Antecedents, Consequences and Treatment of Drug Abuse: A Cognitive Science Perspective
Annual Meeting of the College on Problems of Drug Dependence
San Fransisco, CA
June 18, 2000
National Institute on Drug Abuse, Bethesda, MD
The prefrontal cortex and mesostriatal system has an important role in many cognitive functions such as planning, working memory, decision-making and forms of inhibition. The role of these functions in determining both the vulnerability to and consequences of drug abuse needs to be explored in detail. Furthermore, cognitive science and drug abuse research have converged over recent years to provide valuable and complimentary perspectives for understanding drug addiction. This symposium provided the CPDD community the opportunity to learn about exciting new advances in cognitive science and drug abuse research. The speakers for this symposium presented (1) an overview of the role of the prefrontal cortex in higher order cognitive function, (2) the effects of drugs of abuse on cognitive abilities related to prefrontal cortical function, (3) discussed the relationship between deficits in higher order cognitive function and increased risk for substance abuse disorders (4) and discussed the role of higher order cognitive functions in treatment interventions. This symposium served to inform the audience of the current and potential role of cognitive science in understanding the antecedents and consequences of drug abuse and its role in the development of prevention and treatment interventions.
EXPLORING THE SOCIAL AND EMOTIONAL FUNCTIONS OF FRONTAL CORTEX
University of Pennsylvania, Philadelphia, PA
The goal of this talk is to provide an overview of prefrontal function that reflects current thinking in cognitive neuroscience, and can serve as a context for the talks that follow. The talk began with the idea of a "frontal lobe syndrome," and the ways in which our understanding of prefrontal function has been refined through experimental research with patients and with neuroimaging of normal subjects. Although the abilities compromised by prefrontal damage have many commonalities, one to another, there does not seem to be a single element that distinguishes them, as a group, from functions not dependent on prefrontal cortex. Many, but not all, involve the ability to resist an easy, available or overlearned response. Many, but not all, involve the coordination of multiple elements of a complex task. Many, but not all, involve holding information about a stimulus or the task instructions in working memory for an interval of time. Finer grained analyses of PFC, aided by functional neuroimaging of normal subjects, has indicated some specialization within prefrontal cortex, with orbitomedial, dorsolateral, and anterior cingulated having at least partially distinct patterns of involvement with different tasks, but simple, principled relations between function and anatomy remain elusive. For example, while it is true that orbitomedial cortex is important for inhibition, the Wisconsin Card Sort test (which has been taken as a test of inhibition, in that the familiar just-used sorting criterion must be inhibited) is associated with dorsolateral cortex, and tasks that do not seem especially dependent on inhibition, such as weighing risks and benefits in a gambling situation are associated with orbitomedial cortex.
I then reviewed current theories of prefrontal function. Overall, these theories can be contrasted on the degree of unity versus modularity they hypothesize in prefrontal function. Variants of a central executive theory, including the Supervisory Attentional System of Shallice, attempt to explain a wide range of phenomena. Working memory theories may also attempt to account for many of the seemingly higher level impairments that follow frontal damage, by showing how working memory deficits can ramify through the system as it performs more complex tasks. Alternative approaches focus on one particular function, such as inhibition or, even more narrowly, the abilityto use "somatic markers" of bodily state in decision making.
IMPAIRED COGNITIVE FUNCTION ASSOCIATED WITH CHRONIC DRUG ABUSE: A COMPARISON OF AMPHETAMINE AND OPIATE ABUSERS
University of Oxford, Oxford, England
Chronic drug abuse may be associated with a wide range of neuropsychological deficits, some of which may reflect disrupted monoaminergic neuromodulation. In this talk, I reviewed some of our recent experimental work directly comparing the neurocognitive deficits of chronic amphetamine abusers and chronic opiate abusers, as well some complementary psychopharmacological studies that may indicate candidate neurochemical bases for some of these impairments. Specifically, our earlier studies found that chronic amphetamine abusers, but not chronic opiate abusers, were markedly impaired in the performance of a computerised decision-making task, previously shown to be selectively impaired by lesions of the orbital prefrontal cortex; and further, that this aspect of their altered cognitive profile can be modelled by reduced plasma tryptophan in normal control volunteers. More recently, we have found that chronic amphetamine abusers also show specific difficulties in the control of an attentional bias in a visual discrimination learning task believed to involve the functioning of the dorsolateral PFC. The implications of these results for our understanding of the underlying neurocognitive impairments in chronic drug abusers, and for further research and treatment development were discussed.
