Interhemispheric transfer time differs between fast and slow healthy adult readers.

The visual system forms the basis of visual word decoding processes. Reading is a left-lateralized function. The interaction between the two hemispheres via the corpus callosum is required for successful reading. It is known that callosal function and morphology are affected in reading disorders. This study investigated the differences in callosal transfer speed of verbal and nonverbal stimuli in healthy university students. We hypothesized that if the callosal transfer has a role in slow reading, transfer speed would differ between slow and fast readers. Moreover, if the difference was affected by the type of stimulus, this will provide information about the level of neural processing at which the difference is based/aroused. Fifty-one participants were grouped as slow (n = 15, 8 female) and fast (n = 36, 22 female) readers. Three types of stimuli (word, legal pseudoword, and non-verbal grating) were presented from the right or left visual field. Latencies of the evoked potentials (N1) were used to measure interhemispheric transfer time. We found that slow readers have a slower right-to-left transfer speed at the parietal site, which is related to the visual word decoding process. The finding was similar to previous studies examining individuals with dyslexia. This difference was not seen with grating stimuli; we suggest that the difference originates at the orthographic visual lexical level rather than at earlier basic visual processing. We did not observe any effect of lexical and sublexical routes on the callosal transfer time because of evaluated time windows.

Right Anterior Theta Hypersynchrony as a Quantitative Measure Associated with Autistic Traits and K-Cl Cotransporter KCC2 Polymorphism.

Our aim was to use theta coherence as a quantitative trait to investigate the relation of the polymorphisms in NKCC1 (rs3087889) and KCC2 (rs9074) channel protein genes to autistic traits (AQ) in neurotypicals. Coherence values for candidate connection regions were calculated from eyes-closed resting EEGs in two independent groups. Hypersynchrony within the right anterior region was related to AQ in both groups (p < 0.05), and variability in this hypersynchrony was related to the rs9074 polymorphism in the total group (p < 0.05). In conclusion, theta hypersynchrony within the right anterior region during eyes-closed rest can be considered a quantitative measure for autistic traits. Replicating our findings in two independent populations with different backgrounds strengthens the validity of the current study.

Auditory Processing Differences Correlate With Autistic Traits in Males.

Autism spectrum disorder (ASD) has high prevalence among males compared to females but mechanisms underlying the differences between sexes are poorly investigated. Moreover, autistic symptoms show a continuity in the general population and are referred to as autistic traits in people without an ASD diagnosis. One of the symptoms of ASD is sensory processing differences both in sensitivity and perception. To investigate sensory processing differences in autistic traits, we examined auditory and visual processing in a healthy population. We recruited 75 individuals (39 females and 36 males, mean age = 23.01 years, SD = 3.23 years) and assessed autistic traits using the Autism Spectrum Quotient, and sensory sensitivity using the Sensory Sensitivity Scales. Sensory processing in the visual domain was examined with the radial motion stimulus and the auditory domain was assessed with the 1,000 Hz pure tone stimulus with electroencephalography-evoked potentials. The results showed that the auditory sensitivity scores of the males (r aud (34) = 0.396, p aud = 0.017) and the visual sensitivity scores of females were correlated with autistic traits (r vis (37) = 0.420, p vis = 0.008). Moreover, the P2 latency for the auditory stimulus was prolonged in the participants with a higher level of autistic traits (r s (61) = 0.411, p = 0.008), and this correlation was only observed in males (r s (31) = 0.542, p = 0.001). We propose that auditory processing differences are related to autistic traits in neurotypicals, particularly in males. Our findings emphasize the importance of considering sex differences in autistic traits and ASD.

Evaluation of temporal and suprasegmental auditory processing in patients with unilateral hearing loss.

