Alcoholics can have deficits in visuoperception and frontal executive function despite sobriety

November 14, 2004

Detoxified alcoholics often have visuospatial and visuoperceptual deficits, characterized by difficulties completing tasks such as putting pieces of a puzzle together or map reading. A new study has found that, even with prolonged sobriety, alcoholics show deficits in visuoperception and frontal executive functioning of the brain. Furthermore, alcoholics utilize a more complex higher-order cognitive system, frontal executive functions, to perform the same tasks as individuals without a history of alcoholism. Results are published in the November issue of Alcoholism: Clinical & Experimental Research.

"Alcoholics often show impairment in visuospatial and visuoperceptual tasks such as copying a complex geometric figure or reading a map," said Edith Sullivan, a professor in the department of psychiatry and behavioral sciences at Stanford University School of Medicine. "These deficits can impair everyday living, in that individuals with visuospatial or visuoperceptual deficits may be unable to accurately assess distance and spatial relations between objects, which could lead, for example, to driving problems."

"Because Western society is largely verbal as opposed to visual-spatial, much emphasis is placed on verbal processes," added Sara Jo Nixon, professor and director of the Neurocognitive Laboratory at the University of Kentucky. "Yet, visual-spatial processes contribute in very significant ways to virtually every aspect of daily life. The capacity to efficiently use visual-spatial cues, detect changes and consistencies, and acquire subtle visual discriminations is fundamental to negotiating a car down a crowded street, a cart through a grocery store, and identifying your child from among a host of similarly clad children on a playground."

For this study, researchers examined visuoperception and perceptual learning with a picture-fragment identification task in 51 recently detoxified nonamnesic alcoholic men (ages 29 to 66 years) compared with 63 "normal," control men (ages 21 to 70 years). Executive function and explicit declarative memory were also assessed.

"The picture fragment task allows us to assess how quickly an individual can identify line drawings of common objects or animals when only partially visible," explained Sullivan. "Individuals with visuoperceptual impairments require a more complete rendition of these drawings before they are able to identify them. Unaffected individuals - that is, controls - are able to invoke a process referred to as 'perceptual closure,' meaning the ability to imagine or fill in parts of the picture that are not actually drawn. The learning component comes into play when these drawings are shown to the subject again after a delay. If after an initial exposure to the test items the subject is able to identify the object or animal in a more fragmented rendition, learning occurred."

Explicit declarative memory, Sullivan added, is memory of factual information that can be recalled by an individual upon command, such as historical information. This is different from implicit memory, which is memory for information without necessarily having conscious awareness of having learned it.

"This study shows that, even with prolonged sobriety, alcoholics show deficits in visuoperception and frontal executive function," said Sullivan. "Furthermore, although alcoholics were able to perform a visuoperceptual learning task at the level of controls, how they performed the task was very different from the way controls performed the task. That is, the underlying component processes used to execute this task were different. Unable to invoke normal visuoperceptual abilities, alcoholics relied on a more complex cognitive system to perform the visuoperceptual learning task than required by controls. The potential problem with this is that if that same system - frontal executive functions - is needed for a competing task, alcoholics may be at a disadvantage because that system would otherwise be engaged, for example, driving, or work-related demands that require sequencing, judgment, decision making, complex tasks requiring organization, planning, and visuospatial information, like dentistry, or using heavy machinery in construction."

"To me the findings suggest that alcoholics will simply have to exert more cognitive energy to complete tasks," said Nixon. "The long-term cost of this expenditure might be seen in any or all of several ways, such as chronic fatigue, lack of vigilance, and distractibility."

Alcoholics, especially older ones, exhibit another difference from controls in terms of memory strategy invoked when performing the incomplete figures task after a day's delay. Controls can enhance visuoperceptual learning (that is, improve identification of incomplete figures) with parallel information recalled from the declarative memory system (that is, the name of the identity of figures). Even though the declarative memory system is intact in nonamnesic alcoholics, they do not appear to take advantage of that information to aid the perceptual memory recall process.

Sullivan and her colleagues plan to continue with their research. "We are currently examining visuoperception and visuoperceptual learning among individuals with alcoholism-related amnesic Korsakoff syndrome," said Sullivan. (Korsakoff's psychosis is characterized by the inability of an individual to retain new information, such as remembering people recently met.)
Alcoholism: Clinical & Experimental Research (ACER) is the official journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism. Co-authors of the ACER paper, "Perceptual learning in detoxified alcoholic men: contributions from explicit memory, executive function, and age," were Rosemary Fama of the Neuroscience Program at SRI International in Menlo Park, California; and Adolf Pfefferbaum of the Neuroscience Program at SRI International as well as the Department of Psychiatry and Behavioral Sciences and Neuroscience Program at Stanford University School of Medicine. The study was funded by the National Institute on Alcohol Abuse and Alcoholism.

Alcoholism: Clinical & Experimental Research

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