Lateralized Readiness Potentials Recorded with Near-Threshold Auditory Stimuli in Subjects Simulating Hearing Loss

<b><i>Introduction:</i></b> Preparatory motor cortical responses like the lateralized readiness potential (LRP) may be useful in revealing persistent attempts to feign hearing loss. Previous studies suggest only a marginal effect of stimulus intensity on the amplitude of the LRP. However, this has not been investigated using low-intensity auditory stimuli to cue NoGo trials. We address this in an experiment where subjects were instructed not to give a manual response to low-instensity stimuli, a situation that is akin to simulating hearing loss. <b><i>Methods:</i></b> The LRP was recorded from normal hearing listeners (<i>N</i> = 10) with 500 and 4,000-Hz pure tones and trains of 4,000 Hz (2-1-2) tonebursts. Electrophysiologic data underwent processing to (i) analyze the effect of the stimulus type on the LRP, (ii) classify results according to manual response with both logistic regression and linear support vector machine (SVM) models, and (iii) derive auditory brainstem responses (ABRs) from the tonebursts. <b><i>Results:</i></b> The amplitude of the LRP did not differ between the 3 stimuli used to elicit the response. Single-trial electrode data from Go and NoGo trials were submitted to supervised binary classification, and the logistic regression model gave a mean accuracy of close to 0.7. The Jewett wave V latencies of the resultant ABRs from some subjects were found to increase between the high (Go) and low (NoGo) intensity tonebursts. <b><i>Conclusion:</i></b> This study shows that auditory stimulus type does not affect the amplitude of the LRP and that the response can be recorded with stimuli that are near the auditory threshold. It can also be recorded with transient stimuli, and this allows for the possibility of simultaneously recording other confirmatory measurements, like ABR.

Efficient visual search for facial emotions in patients with major depression

Background Major depressive disorder has been associated with specific attentional biases in processing emotional facial expressions: heightened attention for negative and decreased attention for positive faces. However, using visual search paradigms, previous reaction-time-based research failed, in general, to find evidence for increased spatial attention toward negative facial expressions and reduced spatial attention toward positive facial expressions in depressed individuals. Eye-tracking analyses allow for a more detailed examination of visual search processes over time during the perception of multiple stimuli and can provide more specific insights into the attentional processing of multiple emotional stimuli. Methods Gaze behavior of 38 clinically depressed individuals and 38 gender matched healthy controls was compared in a face-in-the-crowd task. Pictures of happy, angry, and neutral facial expressions were utilized as target and distractor stimuli. Four distinct measures of eye gaze served as dependent variables: (a) latency to the target face, (b) number of distractor faces fixated prior to fixating the target, (c) mean fixation time per distractor face before fixating the target and (d) mean fixation time on the target. Results Depressed and healthy individuals did not differ in their manual response times. Our eye-tracking data revealed no differences between study groups in attention guidance to emotional target faces as well as in the duration of attention allocation to emotional distractor and target faces. However, depressed individuals fixated fewer distractor faces before fixating the target than controls, regardless of valence of expressions. Conclusions Depressed individuals seem to process angry and happy expressions in crowds of faces mainly in the same way as healthy individuals. Our data indicate no biased attention guidance to emotional targets and no biased processing of angry and happy distractors and targets in depression during visual search. Under conditions of clear task demand depressed individuals seem to be able to allocate and guide their attention in crowds of angry and happy faces as efficiently as healthy individuals.

Motor Behaviour Mimics the Gaze Response in Establishing Joint Attention, but Individual Differences in Adopting the Intentional Stance Towards Robots Moderate Responses to Joint Attention

Leading another person’s gaze to establish joint attention facilitates social interaction. Previously it was found that we look back at agents who engage in joint attention frequently and more quickly than agents who display this behaviour less often. This paper serves to fill in two knowledge gaps on the topic. Firstly, we examine whether this looking-back behaviour is replicated by a manual response. In an online, eyetracker-free task in which participant were asked to select one of two objects, one robot identity followed the selection most of the time, whilst the other looked at the other object most of the time. Participants moved back to the robot more quickly if the robot which most of the time followed their movement looked at the same object relative to when it did not. We found no such difference for the robot which most of the time did not follow participants. Secondly, we used the current datasets and datasets from prior experiments to look into how individual differences in autistic traits and readiness to adopt the intentional stance toward artificial agents affect how participants’ behaviour changed over time during the experiments. The results showed that individual differences in adopting the intentional stance influenced participants’ motor responses overtime, but not their gaze behaviour. Taken together, this indicates that whereas individual differences may not fully predicate reflexive social behaviour, its evoked gaze behaviour is likely coupled with motor actions.

