Spatial and temporal (non)binding of audiovisual rhythms in sensorimotor synchronisation.

Human movement synchronisation with moving objects strongly relies on visual input. However, auditory information also plays an important role, since real environments are intrinsically multimodal. We used electroencephalography (EEG) frequency tagging to investigate the selective neural processing and integration of visual and auditory information during motor tracking and tested the effects of spatial and temporal congruency between audiovisual modalities. EEG was recorded while participants tracked with their index finger a red flickering (rate fV = 15 Hz) dot oscillating horizontally on a screen. The simultaneous auditory stimulus was modulated in pitch (rate fA = 32 Hz) and lateralised between left and right audio channels to induce perception of a periodic displacement of the sound source. Audiovisual congruency was manipulated in terms of space in Experiment 1 (no motion, same direction or opposite direction), and timing in Experiment 2 (no delay, medium delay or large delay). For both experiments, significant EEG responses were elicited at fV and fA tagging frequencies. It was also hypothesised that intermodulation products corresponding to the nonlinear integration of visual and auditory stimuli at frequencies fV ± fA would be elicited, due to audiovisual integration, especially in Congruent conditions. However, these components were not observed. Moreover, synchronisation and EEG results were not influenced by congruency manipulations, which invites further exploration of the conditions which may modulate audiovisual processing and the motor tracking of moving objects.

Impacts of COVID-19 Sanitary Cues on Hedonic Appreciation of Foods.

The COVID-19 pandemic led to several lifestyle changes, including eating behavior. Herein, we aimed to evaluate how pandemic-related sanitary cues presented in food videos impact food appraisal and desire to eat, and their priming after-effects on subsequent food pictures presented without such cues. In two online sessions, separated by 4 to 7 days, participants watched either a Non-Pandemic or a Pandemic video of a woman eating, the latter containing sanitary elements adopted during the pandemic. The order of the videos was counterbalanced across participants over the two experimental sessions. Videos were followed by images of food from different categories. After observing both videos and each picture, participants were instructed to evaluate the visual aspect, expected smell and flavor, and rate their desire to eat. Our study demonstrated (1) higher hedonic responses to the Non-Pandemic compared to the Pandemic video, (2) a priming effect showing higher appreciation for sweet foods after the Non-Pandemic compared to the Pandemic video, (3) that food exposure gradually increases one's desire to eat, but such effects are impacted by pandemic sanitary cues, and (4) greater hedonic responses are given for sweet and high-calorie foods compared to salty and low-calorie ones, irrespective of pandemic priming. Finally, depression and anxiety symptoms were associated with lower smell evaluations only in the Pandemic condition.

Lateralised dynamic modulations of corticomuscular coherence associated with bimanual learning of rhythmic patterns.

Human movements are spontaneously attracted to auditory rhythms, triggering an automatic activation of the motor system, a central phenomenon to music perception and production. Cortico-muscular coherence (CMC) in the theta, alpha, beta and gamma frequencies has been used as an index of the synchronisation between cortical motor regions and the muscles. Here we investigated how learning to produce a bimanual rhythmic pattern composed of low- and high-pitch sounds affects CMC in the beta frequency band. Electroencephalography (EEG) and electromyography (EMG) from the left and right First Dorsal Interosseus and Flexor Digitorum Superficialis muscles were concurrently recorded during constant pressure on a force sensor held between the thumb and index finger while listening to the rhythmic pattern before and after a bimanual training session. During the training, participants learnt to produce the rhythmic pattern guided by visual cues by pressing the force sensors with their left or right hand to produce the low- and high-pitch sounds, respectively. Results revealed no changes after training in overall beta CMC or beta oscillation amplitude, nor in the correlation between the left and right sides for EEG and EMG separately. However, correlation analyses indicated that left- and right-hand beta EEG-EMG coherence were positively correlated over time before training but became uncorrelated after training. This suggests that learning to bimanually produce a rhythmic musical pattern reinforces lateralised and segregated cortico-muscular communication.

