A survey of experimental stimulus presentation code sharing in major areas of psychology.

Computer code plays a vital role in modern science, from the conception and design of experiments through to final data analyses. Open sharing of code has been widely discussed as being advantageous to the scientific process, allowing experiments to be more easily replicated, helping with error detection, and reducing wasted effort and resources. In the case of psychology, the code used to present stimuli is a fundamental component of many experiments. It is not known, however, the degree to which researchers are sharing this type of code. To estimate this, we conducted a survey of 400 psychology papers published between 2016 and 2021, identifying those working with the open-source tools Psychtoolbox and PsychoPy that openly share stimulus presentation code. For those that did, we established if it would run following download and also appraised the code's usability in terms of style and documentation. It was found that only 8.4% of papers shared stimulus code, compared to 17.9% sharing analysis code and 31.7% sharing data. Of shared code, 70% ran directly or after minor corrections. For code that did not run, the main error was missing dependencies (66.7%). The usability of the code was moderate, with low levels of code annotation and minimal documentation provided. These results suggest that stimulus presentation code sharing lags behind other forms of code and data sharing, potentially due to less emphasis on such code in open-science discussions and in journal policies. The results also highlight a need for improved documentation to maximize code utility.

Revisiting the effects of transcranial direct current stimulation on pattern-reversal visual evoked potentials.

Despite increasing growth of interest in transcranial direct current stimulation (tDCS), its underlying mechanisms are still unclear. With many claims based on the anodal-excitation and cathodal-inhibition dichotomy originally observed in the motor cortex, surprisingly few studies have examined these fundamental polarity-specific effects beyond the motor cortex. The after-effects of tDCS on the visual cortex are of particular interest because of their potential application to vision restoration and migraine treatment. Yet the limited studies revealed conflicting results. Here we investigated whether polarity-specific tDCS effects exist in the visual cortex. In a counterbalanced within-subject crossover design, 20 healthy subjects each completed three sessions of anodal, cathodal and sham tDCS (2 mA for 20 min) applied over the visual cortex. Pattern-reversal visual evoked potentials (VEP) and their habituation slopes were measured at five time-points immediately before, after and every 15 min following the end of tDCS. Compared to sham, we found no significant tDCS induced after-effects on VEP amplitudes or habituation slopes, supported by strong evidence from Bayesian statistics. Neither were there any after-effects of tDCS on EEG power of the frequency of stimulus presentation, theta or alpha band. In conclusion, our results challenge previous findings of robust polarity-dependent after-effects of tDCS over the visual cortex.

The role of superior temporal sulcus in the control of irrelevant emotional face processing: A transcranial direct current stimulation study.

Emotional faces are often salient cues of threats or other important contexts, and may therefore have a large effect on cognitive processes of the visual environment. Indeed, many behavioral studies have demonstrated that emotional information can modulate visual attention and eye movements. The aim of the present study was to investigate (1) how irrelevant emotional face distractors affect saccadic behaviors and (2) whether such emotional effects reflect a specific neural mechanism or merely biased selective attention. We combined a visual search paradigm that incorporated manipulation of different types of distractor (fearful faces or scrambled faces) and delivered anodal transcranial direct current stimulation (tDCS) over the superior temporal sulcus and the frontal eye field to investigate the functional roles of these areas in processing facial expressions and eye movements. Our behavioral data suggest that irrelevant emotional distractors can modulate saccadic behaviors. The tDCS results showed that while rFEF played a more general role in controlling saccadic behavior, rSTS is mainly involved in facial expression processing. Furthermore, rSTS played a critical role in processing facial expressions even when such expressions were not relevant to the task goal, implying that facial expressions and processing may be automatic irrespective of the task goal.

Modulating inhibitory control with direct current stimulation of the superior medial frontal cortex.

The executive control of voluntary action involves not only choosing from a range of possible actions but also the inhibition of responses as circumstances demand. Recent studies have demonstrated that many clinical populations, such as people with attention-deficit hyperactivity disorder, exhibit difficulties in inhibitory control. One prefrontal area that has been particularly associated with inhibitory control is the pre-supplementary motor area (Pre-SMA). Here we applied non-invasive transcranial direct current stimulation (tDCS) over Pre-SMA to test its role in this behavior. tDCS allows for current to be applied in two directions to selectively excite or suppress the neural activity of Pre-SMA. Our results showed that anodal tDCS improved efficiency of inhibitory control. Conversely, cathodal tDCS showed a tendency towards impaired inhibitory control. To our knowledge, this is the first demonstration of non-invasive intervention tDCS altering subjects' inhibitory control. These results further our understanding of the neural bases of inhibitory control and suggest a possible therapeutic intervention method for clinical populations.