Anton A. Varlamov

Tactile perception encompasses several submodalities that are realized with distinct sensory subsystems. The processing of those submodalities and their interactions remains understudied. We developed a paradigm consisting of three types of touch tuned in terms of their force and velocity for different submodalities: discriminative touch (haptics), affective touch (C-tactile touch), and knismesis (alerting tickle). Touch was delivered with a high-precision robotic rotary touch stimulation device. A total of 39 healthy individuals participated in the study. EEG cluster analysis revealed a decrease in alpha and beta range (mu-rhythm) as well as theta and delta increase most pronounced to the most salient and fastest type of stimulation. The participants confirmed that slower stimuli targeted to affective touch low-threshold receptors were the most pleasant ones, and less intense stimuli aimed at knismesis were indeed the most ticklish ones, but those sensations did not form an EEG cluster, probably implying their processing involves deeper brain structures that are less accessible with EEG.

Autism is a relatively common neurodevelopmental condition that affects social communication and behavior, affecting the overall quality of life. The prevalence of autism is constantly increasing, but timely diagnosis allows for effective treatment. The aim of our research was to construct a Russian version of the RAADS-14, a brief self-report questionnaire originally designed for autism screening, and to perform its initial validation to provide a reference point in developing autism self-assessment tools for the Russian-speaking population. Psychometric properties of the RAADS-14 Rus were evaluated on a sample of 1724 participants, including a general sample of non-psychiatric young adults (n = 794) and adults with clinically established ASD (n = 49); a brief Russian inventory assessing Big Five personality traits (FFQ) was administered to a part of the sample (n = 364) to provide the first assessment of criterion validity. Confirmatory factor analysis of the RAADS-14 Rus confirmed the factor structure of the original Swedish version yielding acceptable fit indices. The discriminating properties were substantially worse than in the original study. The correlations between the RAADS-14 Rus domain scores and the Big Five factors were similar to previously obtained findings. Overall, the results suggest that the RAADS-14 Rus can be used as a screening tool for ASD in adults with proper caution and considering its discriminating properties.

Individuals with ASD are known to have a tendency to have tactile sensory processing issues that could be associated with their impairment as regards social communication. The alterations in tactile processing in autistic subjects are usually accompanied by hypersensitivity and other unpleasant emotions induced by tactile contact. In our study, we investigated the impact of the velocity and the force of a tactile stroke received impersonally by a custom-built robotic device. A total of 21 adults with ASD and 22 adults from a control group participated in our study. The participants’ responses were assessed according to subjective scales, EEG changes, and the dynamics of saliva antioxidants and oxytocin. It was found that the oxytocin level was significantly lower in subjects with ASD but increased after tactile stimulation. However, contrary to expectations, the increase in the oxytocin level in the target group negatively correlated with the subjective pleasantness of tactile stimulation and was probably associated with a stress-induced effect. The basic levels of antioxidants did not differ between the TD and ASD groups; however, these had significantly increased in individuals with ASD by the end of the study. The EEG findings, which revealed enhanced antioxidant levels, contributed to the relief of the cognitive control during the study.

The aim of our research was to construct and validate a Russian version of the RAADS-14 (the RAADS-14 Rus), a brief self-report questionnaire designed for assessment of autistic traits, to provide a reference point in developing autism self-assessment tools in Russian-speaking population. The data were collected for 1724 participants, including a general sample of non-psychiatric young adults (n=849) and adults with ASD (n=49). Confirmatory factor analysis revealed that the RAADS-14 Rus has the same factor structure as the original Swedish version yielding acceptable fit indices. The discriminating properties, however, were substantially worse than in the original study (AUC = .92 vs .99); it stems from higher mean RAADS-14 scores for the Russian control sample vs the original controls (mean = 13.9 vs 3.9) confirming prior anecdotal evidences of greater mean scores yielded by international ASD assessment tools on Russian-speaking populations. The correlations between the RAADS-14 Rus domain scores and the Big Five factors were similar to previously obtained findings. The results of the study indicate that the RAADS-14 Rus can be used for assessment of autistic traits and, with some reservations, as an ASD screening tool for adult Russian-speaking population. Further research is necessary to develop more precise screening tools.

Affective touch plays an important role in human social bonding, affiliative behavior, and in general emotional well-being. A system of unmyelinated low-threshold mechanosensitive C-type afferents innervating hairy skin (C-tactile or CT system) is postulated to provide the neurophysiological background of affective touch perception. C-tactile afferents respond optimally to soft and slow strokes, and this response correlates positively with pleasure ratings of tactile stimuli. As gentle touch is consistently associated with oxytocin release further promoting prosocial behavior, it has been suggested that this effect is mediated by the response of C-tactile afferents. This study assesses a possible link between CT-optimal touch, its subjective pleasantness, EEG indices of cortical arousal, and peripheral oxytocin response. EEG was recorded in 28 healthy volunteers during resting state and tactile stimulation[gentle slow brush strokes on forearm (CT-targeted touch) and palm (non-CT-targeted touch)]. Saliva samples were collected before and after the touch stimulation. Oxytocin concentration increase was significantly associated with greater subjective ratings of CT-targeted touch but not of non-CT-targeted touch, and with lower peak alpha frequency values indicating decreased cortical arousal. The findings suggest that CT-targeted stimulation triggers oxytocin release but only when the touch is perceived at an individual level as having clearly positive affective salience. This corresponds to previous studies reporting that oxytocin response to touch can be related to different personality factors, and bears important implications for planning touch-based interventions in social and medical care.

The research is a pilot electroencephalographic study of C-tactile (CT) perception in persons with autism, as abnormalities of such perception may contribute to communicative deficit in this group. Three types of stimulation were performed: slow (2-3 cm/sec) stroking with a soft brush, a hard brush, and an artificial peacock feather. The stimulation was performed in two regions: back of a forearm, rich in CT afferents, and palm, where their density is lower. Young individuals with ASD and their typically developing peers participated in the study. Unlike the controls, the ASD participants did not show pleasant behavior reaction and fractal dimension increase. The ASD participants also showed Hjorth complexity and alpha power increase accompanying negative affect, which was uncommon for the controls.