Summary: Researchers report on the combined structural, functional and anatomical changes that occur in those born blind that are not present in the brains of people born with sight.
Source: Massachusetts Eye and Ear Infirmary.
The brains of those who are born blind make new connections in the absence of visual information, resulting in enhanced, compensatory abilities such as a heightened sense of hearing, smell and touch, as well as cognitive functions (such as memory and language) according to a new study led by Massachusetts Eye and Ear researchers. The report, published online today in PLOS One, describes for the first time the combined structural, functional and anatomical changes in the brain evident in those born with blindness that are not present in normally sighted people.
“Our results demonstrate that the structural and functional neuroplastic brain changes occurring as a result of early ocular blindness may be more widespread than initially thought,” said lead author Corinna M. Bauer, Ph.D., a scientist at Schepens Eye Research Institute of Mass. Eye and Ear and an instructor of ophthalmology at Harvard Medical School. “We observed significant changes not only in the occipital cortex (where vision is processed), but also areas implicated in memory, language processing, and sensory motor functions.”
The researchers used MRI multimodal brain imaging techniques (specifically, diffusion-based and resting state imaging) to reveal these changes in a group of 12 subjects with early blindness (those born with or who have acquired profound blindness prior to the age of three), and they compared the scans to a group of 16 normally sighted subjects (all subjects were of the same age range). On the scans of those with early blindness, the team observed structural and functional connectivity changes, including evidence of enhanced connections, sending information back and forth between areas of the brain that they did not observe in the normally sighted group.
These connections that appear to be unique in those with profound blindness suggest that the brain “rewires” itself in the absence of visual information to boost other senses. This is possible through the process of neuroplasticity, or the ability of our brains to naturally adapt to our experiences.
The researchers hope that increased understanding of these connections will lead to more effective rehabilitation efforts that will enable blind individuals to better compensate for the absence of visual information.
“Even in the case of being profoundly blind, the brain rewires itself in a manner to use the information at its disposal so that it can interact with the environment in a more effective manner,” said senior author Lotfi Merabet, O.D., Ph.D., director of the Laboratory for Visual Neuroplasticity at the Schepens Eye Research Institute of Mass. Eye and Ear and an associate professor of ophthalmology at Harvard Medical School. “If the brain can rewire itself – perhaps through training and enhancing the use of other modalities like hearing, and touch and language tasks such as braille reading – there is tremendous potential for the brain to adapt.”
In addition to Drs. Bauer and Merabet, authors on the PLOS One paper include Gabriella V. Hirsch, of Schepens Eye Research Institute of Mass. Eye and Ear, Lauren Zajac and Bang-Bon Koo of the Center for Biomedical Imagine at Boston University School of Medicine, and Olivier Collignon of the Crossmodal Perception and Plasticity Laboratory of the University of Trento.
Funding: Support for the study includes NIH/NEI grant R01 EY019924, the Low Vision Research Award from Research to Prevent Blindness and the Lions Clubs International Foundation.
Source: Suzanne Day – Massachusetts Eye and Ear Infirmary
Image Source: NeuroscienceNews.com image is credited to Boston University Medical School Center for Biomedical Imaging.
Original Research: Full open access research for “Multimodal MR-imaging reveals large-scale structural and functional connectivity changes in profound early blindness” by Corinna M. Bauer, Gabriella V. Hirsch, Lauren Zajac, Bang-Bon Koo, Olivier Collignon, and Lotfi B. Merabet in PLOS ONE. Published online March 22 2017 doi:10.1371/journal.pone.0173064
Multimodal MR-imaging reveals large-scale structural and functional connectivity changes in profound early blindness
In the setting of profound ocular blindness, numerous lines of evidence demonstrate the existence of dramatic anatomical and functional changes within the brain. However, previous studies based on a variety of distinct measures have often provided inconsistent findings. To help reconcile this issue, we used a multimodal magnetic resonance (MR)-based imaging approach to provide complementary structural and functional information regarding this neuroplastic reorganization. This included gray matter structural morphometry, high angular resolution diffusion imaging (HARDI) of white matter connectivity and integrity, and resting state functional connectivity MRI (rsfcMRI) analysis. When comparing the brains of early blind individuals to sighted controls, we found evidence of co-occurring decreases in cortical volume and cortical thickness within visual processing areas of the occipital and temporal cortices respectively. Increases in cortical volume in the early blind were evident within regions of parietal cortex.
Investigating white matter connections using HARDI revealed patterns of increased and decreased connectivity when comparing both groups. In the blind, increased white matter connectivity (indexed by increased fiber number) was predominantly left-lateralized, including between frontal and temporal areas implicated with language processing. Decreases in structural connectivity were evident involving frontal and somatosensory regions as well as between occipital and cingulate cortices.
Differences in white matter integrity (as indexed by quantitative anisotropy, or QA) were also in general agreement with observed pattern changes in the number of white matter fibers. Analysis of resting state sequences showed evidence of both increased and decreased functional connectivity in the blind compared to sighted controls. Specifically, increased connectivity was evident between temporal and inferior frontal areas.
Decreases in functional connectivity were observed between occipital and frontal and somatosensory-motor areas and between temporal (mainly fusiform and parahippocampus) and parietal, frontal, and other temporal areas. Correlations in white matter connectivity and functional connectivity observed between early blind and sighted controls showed an overall high degree of association. However, comparing the relative changes in white matter and functional connectivity between early blind and sighted controls did not show a significant correlation. In summary, these findings provide complimentary evidence, as well as highlight potential contradictions, regarding the nature of regional and large scale neuroplastic reorganization resulting from early onset blindness.
“Multimodal MR-imaging reveals large-scale structural and functional connectivity changes in profound early blindness” by Corinna M. Bauer, Gabriella V. Hirsch, Lauren Zajac, Bang-Bon Koo, Olivier Collignon, and Lotfi B. Merabet in PLOS ONE. Published online March 22 2017 doi:10.1371/journal.pone.0173064