Blocks Of Trials Research Articles

Attractor-Like Dynamics Extracted from Human Electrocorticographic Recordings Underlie Computational Principles of Auditory Bistable Perception.

In bistable perception, observers experience alternations between two interpretations of an unchanging stimulus. Neurophysiological studies of bistable perception typically partition neural measurements into stimulus-based epochs and assess neuronal differences between epochs based on subjects' perceptual reports. Computational studies replicate statistical properties of percept durations with modeling principles like competitive attractors or Bayesian inference. However, bridging neuro-behavioral findings with modeling theory requires the analysis of single-trial dynamic data. Here, we propose an algorithm for extracting nonstationary timeseries features from single-trial electrocorticography (ECoG) data. We applied the proposed algorithm to 5-min ECoG recordings from human primary auditory cortex obtained during perceptual alternations in an auditory triplet streaming task (six subjects: four male, two female). We report two ensembles of emergent neuronal features in all trial blocks. One ensemble consists of periodic functions that encode a stereotypical response to the stimulus. The other comprises more transient features and encodes dynamics associated with bistable perception at multiple time scales: minutes (within-trial alternations), seconds (duration of individual percepts), and milliseconds (switches between percepts). Within the second ensemble, we identified a slowly drifting rhythm that correlates with the perceptual states and several oscillators with phase shifts near perceptual switches. Projections of single-trial ECoG data onto these features establish low-dimensional attractor-like geometric structures invariant across subjects and stimulus types. These findings provide supporting neural evidence for computational models with oscillatory-driven attractor-based principles. The feature extraction techniques described here generalize across recording modality and are appropriate when hypothesized low-dimensional dynamics characterize an underlying neural system.SIGNIFICANCE STATEMENT Irrespective of the sensory modality, neurophysiological studies of multistable perception have typically investigated events time-locked to the perceptual switching rather than the time course of the perceptual states per se. Here, we propose an algorithm that extracts neuronal features of bistable auditory perception from largescale single-trial data while remaining agnostic to the subject's perceptual reports. The algorithm captures the dynamics of perception at multiple timescales, minutes (within-trial alternations), seconds (durations of individual percepts), and milliseconds (timing of switches), and distinguishes attributes of neural encoding of the stimulus from those encoding the perceptual states. Finally, our analysis identifies a set of latent variables that exhibit alternating dynamics along a low-dimensional manifold, similar to trajectories in attractor-based models for perceptual bistability.

Perceptual Difficulty Regulates Attentional Gain Modulations in Human Visual Cortex.

Perceptual difficulty is sometimes used to manipulate selective attention. However, these two factors are logically distinct. Selective attention is defined by priority given to specific stimuli based on their behavioral relevance, whereas perceptual difficulty is often determined by perceptual demands required to discriminate relevant stimuli. That said, both perceptual difficulty and selective attention are thought to modulate the gain of neural responses in early sensory areas. Previous studies found that selectively attending to a stimulus or increasing perceptual difficulty enhanced the gain of neurons in visual cortex. However, some other studies suggest that perceptual difficulty can have either a null or even reversed effect on gain modulations in visual cortex. According to Yerkes-Dodson's Law, it is possible that this discrepancy arises because of an interaction between perceptual difficulty and attentional gain modulations yielding a nonlinear inverted-U function. Here, we used EEG to measure modulations in the visual cortex of male and female human participants performing an attention-cueing task where we systematically manipulated perceptual difficulty across blocks of trials. The behavioral and neural data implicate a nonlinear inverted-U relationship between selective attention and perceptual difficulty: a focused-attention cue led to larger response gain in both neural and behavioral data at intermediate difficulty levels compared with when the task was more or less difficult. Moreover, difficulty-related changes in attentional gain positively correlated with those predicted by quantitative modeling of the behavioral data. These findings suggest that perceptual difficulty mediates attention-related changes in perceptual performance via selective neural modulations in human visual cortex.SIGNIFICANCE STATEMENT Both perceptual difficulty and selective attention are thought to influence perceptual performance by modulating response gain in early sensory areas. That said, less is known about how selective attention interacts with perceptual difficulty. Here, we measured neural gain modulations in the visual cortex of human participants performing an attention-cueing task where perceptual difficulty was systematically manipulated. Consistent with Yerkes-Dodson's Law, our behavioral and neural data implicate a nonlinear inverted-U relationship between selective attention and perceptual difficulty. These results suggest that perceptual difficulty mediates attention-related changes in perceptual performance via selective neural modulations in visual cortex, extending our understanding of the attentional operation under different levels of perceptual demands.

