The aim of this thesis was to clarify the neurophysiological mechanisms underpinning the concept of movement conscious processing. This concept represents the core of reinvestment theory (Masters, 1992) which is a motor-control based explanation of motor-skill failures (i.e., choking) under psychological pressure, and whose predictions are relevant to the sporting world, the performing arts, and the motoric rehabilitation. The four experimental chapters that come discuss mixed-model design experiments in which participants extensively practiced a variety of motor tasks under different training conditions (between-participant factor), practice blocks and psychological climates (within-participant factor). Specifically, I manipulated training conditions in order for my participants to execute the motor tasks with either a comparatively high versus low degree of conscious processing. After an initial acquisition phase, they performed the tasks under high versus low evaluative and competitive psychological climates (psychological pressure). In all studies, alongside fine-grained measures of motor performance (e.g., movement chunking and kinematics), I monitored self-reports of conscious processing, and recorded electroencephalographic (EEG) activity during and/or in preparation for the tasks. In particular, I centred my analysis on two measures connected to representative of alpha frequency neuroelectric oscillations, namely power and connectivity. Specifically, based on previous research I focused my analyses around temporal power and frontotemporal connectivity in the left-hemisphere, as they have been identified as putative measures of conscious processing (Hatfield et al., 2013), and within the high-alpha band, as it is deemed to be more sensitive to the task related changes (Babiloni et al., 2011).
Chapter 2 describes a study (Bellomo, Cooke, & Hardy, 2018) which was planned to offer a comprehensive test of the predictions of reinvestment theory and enable us to understand how conscious processing is linked to the concept of motor chunking. Participants used the index finger of their dominant hand to perform a sequence learning task either following an explicit/trial-and-error (high-conscious processing) or implicit/errorless (low-conscious processing) practice schedule. After an acquisition phase, they performed the task under high-psychological pressure. Results showed that explicit acquisition resulted in quicker sequence acquisition, reduced conscious processing, and increased cortical efficiency (left-temporal high-alpha power). Moreover, self-reported conscious processing tended to increase under pressure among explicit trainees only. In contrast to reinvestment theory, this had no adverse effect on performance. However, this might have been due to either the motor-simplicity of the task, or due to movements not being fully automatized. In addition, since we observed a disconnect between self-reports and EEG measures of conscious processing, we questioned the specific sensitivity of these neurophysiological measures.
Chapter 3 describes a study that attempted to address the limitations of the previous study by increasing the motoric complexity of the sequence learning task (i.e., participants used four fingers on their non-dominant hand), introducing an over-night sleep period to foster movement automatization, and dichotomising the training schedule based on the amount of movement-specific declarative knowledge. This decision was taken in the hope of clarifying whether these EEG measures are actually sensitive to verbal activity functional to movement execution. Specifically, a to-be-learned repeating sequence was alternated with random button presses. This was unbeknownst to the members of the implicit group, in order to prevent any explicit processing. On the contrary, participants of the explicit group were showed the repeating sequence and given the possibility of verbalising it with an acronym (since buttons were labelled with letters). As in the previous study, participants underwent an acquisition phase on a first day. However, this was followed by an overnight sleep before they returned to complete the retention, and the low and high- pressure conditions on a second day. Results questioned the specific sensitivity of left-temporal EEG measures to movement-specific verbal activity. However, the additional consideration of other sites and pairs contributed to improving our understanding of the electroencephalographic features of movement-specific declarative knowledge.
Chapter 4 and 5 describe the results of a study which was designed to scrutinise the specific sensitivity of the aforementioned left-temporal EEG measures to the semantic content of verbal activity happening prior to movement execution. Specifically, via a self-talk intervention, participants were induced into rehearsing either movement-relevant (i.e., instructional self-talk) or movement-irrelevant (i.e., motivational self-talk) verbalisations prior to movement execution. Chapter 4 focused specifically on left-temporal alpha power and left-frontotemporal alpha connectivity and provided evidence against the idea of a specific sensitivity of these EEG measures to movement-relevant verbalisations. Chapter 5 tested additional hypotheses linked to putative mechanisms underpinning the effects of instructional and motivational self-talk on motor performance. Results showed that the instructional group was characterised by more top-down control of action, while the motivational group was characterised by increased bodily arousal and effort, which, as suggested by performance data, was not fully matching the fine control requirements of the putting task.
Taken together these studies, provided evidence against the idea of a left-temporal power and left-frontotemporal connectivity as measures of verbal processes relevant for motor behaviour typical of conscious processing. However, they also put the base for a re-discussion of the concept of conscious processing as a cognitive phenomenon which might consist of an explicit control of movement implemented in modalities other than the verbal one, such as visual or kinaesthetic.