Biology subjects

Lingareddy, S.

Publications and source records attributed to Lingareddy, S..

3 recordsLinked to original sources

bioRxiv2025

Individuals born with congenital cataracts exhibit both persisting impairment and considerable recovery of white matter microstructure after sight restoration

IntroductionIndividuals born with dense bilateral cataracts, for whom sight was restored later in life (congenital cataract reversal individuals), provide a unique opportunity to explore the impact of early (visual) experience on the development of the human brain. MethodsUsing diffusion MRI we assessed white matter microstructure in a sample of 20 congenital cataract reversal individuals using along-the-tract analysis of major visual white matter tracts and non-visual control tracts. We additionally recruited three control groups: 8 permanently congenitally blind individuals, 11 individuals with reversed later-onset cataracts (developmental cataract reversal individuals), and 24 age- and sex-matched typically sighted controls. ResultsDiffusion tensor metrics exhibited significant group differences which were specific to visual tracts. Compared to normally sighted controls, congenitally blind and congenital cataract reversal individuals both showed impaired white matter integrity. However, differences were much more spatially extensive for permanently congenitally blind individuals, and a direct comparison revealed relatively higher tract integrity for congenital cataract reversal individuals, suggesting a high degree of recovery following sight restoration. DiscussionThe present pattern of results is compatible with the idea of both a sensitive period for white matter development and significant white matter plasticity later in life. We propose that group differences are largely driven by differences in myelination. Thus, the considerable recovery in congenital cataract reversal individuals would suggest that life-long myelin plasticity may remain higher than neuronal structural plasticity.

neuroscience↗

bioRxiv2024

Altered visual cortex excitatory/inhibitory ratio following transient congenital visual deprivation in humans

Non-human animal models have indicated that the ratio of excitation to inhibition (E/I) in neural circuits is experience dependent and changes across development. Here, we assessed 3T Magnetic Resonance Spectroscopy (MRS) and electroencephalography (EEG) markers of cortical E/I ratio in ten individuals who had been treated for dense bilateral congenital cataracts, after an average of 12 years of blindness, to test for dependence of the E/I ratio in humans on early visual experience. First, participants underwent MRS scanning at rest with their eyes opened and eyes closed, to obtain visual cortex Gamma-Aminobutyric Acid (GABA+) concentration, Glutamate/Glutamine (Glx) concentration and the concentration ratio of Glx/GABA+, as measures of inhibition, excitation, and E/I ratio respectively. Subsequently, EEG was recorded to assess aperiodic activity (1-20 Hz) as a neurophysiological measure of the cortical E/I ratio, during rest with eyes open and eyes closed, and during flickering stimulation. Across conditions, congenital cataract-reversal individuals demonstrated a significantly lower visual cortex Glx/GABA+ ratio, and a higher intercept and steeper aperiodic slope at occipital electrodes, compared to age-matched sighted controls. In the congenital cataract-reversal group, a lower Glx/GABA+ ratio was associated with better visual acuity, and Glx concentration correlated positively with the aperiodic intercept in the conditions with visual input. We speculate that these findings result from an increased E/I ratio of the visual cortex as a consequence of congenital blindness, which might require commensurately increased inhibition in order to balance the additional excitation from restored visual input. The lower E/I ratio in congenital cataract-reversal individuals would thus be a consequence of homeostatic plasticity.

neuroscience↗

bioRxiv2021

Typical resting state activity of the brain requires visual input during an early sensitive period

Sensory deprivation, following a total loss of one sensory modality e.g. vision, has been demonstrated to result in intra- and cross-modal plasticity. It is yet not known to which extent intra- and cross-modal plasticity as a consequence of blindness reverse if sight is restored. Here, we used functional magnetic resonance imaging to acquire blood oxygen level dependent (BOLD) resting state activity during an eyes open and an eyes closed state in congenital cataract-reversal individuals, developmental cataract-reversal individuals, congenitally permanently blind individuals and sighted controls. The amplitude of low frequency fluctuations (ALFF) of the BOLD signal - a neural marker of spontaneous brain activity during rest - was analyzed. As has been shown before, in normally sighted controls we observed an increase in ALFF during rest with the eyes open compared to rest with eyes closed in visual association areas and in parietal cortex but a decrease in auditory and sensorimotor regions. In congenital cataract-reversal individuals, we found an increase of the amplitude of slow BOLD fluctuations in visual cortex during rest with eyes open compared to rest with eyes closed too but this increase was larger in amplitude than in normally sighted controls. At the same time, congenital cataract-reversal individuals lagged a similar increase in parietal regions and did not show the typical decrease of ALFF in auditory and sensorimotor cortex. Congenitally blind individuals displayed an overall higher amplitude in slow BOLD fluctuations in visual cortex compared to sighted individuals and compared to congenital cataract-reversal individuals in the eyes closed condition. Higher ALFF in visual cortex of congenital cataract-reversal individuals than in normally sighted controls during eyes open might indicate an altered excitatory-inhibitory balance of visual neural circuits. By contrast, the lower parietal increase and the missing downregulation in auditory and sensorimotor regions suggest a reduced influence of the visual system on multisensory and the remaining sensory systems after restoring sight in congenitally blind individuals. These results demonstrate a crucial dependence of multisensory neural networks on visual experience during a sensitive phase in human brain development.

neuroscience↗