New Delhi

Grayand white matter might both work together to support cognitive health among older adults in India and health of the brain's white matter wiring may help soften the cognitive effects of gray matter loss, a study has revealed.

"Gray matter and superficial white matter are physically close and may play different roles: gray matter processes information, while superficial white matter helps nearby brain regions communicate," first author Yingxu Liu, a postdoctoral scholar at the University of Southern California's school of medicine, said.

"Our findings suggest that cognitive health depends not only on how much gray matter is preserved, but also on the condition of the wiring that connects it," Liu said.

The study, published in Alzheimer's and Dementia: The Journal of the Alzheimer's Association, analysed brain scans and cognitive assessments from 459 community-dwelling adults aged 60 and older across India. Data for the analysis came from the Harmonised Diagnostic Assessment of Dementia for the Longitudinal Aging Study in India, or 'LASI-DAD'.

The study is among the first to examine the brain's superficial white matter in a community-based population from a low- and middle-income country, they added.

An advanced form of diffusion MRI (magnetic resonance imaging) was used to assess neurite density -- the small projections that allow nerve cells to send and receive signals -- and the amount of freely moving water around them.

Participants also completed tests of language, memory, executive function and visuospatial ability.

A lower neurite density or more free water can indicate a tissue disruption associated with processes such as loss of myelin, inflammation, or swelling, the researchers said.

A healthier superficial white matter was most consistently associated with stronger language skills, with clearest links appearing in frontotemporal areas involved in recognising words, speaking fluently, and holding language information in mind.

Further, decrease in gray matter remained the strongest overall predictors of cognition.

However, the relationship between gray matter and cognitive performance was found to depend in part on superficial white matter -- when this local wiring showed poorer integrity, gray matter loss was seen more strongly tied to worse language performance and cognitive impairment.