Florian Waszak

Two modes of sensorimotor integration in intention-based and stimulus-based actions

Human actions may be driven endogenously (to produce desired environmental effects) or exogenously (to accommodate to environmental demands). There is a large body of evidence indicating that these two kinds of action are controlled by different neural substrates. However, only little is known about what happens—in functional terms—on these different “routes to action”. Ideomotor approaches claim that actions are selected with respect to their perceptual consequences. We report experiments that support the validity of the ideomotor principle and that, at the same time, show that it is subject to a far-reaching constraint: It holds for endogenously driven actions only! Our results suggest that the activity of the two “routes to action” is based on different types of learning: The activity of the system guiding stimulus-based actions is accompanied by stimulus–response (sensorimotor) learning, whereas the activity of the system controlling intention-based actions results in action–effect (ideomotor) learning.

Mechanisms of intentional binding and sensory attenuation: The role of temporal prediction, temporal control, identity prediction, and motor prediction.

Sensory processing of action effects has been shown to differ from that of externally triggered stimuli, with respect both to the perceived timing of their occurrence (intentional binding) and to their intensity (sensory attenuation). These phenomena are normally attributed to forward action models, such that when action prediction is consistent with changes in our environment, our experience of these effects is altered. Although much progress has been made in recent years in understanding sensory attenuation and intentional binding, a number of important questions regarding the precise nature of the predictive mechanisms involved remain unanswered. Moreover, these mechanisms are often not discussed in empirical papers, and a comprehensive review of these issues is yet to appear. This review attempts to fill this void. We systematically investigated the role of temporal prediction, temporal control, identity prediction, and motor prediction in previous published reports of sensory attenuation and intentional binding. By isolating the individual processes that have previously been contrasted and incorporating these experiments with research in the related fields of temporal attention and stimulus expectation, we assessed the degree to which existing data provide evidence for the role of forward action models in these phenomena. We further propose a number of avenues for future research, which may help to better determine the role of motor prediction in processing of voluntary action effects, as well as to improve understanding of how these phenomena might fit within a general predictive processing framework. Furthermore, our analysis has important implications for understanding disorders of agency in schizophrenia.

Action effect anticipation: Neurophysiological basis and functional consequences

Voluntary actions are thought to be selected with respect to their intended goal. Converging data suggests that medial frontal cortex plays a crucial role in linking actions to their predicted effects. Recent neuroimaging data also suggests that during action selection, the brain pre-activities the representation of the predicted action effect. We review evidence of action effect prediction, both in terms of its neurophysiological basis as well as its functional consequences. By assuming that action preparation includes activation of the predicted sensory consequences of the action, we provide a mechanism to understand sensory attenuation and intentional binding. In this account, sensory attenuation results from more difficult discrimination between the observed action effect and the pre-activation of the predicted effect, as compared to when no (or incorrect) prediction is present. Similarly, a predicted action effect should also reach the threshold of awareness faster (intentional binding), if its perceptual representation is pre-activated. By comparing this potential mechanism to mental imagery and repetition suppression we propose a possible neural basis for the processing of predicted action effects.

Intention-based and stimulus-based mechanisms in action selection

Human actions can be classified as being either more stimulus-based or more intention-based. According to the ideomotor framework of action control, intention-based actions primarily refer to anticipated action effects (in other words response-stimulus [R-S] bindings), whereas stimulus-based actions are commonly assumed to be more strongly determined by stimulus-response [S-R] bindings. We explored differences in the functional signatures of both modes of action control in a temporal bisection task. Participants either performed a choice response by pressing one out of two keys in response to a preceding stimulus (stimulus-based action), or pressed one out of two keys to produce the next stimulus (intention-based action). In line with the ideomotor framework, we found intention-based actions to be shifted in time towards their anticipated effects (the next stimulus), whereas stimulus-based actions were shifted towards their preceding stimulus. Event-related potentials (ERPs) in the EEG revealed marked differences in action preparation for the two tasks. The data as a whole provide converging evidence for functional differences in the selection of motor actions as a function of their triggering conditions, and support the notion of two different modes of action selection, one being exogenous or mainly stimulus-driven, the other being endogenous or mainly intention-driven.

The flexible mind is associated with the catechol-O-methyltransferase (COMT) Val(158)Met polymorphism: Evidence for a role of dopamine in the control of task-switching

Genetic variability related to the catechol-O-methyltransferase (COMT) gene (Val158Met polymorphism) has received increasing attention as a possible modulator of cognitive control functions. Recent evidence suggests that the Val158Met genotype may differentially affect cognitive stability and flexibility, in such a way that Val/Val homozygous individuals (who possess low prefrontal dopamine levels) may show more pronounced cognitive flexibility than Met/-carriers (who possess high prefrontal dopamine levels). To test this, healthy humans (n=87), genotyped for the Val158Met polymorphism at the COMT gene, performed a task-switching paradigm, which provides a relatively diagnostic index of cognitive flexibility. As predicted, Met/-carriers showed larger switching costs (i.e., less cognitive flexibility), F(1,85)=4.28, p<0.05, than Val/Val homozygous individuals. Our findings support the idea that low prefrontal dopamine levels promote cognitive flexibility.