Object motion influences feedforward motor responses during mechanical stopping of virtual projectiles: a preliminary study

An important window into sensorimotor function is how humans interact and stop moving projectiles, such as stopping a door from closing shut or catching a ball. Previous studies have suggested that humans time the initiation and modulate the amplitude of their muscle activity based on the momentum of the approaching object. However, real-world experiments are constrained by laws of mechanics, which cannot be manipulated experimentally to probe the mechanisms of sensorimotor control and learning. An augmented-reality variant of such tasks allows for experimental manipulation of the relationship between motion and force to obtain novel insights into how the nervous system prepares motor responses to interact with moving stimuli. Existing paradigms for studying interactions with moving projectiles use massless objects and are primarily focused on quantifying gaze and hand kinematics. Here, we developed a novel collision paradigm using a robotic manipulandum where participants mechanically stopped a virtual object moving in the horizontal plane. On each block of trials, we varied the virtual object's momentum by increasing either its velocity or mass. Participants stopped the object by applying a force impulse that matched the object momentum. We observed that hand force increased as a function of object momentum linked to changes in virtual mass or velocity, similar to results from studies involving catching free-falling objects. In addition, increasing object velocity resulted in later onset of hand force relative to the impending time-to-contact. These findings show that the present paradigm can be used to determine how humans process projectile motion for hand motor control.

On the latency of object recognition and affect: Evidence from speeded reaction time tasks.

According to the semantic primacy hypothesis of emotion generation, stimuli must be semantically categorized to evoke emotions. This hypothesis was tested in two speeded reaction time experiments that also explored the processes underlying valence judgments. Participants viewed pleasant and unpleasant pictures. In different blocks of trials, they pressed a key as soon as they experienced the feeling evoked by a picture, recognized the depicted object, or detected the valence (pleasant/unpleasant) of the picture. Object recognition was significantly earlier than affect onset, and the two latencies were positively correlated. The latency of valence detection was in between the latencies of object recognition and affect and correlated with both. Experiment 2 additionally found that blurring the pictures delayed the onset of affect and that this effect was partially mediated by delayed object recognition. In contrast, false-coloring the pictures was found to delay affect mainly by reducing its intensity. Coloring also delayed valence judgments of pleasant pictures. The findings provide further chronometric support for the semantic primacy hypothesis of emotion generation and shed light on the processes underlying valence judgments. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Patients with psychotic disorders exhibit different audio-visual perceptual decision biases and metacognitive abilities

IntroductionIn the inherently noisy real world, we can rarely have full certainty about what we have just seen or heard. Thus, making a perceptual decision on sensory information, and simultaneously tracking our varying levels of certainty in these decisions (i.e., metacognitive abilities) are crucial components of everyday life.Hallucinations, such as confidently reporting a human voice or face when none was present, are a hallmark of psychotic disorders but also occur among the normal population. Particularly in patients with psychotic disorders, these misperceptions are linked to confident beliefs in their actual existence. However, whether patients’ confidence is only increased during such erroneous perceptions and whether perceptual and metacognitive decisions arise from supramodal mechanisms across sensory modalities remains unknown.ObjectivesIn the laboratory, we tested perceptual and metacognitive decisions under varying levels of sensory certainty in healthy adults and patients with psychotic disorders admitted to a psychiatry ward (Ncon=32, Npat=12; age = 19-49; F2x.x diagnoses).MethodsSpecifically, participants had to detect human voices or faces against briefly presented noisy backdrops and subsequently rate their confidence in the accuracy of their perceptual decision (Fig 1A,B,C). We further hypothesised that probabilistic cues prior to blocks of trials can bias participants’ choices and hallucination probability (i.e., confident false alarms).ResultsPatients exhibited higher perceptual sensitivity in the auditory than the visual task, alongside a generally stronger decision bias towards fewer ‘voice/face’ choices (Fig 2A,B). This bias was more pronounced in the visual domain. Decision performance was overall higher on the auditory task but lower for patients (predicted minimum > 55%; Fig 2C). Strong correlations between auditory accuracy and PANSS hallucination scores of patients and LSHS scores of healthy participants suggest an effect of these hallucinatory experiences on accurate perception.Metacognitive abilities were reduced in patients across both modalities: They exhibited general overconfidence, which was stronger for incorrect trials (Fig 3A). Patients’ confidence ratings were inversely related to the probability of choosing ‘voice/face’. Combining both perceptual and confidence decisions, patients showed higher hallucinations probability in the auditory task, particularly in more difficult trials (i.e., with less informative sensory evidence; Fig 3B).Image:Image 2:Image 3:ConclusionsIn sum, patients with psychotic disorders exhibit increased decision bias accompanied by increased confidence, and thus a reduced fidelity in their metacognitive abilities. The modality differences are in line with phenomenology and reported hallucination rates. These results suggest stronger priors in psychotic disorders resulting in worse perceptual acuity and assessment of this perception.Disclosure of InterestNone Declared

