from other gut organs that do not normally mediate conscious sensation. We compared the central processing of human esophageal, duodenal, and rectal sensation using cortical evoked potentials (CEP) in 10 healthy volunteers (age range 21-34 yr). Esophageal and duodenal CEP had similar morphology in all subjects, whereas rectal CEP had two different but reproducible morphologies. The rectal CEP latency to the first component P1 (69 ms) was shorter than both duodenal (123 ms; P = 0.008) and esophageal CEP latencies (106 ms; P = 0.004). The duodenal CEP amplitude of the P1-N1 component (5.0 microV) was smaller than that of the corresponding esophageal component (5.7 microV; P = 0.04) but similar to that of the corresponding rectal component (6.5 microV; P = 0.25). This suggests that rectal sensation is either mediated by faster-conducting afferent pathways or that there is a difference in the orientation or volume of cortical neurons representing the different gut organs. In conclusion, the physiological and anatomic differences between gut organs are reflected in differences in the characteristics of their afferent pathways and cortical processing.