Can the reward associated with gaze leading train faster gaze shifts to a jointly attended target?

We investigated whether the reward that has previously been associated with initiated joint attention (the experience of having one’s gaze followed by someone else; Pfeiffer et al., 2014, Schilbach et al., 2010) can influence gaze behaviour and, similarly to monetary rewards (Blaukopf & DiGirolamo, 2005; Manohar et al., 2017; Milstein & Dorris, 2007), elicit learning effects. To this end, we adapted Milstein and Dorris (2007) gaze contingent paradigm, so it required participants to look at an anthropomorphic avatar and then conduct a saccade towards the left or right peripheral target. If participants were fast enough, they could experience social reward in terms of the avatar looking at the same target as they did and thus engaging with them in joint attention. One side had higher reward probability than the other (80 % vs 20 %; on the other fast trials the avatar would simply keep staring ahead). We expected that if participants learned about the reward contingency and if they found the experience of having their gaze followed rewarding, their latency and success rate would improve for saccades to the high rewarded targets. Although our current study did not demonstrate that such social reward has a long lasting effect on gaze behaviour, we found that latencies became shorter over time and that latencies were longer on congruent trials (target location was identical to the previous trial) than on noncongruent trials (target location different than on the previous trial), which could reflect inhibition of return.

Influence of the Inter-Trial Interval, Movement Observation, and Hand Dominance on the Previous Trial Effect

Previous studies have shown that current movement is influenced by the previous movement, which is known as the previous trial effect. In this study, we investigated the influence of the inter-trial interval, movement observation, and hand dominance on the previous trial effect of the non-target discrete movement. Right-handed healthy humans abducted the index finger in response to a start cue, and this task was repeated with constant inter-trial intervals. The absolute difference in the reaction time (RT) between the previous and current trials increased as the inter-trial interval increased. The absolute difference in RT reflects the reproducibility of the time taken for the motor execution between two consecutive trials. Thus, the finding supported the view that there is a carryover of movement information from one trial to the next, and that the underlying reproducibility of the RT between the two consecutive trials decays over time. This carryover of movement information is presumably conveyed by implicit short-term memory, which also decays within a short period of time. The correlation coefficient of the RT between the previous and current trials decreased with an increase in the inter-trial interval, indicating that the common responsiveness of two consecutive trials weakens over time. The absolute difference was smaller when the response was performed while observing finger movement, indicating that a carryover of the visual information to the next trial enhances the reproducibility of the motor execution process between consecutive trials. Hand dominance did not influence the absolute difference or correlation coefficient, indicating that the central process mediating previous trial effect of hand movement is not greatly lateralized.

Serial Dependence of Emotion Within and Between Stimulus Sensory Modalities

How we perceive the world is not solely determined by what we sense at a given moment in time, but also by what we processed recently. Here we investigated whether such serial dependencies for emotional stimuli transfer from one modality to another. Participants were presented a random sequence of emotional sounds and images and instructed to rate the valence and arousal of each stimulus (Experiment 1). For both ratings, we conducted an intertrial analysis, based on whether the rating on the previous trial was low or high. We found a positive serial dependence for valence and arousal regardless of the stimulus modality on two consecutive trials. In Experiment 2, we examined whether passively perceiving a stimulus is sufficient to induce a serial dependence. In Experiment 2, participants were instructed to rate the stimuli only on active trials and not on passive trials. The participants were informed that the active and passive trials were presented in alternating order, so that they were able to prepare for the task. We conducted an intertrial analysis on active trials, based on whether the rating on the previous passive trial (determined in Experiment 1) was low or high. For both ratings, we again observed positive serial dependencies regardless of the stimulus modality. We conclude that the emotional experience triggered by one stimulus affects the emotional experience for a subsequent stimulus regardless of their sensory modalities, that this occurs in a bottom-up fashion, and that this can be explained by residual activation in the emotional network in the brain.

Performance Errors Influence Voluntary Task Choices

Humans adjust their behavior after they committed an error, but it is unclear whether and how error commissions influence voluntary task choices. In the present article, we review different accounts on effects of errors in the previous trial (transient error effects) and overall error probabilities (sustained error effects) on behavioral adaptation. Based on this review, we derived five statistical models how errors might influence voluntary task choices. We analyzed the data of three experiments in which participants voluntarily selected one of two tasks before each trial whereby task difficulty, and concomitantly error probability, increased successively for the selected/performed tasks. Model comparison suggested that choice behavior was best explained by a combination of error probability of the performed task, error probability of the alternative task, and whether the previous response was correct or incorrect. The results revealed that participants were most likely to switch tasks in situations where the error probability of the performed task was high, the error probability of the alternative task was low, and after an error on the previous trial. We conclude that task selection processes are influenced by transient and sustained error effects.