On the interplay between time and space perception in discontinuous stimulus displays

The present study examined whether and how the mutual perceptual biases of temporal and spatial information, known as the kappa and the tau effects, depend on the duration and spatial extent of sensory stimulation as well as on the magnitude of spatio-temporal discrepancy. Three small circles were presented in succession at different spatial positions. The time points of presentation and the spatial position of the second circle systematically varied. Participants judged either whether the temporal interval between the first and the second circle was longer than the interval between the second and the third circle (Experiment 1) or whether the spatial distance between the first and the second circle was larger than the distance between the second and the third circle (Experiment 2), or both in separate blocks of trials (Experiment 3). The impact of spatial information on temporal perception (i.e., the kappa effect) increased with velocity of motion presumably imputed by the participants to the static displays and decreased with spatio-temporal discrepancy. No inverse biases (i.e., no tau effects) were observed. These results are considered as an indication that integration of spatial and temporal signals follow the same basic principles as multisensory integration of redundant signals, such as those from vision and touch.

Mechanisms of adjustments to different types of uncertainty in the reward environment across mice and monkeys.

Despite being unpredictable and uncertain, reward environments often exhibit certain regularities, and animals navigating these environments try to detect and utilize such regularities to adapt their behavior. However, successful learning requires that animals also adjust to uncertainty associated with those regularities. Here, we analyzed choice data from two comparable dynamic foraging tasks in mice and monkeys to investigate mechanisms underlying adjustments to different types of uncertainty. In these tasks, animals selected between two choice options that delivered reward probabilistically, while baseline reward probabilities changed after a variable number (block) of trials without any cues to the animals. To measure adjustments in behavior, we applied multiple metrics based on information theory that quantify consistency in behavior, and fit choice data using reinforcement learning models. We found that in both species, learning and choice were affected by uncertainty about reward outcomes (in terms of determining the better option) and by expectation about when the environment may change. However, these effects were mediated through different mechanisms. First, more uncertainty about the better option resulted in slower learning and forgetting in mice, whereas it had no significant effect in monkeys. Second, expectation of block switches accompanied slower learning, faster forgetting, and increased stochasticity in choice in mice, whereas it only reduced learning rates in monkeys. Overall, while demonstrating the usefulness of metrics based on information theoryin examiningadaptive behavior, our study provides evidence for multiple types of adjustments in learning and choice behavior according to uncertainty in the reward environment.

Effects of a neutral warning signal under increased temporal uncertainty.

