"A volume deficit of the anterior vermis, but not the prefrontal or parietal cortex, was a unique predictor of balance scores," she said. "Volume deficits of the vermis and thalamus, but not the prefrontal cortex, were unique predictors of card-sorting scores, and a volume deficit of cerebellar hemispheric white matter, but not partietal cortex, was a predictor of visuospatial test performance."
The detection of relationships between brain structures and specific functions has been elusive in alcohol research, said Sullivan. "One reason may be that the approach to seeking them, that is, connecting one cortical brain locus with one behavior, was too simplified and too restricted to the cerebral cortex and excluded brain stem structures such as the pons and cerebellum."
Researchers know that two areas of neuropsychological functioning commonly compromised by chronic alcoholism are executive functions (such as problem solving, putting things in order, working memory, doing multiple tasks at once) and balance (the ability to walk a straight line or stand on one foot, especially with eyes closed or in the dark). Executive functions are typically disrupted by lesions of the prefrontal cortex, whereas balance and postural stability are disrupted by lesions of the cerebellum.
"The main idea expressed in this paper is that the compounded set of lesions may work together to disadvantage both types of functions," said Sullivan. "Indeed, in our previous research we have reported disproportionately greater deficits in executive and balance functions, compared with other components of function. A novelty of the current analysis is the observation that the extent of cerebellar volume shrinkage, which is related to the degree of balance problems, was also predictive of executive function deficits. Thus, it may be that the cerebellum, via brain circuitry, can exert a significant effect on functions of the prefrontal cortex."
Sullivan said she plans to challenge these initial findings with more tests of balance and sensorimotor integration, which typically require cerebellar functioning, and anticipatory responses, which typically require frontal lobe functioning, as well as more refined forms of brain imaging.
Part One: Alcohol Compounds Damage