Pitfalls in quantifying exploration in reward-based motor learning and how to avoid them

When learning a movement based on binary success information, one is more variable following failure than following success. Theoretically, the additional variability post-failure might reflect exploration of possibilities to obtain success. When average behavior is changing (as in learning), variability can be estimated from differences between subsequent movements. Can one estimate exploration reliably from such trial-to-trial changes when studying reward-based motor learning? To answer this question, we tried to reconstruct the exploration underlying learning as described by four existing reward-based motor learning models. We simulated learning for various learner and task characteristics. If we simply determined the additional change post-failure, estimates of exploration were sensitive to learner and task characteristics. We identified two pitfalls in quantifying exploration based on trial-to-trial changes. Firstly, performance-dependent feedback can cause correlated samples of motor noise and exploration on successful trials, which biases exploration estimates. Secondly, the trial relative to which trial-to-trial change is calculated may also contain exploration, which causes underestimation. As a solution, we developed the additional trial-to-trial change (ATTC) method. By moving the reference trial one trial back and subtracting trial-to-trial changes following specific sequences of trial outcomes, exploration can be estimated reliably for the three models that explore based on the outcome of only the previous trial. Since ATTC estimates are based on a selection of trial sequences, this method requires many trials. In conclusion, if exploration is a binary function of previous trial outcome, the ATTC method allows for a model-free quantification of exploration.

The Malleability of Attentional Capture

We suggest that consideration of trial-by-trial variations, individual differences, and training data will enrich the current framework in Luck et al. (2020). We consider whether attentional capture is modulated by trial-by-trial fluctuations of attentional state and experiences on the previous trial. We also consider whether individual differences may affect attentional capture while highlighting potential challenges in using the color-singleton task to measure individual differences. Finally, performance in the color-singleton task can be modified dramatically with practice but the underlying mechanisms are not entirely clear. Understanding the malleability of attentional capture may broaden the current framework and resolve outstanding questions. The version of record of this manuscript will be available in Visual Cognition (2021), https://doi.org/10.1080/13506285.2021.1915903

Disrupting short-term memory in premotor but not visual cortex affects serial dependence in visuomotor integration

Human behavior is biased by past experience. For example, when intercepting a moving target, the speed of previous targets will bias responses in future trials. Neural mechanisms underlying this so-called serial dependence are still under debate. Here, we tested the hypothesis that the previous trial leaves a neural trace in brain regions associated with encoding task-relevant information at visual and/or motor regions. We reasoned that injecting noise by means of transcranial magnetic stimulation (TMS) over premotor and visual areas would degrade such memory traces and hence reduce serial dependence. To test this hypothesis, we applied bursts of TMS pulses to right visual motion processing region hV5/MT+ and to left dorsal premotor cortex during inter-trial intervals of a coincident timing task performed by twenty healthy human participants (15 female). Without TMS, participants presented a bias towards the speed of the previous trial when intercepting moving targets. TMS over dorsal premotor cortex decreased serial dependence in comparison to the control Vertex stimulation, whereas TMS applied over hV5/MT+ did not. In addition, TMS seems to have specifically affected the memory trace that leads to serial dependence, as we show no evidence that participants’ behavior worsened after applying TMS. These results provide causal evidence that an implicit short-term memory mechanism in premotor cortex keeps information from one trial to the next, and that this information is blended with current trial information so that it biases behavior in a visuomotor integration task with moving objects.Significance StatementHuman perception and action are biased by the recent past. For example, the speed from previously experienced moving targets biases responses when hitting moving objects. The origin of such serial bias is still not fully understood, but a few components seem to be fundamental for its emergence: the brain needs to keep previous trial information in short-term memory and blend it with incoming information. Here, we present evidence that a premotor area has a potential role in storing previous trial information in implicit short-term memory in a visuomotor integration task, and that this information is responsible for causing biases on ongoing behavior. These results corroborate the perspective that areas associated with processing information of a stimulus or task also participate in maintaining that information in short-term memory even when this information is no longer relevant for current behavior.

Evaluating cross contamination on a shared ventilator

BackgroundDisasters have the potential to cause critical shortages of life-saving equipment. It has been postulated that during patient surge, multiple individuals could be maintained on a single ventilator. This was supported by a previous trial that showed one ventilator could support four sheep. The goal of our study is to investigate if cross contamination of pathological agents occurs between individuals on a shared ventilator with strategically placed antimicrobial filters.MethodsA multipatient ventilator circuit was assembled using four sterile, parallel standard tubing circuits attached to four 2 L anaesthesia bags, each representing a simulated patient. Each ‘patient’ was attached to a Heat and Moisture Exchange filter. An additional bacterial/viral filter was attached to each expiratory limb. ‘Patient-Lung’ number 1 was inoculated with an isolate of Serratia marcescens, and the circuit was run for 24 hours. Each ‘lung’ and three points in the expiratory limb tubing were washed with broth and cultured. All cultures were incubated for 48 hours with subcultures performed at 24 hours.ResultsWashed cultures of patient 2, 3 and 4 failed to demonstrate growth of S. marcescens. Cultures of the distal expiratory tubing, expiratory limb connector and expiratory limb prefilter tubing yielded no growth of S. marcescens at 24 or 48 hours.ConclusionBased on this circuit configuration, it is plausible to maintain four individuals on a single ventilator for 24 hours without fear of cross contamination.