Brendan Keane

Many characteristics of goal-directed movements, such as their initiation time, initial direction, and speed, are influenced both by the details of previously executed movements (i.e. action history), and by the degree to which previous movements were rewarded or punished (i.e. reward history). In reinforcement learning terms, when movements are externally cued, action and reward history jointly define the probability and magnitude of positive/negative outcomes of available options, and therefore their pre-stimulus expected value. To dissociate which of these neurocomputational variables influence sensorimotor brain processing, we studied how reach behaviour and evoked brain responses are affected by independent manipulations of action and reward history. We found that movements were initiated earlier both for more frequently repeated targets and targets associated with higher reward magnitude, but only movements to highly rewarded targets had higher movement speeds. Classical visually-evoked encephalographic (EEG) potentials (P1/N1) were not affected by either reward magnitude or target probability. There were, however, amplified midline ERP responses at centroparietal electrodes for rewarded targets and movements compared to control, but no differences between more frequently presented targets and control. Critically, the spatial precision of decoded target locations extracted from a multivariate linear decoding model of EEG data was greater for target locations associated with higher reward magnitude than for control target locations (∼150-300ms after target presentation). Again, there were no differences in the precision of decoded target direction representations between more frequent target locations and control target locations. These data suggest that the expected reward magnitude associated with an action, rather than its long-run expected value, determines the precision of early sensorimotor processing. Significance Statement: We move more quickly and more accurately toward goals that we value more highly, and this is due partly to enhanced motor preparation. However, our expectations about the value of an action depend both on the probability of its requirement and the magnitude of the reward associated with it. Here we disentangled the influence of reward magnitude and probability on early sensorimotor processing via a multivariate linear decoding approach to extract target direction from scalp encephalograms. We found that the spatial precision of decoded target direction was greater for high reward targets but not for more probable targets. Thus, early sensorimotor processing is sharpened when the magnitude of reward associated with movement to a cued target is high. Highlights: The direction of movement can be reliably decoded from the scalp EEG from ∼80ms after target presentation. The neural representation of movement direction is more precise for targets that are associated with high reward, but not for targets that are more probable. The magnitude of reward associated with movement to a presented target, rather than the long-run expected value of the movement, sharpens the spatial precision of early sensorimotor processing.

Recent history influences subsequent perception, decision‐making and motor behaviours. In this article, we address a discrepancy in the effects of recent sensory history on the perceived timing of auditory and visual stimuli. In the synchrony judgement (SJ) task, similar timing relationships in consecutive trials seem more synchronous (i.e. less like the repeated temporal order). This effect is known as rapid recalibration and is consistent with a negative perceptual aftereffect. Interestingly, the opposite is found in the temporal order judgement (TOJ) task (positive rapid recalibration). We aimed to determine whether a simple bias to repeat judgements on consecutive trials (choice‐repetition bias) could account for the discrepant results in these tasks. Preliminary simulations and analyses indicated that a choice‐repetition bias could produce apparently positive rapid recalibration in the TOJ and not the SJ task. Our first experiment revealed no evidence of rapid recalibration of TOJs, but negative rapid recalibration of associated confidence. This suggests that timing perception was rapidly recalibrated, but that the negative recalibration effect was obfuscated by a positive bias effect. In our second experiment, we experimentally mitigated the choice‐repetition bias effect and found negative rapid recalibration of TOJs. We therefore conclude that timing perception is negatively rapidly recalibrated, and this is observed consistently across timing tasks. These results contribute to a growing body of evidence that indicates multisensory perception is constantly undergoing recalibration, such that perceptual synchrony is maintained. This work also demonstrates that participants’ task responses reflect judgements that are contaminated by independent biases of perception and decision‐making.

A substantial question in understanding expert behavior is isolating where experts look, and which aspects of their environment they process. While tracking the position of gaze provides some insight into this process, our ability to attend covertly to regions of space other than the current point of fixation, severely limits the diagnostic power of such data. Over the past decade, evidence has emerged suggesting that microscopic eye movements present during periods of fixation may be linked to the spatial distribution of covert attention, potentially offering a powerful tool for studying expert behavior. To date, the majority of studies in this field have tested the link under the constraints of a trial by trial, forced-response task. In the current study we sought to examine the effect when participants performed a continuous, divided-attention task, with the hope of bridging the gap to a range of more ecological, real-world tasks. We report various aspects of the eye movement and response data including (i) the relationship between microsaccades and drift correction, (ii) response behavior in brief time periods immediately following a microsaccade, (iii) response behavior briefly preceding a microsaccade. Analysis failed to reveal a link between task accuracy and the direction of a microsaccade. Most striking however, we found evidence for a timelocked relationship between the side of space responded to and the direction of the most recent microsaccade. The paper hence provides preliminary evidence that microsaccades may indeed be used to track the ongoing allocation of spatial attention.

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Recent findings indicate that timing perception is systematically changed after only a single presentation of temporal asynchrony. This effect is known as rapid recalibration. In the synchrony judgement task, similar timing relationships in consecutive trials seem more synchronous ( positive rapid recalibration; Van der Burg et al., 2013, 2015). Interestingly, the direction of this effect is reversed for temporal order judgements ( negative rapid recalibration; Roseboom, 2019). We aimed to determine whether negative rapid recalibration of temporal order judgements (TOJs) reflects genuine rapid temporal recalibration, or a choice-repetition bias unrelated to timing perception. In our first experiment we found no evidence of rapid recalibration of TOJs, but positive rapid recalibration of associated confidence. This suggests that timing perception had rapidly recalibrated, but that this was undetectable in TOJs, plausibly because the positive recalibration effect was obfuscated by a large negative bias effect. In our second experiment, we dissociated participants’ previous TOJ from the most recently presented timing relationship, mitigating the choice-repetition bias effect, and found evidence of positive rapid recalibration of TOJs. We therefore conclude that timing perception is rapidly recalibrated positively for both synchrony and temporal order judgements. It remains unclear whether rapid recalibration occurs at the level of sensory processing, leading to similar effects in all subsequent judgements, or reflects a generalised decision-making strategy.

It has been demonstrated that people have insight into the accuracy of their own decision-making processes. This is evident from correlations between decisional confidence and objective task performance, and is often described as a form of metacognition, as it requires that the brain has formed an accurate reportable estimate of the precision with which it has encoded information. Metacognitive insight has been demonstrated for judgments concerning diverse visual properties, including orientation (de Gardelle & Mamassian, 2014), contrast discrimination (Fleming, Weil, Nagy, Dolan, & Rees, 2010), and direction (Ratcliff & Starns, 2013). Here we report that the human brain also forms reportable estimates of the precision with which it has encoded temporal relationships. We examined metacognitive insight into precision during a subjective timing task (audio-visual temporal order judgments), and into accuracy during an objective timing task (a three alternative audio-visual odd-one-out task varying audio-visual temporal offset). In both tasks we found that people expressed levels of confidence that were well correlated with performance. This cannot be attributed to low confidence on trials wherein people simply missed the stimulus presentation, or suffered a lapse in concentration, as participants were required to indicate when this happened, and such trials were repeated. Our data indicate that the human brain accurately estimates the precision with which it has encoded audio-visual timing relationships on a trial-by-trial basis. Meeting abstract presented at VSS 2015