KEIO , Japan, Aug. 28 (UPI) -- A researcher in Japan warned that alcoholism can reduce brain functionality, even when there seems to be no apparent structural damage.

Dr. Motoichiro Kato of Keio University in Japan found activation in key areas of the brain lower in recovering alcoholics than among non-alcoholics even when there was no sign of structural brain damage.

The researchers used functional magnetic resonance imaging to find localized changes in brain function of two groups of subjects given a word-matching exercise. One group was made up of alcoholics whose onset ages were less than 30 years of age and who were abstinent for an average of 40 months. The other group was community-based control subjects matched on age and education.

Results show that long-term memory retrieval induced by the task led to lower brain activity in the prefrontal lobes, anterior cingulate cortex, thalamus and ventral striatum of the alcoholics than in the controls, reported the study published in Alcoholism: Clinical & Experimental Research.

"We call this phenomenon 'latent lesions'or 'subclinical pathology,'" Kato said in a statement. "Latent lesions may occur without apparent cognitive impairments, so that people continue drinking alcohol without noticing damage to their brain."