Hand preference of individuals with blindness in everyday activities: The effects of age of sight loss, age, and gender

Are blind individuals immune to bodily illusions? Somatic rubber hand illusion in the blind revisited

Multisensory awareness of one's own body relies on the integration of signals from various sensory modalities such as vision, touch, and proprioception. But how do blind individuals perceive their bodies without visual cues, and does the brain of a blind person integrate bodily senses differently from a sighted person? To address this question, we aimed to replicate the only two previous studies on this topic, which claimed that blind individuals do not experience the somatic rubber hand illusion, a bodily illusion triggered by the integration of correlated tactile and proprioceptive signals from the two hands. We used a larger sample size than the previous studies and added Bayesian analyses to examine statistical evidence in favor of the lack of an illusion effect. Moreover, we employed tests to investigate whether enhanced tactile acuity and cardiac interoceptive accuracy in blind individuals could also explain the weaker illusion. We tested 36 blind individuals and 36 age- and sex-matched sighted volunteers. The results show that blind individuals do not experience the somatic rubber hand illusion based on questionnaire ratings and behavioral measures that assessed changes in hand position sense toward the location of the rubber hand. This conclusion is supported by Bayesian evidence in favor of the null hypothesis. The findings confirm that blind individuals do not experience the somatic rubber hand illusion, indicating that lack of visual experience leads to permanent changes in multisensory bodily perception. In summary, our study suggests that changes in multisensory integration of tactile and proprioceptive signals may explain why blind individuals are "immune" to the nonvisual version of the rubber hand illusion.

The perception of affective and discriminative touch in blind individuals

Enhanced tactile acuity in blindness is among the most widely reported results of neuroplasticity following prolonged visual deprivation. However, tactile submodalities other than discriminative touch are profoundly understudied in blind individuals. Here, we examined the influence of blindness on two tactile submodalities, affective and discriminative touch, the former being vital for social functioning and emotional processing. We tested 36 blind individuals and 36 age- and sex-matched sighted volunteers. In Experiment 1, we measured the perception of affective tactile signals by asking participants to rate the pleasantness of touch delivered on the palm (nonhairy skin, sparsely innervated with C tactile [CT] fibers) or the forearm (hairy skin, densely innervated with CT fibers) in a CT-optimal versus a CT-nonoptimal manner using a paradigm grounded in studies on tactile sensory neurophysiology. In Experiment 2, we implemented a classic task assessing discriminative touch abilities, the grating orientation task. We found that blind individuals rated the touch as more pleasant when delivered on the palm than on the forearm, while the opposite pattern was observed for sighted participants, who rated stimulation on the forearm as more pleasant than stimulation on the palm. We also replicated the previous findings showing enhanced discriminative tactile acuity in blind individuals. Altogether, our results suggest that blind individuals might experience affective touch differently than sighted individuals, with relatively greater pleasantness perceived on the palm. These results provide a broader insight into somatosensory perception in blind individuals, for the first time taking into consideration the socioemotional aspect of touch.

Investigating predictability aspects of phonological type errors in braille spelling

BACKGROUND

Τhe present study focuses on mechanical processes of braille writing conducted by the fingers. Analyzing and attempting to understand the perceptive feedback of the fingers is in specific situations important to develop methods to minimize phonological type errors.

AIM

During a braille spelling task, the authors examined the phonological errors and traced the most and the least error prone finger(s). The authors also examined if it was possible to predict the type of phonological errors in braille writing based on four independent variables relevant to braille code.

METHOD

The error rate of twenty nine participants was estimated by normalizing the frequency of errors performed by each finger in relation to the frequency of the executed keystrokes. Additionally, a multinomial logistic regression examined the potential effect of the column of the braille cell, the dot density of the braille characters and the word length on the type of phonological errors, while a chi-square test has been performed between types of error and fingers.

RESULTS

The fingers were not equally error prone to phonological type errors. The multinomial logistic regression analysis revealed that when a replacement error appeared, the odds for an omission error were significantly less in the right column as well as in short words, while the probability for an addition error was significantly less in both cell columns. In contrast, when a replacement error appeared, the participants tended to perform more omission errors in words with rare density.

CONCLUSIONS

The right ring finger was the most error prone, while the right middle finger was the least error prone. The multivariate logistic regression model showed that all the independent variables, particularly the cell column, exhibited a statistically significant relation with the types of errors.

Electroencephalographic and Neuroimaging Asymmetry Correlation in Patients with Attention-Deficit Hyperactivity Disorder

The present study explores the correlation between electroencephalographic and neuroimaging asymmetry index from EEG-MRI functional connectome and EEG power analysis in inattention, motion, and mixed profile subgroups of ADHD. Sixty-two subjects from Healthy Brain Network Biobank of the Child Mind Institute dataset were selected basing on the quotient score. From both MRI and EEG asymmetry index, Pearson's correlation, ANOVA, and partial least square analysis were performed matching left and right brain parcels and channels. The asymmetry index significantly correlated across subjects between fMRI and power-EEG in the inattention group in frontal and temporal areas for theta and alpha bands, an anticorrelation in the same areas for delta band was found. Significant patterns of hemispheric asymmetry index have been reported, involving EEG bands that underlie cognitive impairments in ADHD. Alpha and theta bands were altered in the inattention group of patients, reflecting widespread deficiency of basic attentional processing.

Tracing the effectiveness of braille reading patterns in individuals with blindness: Handedness and error analysis

Braille reading is a very demanding active tactile process. Forefingers of both hands play a predominant role in braille reading, because the pulps are extremely sensitive in tactile exploration and recognition. The main objective of the present study was to investigate the potential effects of handedness on braille reading patterns during braille text reading. Thirty-two Greek students (from Grades 3 to 12) with visual impairments, who used systematically the braille code as a reading medium, participated in this study. Handedness was assessed through a modified version of the Edinburgh Handedness Inventory, while their reading level was estimated via a standardized test. In turn, participants read 18 texts, which were chosen randomly from their textbooks. Results indicated that handedness affected braille readers’ selected reading patterns during text reading. A variety of reading patterns were recorded and the selected data were correlated with tactile reading strategies in terms of dominant hands and fingers. It seems that readers who selected one-hand braille reading patterns performed significantly more errors with the index of their dominant hand, whereas those who chose to read with both hands faced more difficulties toward the effective collaboration of the indices of their hands. Finally, the findings of the present study are discussed in relation to educational practice, relevant theory, and subsequent research.

The contributions of vision and haptics to reaching and grasping

This review aims to provide a comprehensive outlook on the sensory (visual and haptic) contributions to reaching and grasping. The focus is on studies in developing children, normal, and neuropsychological populations, and in sensory-deprived individuals. Studies have suggested a right-hand/left-hemisphere specialization for visually guided grasping and a left-hand/right-hemisphere specialization for haptically guided object recognition. This poses the interesting possibility that when vision is not available and grasping relies heavily on the haptic system, there is an advantage to use the left hand. We review the evidence for this possibility and dissect the unique contributions of the visual and haptic systems to grasping. We ultimately discuss how the integration of these two sensory modalities shape hand preference.