Immediate neural plasticity shapes motor performance

The consolidation of motor skills necessitates long-lasting changes in the nervous system. For the most part, plasticity has been documented in motor systems after training and longterm adaptation. However, there has been no demonstration of immediate neural changes associated with the rapid adaptat ion of motor behavior required to interact with a dynamic environment. To a ddress this issue, we explored the changes in performance (reaction time) o f rhesus monkeys that executed saccadic eye movements to one of two visual stimuli while monitoring the preparatory activity of neurons in the superio r colliculus, a structure close to the motor output. Similar to the well es tablished sequential effects observed in human manual responses, each monke y displayed reaction times to target locations that were organized in a seq uential pattern, becoming progressively shorter with each preceding repeate d movement and longer with each preceding nonrepeated movement. This sequen tial pattern of performance modification was associated with concordant cha nges in the preparatory activity of superior colliculus neurons in advance of the saccadic target presentation. These data indicate that neural proper ties are continuously shaped by use-related experience in a manner consiste nt with the progressive adaptation of motor behavior.