Increased Functional Connectivity in Blind Children
Wednesday, Nov. 30, 2016
While blind people — as well as other people who have sensory loss — face daunting challenges when dealing with daily life, it is clear that they are somehow able to make adjustments to their sensory loss in order to interact with their environments.
How are they able to do this? Evidence suggests that when the brain is deprived of input from one sensory modality (such as vision), it reorganizes itself to reinforce or boost other senses.
According to Laura Ortiz-Terán, MD, PhD, a research fellow in radiology at Massachusetts General Hospital, that mechanism is called cross-modal neuroplasticity, in which the brain will recruit other modalities to compensate for the one that is missing.
In the past, Dr. Ortiz-Terán and her colleagues have carried out studies on adults in which they observed that multimodal integration regions are prominent sites of neuroplastic reorganization.
In this study, presented Tuesday, Dr. Ortiz-Terán and her colleagues investigated the network connectivity differences in blind children compared to sighted controls.
Dr. Ortiz-Terán recruited 17 blind children ages 7-12, and 18 sighted matched controls. Inclusion criteria included active participation in school and normal IQ, while exclusion criteria included having another sensory deficit other than blindness, co-morbid neuropsychiatric conditions, and history of obstetric trauma with cerebral hypoxia.
The study participants were scanned on a 3 Tesla MRI scanner, and following pre-processing, Dr. Ortiz-Terán and her colleagues applied whole brain-weighted-degree connectivity and step-wise connectivity graph theory analyses.
"We found that there is increased connectivity in these multimodal integration areas in blind children compared to sighted controls," Dr. Ortiz-Terán said. "Meaning that all the recruitment that they are doing in these unimodal areas is going through those multimodal integration networks."
In a weighted-degree analysis, Dr. Ortiz-Terán and her colleagues demonstrated that blind children showed enhanced connectivity in the bilateral ventral premotor, middle cingulate cortex/supplementary motor area and right temporal parietal junction. They also found that several of these connectivity changes positively correlated to age.
Using step-wise connectivity analysis, the researchers found that blind children, compared to controls, demonstrated increased functional streams along certain multimodal integration regions, including the anterior insula and temporoparietal junction bilaterally and the right lateral cortex.
The researchers also used the Allen Human Brain Atlas to investigate whether genetic transcription profiles were associated with the ability of areas of the brain to display adaptive changes after sensory loss.
"We found out that those genes — basically the CREB family — which are expressed only as needed for neuroplasticity, are the ones showing up more in these multimodal brain regions in blind children," Dr. Ortiz-Terán said. "The neuroplasticity genes involved in learning are more expressed in multimodal integration areas in blind children, which means these children are using these to learn more than sighted children."