Variation in error-based and reward-based human motor1 learning is related and associated with entorhinal volume 2 3 Anouk J. de Brouwer1, Mohammad R. Rashid2, J. Abstract 13Error-based and reward-based processes are critical for motor learning, and are thought to be 14 supported via distinct neural pathways. However, recent behavioral work in humans suggests that 15 both learning processes are supported by cognitive strategies and that these contribute to 16 individual differences in motor learning ability. While it has been speculated that medial temporal 17 lobe regions may support this strategic component to learning, direct evidence is lacking. Here 18 we first show that faster and more complete learning during error-based visuomotor adaptation is 19 associated with better learning during reward-based shaping of reaching movements. This result 20 suggests that strategic processes, linked to faster and better learning, drive individual differences 21 in both error-based and reward-based motor learning. We then show that right entorhinal cortex 22 volume was larger in good learning individuals-classified across both motor learning tasks-23 compared to their poorer learning counterparts. This suggests that strategic processes underlying 24 both error-and reward-based learning are linked to neuroanatomical differences in entorhinal 25 cortex. 26 27 Significance Statement 30While it is widely appreciated that humans vary greatly in their motor learning abilities, little is 31 known about the processes and neuroanatomical bases that underlie these differences. Here, 32 using a data-driven approach, we show that individual variability in error-based and reward-based 33 motor learning is tightly linked, and related to the use of cognitive strategies. We further show that 34 structural differences in entorhinal cortex predict this intersubject variability in motor learning, with 35 larger entorhinal volumes being associated with better overall error-based and reward-based 36 learning. Together, these findings provide support for the notion that the ability to recruit strategic 37 processes underlies intersubject variability in both error-based and reward-based learning, which 38 itself may be linked to structural differences in medial temporal cortex. 39When considering the neural bases of such interactions, it is important to distinguish between two 62 main forms of learning. Error-based learning is the form of learning by which we refine and adjust 63 our movements to changes in the body or the environment based on observable errors, such as 64 when missing the bullseye in archery. Such learning is thought arise from two separate processes 65 acting in parallel: An implicit process that is driven by the error between predicted and observed 66 sensory feedback (17,18) and an explicit process that is driven by the error between the target 67 and the sensory feedback (i.e., the task error) (19). The implicit process is nonconscious (i.e., 68 resistant to voluntary control), adapts and de-adapts gradually and is relian...

In daily tasks, we are often confronted with competing potential targets and must select one to act on. It has been suggested that, prior to target selection, the human brain encodes the motor goals of multiple, potential targets. However, this view remains controversial and it has been argued that only a single motor goal is encoded, or that motor goals are only specified after target selection. To investigate this issue, we measured participants’ gaze behaviour while viewing two potential reach targets, one of which was cued after a preview period. We applied visuomotor rotations to dissociate each visual target location from its corresponding motor goal location; i.e., the location participants needed to aim their hand toward to bring the rotated cursor to the target. During the preview period, participants most often fixated both motor goals but also frequently fixated one, or neither, motor goal location. Further gaze analysis revealed that on trials in which both motor goals were fixated, both locations were held in memory simultaneously. These findings show that, at the level of single trials, the brain most often encodes multiple motor goals prior to target selection, but may also encode either one or no motor goals. This result may help reconcile a key debate concerning the specification of motor goals in cases of target uncertainty.