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 2004 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."
Function, Memory AffectedFor 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 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."
Brain Processes Different for Alcoholics"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."
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.