Han and Proctor (2022a, Quarterly Journal of Experimental Psychology, 75[4], 754-764) reported that in a visual two-choice task, compared with a no-warning condition, a neutral warning tone caused shorter reaction times (RTs) but at the expense of an increase in error percentages (a speed-accuracy trade-off) at a constant 50-ms foreperiod but shorter RTs without an increase in error percentages at a 200-ms foreperiod. Also, the spatial compatibility of stimulus-response mappings was found to interact with the foreperiod effect on RT. We conducted three experiments to investigate whether these findings can be replicated without the constancy of foreperiod within a trial block. In Experiments 1 and 2, participants performed the same two-choice task as in Han and Proctor's study but with the foreperiod randomly varied among 50, 100, and 200 ms and RT feedback provided after each response. Results showed that as the foreperiod increased, RT decreased while EP increased, demonstrating a consistent speed-accuracy trade-off. Also, the mapping effect was found to be largest at the 100-ms foreperiod. In Experiment 3, RT feedback was not provided, and the warning tone speeded responses without evidence of an increase in error percentage. We conclude that the enhanced information processing at a 200-ms foreperiod depends on constancy of foreperiod within a trial block, whereas the mapping-foreperiod interaction found in Han and Proctor is relatively unaffected by increased temporal uncertainty.

Restart errors reaction time of a two-step inhibition process account for the violation of the race model's independence in multi-effector selective stop signal task.

Goal-oriented actions often require the coordinated movement of two or more effectors. Sometimes multi-effector movements need to be adjusted according to a continuously changing environment, requiring stopping an effector without interrupting the movement of the others. This form of control has been investigated by the selective Stop Signal Task (SST), requiring the inhibition of an effector of a multicomponent action. This form of selective inhibition has been hypothesized to act through a two-step process, where a temporary global inhibition deactivating all the ongoing motor responses is followed by a restarting process that reactivates only the moving effector. When this form of inhibition takes place, the reaction time (RT) of the moving effector pays the cost of the previous global inhibition. However, it is poorly investigated if and how this cost delays the RT of the effector that was required to be stopped but was erroneously moved (Stop Error trials). Here we measure the Stop Error RT in a group of participants instructed to simultaneously rotate the wrist and lift the foot when a Go Signal occurred, and interrupt both movements (non-selective Stop version) or only one of them (selective Stop version) when a Stop Signal was presented. We presented this task in two experimental conditions to evaluate how different contexts can influence a possible proactive inhibition on the RT of the moving effector in the selective Stop versions. In one context, we provided the foreknowledge of the effector to be inhibited by presenting the same selective or non-selective Stop versions in the same block of trials. In a different context, while providing no foreknowledge of the effector(s) to be stopped, the selective and non-selective Stop versions were intermingled, and the information on the effector to be stopped was delivered at the time of the Stop Signal presentation. We detected a cost in both Correct and Error selective Stop RTs that was influenced by the different task conditions. Results are discussed within the framework of the race model related to the SST, and its relationship with a restart model developed for selective versions of this paradigm.

Can masked gaze and arrow stimuli elicit overt orienting of attention? A registered report

Viewing an averted gaze can elicit saccades towards the corresponding location. Here, the automaticity of this gaze-following behaviour phenomenon was further tested by exploring whether such an effect can be detected in response to briefly-presented masked averted gazes. Participants completed an oculomotor interference task consisting of making leftward/rightward saccades according to a symbolic instruction cue. Crucially, either a task-irrelevant averted-gaze face or an arrow (i.e., a non-social control stimulus) was also presented in different blocks of trials. Faces and arrows were presented for either 1000 ms, or 8 ms and then backward-masked, to reduce the likelihood of conscious processing. Worse oculomotor performance emerged when the saccade direction did not match (vs match) that suggested by the task-irrelevant gaze/arrow stimuli in the unmasked condition. However, in the masked condition, no oculomotor interference occurred for any task-irrelevant stimulus. Results enrich knowledge about boundary conditions for gaze/arrow-driven orienting using ecological attention measures.