Realistic precision and accuracy of online experiment platforms, web browsers, and devices

Due to increasing ease of use and ability to quickly collect large samples, online behavioural research is currently booming. With this popularity, it is important that researchers are aware of who online participants are, and what devices and software they use to access experiments. While it is somewhat obvious that these factors can impact data quality, the magnitude of the problem remains unclear. To understand how these characteristics impact experiment presentation and data quality, we performed a battery of automated tests on a number of realistic set-ups. We investigated how different web-building platforms (Gorilla v.20190828, jsPsych v6.0.5, Lab.js v19.1.0, and psychoJS/PsychoPy3 v3.1.5), browsers (Chrome, Edge, Firefox, and Safari), and operating systems (macOS and Windows 10) impact display time across 30 different frame durations for each software combination. We then employed a robot actuator in realistic set-ups to measure response recording across the aforementioned platforms, and between different keyboard types (desktop and integrated laptop). Finally, we analysed data from over 200,000 participants on their demographics, technology, and software to provide context to our findings. We found that modern web platforms provide reasonable accuracy and precision for display duration and manual response time, and that no single platform stands out as the best in all features and conditions. In addition, our online participant analysis shows what equipment they are likely to use.

Saccadic eye movements in dual tasking: No impairment of spatial planning, but delayed execution of saccades

In the target–distractor saccade task, a target and an irrelevant distractor are simultaneously presented and the task itself consists of a target-directed saccade. Findings usually show that as saccade latency increases, saccade trajectory deviation towards the distractor decreases. We presented this saccade task in two dual-task experiments to address the open question of whether performance of an auditory–manual task simply delays the temporal execution of a saccade, or whether it also interferes with the spatial planning of the saccade trajectory. We measured saccade latency, as a measure of a delay in execution, and saccade trajectory deviation, as a measure of the spatial planning. In Experiment 1, the auditory–manual task was a two-choice reaction time (two-CRT) task, and in Experiment 2, it was a go-no-go task. Performing the two tasks in close temporal succession shortly delayed the temporal execution of the saccade, but did not influence the spatial planning of the saccade trajectory. This result pattern was more pronounced when the auditory–manual task required the selection and execution of one of two possible manual responses (Experiment 1), less pronounced when the auditory–manual task required the decision to execute a button press (go condition, Experiment 2), and absent when the auditory–manual task required the decision to inhibit a button press (no-go condition, Experiment 2). Taken together, the manual response rather than the response selection process of the auditory–manual task led to a delay of saccade execution, but not to an impairment of the spatial planning of the saccade trajectory.

An fMRI study of initiation and inhibition of manual responses in people who stutter

Developmental stuttering is a speech motor disorder characterised by difficulties initiating speech and frequent interruptions to the speech flow. Previous work suggests that people who stutter (PWS) have an overactive response suppression mechanism. Imaging studies of speech production in PWS consistently reveal greater activity of the right inferior frontal cortex, an area robustly implicated in inhibitory control of both manual and spoken responses. Here, we used a manual response version of the stop-signal task during fMRI to investigate neural differences related to response initiation and inhibition in PWS. Behaviourally, PWS were slower to respond to ‘go’ stimuli than people who are typically fluent (PWTF), but there was no difference in stop-signal reaction time. Our fMRI results were consistent with these behavioural results. The fMRI analysis revealed the expected networks associated with manual response initiation and inhibition in both groups. However, all contrasts between the two groups were characterised by overactivity in PWS relative to PWTF. This overactivity was significantly different for the initiation of responses (i.e. the ‘go’ trials) but not for response inhibition (i.e. the ‘stop’ trials). One explanation of these results is that PWS are consistently in a heightened inhibition state, i.e. areas of the inhibition network are more active, generally. This interpretation is consistent with predictions from the global response suppression hypothesis.

To look or not to look: Subliminal abrupt-onset cues influence constrained free-choice saccades

Subliminal cues have been shown to capture attention and modulate manual response behaviour but their impact on eye movement behaviour is not well-studied. In two experiments, we examined if subliminal cues influence constrained free-choice saccades and if this influence is under strategic control as a function of task-relevancy of the cues. On each trial, a display containing four filled circles at the centre of each quadrant was shown. A central coloured circle indicated the relevant visual field on each trial (Up or Down in Experiment 1; Left or Right in Experiment 2). Next, abrupt-onset cues were presented for 16 ms at one of the four locations. Participants were then asked to freely choose and make a saccade to one of the two target circles in the relevant visual field. The analysis of the frequency of saccades, saccade endpoint deviation and saccade latency revealed a significant influence of the relevant subliminal cues on saccadic decisions. Latency data showed reduced capture by spatially-irrelevant cues under some conditions. These results indicate that spatial attentional control settings as defined in our study could modulate the influence of subliminal abrupt-onset cues on eye movement behaviour. We situate the findings of this study in the attention-capture debate and discuss the implications for the subliminal cueing literature.