Auditory perception of ambiguous and non-ambiguous sound in early and late blind children: A functional connectivity study

INTRODUCTION

Auditory perception and associated cognition involve visual and auditory cortical areas for inference of meaningful soundscape.

OBJECTIVE

To investigate auditory perception of ambiguous and non-ambiguous stimulation in auditory and visual cortical networks for categorical discrimination.

METHODOLOGY

Functional mapping was carried out in twenty early (EB), twenty late blind (LB) and fifteen healthy children, during auditory ambiguous and non-ambiguous stimulation task in a 3 T MR scanner to estimate hemodynamic signal alteration and its effect on functional connectivity. The degree of amplitude low-frequency fluctuation (ALFF), correlation analysis and multiple comparison was carried out to map the impact of duration of education and onset of blindness (EB and LB).

RESULTS AND DISCUSSION

Increased functional connectivity (FC) and cross-modal reorganization was observed in auditory, visual and language networks in EB children. FC was increased in contralateral hemisphere in both the blind children (EB and LB) groups and was positively correlated with duration of education performance. Cognitive assessment scores correlated (p < 0.01) with cluster coefficient of FC and BOLD response.

CONCLUSION

FC alterations depend on onset age and audio-haptic training in children associated with increased auditory language and memory perception.

Evaluation of Memory and Language Network in Children and Adolescents with Visual Impairment: A Combined Functional Connectivity and Voxel-based Morphometry Study

Functional network changes associated with Braille reading are different in early blind (EB) and late blind (LB) participants. The objectives were to study the functional connectivity (of memory and language areas based on blood oxygen level-dependent [BOLD] mapping) and structural changes in EB and LB children and adolescents. A total of 110 participants (all right-handed) were recruited in two age groups of 6-12 years (children) and 13-19 years (adolescents) consisting of EB (n = 20), LB (n = 20), and sighted controls (SC, n = 15) in each group. Group differences were estimated between children and adolescent groups. Structural changes in visual cortex and medial temporal area, increased BOLD activations and altered functional connectivity in the primary visual cortex, inferior frontal gyrus, middle temporal gyrus, and hippocampus during Braille reading task were observed in adolescents as compared with children blind groups (pFDR corrected <0.05). Functional results were positively correlated with duration of Braille reading and age at onset in EB and LB groups (p ≤ 0.01). Visual, language, and learning memory networks were different in adolescents and children of both EB and LB groups, and also between EB and LB groups suggesting cross-modal plasticity. The functional and structural results revealed education dependent cross-modal plasticity in visually impaired participants. Memory and language network were affected more in the LB group than the EB group, and more in children than adolescents.

Visual Cortex Alterations in Early and Late Blind Subjects During Tactile Perception

Involvement of visual cortex varies during tactile perception tasks in early blind (EB) and late blind (LB) human subjects. This study explored differences in sensory motor networks associated with tactile task in EB and LB subjects and between children and adolescents. A total of 40 EB subjects, 40 LB subjects, and 30 sighted controls were recruited in two subgroups: children (6-12 years) and adolescents (13-19 years). Data were acquired using a 3T MR scanner. Analyses of blood oxygen level dependent (BOLD), functional connectivity (FC), correlation, and post hoc test for multiple comparisons were carried out. Difference in BOLD activity was observed in EB and LB groups in visual cortex during tactile perception, with increased FC of visual with dorsal attention and sensory motor networks in EB. EB adolescents exhibited increased connectivity with default mode and salience networks when compared with LB. Functional results correlated with duration of training, suggestive of better performance in EB. Alteration in sensory and visual networks in EB and LB correlated with duration of tactile training. Age of onset of blindness has an effect in cross-modal reorganization of visual cortex in EB and multimodal in LB in children and adolescents.