Abstract TP215: Prenatal Alcohol Exposure Impairs Long-term Behavioral Recovery Following Ischemic Stroke In Sprague Dawley Rats

Background and Purpose: Early life adversity is an important risk factor for cardiometabolic diseases in adulthood. There is very little information on prenatal insults and adult stroke outcomes. The present study tested the hypothesis that prenatal alcohol exposure (PAE) impedes long-term recovery from ischemic stroke in rats. Methods: Pregnant Sprague Dawley rats (in-house bred) were exposed to 10% alcohol or air, for 1 hour from gestational day 8 through 18 using the rodent alcohol inhalation system. Adult offspring (5-6 mo old) were subjected to endothelin-1 induced MCAo and outcomes were evaluated after 180 days. Long-term cognitive outcomes were determined using the Barnes maze and fear conditioning/extinction test. Results: In the Barnes maze test, control males showed shorter latency to reach the goal box over 3-day learning period (p=0.002), as assessed by the slope of the curve (-27.66, significantly different from 0; p=0.005). In contrast, the latency over the 3-day learning period did not improve in PAE males (-9.674, not significantly different from 0; p=0.22). In females, the latency to escape box during the learning trials was not different between the control and PAE. The fear conditioning data indicate that percent freezing over trials was similar in control and PAE-males. However, the PAE females exhibited a diminished freezing response as compared to control females (p=0.01). In the context of fear extinction, control males showed a reduction in freezing response to repeated tones over the trial blocks (p=0.004) compared to PAE-males. The control and PAE females showed similar freezing responses with repeated tones. Conclusions: The present findings support the hypothesis that PAE modifies long-term cognitive changes after stroke, and further show that different cognitive domains are affected by PAE in males and females.

Effects of repeating or not repeating trials immediately when errors occur during training of equivalence classes with college students

ABSTRACT To establish baseline conditional relations during equivalence class formation, an opportunity to immediately respond a second time to the same trial following an error is typically not provided in studies with adults of typical development. Rather, the entire trial block is repeated until a specified mastery criterion is met. The present study is the first to compare immediately repeating a trial to not repeating that specific trial when baseline relations training errors occur. In this study, adults of typical development learned two different sets of two 4-member equivalence classes of abstract stimuli. A within-subjects design was used to compare the effects of immediately repeating or not repeating an incorrect trial. Results showed that equivalence classes were learned with similar accuracy and efficiency regardless of condition. However, maintenance of classes was significantly higher for participants in the repeating a trial condition, and participants strongly preferred this condition. Implications of these findings are discussed.

A value accumulation account of unhealthy food choices: testing the influence of outcome salience under varying time constraints

People often engage in unhealthy eating despite having an explicit goal to follow a healthy diet, especially under certain conditions such as a lack of time. A promising explanation from the value accumulation account is that food choices are based on the sequential consideration of the values of multiple outcomes, such as health and taste outcomes. Unhealthy choices may result if taste is considered before health. We examined whether making a health outcome more salient could alter this order, thereby leading to more healthy choices even under time pressure. Two studies examined the time-dependent effect of outcome values and salience on food choices. Participants first completed priming trials on which they rated food items on healthiness (health condition), tastiness (taste condition), or both healthiness and tastiness (control condition). They then completed blocks of binary choice trials between healthy and tasty items. The available response time was manipulated continuously in Study 1 (N = 161) and categorically in Study 2 (N = 318). As predicted, results showed that the values of health and taste outcomes influenced choices and that priming led to more choices in line with the primed outcomes even when time was scarce. We did not obtain support for the prediction that the priming effect is time-dependent in the sense that primed outcomes are considered before non-primed outcomes. Together, these findings suggest that increasing the value and salience of a health outcome may be effective ways to increase healthy choices, even under poor conditions such as time pressure.

An Effect of Gaze Direction in Cocktail Party Listening.

It is well established that gaze direction can influence auditory spatial perception, but the implications of this interaction for performance in complex listening tasks is unclear. In the current study, we investigated whether there is a measurable effect of gaze direction on speech intelligibility in a "cocktail party" listening situation. We presented sequences of digits from five loudspeakers positioned at 0°, ± 15°, and ± 30° azimuth, and asked participants to repeat back the digits presented from a designated target loudspeaker. In different blocks of trials, the participant visually fixated on a cue presented at the target location or at a nontarget location. Eye position was tracked continuously to monitor compliance. Performance was best when fixation was on-target (vs. off-target) and the size of this effect depended on the specific configuration. This result demonstrates an influence of gaze direction in multitalker mixtures, even in the absence of visual speech information.

Implicit spatial sequential learning facilitates attentional selection in covert visual search. An event-related potentials study.