OBJECTIVES: To determine the temporal order, resolution, and perception of prosody skills in Single-Sided Deafness (SSD) compared to an age- and sex-matched normal hearing group's same side ear and both ears. METHODS: This was a Case-Control study including 30 subjects with SSD, and age- and sex-matched 30 subjects with bilateral normal hearing (total of 60 subjects- mean age: 38.7 ± 11.6 years). The Montreal Cognitive Assessment (MoCA), Frequency Pattern Test (FPT), Duration Pattern Test (DPT), Random Gap Detection Test (RGDT), Evaluation of Motor Response Time and Emotional Prosody Assessment were performed on the clinically normal ear in the SSD group, the same side ear in the normal hearing group, and both ears of the normal hearing group (the SSD, MNH, and BNH groups, respectively). RESULTS: Individuals with SSD had worse results in DPT (p < .001), gap detection at 0.5 kHz (p < .001), gap detection at 4 kHz (p < .001), and composite score (p < .001) than the BNH group. For reaction time measurements, the SSD group had slower performance scores than the BNH group for DPT (p < .001) and FPT (p < .001). CONCLUSIONS: Poor temporal processing ability and reduced reaction times may help explain the difficulties in those with SSD in performing daily living activities such as speech understanding in noise and requires more processing efforts. However, there were no significant differences between the groups in frequency pattern performance and emotional prosody skills, supporting the claim that fundamental frequency is one of the most important measures of perception in emotional prosody. We demonstrated that unilateral hearing is adequate to analyze frequency patterns to aid in prosody perception. Analysis of reaction times in temporal processing and emotional prosody could provide different perspectives of auditory processing. Slower reaction time of SSD should be considered for habilitation purposes.

Development of Sensory Sensitivity Scales (SeSS): Reliability and validity analyses.

BACKGROUND: Although adults are known to have sensory sensitivity differences, existing sensitivity scales have been mostly developed for children. The limited number of adult scales measure social/emotional features and modalities together. AIMS: To develop scales for adults that evaluate visual, auditory and somatosensory sensitivities as separate domains and independent of social/emotional features. METHODS AND PROCEDURES: Two consecutive studies (visual-auditory part and somatosensory part) were conducted using the same methods. Both studies included a pilot (n1 = 405 and n2 = 294) and a main group (n1 = 425 and n2 = 603). An exploratory factor analysis produced a single-factor solution for the visual and auditory domains and a three-factor solution for the somatosensory domain (touch, pain, and itch) of Sensory Sensitivity Scales. OUTCOMES AND RESULTS: A confirmatory factor analysis revealed good construct validity in the the visual (CFI = .973, TLI = .965, and RMSEA = .075) auditory (CFI = .943, TLI = .927, and RMSEA = .074) and somatosensory (CFI = .955, TLI = .946, and RMSEA = .048) scales. The categories were internally consistent (αv = .86, αa = .79, αs = .69). As an indicator of convergent validity, higher autistic traits were related to higher sensitivity (rs-v = .17, rs-a = .25, rs-s = .14). CONCLUSIONS AND IMPLICATIONS: Sensory Sensitivity Scales (SeSS) can be used to screen sensory sensitivity variability or identify and follow up the outcome of sensory interventions in adults.

Corpus callosum has different channels for transmission of spatial frequency information.

Many studies suggest that separate retinocortical channels with different conduction speeds transmit the information about high and low spatial frequencies (SF). Similarly, separate callosal channels may be responsible for the transfer of different SFs. To test this hypothesis, interhemispheric transfer time (IHTT) was estimated using visual evoked potentials (VEPs) elicited by reversal of different SF checkerboard patterns, which were presented either in the right or left visual hemifield. VEPs were recorded from homologous occipital and parietal leads in 11 subjects. The P100 latencies obtained from directly stimulated hemispheres were defined as retinocortical conduction times. The difference in P100 latencies obtained from directly and indirectly stimulated hemispheres was defined as IHTT (i.e., contralateral P100 latency values subtracted from the ipsilateral latency values). The results, showing faster retinocortical transfer for low SF than for high SF, and the shortest transfer time at parietal leads only for low SF, indicate that the presented stimuli are transferred on separate retinocortical channels. Concerning the interhemispheric transfer (VEP-IHTT), faster right-to-left than left-to-right transfer for both low and high SF stimuli was found, which is in congruence with previous studies. Most important however, the VEP-IHTT was faster for low SF than high SF. These different interhemispheric transfer speeds support the hypothesis that transferring low SF, compared with high SF information, relies on larger callosal fibers. Thus, we conclude that indeed distinct callosal channels respond selectively to the SF content of visual stimuli.

Aspects of foot preference: differential relationships of skilled and unskilled foot movements with motor asymmetry.

In this research different aspects of foot preference were examined in 50 participants. The relationship between foot preference, hand preference, and hand/foot-tapping performance was analysed in detail. For foot preference, a practical behavioural test consisting of 14 daily foot movements was developed. After statistical analysis, five items were dropped. The test-retest reliabilities of the nine-item foot preference test and the foot-tapping task were found to be high. The factor analysis indicated a two-factor structure (skilled and unskilled foot movements). Foot preference in skilled and unskilled movements was correlated with hand preference and foot/hand-tapping speed. This correlation was found to be higher in skilled movements than in unskilled movements. Additionally, foot preference for skilled movements was strongly lateralised. The results indicate that the motor control of fine movements is similar for upper and lower limbs. The fact of lateralisation indicates that skilled and unskilled foot movements utilise different pathways. We propose that the asymmetrical lateral (corticospinal) pathway controls skilled movements while the medial pathways control unskilled movements. We therefore suggest that both skilled and unskilled foot tasks should be evaluated separately in order to assess foot preference.