A New Look at Sensory Attenuation Action-Effect Anticipation Affects Sensitivity, Not Response Bias

The systematic association of an action that a person performs with its sensory effects is thought to attenuate that person’s perception of the effect of the action. However, whether learned sensorimotor contingencies truly affect perception, rather than just inducing a response bias, has yet to be determined. The experiment presented in this article comprised two parts: an action-effect association phase and a test phase, during which the actions’ perceptual effects were tested. During the association phase, specific actions (left-key and right-key presses) were associated with specific visual effects (tilted Gabor patches). In the test phase, participants’ left-key presses and right-key presses triggered the onset of a low-contrast tilted Gabor patch in 50% of trials (no stimulus was presented on the remaining 50% of trials). Participants were required to report the presence or absence of this tilted Gabor patch. Our results showed that participants’ sensitivity (d′) to the Gabor patches was reduced by 10% when the patches were triggered by the action they had previously been associated with. This finding indicates that a person’s action does not induce a response bias (c), but changes the perception (d′) of the learned action effect.

Stimulus-response bindings in priming

Highlights • S–R bindings are more flexible and pervasive than previously thought.• S–R bindings can simultaneously encode multiple stimulus and response representations.• S–R bindings can be encoded or retrieved in the absence of attention or awareness.• S–R bindings complicate interpretations of priming, but are interesting in their own right.• S–R bindings enable rapid yet context-dependent behaviors.

Interaction of Task Readiness and Automatic Retrieval in Task Switching: Negative Priming and Competitor Priming

When subjects switch between tasks, performance is slower after a task switch than after a task repetition, even when preparation time is long. We report two experiments that support the idea that a large part of these residual task shift costs can be due to stimulus-cued retrieval of previous task episodes. We demonstrate that there are two different factors at work: (1) facilitation of response to the current distractor stimulus, appropriate to the previously relevant, competing task (competitor priming), and (2) impaired processing of previously suppressed responses (negative priming). Negative priming was contingent on the size of the stimulus set, suggesting that distractor suppression comes into effect only if the distractors are highly activated. Importantly, both types of interference interacted with task readiness: Whereas in the nondominant task (picture naming), switch and nonswitch trials were equally affected, the dominant task (word reading) showed priming effects on switch trials only. Thus, the retrieval of previous processing episodes has a selective impact on situations in which task competition is high.

ERP correlates of action effect prediction and visual sensory attenuation in voluntary action

Sensory attenuation of voluntary action effects has been widely reported in both somatosensory and auditory domains. However, relatively little research has focused on physiological measures of sensory attenuation of visual action effects. One previous study found, perhaps surprisingly, that both auditory and visual sensory attenuation were manifested as decreased ERP amplitude over the vertex. The present study aimed to extend these findings using a novel paradigm in which voluntary actions were either associated with a visual action effect or to no effect. Crucially, this allowed us to explore both sensory attenuation (by comparing ERPs to action-triggered versus externally triggered stimuli) and action effect prediction (by comparing actions that triggered a stimulus with actions that did not). With regard to sensory attenuation, we found that attenuation of cortical responses to visual action effects was manifested in a reduced activation of a frontoparietal network, from 150 ms after stimulus. Differences between actions that produced an effect and those that did not were observed in lateralized motor potentials and may reflect the cortical correlates of the action effect prediction. We also observed a re-activation of lateralized motor activity following onset of the action effect, suggesting a common representation of action effects in visual and motor cortices. Taken together, these findings help to elucidate the cortical mechanisms of voluntary action as well as their sensory consequences and inform how our interaction with the external world is processed and controlled.

Intention and attention in ideomotor learning

Human actions may be carried out in response to exogenous stimuli (stimulus based) or they may be selected endogenously on the basis of the agents intentions (intention based). We studied the functional differences between these two types of action during action–effect (ideomotor) learning. Participants underwent an acquisition phase, in which each key-press (left/right) triggered a specific tone (low pitch/high pitch) either in a stimulus-based or in an intention-based action mode. Consistent with previous findings, we demonstrate that auditory action effects gain the ability to prime their associated responses in a later test phase only if the actions were selected endogenously during acquisition phase. Furthermore, we show that this difference in ideomotor learning is not due to different attentional demands for stimulus-based and intention-based actions. Our results suggest that ideomotor learning depends on whether or not the action is selected in the intention-based action mode, whereas the amount of attention devoted to the action–effect is less important.