Developmental environment has lasting effects on amphibian post-metamorphic behavior and thermal physiology.

Environmental challenges early in development can result in complex phenotypic trade-offs and long-term effects on individual physiology, performance and behavior, with implications for disease and predation risk. We examined the effects of simulated pond drying and elevated water temperatures on development, growth, thermal physiology and behavior in a North American amphibian, Rana sphenocephala. Tadpoles were raised in outdoor mesocosms under warming and drying regimes based on projected climatic conditions in 2070. We predicted that amphibians experiencing the rapid pond drying and elevated pond temperatures associated with climate change would accelerate development, be smaller at metamorphosis and demonstrate long-term differences in physiology and exploratory behavior post-metamorphosis. Although both drying and warming accelerated development and reduced survival to metamorphosis, only drying resulted in smaller animals at metamorphosis. Around 1 month post-metamorphosis, animals from the control treatment jumped relatively farther at high temperatures in jumping trials. In addition, across all treatments, frogs with shorter larval periods had lower critical thermal minima and maxima. We also found that developing under warming and drying resulted in a less exploratory behavioral phenotype, and that drying resulted in higher selected temperatures in a thermal gradient. Furthermore, behavior predicted thermal preference, with less exploratory animals selecting higher temperatures. Our results underscore the multi-faceted effects of early developmental environments on behavioral and physiological phenotypes later in life. Thermal preference can influence disease risk through behavioral thermoregulation, and exploratory behavior may increase risk of predation or pathogen encounter. Thus, climatic stressors during development may mediate amphibian exposure and susceptibility to predators and pathogens into later life stages.

Action Experience and Action Discovery in Medicated Individuals with Parkinson's Disease.

Parkinson's disease (PD) is a neurodegenerative disorder that markedly affects voluntary action. While regular dopamine treatment can help restore motor function, dopamine also influences cognitive portions of the action system. Previous studies have demonstrated that dopamine medication boosts action-effect associations, which are crucial for the discovery of new voluntary actions. In the present study, we investigated whether neural processes involved in the discovery of new actions are altered in PD participants on regular dopamine treatment, compared to healthy age-matched controls. We recorded brain electroencephalography (EEG) activity while PD patients and age-matched controls performed action discovery (AD) and action control tasks. We found that the novelty P3, a component normally present when there is uncertainty about the occurrence of the sensory effect, was enhanced in PD patients. However, AD was maintained in PD patients, and the novelty P3 demonstrated normal learning-related reductions. Crucially, we found that in PD patients the causal association between an action and its resulting sensory outcome did not modulate the amplitude of the feedback correct-related positivity (fCRP), an EEG component sensitive to the association between an action and its resulting effect. Collectively, these preliminary results suggest that the formation of long-term action-outcome representations may be maintained in PD patients on regular dopamine treatment, but the initial experience of action-effect association may be affected.

Basal ganglia and cortical networks for sequential ordering and rhythm of complex movements.

Voluntary actions require the concurrent engagement and coordinated control of complex temporal (e.g., rhythm) and ordinal motor processes. Using high-resolution functional magnetic resonance imaging (fMRI) and multi-voxel pattern analysis (MVPA), we sought to determine the degree to which these complex motor processes are dissociable in basal ganglia and cortical networks. We employed three different finger-tapping tasks that differed in the demand on the sequential temporal rhythm or sequential ordering of submovements. Our results demonstrate that sequential rhythm and sequential order tasks were partially dissociable based on activation differences. The sequential rhythm task activated a widespread network centered around the supplementary motor area (SMA) and basal-ganglia regions including the dorsomedial putamen and caudate nucleus, while the sequential order task preferentially activated a fronto-parietal network. There was also extensive overlap between sequential rhythm and sequential order tasks, with both tasks commonly activating bilateral premotor, supplementary motor, and superior/inferior parietal cortical regions, as well as regions of the caudate/putamen of the basal ganglia and the ventro-lateral thalamus. Importantly, within the cortical regions that were active for both complex movements, MVPA could accurately classify different patterns of activation for the sequential rhythm and sequential order tasks. In the basal ganglia, however, overlapping activation for the sequential rhythm and sequential order tasks, which was found in classic motor circuits of the putamen and ventro-lateral thalamus, could not be accurately differentiated by MVPA. Overall, our results highlight the convergent architecture of the motor system, where complex motor information that is spatially distributed in the cortex converges into a more compact representation in the basal ganglia.

Reliance on visual attention during visuomotor adaptation: an SSVEP study.