[Reliability and validity of Turkish version of magical ideation scale in university students]. / Büyüsel düsünce olçegi'nin Türkçe formunun universite ogrencilerindeki geçerlik ve güvenilirligi.

OBJECTIVE: Schizoptypal disorder shares many clinical, neuropsychological and neurophysiological features with schizophrenia and is included in the schizophrenia spectrum. Patients with schizotypal disorder or individuals with mild schizotypal features are therefore highly valuable in the study of neuropsychological and neurophysiological characteristics of psychosis, and in particular schizophrenia, as they are likely to be free of the potential confounding factors of medication, chronic hospitalization and manifest psychosis. We report here the psychometric properties of the Turkish version of the Magical Ideation Scale (MIS), a self-report questionnaire that focuses on delusion-like beliefs and hallucination-like experiences and that has been used to quantify an important dimension of schizotypy. METHOD: Internal consistency and high cut-off scores were studied in 332 medical students. Forty-three students were readministered the scale 3 weeks later, and 96 received the Paranormal Belief Scale-R (PBS-R) along with the MIS, in order to measure test-retest reliability and convergent validity, respectively. RESULTS: The internal consistency of the scale is satisfactory with a Cronbach alpha coefficient of 0.78. Test-retest scores are highly correlated (r= 0.84). The high cut-off score is 21 for males, 23 for females, and 22 for the whole sample. Convergent validity was established by the significant correlation between the total MIS and PBS-R scores (r= 0.61). CONCLUSIONS: The scale is valid and reliable for studies that require a standard quantification of schizotypal signs and symptoms in young university students.

Line bisection task performance and resting EEG alpha power.

Neurologically normal subjects generally err to the left of veridical center when performing a line bisection task, a phenomenon termed "pseudoneglect." We hypothesized that resting electroencephalogram (EEG) alpha oscillations may show relationships with attentional mechanisms and give some clues about the underlying mechanisms of pseudoneglect. We recorded resting EEGs of 41 subjects and tested them with a paper-pencil line bisection task. Our results showed that line bisection scores of men (n=18) were less biased and their performance was higher compared to those of women (n=20), but these differences only approached significance. The eyes open resting EEG alpha power of women was significantly and positively correlated with their line bisection performance. In general, significant relationships were related to the left hand performance when the lines were presented in the left hemispace. Greater resting alpha power was correlated with lower absolute bisection score or, in other words, higher bisection performance. Greater alpha power also correlated with diminished leftward bisection bias (or reduced pseudo-neglect). The resting EEG alpha of men was weakly associated with bisection performance. Results discussed in terms of Kinsbourne's activation-orientation theory and Basar's view on brain oscillations.

[Reliability and validity of a handedness questionnaire]. / El tercihi anketinin geçerlik ve güvenilirligi.

OBJECTIVE: In this study, the validity and reliability of the hand preference item of a 13-item questionnaire adapted from Chapman and Chapman (1987) were investigated. METHOD: This questionnaire requires subjects to indicate which hand they usually use for various actions as follows: writing, drawing, throwing, using a hammer, using a toothbrush, using an eraser on paper, using scissors, holding a match when striking it, stirring a can of paint, using a spoon, using a screwdriver, twisting off the lid of a jar, and using a knife. Each item was scored as "1" for right, "2" for either, or "3" for left, and the handedness of subjects was scored from 13 (the strongest right-hand preference) to 39 (the strongest left-hand preference). In this study, 449 subjects filled in the questionnaire, and 43 subjects attended the test-retest study 3 weeks after the first examination. In order to determine the validity of the questionnaire, fine motor performance was measured using a finger tapping task, and the eye and foot preferences of the subjects were evaluated. RESULTS: The test-retest reliability (r=.993) and internal consistency (Cronbach's Alpha=.97) were found to be high. In item-total score analysis, the best single item was "using a hammer", while the worst item was "twisting off the lid of a jar". Factor analysis yielded two factors, skilled and unskilled activities. Handedness scores were found to show a significant correlation with foot preference scores and the dominance score of the finger tapping task. CONCLUSION: The results suggest that the handedness questionnaire is reliable and valid in measuring handedness.