DOSE-RELATED COGNITIVE EFFECTS OF CHRONIC DRUG ABUSE
Johns Hopkins Bayview Medical Center, Baltimore, MD
This presentation examined the dose-related association between chronic cocaine use and neurobehavioral performance. A battery of neuropsychological tests was administered to 30, 4 week - abstinent chronic cocaine abusers and 21 non-drug using controls matched for age, education, and intelligence. After controlling for age, education, and intellectual ability, greater use of cocaine (grams per week) was associated with larger decrements on tests measuring executive functioning, visuoperception, psychomotor speed, and manual dexterity. Dose-related effects were found primarily on complex tasks of higher cortical functioning involving an integration of multiple cognitive abilities (i.e., attention/planning/ mental flexibility - executive functioning, psychomotor functioning). The neurobehavioral substrate associated with these behaviors is probably the prefrontal cortex. Dose-related effects were found on Trails B, the Wisconsin Card Sorting Task (WCST), and a match-to-sample reaction time test. Due to their high sensitivity these tests generally detect decrements related to neurologic dysfunction. The Trails B and WCST tasks both involve cognitive flexibility, but the WCST also involves the ability to use feedback to monitor and change behavior. The computer administered Repetition of Numbers Reaction Time Task requires the participant to respond when a number presented on the computer monitor is identical to the number preceding it (match-to-sample). The heaviest cocaine users showed slower median reaction times and made more errors of omission (true positive) and commission (false positive). False positive errors may reflect a tendency to be impulsive. Dose-related decrements were also found in attention/concentration. For example, heavier cocaine use was related to lower performance on the cancellation test for randomly placed symbols, a measure of attention and concentration. In addition, adverse associations were found between cocaine use and performance on a memory test that is sensitive to attentional problems (RAVLT Trial 1). These results suggest that chronic cocaine use is associated with persistent decrements in cognitive function that are most pronounced in heavy users. Knowledge of specific cognitive processing deficits in chronic cocaine abuse would be useful for designing individually tailored drug treatment programs.
EXECUTIVE COGNITIVE FUNCTION, ANTISOCIAL BEHAVIOR AND DRUG ABUSE
University of Kentucky, Lexington, KY
Low executive functioning has been found to be related to increased drug and alcohol use and an increased likelihood of developing a substance use disorder (SUD; including alcohol) (Giancola and Tarter 1999). Executive functioning can be defined as the planning, initiation, and self-regulation of goal-directed behavior. Our research has shown that pre-adolescent boys with a family history of an SUD show lower executive functioning compared with those with a negative family history of disorder (Giancola et al. 1996). It has also shown that female adolescents with an SUD show lower executive functioning compared with controls (Giancola et al. 1998). These data suggest that low executive functioning may be a risk factor for pathological drug abuse.
Other research we have conducted has indicated that low executive functioning is related to increased disruptive, delinquent, and violent forms of anti-social behavior in persons at high risk for an SUD (Giancola et al. 1996), those with an SUD (Giancola et al. 1998a), those with a conduct disorder (Giancola et al. 1998b), and in normal controls (Giancola and Zeichner 1994). Other than past drug use, it has also been found that antisocial behavior is one of the strongest predictors of drug use and an SUD diagnosis (Biederman et al. 1997; Wood et al. 1995). As such, it has been hypothesized that heightened antisocial behavior may serve as a functional mechanism between low executive functioning and increased drug use (Giancola and Tarter 1999).
A recent prospective study conducted at our research center using a sample of boys with and without a family history of an SUD found that low executive functioning at age 10 - 12 predicted antisocial behavior at age 14 which then predicted drug use at age 16 (Giancola and Parker 2000). There was no direct relation between executive functioning and drug use suggesting that antisocial behavior may be a necessary functional mechanism predisposing toward drug use.