Prefrontal Cortex Activation During Motor Sequence Learning Under Interleaved and Repetitive Practice: A Two-Channel Near-Infrared Spectroscopy Study

Abstract

Training under high interference conditions through interleaved practice (IP) results in performance suppression during training but enhances long-term performance relative to repetitive practice (RP) involving low interference. Previous neuroimaging work addressing this contextual interference effect of motor learning has relied heavily on the blood-oxygen-level-dependent (BOLD) response using functional magnetic resonance imaging (fMRI) methodology resulting in mixed reports of prefrontal cortex (PFC) recruitment under IP and RP conditions. We sought to clarify these equivocal findings by imaging bilateral PFC recruitment using functional near-infrared spectroscopy (fNIRS) while discrete key pressing sequences were trained under IP and RP schedules and subsequently tested following a 24-h delay. An advantage of fNIRS over the fMRI BOLD response is that the former measures oxygenated and deoxygenated hemoglobin changes independently allowing for assessment of cortical hemodynamics even when there is neurovascular decoupling. Despite slower sequence performance durations under IP, bilateral PFC oxygenated and deoxygenated hemoglobin values did not differ between practice conditions. During test, however, slower performance from those previously trained under RP coincided with hemispheric asymmetry in PFC recruitment. Specifically, following RP, test deoxygenated hemoglobin values were significantly lower in the right PFC. The present findings contrast with previous behavioral demonstrations of increased cognitive demand under IP to illustrate a more complex involvement of the PFC in the contextual interference effect. IP and RP incur similar levels of bilateral PFC recruitment, but the processes underlying the recruitment are dissimilar. PFC recruitment during IP supports action reconstruction and memory elaboration while RP relies on PFC recruitment to maintain task variation information in working memory from trial to trial. While PFC recruitment under RP serves to enhance immediate performance, it does not support long-term performance.

Hypohydration alters pre-frontal cortex haemodynamics, but does not impair motor learning

“…Given the contralateral motor control required for such performances, it is logical to expect the right PFC to have been more active, due to its role in motor routine development and subsequent downstream descending command (Doyon et al 2009). Additionally, Immink et al (2021) have recently recounted the importance of the right PFC within the frontoparietal motor learning network (extending to the right SMA, pre-motor cortex, M1, and posterior parietal cortex). These authors examined the effects of interleaved and repetitive (blocked) practice on bilateral motor sequence learning, finding that repetitive practice resulted in greater PFC activation during a delayed retention test (Immink et al 2021).…”

“…Additionally, Immink et al (2021) have recently recounted the importance of the right PFC within the frontoparietal motor learning network (extending to the right SMA, pre-motor cortex, M1, and posterior parietal cortex). These authors examined the effects of interleaved and repetitive (blocked) practice on bilateral motor sequence learning, finding that repetitive practice resulted in greater PFC activation during a delayed retention test (Immink et al 2021). The authors reasoned that the low contextual interference encountered by the interleaved practice group enabled more favourable motor learning to occur and promoted more efficient PFC activation during the retention test compared to the repetitive practice group (Immink et al 2021).…”

“…These authors examined the effects of interleaved and repetitive (blocked) practice on bilateral motor sequence learning, finding that repetitive practice resulted in greater PFC activation during a delayed retention test (Immink et al 2021). The authors reasoned that the low contextual interference encountered by the interleaved practice group enabled more favourable motor learning to occur and promoted more efficient PFC activation during the retention test compared to the repetitive practice group (Immink et al 2021). Lin et al (2011) have also compared the effects of interleaved and repetitive practice on cortical function using fMRI, and report greater BOLD responses among key structures within the motor learning network (right pre-frontal and pre-motor cortices).…”

“…When cortical tissue is activated, variations in these chromophores arise, so that it can be used to quantify changes in neuronal function in response to task performance (Herold et al 2018;Thomas and Nam 2000). Others (Hatakenaka et al 2007;Immink et al 2021;Ono et al 2015) have examined the PFC during motor learning using fNIRS, however, the present study is the first to apply this methodology within the context of motor learning and hydration.…”

“…First, an early (fast learning) stage where rapid improvements in behavioural performance occur (Penhune and Steele 2012). Second, consolidation where performance becomes robust or asymptotic (Doyon et al 2018;Penhune and Steele 2012) and third, an automatization phase (slow learning), where the sequence can be performed implicitly with little attentional requirement and/ or reactivation can occur (Doyon et al 2009;Immink et al 2020;Penhune and Steele 2012). Enabling this process are several neural structures including regions within the pre-frontal cortex (PFC), supplementary motor area (SMA), pre-motor cortex, primary motor cortex (M1), the associative and caudal regions of the basal ganglia, and the cerebellum (Doyon et al 2009(Doyon et al , 2018Immink et al 2020).…”