Multiple Motor Learning Processes in Humans: Defining Their Neurophysiological Bases

Abstract

Learning new motor behaviors or adjusting previously learned actions to account for dynamic changes in our environment requires the operation of multiple distinct motor learning processes, which rely on different neuronal substrates. For instance, humans are capable of acquiring new motor patterns via the formation of internal model representations of the movement dynamics and through positive reinforcement. In this review, we will discuss how changes in human physiological markers, assessed with noninvasive brain stimulation techniques from distinct brain regions, can be utilized to provide insights toward the distinct learning processes underlying motor learning. We will summarize the findings from several behavioral and neurophysiological studies that have made efforts to understand how distinct processes contribute to and interact when learning new motor behaviors. In particular, we will extensively review two types of behavioral processes described in human sensorimotor learning: (1) a recalibration process of a previously learned movement and (2) acquiring an entirely new motor control policy, such as learning to play an instrument. The selected studies will demonstrate in-detail how distinct physiological mechanisms contributions change depending on the time course of learning and the type of behaviors being learned.

Updates in Motor Learning: Implications for Physical Therapist Practice and Education

“…3 ), it is possible that instructive and reinforcement motor learning are more heavily engaged in the initial, cognitive stage of learning when performance is variable and the learner has to explore different movement solutions, whereas the associative stage engages primarily reinforcement and use-dependent mechanisms as the learner continues to refine their behavior with extensive practice. In the autonomous stage, further adjustments to motor behavior and a shift to automaticity may primarily be driven by sensorimotor adaptation and continued movement practice (similar to that suggested by the authors of previous reviews 21 , 40 ). This working theory aligns with Gentile’s description of explicit and implicit processes that contribute to motor skill acquisition.…”

“…Rather, there are multiple mechanisms of motor learning that can occur in parallel or in isolation to ultimately lead to sustained changes in motor behaviors. 19 , 21 In this section, we provide an overview of 4 widely studied motor learning mechanisms: use-dependent, instructive, reinforcement, and sensorimotor adaptation-based motor learning. We will describe the key features of these mechanisms including the primary behavioral drivers, neural substrates, cognitive involvement, and timescales.…”

“…After a movement success or failure, the learner does not receive information about how the movement needs to be modified (or not) in order to be successful. 21 This type of nondirectional external feedback prompts the learner to explore different movements and select actions that have the highest probability of success, while avoiding actions with low probability of success (reviewed in Sutton and Barto 46 and Lee et al 47 ).…”

Non-invasive stimulation of the motor cerebellum has potential cognitive confounds

“…Rather than affecting motor adaptation solely via a cerebellar-motor circuit, a plausible alternative suggestion is that the effect of cerebellar stimulation may result from modulation of the cerebellar-cognitive network (i.e. through modifying explicit mechanisms such as the use of strategies [16]), or an interplay between both circuits (see also [17]). This could potentially explain the difficulties seen in studies attempting to separately modulate the implicit and explicit components of motor adaptation [18], and could plausibly explain the results of work reporting effects of cerebellar stimulation on motor savings [13], as recent research suggests savings may be linked to explicit learning mechanisms [19].…”

Recognition capability of one’s own skilled movement is dissociated from acquisition of motor skill memory

“…Previous studies demonstrated that motor skill learning relies on several processes such as use-dependent plasticity, reinforcement, and error-based learning 15 , 16 . In addition, the contribution of each of these processes varies with learning phase (i.e., early or late phase) 17 . Therefore, some previous neuroimaging studies adopted a several-weeks practice schedule to clarify time-dependent acquisition of memory representation of motor skill components 18 – 20 .…”