Mind Wandering and Task-Focused Attention: ERP Correlates.

Previous studies looking at how Mind Wandering (MW) impacts performance in distinct Focused Attention (FA) systems, using the Attention Network Task (ANT), showed that the presence of pure MW thoughts did not impact the overall performance of ANT (alert, orienting and conflict) performance. However, it still remains unclear if the lack of interference of MW in the ANT, reported at the behavioral level, has a neurophysiological correspondence. We hypothesize that a distinct cortical processing may be required to meet attentional demands during MW. The objective of the present study was to test if, given similar levels of ANT performance, individuals predominantly focusing on MW or FA show distinct cortical processing. Thirty-three healthy participants underwent an EEG high-density acquisition while they were performing the ANT. MW was assessed following the ANT using an adapted version of the Resting State Questionnaire (ReSQ). The following ERP's were analyzed: pN1, pP1, P1, N1, pN, and P3. At the behavioral level, participants were slower and less accurate when responding to incongruent than to congruent targets (conflict effect), benefiting from the presentation of the double (alerting effect) and spatial (orienting effect) cues. Consistent with the behavioral data, ERP's waves were discriminative of distinct attentional effects. However, these results remained true irrespective of the MW condition, suggesting that MW imposed no additional cortical demand in alert, orienting, and conflict attention tasks.

Ostracism via virtual chat room-Effects on basic needs, anger and pain.

Ostracism is characterized by a social pain provoked by being excluded and ignored. In order to address the effects of social ostracism in virtual non-physical interactions, we developed a more realistic paradigm as an alternative to Cyberball and assessed its effects on participant's expression of basic social needs, emotional experience and painful feeling. The chat room consisted of controlled social dialogue interactions between participants and two other (confederate) chat room partners. Exclusion was manipulated by varying the number of messages a participant received (15% and 33% in exclusion and inclusion, respectively). Analysis of participant (N = 54) responses revealed that exclusion induced a lower experience of basic-need states and greater anger, compared with included participants. In addition, excluded participants reported higher levels of two specific self-pain feelings, namely tortured and hurt. Our findings suggest that this procedure is effective in inducing social ostracism in a realistic and yet highly controlled experimental procedure.

Human biological and nonbiological point-light movements: Creation and validation of the dataset.

Human action perception is so powerful that people can identify movement efficiently in the absence of pictorial information, such as in point-light displays. Interest is growing in this type of stimulus for research in neuroscience. This interest stems from the advantage of separating the component of pure human action kinematics from other pictorial information, such as facial expression and muscle contraction. Although several groups have previously developed datasets of human point-light actions, due to the lack of datasets composed of daily actions with short durations, we developed 20 biological and 40 control (scrambled) point-light movements by using the technique of recording people wearing reflector patches. The videos are about 1 s long. Subsequently, we performed a judgment task in which 100 participants (50 male and 50 female) evaluated each video according to three categories: human action resemblance, performed action, and gender of actor. We present the mean scores of each evaluation for each video, and further propose a selection of the most suitable videos to be used as human point-light action displays and scrambled point-light displays for control. Finally, we discuss our findings on the gender attributions of the point-light displays.

Tuning and disrupting the brain-modulating the McGurk illusion with electrical stimulation.

In the so-called McGurk illusion, when the synchronized presentation of the visual stimulus /ga/ is paired with the auditory stimulus /ba/, people in general hear it as /da/. Multisensory integration processing underlying this illusion seems to occur within the Superior Temporal Sulcus (STS). Herein, we present evidence demonstrating that bilateral cathodal transcranial direct current stimulation (tDCS) of this area can decrease the McGurk illusion-type responses. Additionally, we show that the manipulation of this audio-visual integrated output occurs irrespective of the number of eye-fixations on the mouth of the speaker. Bilateral anodal tDCS of the Parietal Cortex also modulates the illusion, but in the opposite manner, inducing more illusion-type responses. This is the first demonstration of using non-invasive brain stimulation to modulate multisensory speech perception in an illusory context (i.e., both increasing and decreasing illusion-type responses to a verbal audio-visual integration task). These findings provide clear evidence that both the superior temporal and parietal areas contribute to multisensory integration processing related to speech perception. Specifically, STS seems fundamental for the temporal synchronization and integration of auditory and visual inputs. For its part, posterior parietal cortex (PPC) may adjust the arrival of incoming audio and visual information to STS thereby enhancing their interaction in this latter area.

