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

Repeating patterns: Predictive processing suggests an aesthetic learning role of the basal ganglia in repetitive stereotyped behaviors

Recurrent, unvarying, and seemingly purposeless patterns of action and cognition are part of normal development, but also feature prominently in several neuropsychiatric conditions. Repetitive stereotyped behaviors (RSBs) can be viewed as exaggerated forms of learned habits and frequently correlate with alterations in motor, limbic, and associative basal ganglia circuits. However, it is still unclear how altered basal ganglia feedback signals actually relate to the phenomenological variability of RSBs. Why do behaviorally overlapping phenomena sometimes require different treatment approaches−for example, sensory shielding strategies versus exposure therapy for autism and obsessive-compulsive disorder, respectively? Certain clues may be found in recent models of basal ganglia function that extend well beyond action selection and motivational control, and have implications for sensorimotor integration, prediction, learning under uncertainty, as well as aesthetic learning. In this paper, we systematically compare three exemplary conditions with basal ganglia involvement, obsessive-compulsive disorder, Parkinson’s disease, and autism spectrum conditions, to gain a new understanding of RSBs. We integrate clinical observations and neuroanatomical and neurophysiological alterations with accounts employing the predictive processing framework. Based on this review, we suggest that basal ganglia feedback plays a central role in preconditioning cortical networks to anticipate self-generated, movement-related perception. In this way, basal ganglia feedback appears ideally situated to adjust the salience of sensory signals through precision weighting of (external) new sensory information, relative to the precision of (internal) predictions based on prior generated models. Accordingly, behavioral policies may preferentially rely on new data versus existing knowledge, in a spectrum spanning between novelty and stability. RSBs may then represent compensatory or reactive responses, respectively, at the opposite ends of this spectrum. This view places an important role of aesthetic learning on basal ganglia feedback, may account for observed changes in creativity and aesthetic experience in basal ganglia disorders, is empirically testable, and may inform creative art therapies in conditions characterized by stereotyped behaviors.

The Brain's Reward Response Occurs Even Without Actual Reward!

What if the brain's response to reward occurs even when there is no reward? Wouldn't that be a further concern for people prone to problem gambling and other forms of addiction, like those related to eating? Electroencephalography was employed to investigate this possibility using probabilistic feedback manipulations and measures of known event-related potentials (ERPs) related to reward processing. We tested the hypothesis-that reward-based ERPs would occur even in the absence of a tangible reward and when manipulations on expectation are implicit. The well-known P300 response potential was a key focus, and was assessed in non-gambling volunteer undergraduates on a task involving experimentally-manipulated probabilities of positive or negative feedback comprising three trial types-80, 50, or 20% positive feedback. A feedback stimulus (F1) followed a guess response between two possible outcomes (implicit win/loss), and then a second feedback stimulus (F2) was presented to confirm an alleged 'win' or 'loss' (explicit win/loss). Results revealed that amplitude of the P300 in F1-locked data (implicit manipulation) was larger (more positive) on average for feedback outcomes that were manipulated to be less likely than expected. The effect is pronounced after increased time on task (later trials), even though the majority of participants were not explicitly aware of our probability manipulations. For the explicit effects in F2-locked data, no meaningful or significant effects were observed. These findings point to the existence of proposed success-response mechanisms that operate not only explicitly but also with implicit manipulations that do not involve any direct indication of a win or loss, and are not associated with tangible rewards. Thus, there seems to be a non-explicit form of perception (we call 'implicit') associated with an internal experience of wins/losses (in the absence of actual rewards or losses) that can be measured in associated brain processes. The potential significance of these findings is discussed in terms of implications for problem gambling.