Motor intentionality and the case of Schneider

I argue that Merleau-Ponty’s use of the case of Schneider in his arguments for the existence of non-conconceptual and non-representational motor intentionality contains a problematic methodological ambiguity. Motor intentionality is both to be revealed by its perspicuous preservation and by its contrastive impairment in one and the same case. To resolve the resulting contradiction I suggest we emphasize the second of Merleau-Ponty’s two lines of argument. I argue that this interpretation is the one in best accordance both with Merleau-Ponty’s general methodology and with the empirical case of Schneider as it was described by Gelb and Goldstein.

Speed, accuracy, and serial order in sequence production

The production of complex sequences like music or speech requires the rapid and temporally precise production of events (e.g., notes and chords), often at fast rates. Memory retrieval in these circumstances may rely on the simultaneous activation of both the current event and the surrounding context (Lashley, 1951). We describe an extension to a model of incremental retrieval in sequence production (Palmer & Pfordresher, 2003) that incorporates this logic to predict overall error rates and speed-accuracy trade-offs, as well as types of serial ordering errors. The model-assumes that retrieval of the current event is influenced by activations of surrounding events. Activations of surrounding events increase over time, such that both the accessibility of distant events and overall accuracy increases at slower production rates. The model's predictions were tested in an experiment in which pianists performed unfamiliar music at 8 different tempi. Model fits to speed-accuracy data and to serial ordering errors support model predictions. Parameter fits to individual data further suggest that working memory contributes to the retrieval of serial order and overall accuracy is influenced in addition by motor dexterity and domain-specific skill.     

Are there age-related differences in learning to optimize speed, accuracy, and energy expenditure?

Studies of age-related differences in manual aiming have indicated that older adults take longer to complete their movements than their younger counterparts because they tend to rely on time-consuming feedback-based control processes. Many authors have suggested that the reliance on feedback is the result of a "play-it-safe" strategy that has been adopted to compensate for a deterioration in accurate and consistent force generation. That is, perhaps because older adults know that their motor systems are not as reliable as the systems were at a younger age, they plan shorter movements that conserve time and space for feedback control to correct their programmed actions. The vast majority of the previous studies that have revealed these age-related differences in aiming, however, have used computer-based tasks that involve the transformation of perceptual into motor space. In the present experiment, older and younger adults completed real aiming movements over three sessions. The results suggest that, when acting in a real environment, the main difference between older and younger adults in movement execution lies in the efficient use of response-related feedback, not in the programming of movement.     

Rocking together: dynamics of intentional and unintentional interpersonal coordination

The current study investigated the interpersonal coordination that occurred between two people when sitting side-by-side in rocking chairs. In two experiments participant pairs rocked in chairs that had the same or different natural periods. By instructing pairs to coordinate their movements inphase or antiphase, Experiment 1 investigated whether the stable patterns of intentional interpersonal coordination were consistent with the dynamics of within person interlimb coordination. By instructing the participants to rock at their own preferred tempo, Experiment 2 investigated whether the rocking chair movements of visually coupled individuals would become unintentionally coordinated. The degree to which the participants fixated on the movements of their co-actor was also manipulated to examine whether visual focus modulates the strength of interpersonal coordination. As expected, the patterns of coordination observed in both experiments demonstrated that the intentional and unintentional interpersonal coordination of rocking chair movements is constrained by the self-organizing dynamics of a coupled oscillator system. The results of the visual focus manipulations indicate that the stability of a visual interpersonal coupling is mediated by attention and the degree to which an individual is able to detect information about a co-actor's movements.     

Effects of imagery training on cognitive performance and use of physiological measures as an assessment tool of mental effort

The effectiveness of motor imagery training on cognitive performance was examined and the physiological mechanisms involved in the contribution of mental practice to motor learning were considered. The subject's mental effort during motor imagery was assessed by using psychophysiological measures and particularly eye blink activity as an 'indirect' measurement of subjects' attention. An electronic flight simulation program (Multiple Attribute Task Battery--MATB) was used to assess performance. Twenty healthy volunteers participated in the study divided in two groups: the control group and the imagery-training group. The subjects of the imagery group were asked for additional imagery training. The subjects of the actual performing group were asked additionally to passively observe the task in order to have equal time of exposure to the task. Performance scores and physiological parameters such as heart rate, respiratory rate, eye blinking activity and muscular activity were recorded during all sessions. The results revealed significantly higher performance level of the imagery-training group than the control group. Heart rate and respiratory rate significantly increased during imagery sessions compared to rest. A slight electromyographic activity was observed during the imagination of movement. Our findings support the notion that mental practice improves motor performance in a task where spatiotemporal or dynamic control of the action is highly required. The effects of mental practice on motor performance could be explained by the existence of a top-down mechanism based on the activation of a central representation of the movements, since the vegetative activation during motor imagery seems to be centrally controlled.     

