Tonelli, A. | bioRxiv Science

bioRxiv2024

Saccadic compression of time as a marker for Developmental Dyslexia

About 10% of the worlds population is dyslexic, experiencing reading impairments unrelated to cognitive deterioration. Due to its impact, identifying the mechanisms subtending dyslexia is paramount. However, while most research focused on the eye movements phenomenology, none investigated their perceptual, transient consequences. In fact, it has been shown that rapid eye movements (i.e., saccades) are accompanied by temporary distortions of space and time. Such distortions have been linked to the receptive fields predictive remapping, which anticipates the movement and compensates for the gazes displacement. Here, we demonstrate that dyslexic children show reduced flexibility in modulating temporal information around the saccadic onset. Moreover, accuracy oscillations within the delta band, phase-locked to the saccades onset, preceded transient temporal compression in typical readers. Conversely, no oscillatory behavior was observed in dyslexic participants, suggesting that the absence of transient temporal distortions originated from the mismatch between the anticipatory remapping and the saccadic onset.

neuroscience↗

bioRxiv2023

Cross-modal interactions and movement-related tactile gating: the role of vision

When engaging with the environment, multisensory cues interact and are integrated to create a coherent representation of the world around us, process that has been suggested to be affected by the lack of visual feedback in blind individuals. In addition, the presence of voluntary movement seems to be responsible for suppressing somatosensory information that is processed by the cortex, which can lead to a worse encoding of tactile information. In this work, we aim to explore how multisensory processing can be affected by active movements and the role of vision in this process. To this end, we measure the precision of 18 sighted controls and 18 blind individuals in a velocity discrimination task. The participants were instructed to detect the stimulus that contained the faster speed, between a sequence of two, in both passive and active touch conditions. The sensory stimulation could be either just tactile or audio-tactile, where a non-informative sound occurred simultaneously with the tactile stimulation. The measure of precision was obtained by computing the Just Noticeable Difference (JND) of each participant. The results show worse precision in the bimodal audio-tactile sensory stimulation in the active condition for the sighted group but not for the blind one. In the sighted group, the noise of the tactile feedback might make them more vulnerable to the noisy interference of the audio modality; however, this is not the case for the blind one, which seems to be only affected by the movement itself. Our work should be considered when developing next-generation haptic devices; moreover, it supports the need for action in the blind population.

neuroscience↗