EEG correlates of tactile perception abnormalities in children with autism spectrum disorder

The aim of the investigation was to study the changes in EEG power and behavioral responses to C-tactile stimulation in typically developing (TD) children and children with autism spectrum disorder (ASD). Materials and Methods. EEG to manually delivered tactile stimuli was recorded for 79 children (ASD=39, TD=40) aged 5 to 10 years. CARS scores were obtained for each participant immediately before the recording session. The study involved recording resting EEG in eyes open condition within 1–2 min and collecting EEG response to tactile stimuli delivered pseudo-randomly for 3 experimental conditions (stroking with a soft brush, stroking with a harsh brush, and stimulation with a spiked roller delivered to the outer side of right forearm, stroking velocity was within 2–5 cm/s). Behavioral responses obtained by video recording during the experiment were assessed and coded. Behavioral responses were classified into 5 patterns: 1) signs of relaxation (facial gesture and body posture); 2) signs of resistance, attempts to withdraw the hand; 3) negative emotions, crying, shouting; 4) positive emotions, smile, laughter; 5) looking at the hand being stimulated. EEG power in 18 narrow frequency bands with a bandwidth of 1 Hz in a range of 2–20 Hz was analyzed. Results. The study revealed two types of response to tactile stimulation. The first type was not specific for particular tactile stimulation type, was accompanied by an increase in beta power (16–20 Hz) mainly in the left hemisphere and was more common in children with ASD. The second type of response was accompanied by an increase in frontal theta power (4–6 Hz) due to C-tactile system stimulation with a soft brush and was observed only in the TD children. The first type of response was accompanied by negative emotions and attempts to withdraw the hand, while the second type was characterized by relaxation. Conclusion. The response of children with ASD to all types of tactile stimulation accompanied by an increase in beta power can be associated with both hypersensitivity and stress reaction of these children to the experimental situation. Selective response to C-tactile stimulation accompanied by an increase in frontal theta power has been found in the control group (TD) only. The results of this study can be useful for better understanding of hypersensitivity in children with ASD and gaining insight into the mechanisms of the disease

Genetic Determinants of Time Perception Mediated by the Serotonergic System

Background: The present study investigates neurobiological underpinnings of individual differences in time perception. Methodology: Forty-four right-handed Russian Caucasian males (18–35 years old) participated in the experiment. The polymorphism of the genes related to the activity of serotonin (5-HT) and dopamine (DA)-systems (such as 5-HTT, 5HT2a, MAOA, DAT, DRD2, COMT) was determined upon the basis of DNA analysis according to a standard procedure. Time perception in the supra-second range (mean duration 4.8 s) was studied, using the duration discrimination task and parametric fitting of psychometric functions, resulting in individual determination of the point of subjective equality (PSE). Assuming the ‘dual klepsydra model ’ of internal duration representation, the PSE values were transformed into equivalent values of the parameter k (kappa), which is a measure of the ‘loss rate ’ of the duration representation. An association between time representation parameters (PSE and k, respectively) and 5-HT-related genes was found, but not with DArelated genes. Higher ‘loss rate ’ (k) of the cumulative duration representation were found for the carriers of genotypes characterized by higher 5-HT transmission, i.e., 1) lower 5-HT reuptake, known for the 5-HTTLPR SS polymorphism compared with LL, 2) lower 5-HT degradation, described for the ‘low expression ’ variant of MAOA VNTR gene compared with ‘high expression ’ variant, and 3) higher 5-HT2a receptor density, proposed for the TT polymorphism of 5-HT2a T102C gene compared with CC