While most studies on implicit sequential learning focus on object learning, the hidden structure of target location and onset time can also be a subject of implicitly gathered knowledge. In our study, we wanted to investigate the effect of implicitly learned spatial and temporal sequential predictability on performance in a localization task in a paradigm in which covert selective attention is engaged. We were also interested in the neural mechanism of the facilitating effect of the predictable spatio-temporal context on visual search processes. Specifically, with the use of an event-related potential technique, we wanted to verify whether perceptual, attentional, and motor processes can be enhanced by the predictive spatio-temporal context of visual stimuli. We analyzed data from 15 young, healthy adults who took part in an experimental electroencephalographic (EEG) study and performed a visual search localization task. Predictable sequences of four target locations and/or target onset times were presented in separate blocks of trials that formed the Space, Space- Time, and Time conditions. One block of trials with randomly presented stimuli served as a control condition. The behavioral results revealed that participants successfully learned only the spatial dimension of target predictability. Although spatial predictability was a response-relevant dimension, we found that attentional selection-instead of motor preparation-was the facilitation mechanism in this type of visual search task. This was manifested by a shorter latency and more negative amplitude of the N2pc component and the lack of an effect on the sLRP component. We observed no effect of predictability on perceptual processing (P1 component). We discuss these results with reference to the current knowledge on sequential learning. Our findings also contribute to the current debate on the predictive coding theory.

On the latency of object recognition and affect: Evidence from temporal order and simultaneity judgments.

According to the semantic primacy hypothesis of emotion generation, stimuli must be semantically categorized to evoke emotions. This hypothesis was tested for the subjective component of emotions in four chronometric experiments in which the conscious recognition of emotion-eliciting objects and the onset of affect was timed using temporal order judgments (TOJs, Exp. 1a, 1b, and 3) and simultaneity judgments (SJs, Exp. 2). Participants viewed pictures that elicited pleasant or unpleasant feelings. At varying intervals before and after picture onset, a visual probe stimulus was presented. In separate blocks of trials, the participants judged when they recognized the object shown in the picture and noticed the feeling evoked by the picture: Before or after the probe (TOJs), or simultaneously/not simultaneously with the probe (SJs). Psychometric functions were fitted to the data of the individual participants to determine the point of subjective simultaneity (PSS) of the target events and the probe. In both tasks, the mean PSS of affect occurred significantly later than the PSS of object recognition, with an average delay of about 120 ms. A positive lag between object recognition and affect was found for nearly all participants and pictures. In addition, the latencies of object recognition and affect were positively correlated. The found temporal order of object recognition and affect is consistent with the findings of previous studies using speeded reaction time tasks. Implications of the findings for the cognition-emotion debate and for bodily feedback theories of emotional experience are discussed. (PsycInfo Database Record (c) 2022 APA, all rights reserved).

Spatial Interactions in Interocular and Monocular "Blur Suppression".

The suppression of blurred images in one eye by clear images in the other eye is thought to contribute to the success of monovision correction. We show that interocular suppression occurs also for low-contrast targets that are not blurred and, to a lesser extent, when clear and low-contrast targets are presented to the same eye. A blurred target presented to one eye may be suppressed when a clear target is presented to the other eye. We sought to determine how this interocular suppression varies according to the separation between the blurred and clear targets and the magnitude of imposed blur. In addition, we examined whether a similar suppression occurs when the clear and blurred targets are imaged in the same eye. Subjects (N = 4) viewed a clear 20/40 Sloan letter surrounded by four 2 × 10 min-arc flanking bars. In different blocks of trials, the gap between the letter and flanking bars varied from 0.5 to 4 bar widths. In addition, the flanking bars were either clear or spatially filtered to simulate 0.5 to 2 D of blur. The contrast required to detect the flanking bars was determined when the letter and flanking bars were presented either dichoptically or monoptically and compared with the thresholds for the bar targets presented alone. In both dichoptic and monoptic viewing conditions, detection thresholds for the blurred flanking bars are highest for the smallest spatial gap and decrease systematically as the gap increases. Thresholds are uniformly higher during dichoptic than monocular viewing, but the proportional change with the bar-to-letter separation is similar in both conditions. Surprisingly, the magnitude of imposed blur has very little influence on the magnitude of threshold elevation in either the dichoptic or monoptic viewing conditions. Because threshold elevation is nearly the same in the presence of 0 to 2 D of blur, we prefer to designate the phenomenon we studied as "contrast suppression." The similar spatial characteristics of suppression during dichoptic and monoptic viewing are consistent with contributions from a common neural mechanism.

