RESUMEN
It has been hypothesized that to perform sensorimotor transformations efficiently, somatosensory information being fed back to a particular motor circuit is organized in accordance with the mechanical loading patterns of the skin that result from the motor activity generated by that circuit. Rearrangements of sensory information to different motor circuits could in this respect constitute a key component of sensorimotor learning. We here explored whether the organization of tactile input from the plantar forepaw of the rat to cortical and striatal circuits is affected by a period of extensive sensorimotor training in a skilled reaching and grasping task. Our data show that the representation of tactile stimuli in terms of both temporal and spatial response patterns changes as a consequence of the training and that spatial changes particularly involve the primary motor cortex. Based on the observed reorganization, we propose that reshaping of the spatiotemporal representation of the tactile afference to motor circuits is an integral component of the learning process that underlies skill acquisition in reaching and grasping.NEW & NOTEWORTHY Sensorimotor transformations are fundamental to the function of the nervous system and determine how patterns of sensory input are converted into appropriate movements. We here investigated the extent to which experience-dependent processes can reshape the organization of somatosensory input feeding into cortico-basal ganglia motor structures. Our data point to a particularly important role for the primary motor cortex in the functional adaptions associated with skilled motor learning.
Asunto(s)
Corteza Cerebral/fisiología , Cuerpo Estriado/fisiología , Actividad Motora/fisiología , Destreza Motora/fisiología , Red Nerviosa/fisiología , Práctica Psicológica , Percepción del Tacto/fisiología , Animales , Conducta Animal/fisiología , Miembro Anterior/fisiología , Corteza Motora/fisiología , Ratas , Percepción Espacial/fisiología , Percepción del Tiempo/fisiologíaRESUMEN
In natural behavior, we fluidly change from one type of activity to another in a sequence of motor actions. Corticostriatal circuits are thought to have a particularly important role in the construction of action sequences, but neuronal coding of a sequential behavior consisting of different motor programs has not been investigated at the circuit level in corticostriatal networks, making the exact nature of this involvement elusive. Here, we show, by analyzing spontaneous self-grooming in rats, that neuronal modulation in motor cortex and dorsal striatum is strongly related to transitions between behaviors. Our data suggest that longer action sequences in rodent grooming behavior emerge from stepwise control of individual behavioral transitions, where future actions are encoded differently depending on current motor state. This state-dependent motor coding was found to differentiate between rare behavioral transitions and as opposed to more habitual sequencing of actions.
Asunto(s)
Cuerpo Estriado , Corteza Motora , Animales , RatasRESUMEN
The basal ganglia are thought to be particularly sensitive to changes in dopaminergic tone, and the realization that reduced dopaminergic signaling causes pronounced motor dysfunction is the rationale behind dopamine replacement therapy in Parkinson's disease. It has, however, proven difficult to identify which neurophysiological changes that ultimately lead to motor dysfunctions. To clarify this, we have here recorded neuronal activity throughout the cortico-basal ganglia-thalamic circuits in freely behaving rats during periods of immobility following acute dopaminergic manipulations, involving both vesicular dopamine depletion and antagonism of D1 and D2 type dopamine receptors. Synchronized and rhythmic activities were detected in the form of betaband oscillations in local field potentials and as cortical entrainment of action potentials in several basal ganglia structures. Analyses of the temporal development of synchronized oscillations revealed a spread from cortex to gradually also include deeper structures. In addition, firing rate changes involving neurons in all parts of the network were observed. These changes were typically relatively balanced within each structure, resulting in negligible net rate changes. Animals treated with D1 receptor antagonist showed a rapid onset of hypokinesia that preceded most of the neurophysiological changes, with the exception of these balanced rate changes. Parallel rate changes in functionally coupled ensembles of neurons in different structures may therefore be the first step in a cascade of neurophysiological changes underlying motor symptoms in the parkinsonian state. We suggest that balanced rate changes in distributed networks are possible mechanism of disease that should be further investigated in conditions involving dopaminergic dysfunction.