Transcranial direct current stimulation modulates ERP-indexed inhibitory control and reduces food consumption.

Food craving can be defined as the "urge to eat a specific food". Previous findings suggest impairment of inhibitory control, specifically a regulatory deficit in the lateral prefrontal circuitry that is associated with a compulsion for food. As demonstrated by three previous studies, bilateral transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (DLPFC) (anode right/cathode left) reduces food craving and caloric intake. We designed the present study to evaluate the neural mechanisms that underlie these effects. We replicated the design of one of these previous studies but included electroencephalographic assessments to register evoked potentials in a Go/No-go task that contained pictures of food and furniture (a control visual stimulus). We collected data from nine women (mean age = 23.4 ± 2 years) in a crossover experiment. We observed that active DLPFC tDCS (anode right/cathode left), compared with sham stimulation, reduced the frontal N2 component and enhanced the P3a component of responses to No-go stimuli, regardless of the stimulus condition (food or furniture). Active tDCS was also associated with a reduction in caloric intake. We discuss our findings in the context of cortico-subcortical processing of craving and tDCS effects on inhibitory control neural circuitry.

Bilateral temporal cortex transcranial direct current stimulation worsens male performance in a multisensory integration task.

Somatosensory integration is a critical cognitive function for human social interaction. Though somatosensory integration has been highly explored in cognitive studies; only a few studies have explored focal modulation of cortical excitability using a speech perception paradigm. In the current study, we aimed to investigate the effects of tDCS applied over the temporal cortex of healthy subjects during a go-no-go task in which stimuli were shapes and non-words. Twenty-eight subjects were randomized to receive cathodal, anodal or sham tDCS bilaterally over the superior temporal cortex (the reference electrode was on deltoid) in a counterbalanced order. The effects on judgment of congruency between shapes and non-words in healthy volunteers were measured by a go-no-go task. Our findings show a significant modification of performance according to the polarity of stimulation, task and subject gender. We found that men performed worse on the no-go condition for congruent stimuli during cathodal tDCS. For reaction time, on the other hand, there was a similar effect for anodal and cathodal stimulation. There were significantly faster responses on incongruent trials during both anodal and cathodal tDCS. Along with previous literature showing gender differences in tasks associated with speech perception, the findings of this study provide additional evidence suggesting that men may have a more focal and restricted neural processing in this multisensory integration task.

Non-invasive brain stimulation to assess and modulate neuroplasticity in Alzheimer's disease.

Alzheimer's disease (AD) is a neurodegenerative and progressive disease related to a gradual decline in cognitive functions such as memory, attention, perceptual-spatial abilities, language, and executive functions. Recent evidence has suggested that interventions promoting neural plasticity can induce significant cognitive gains especially in subjects at risk of or with mild AD. Transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) are non-invasive techniques that can induce significant and long-lasting changes in focal and non-focal neuroplasticity. In this review, we present initial preliminary evidence that TMS and tDCS can enhance performance in cognitive functions typically impaired in AD. Also, we reviewed the initial six studies on AD that presented early findings showing cognitive gains such as in recognition memory and language associated with TMS and tDCS treatment. In addition, we showed that TMS has also been used to assess neuroplasticity changes in AD supporting the notion that cortical excitability is changed in AD due to the neurodegenerative process. Due to the safe profile, cost of these tools, and initial clinical trials results, further studies are warranted in order to replicate and extend the initial findings of rTMS and tDCS as cognitive enhancers in AD. Further trials should explore different targets of stimulation along with different paradigms of stimulation including combination with behavioural interventions.