Steady, Aim, Fire! Optimized Instructions Enhance Performance and Reduce Intra-Trial Variability in a Shooting Task.

The present study examined the influence of the individual and sequential combination of the key components of OPTIMAL (Optimizing Performance Through Intrinsic Motivation and Attention for Learning) theory (i.e., enhanced expectancies, autonomy support, and external focus), on the performance of a laser-pistol shooting task. In addition to shooting accuracy, intra-trial variability in the sway of forearm/pistol motion prior to movement execution (pulling the trigger) was the primary variable of interest. In a between-within-subject design, thirty-six participants (Mage = 21.27 ± 1.75 years) were randomized into either a control or an optimized group. Enhanced expectancies, autonomy support, and an external focus were implemented via sequential blocks of trials for participants in the optimized group. Participants in the control group performed all trials under "neutral" conditions. Our results showed that motor performance was enhanced for participants in the optimized group compared to those in the control group. Moreover, greater reductions in forearm sway leading up to the trigger pull were observed for the optimized group compared to the control group. These findings suggest higher movement effectiveness and efficiency, potentially through better attunement to task and environmental constraints, when implementing optimized instructions in a self-initiated fine motor task.

The effect of adulteration with a bitter tastant, denatonium benzoate, on the reinforcing value of sucrose

According to the Multiplicative Hyperbolic Model of reinforcer value (MHM), the value of a reinforcer is an increasing hyperbolic function of its size (q). A recent experiment examined the effect of adulterating a sucrose solution with citric acid on the value of a sucrose reinforcer. In contrast to expectations derived from MHM, the effect of citric acid was consistent with the summation of positive (sucrose) and negative (citric acid) values. The present experiment extended these observations to a bitter tastant, denatonium benzoate (DB). Rats were trained under an adjusting-magnitude schedule in which a response on lever B delivered a fixed volume of a sucrose/DB mixture, while a response on lever A delivered a sucrose solution, the volume of which, qA, was adjusted according to the rats’ choices. When B was preferred in a given block of trials, qA was increased in the following block; when A was preferred, qA was reduced in the following block. qB was varied across five phases of the experiment and the corresponding indifference magnitudes of A were measured. The results indicated that, as was the case with citric acid, the value of the mixture reflected the summation of positive (sucrose) and negative (DB) values.

Visuo-tactile heading perception.

Self-motion through an environment induces various sensory signals, i.e., visual, vestibular, auditory, or tactile. Numerous studies have investigated the role of visual and vestibular stimulation for the perception of self-motion direction (heading). Here, we investigated the rarely considered interaction of visual and tactile stimuli in heading perception. Participants were presented optic flow simulating forward self-motion across a horizontal ground plane (visual), airflow toward the participants' forehead (tactile), or both. In separate blocks of trials, participants indicated perceived heading from unimodal visual or tactile or bimodal sensory signals. In bimodal trials, presented headings were either spatially congruent or incongruent with a maximum offset between visual and tactile heading of 30°. To investigate the reference frame in which visuo-tactile heading is encoded, we varied head and eye orientation during presentation of the stimuli. Visual and tactile stimuli were designed to achieve comparable precision of heading reports between modalities. Nevertheless, in bimodal trials heading perception was dominated by the visual stimulus. A change of head orientation had no significant effect on perceived heading, whereas, surprisingly, a change in eye orientation affected tactile heading perception. Overall, we conclude that tactile flow is more important to heading perception than previously thought.NEW & NOTEWORTHY We investigated heading perception from visual-only (optic flow), tactile-only (tactile flow), or bimodal self-motion stimuli in different conditions varying in head and eye position. Overall, heading perception was body or world centered and non-Bayes optimal and revealed a centripetal bias. Although being visually dominated, tactile flow revealed a significant influence during bimodal heading perception.