Visuomotor adaptation involves the learning of a new mapping between a spatial goal and well-learned movements. In order to learn a new visuomotor transformation, visual attention is needed to monitor movements and their visual consequences. Once a transformation is learnt, it can be executed automatically without attentional control. Using steady-state visual evoked potentials (SSVEPs) measured from EEG activity, we examined how visual attention changes during the early phase of visuomotor adaptation. SSVEPs were elicited by a green disc flickering at 15 Hz which was either the movement target or the cursor that participants controlled. Participants performed an adapted continuous visuomotor adaptation task with either 60° or 120° screen cursor rotation, and changes in 15-Hz SSVEP power were examined. Participants' performance improved over time in all conditions, with the rate of learning significantly influenced by the degree of rotation. SSVEPs at 15 Hz showed a significant change over time with adaptation for 60° rotations, but not for 120° rotations, such that SSVEPs elicited by the stimuli were significantly lower for 60° compared with 120° rotation conditions over the last adaptation blocks. This suggests that visual attention to the movement target and feedback reduces over time as performance improves during visuomotor adaptation for easier rotations, but must be maintained throughout the task for more difficult 120° rotations that might require more strategic control.

A behavioral task for investigating action discovery, selection and switching: comparison between types of reinforcer.

Action discovery and selection are critical cognitive processes that are understudied at the cellular and systems neuroscience levels. Presented here is a new rodent joystick task suitable to test these processes due to the range of action possibilities that can be learnt while performing the task. Rats learned to manipulate a joystick while progressing through task milestones that required increasing degrees of movement accuracy. In a switching phase designed to measure action discovery, rats were repeatedly required to discover new target positions to meet changing task demands. Behavior was compared using both food and electrical brain stimulation reward (BSR) of the substantia nigra as reinforcement. Rats reinforced with food and those with BSR performed similarly overall, although BSR-treated rats exhibited greater vigor in responding. In the switching phase, rats learnt new actions to adapt to changing task demands, reflecting action discovery processes. Because subjects are required to learn different goal-directed actions, this task could be employed in further investigations of the cellular mechanisms of action discovery and selection. Additionally, this task could be used to assess the behavioral flexibility impairments seen in conditions such as Parkinson's disease and obsessive-compulsive disorder. The versatility of the task will enable cross-species investigations of these impairments.

Agency attribution: event-related potentials and outcome monitoring.

Knowledge about the effects of our actions is an underlying feature of voluntary behavior. Given the importance of identifying the outcomes of our actions, it has been proposed that the sensory outcomes of self-made actions are inherently different from those of externally caused outcomes. Thus, the outcomes of self-made actions are likely to be more motivationally significant for an agent. We used event-related potentials to investigate the relationship between the perceived motivational significance of an outcome and the attribution of agency in the presence of others. In our experiment, we assessed agency attribution in the presence of another agent by varying the degree of contiguity between participants' self-made actions and the sensory outcome. Specifically, we assessed the feedback correct-related positivity (fCRP) and the novelty P3 measures of an outcome's motivational significance and unexpectedness, respectively. Results revealed that both the fCRP and participants' agency attributions were significantly influenced by action-outcome contiguity. However, when action-outcome contiguity was ambiguous, novelty P3 amplitude was a reliable indicator of agency attribution. Prior agency attributions were also found to influence attribution in trials with ambiguous and low action-outcome contiguity. Participants' use of multiple cues to determine agency is consistent with the cue integration theory of agency. In addition to these novel findings, this study supports growing evidence suggesting that reinforcement processes play a significant role in the sense of agency.

Creating a movement heuristic for voluntary action: electrophysiological correlates of movement-outcome learning.

Performance of voluntary behavior requires the selection of appropriate movements to attain a desired goal. We propose that the selection of voluntary movements is often contingent on the formation of a movement heuristic or set of internal rules governing movement selection. We used event-related potentials (ERPs) to identify the electrophysiological correlates of the formation of movement heuristics during movement-outcome learning. In two experiments, ERPs from non-learning control tasks were compared to a movement-learning task in which a movement heuristic was formed. We found that novelty P3 amplitude was negatively correlated with improved performance in the movement-learning task. Additionally, enhancement of novelty P3 amplitude was observed during learning even after controlling for memory, attentional and inter-stimulus interval parameters. The feedback correct-related positivity (fCRP) was only elicited by sensory effects following intentional movements. These findings extend previous studies demonstrating the role of the fCRP in performance monitoring and the role of the P3 in learning. In particular, the present study highlights an integrative role of the fCRP and the novelty P3 for the acquisition of movement heuristics. While the fCRP indicates that the goal of intentional movements has been attained, the novelty P3 engages stimulus-driven attentional mechanisms to determine the primary aspects of movement and context required to elicit the sensory effect.