The cognitive processes underlying routine and novel naturalistic action performance: examining the role of executive function and memory

Naturalistic actions are multistep activities involving the manipulation of objects to achieve a goal. They can either be routine actions (NA) performed many times or novel actions (NNA) unfamiliar prior to instruction. The aim of this study was to examine and compare the role of memory and executive function in NA and NNA enactment and explore the neuroanatomical substrates involved in enactment performance. Individuals with stroke have been shown to be impaired in NA and NNA performance, which can prevent them from living independently. Thus, this research aims to better inform rehabilitation efforts targeted at improving functionality in these patients. In order to investigate these questions, the relationship between NA and NNA performance and memory and executive function measures was examined in stroke participants and healthy older adults. In Experiment 1, participants were asked to view and perform a NNA over three learning trials. As expected, NNA performance improved across trials. In comparing NAs and NNAs, stroke participants performed better on NNA Trial 1 than NA enactment whereas controls showed the reverse pattern. Hierarchical regression analysis demonstrated that associative memory predicted NNA omission (omitted a step) error rate whereas episodic memory predicted NA omission error rate. Commission (committed a step in error) error rate was not predicted by neuropsychological measures. In Experiment 2, the role of executive function in NNAs was further investigated by dividing attention either at encoding or retrieval of a NNA. Stroke participants were divided into high and low error producers. Overall, participants made more errors when attention was divided at encoding. Although high error producers did not exhibit differentially poorer performance than low error producers and controls, they had significantly longer NNA completion times when attention was divided at retrieval, suggesting difficulties with task switching. Experiment 3 examined the influence of lesions on NA and NNA enactment. Results suggest a role of the extended hippocampal-diencephalic system, prefrontal cortex, and basal ganglia in naturalistic action performance. In summary, behavioural and neuroimaging findings from this study demonstrate that episodic memory, associative memory, executive function and motor-procedural memory are involved in NA and NNA performance.