Response inhibition in motor and oculomotor conflict tasks: Different mechanisms,different dynamics?

Previous research has shown that the appearance of task-irrelevant abrupt onsets influences saccadic eye movements during visual search and may slow down manual reactions to target stimuli. Analysis of reaction time distributions in the present study offers evidence suggesting that top-down inhibition processes actively suppress oculomotor or motor responses elicited by a salient distractor, in order to resolve the conflict that arises when reflex-like and deliberate responses are in opposition. Twenty-six participants carried out a variation of the oculomotor capture task. They were instructed to respond with either a saccade toward or with a button press at the side of the hemifield in which a target color singleton appeared. A distractor stimulus could appear either in the same or in the opposite hemifield. Delta plots revealed competition between reflex-like and deliberate response activation, and highlighted selective inhibition of automatic responses: While participants generally responded more slowly in incongruent compared to congruent situations, this effect diminished and even reversed in the slowest speed quantiles. These effects were present in both the oculomotor and motor response-mode conditions.     

Adolescent development of motor imagery in a visually guided pointing task

The development of action representation during adolescence was investigated using a visually guided pointing motor task (VGPT) to test motor imagery. Forty adolescents (24 males; mean age 13.1 years) and 33 adults (15 males; mean age 27.5 years) were instructed to both execute and imagine hand movements from a starting point to a target of varying size. Reaction time (RT) was measured for both Execution (E) and Imagery (I) conditions. There is typically a close association between time taken to execute and image actions in adults because action execution and action simulation rely on overlapping neural circuitry. Further, representations of actions are governed by the same speed-accuracy trade-off as real actions, as expressed by Fitts’ Law. In the current study, performance on the VGPT in both adolescents and adults conformed to Fitts’ Law in E and I conditions. However, the strength of association between E and I significantly increased with age, reflecting a refinement in action representation between adolescence and adulthood.     

Morphological changes in dendritic spines of Purkinje cells associated with motor learning

Experience-dependent changes of spine structure and number may contribute to long-term memory storage. Although several studies demonstrated structural spine plasticity following associative learning, there is limited evidence associating motor learning with alteration of spine morphology. Here, we investigated this issue in the cerebellar Purkinje cells using high voltage electron microscopy (HVEM). Adult rats were trained in an obstacle course, demanding significant motor coordination to complete. Control animals either traversed an obstacle-free runway or remained sedentary. Quantitative analysis of spine morphology showed that the density and length of dendritic spines along the distal dendrites of Purkinje cells were significantly increased in the rats that learned complex motor skills compared to active or inactive controls. Classification of spines into shape categories indicated that the increased spine density and length after motor learning was mainly attributable to an increase in thin spines. These findings suggest that motor learning induces structural spine plasticity in the cerebellar Purkinje neurons, which may play a crucial role in acquiring complex motor skills.     

Explorations of anticipatory behavioral control (ABC): a report from the cognitive psychology unit of the University of Würzburg

The report comprises recent theoretical considerations, experimental research, and simulations which all aim at a clarification of anticipatory mechanisms of behavioral control.     

A study of reaching actions in walking infants

Acquiring motor skills transforms the perceptual and cognitive world of infants and expands their exploratory engagement with objects. This study investigated how reaching is integrated with walking among infant walkers (n = 23, 14.5–15.5 months). In a walk-to-reach paradigm, diverse object retrieval strategies were observed. All infants were willing to use their upper and lower bodies in concert, and the timing of this coordination reflected features of their environment. Infants with an older walking age (months since walking onset) retrieved items more rapidly and exploited their non-reaching hand more effectively during object retrieval than did same-age infants with a younger walking age. This suggests that the actions of the upper- and lower-body are flexibly integrated and that this integration may change across development. Mechanisms that shape sophisticated upper-body use during upright object retrieval are discussed. Infants flexibly integrate emerging motor skills in the service of object retrieval in ways not previously documented.