Courtney L. Brown

Behavioral economic analysis of withdrawal- and cue-elicited craving for tobacco: an initial investigation.

INTRODUCTION The role of craving in nicotine dependence remains controversial and may be a function of measurement challenges. The current study used behavioral economic approach to test the hypotheses that subjective craving from acute withdrawal and exposure to tobacco cues dynamically increases the relative value of cigarettes. METHODS Using a 2 (1-hr/12-hr deprivation) × 2 (neutral/tobacco cues) within-subjects design, 33 nicotine dependent adults completed 2 laboratory sessions. Assessment included subjective craving and behavioral economic indices of cigarette demand, namely Intensity (i.e., cigarette consumption at zero cost), O(max) (i.e., maximum total expenditure), Breakpoint (i.e., highest acceptable price for cigarettes), P(max) (i.e., price at which consumption becomes sensitive to price), and elasticity (i.e., price sensitivity). Behavioral economic indices were generated using a Cigarette Purchase Task in which participants selected between cigarettes for a subsequent 2-hr self-administration period and money. RESULTS Main effects of deprivation and tobacco cues were present for subjective craving and multiple behavioral economic indices of cigarette demand. Interestingly, deprivation significantly increased Breakpoint (p ≤ .01) and P(max) (p ≤ .05) and had trend-level effects on Intensity and O(max) (p ≤ .10); whereas cues significantly reduced elasticity (p ≤ .01), reflecting lower sensitivity to increasing prices. Heterogeneous associations were evident among the motivational variables but with aggregations suggesting variably overlapping motivational channels. CONCLUSIONS These findings further support a behavioral economic approach to craving and a multidimensional conception of acute motivation for addictive drugs. Methodological considerations, including potential order effects, and the need for further refinement of these findings are discussed.

Dissociable brain signatures of choice conflict and immediate reward preferences in alcohol use disorders.

Impulsive delayed reward discounting (DRD) is an important behavioral process in alcohol use disorders (AUDs), reflecting incapacity to delay gratification. Recent work in neuroeconomics has begun to unravel the neural mechanisms supporting DRD, but applications of neuroeconomics in relation to AUDs have been limited. This study examined the neural mechanisms of DRD preferences in AUDs, with emphasis on dissociating activation patterns based on DRD choice type and level of cognitive conflict. Heavy drinking adult men with (n = 13) and without (n = 12) a diagnosis of an AUD completed a monetary DRD task during a functional magnetic resonance imaging scan. Participant responses were coded based on choice type (impulsive versus restrained) and level of cognitive conflict (easy versus hard). AUD+ participants exhibited significantly more impulsive DRD decision‐making. Significant activation during DRD was found in several decision‐making regions, including dorsolateral prefrontal cortex (DLPFC), insula, posterior parietal cortex (PPC), and posterior cingulate. An axis of cognitive conflict was also observed, with hard choices associated with anterior cingulate cortex and easy choices associated with activation in supplementary motor area. AUD+ individuals exhibited significant hyperactivity in regions associated with cognitive control (DLPFC) and prospective thought (PPC) and exhibited less task‐related deactivation of areas associated with the brains default network during DRD decisions. This study provides further clarification of the brain systems supporting DRD in general and in relation to AUDs.

The neuroeconomics of alcohol demand: An initial investigation of the neural correlates of alcohol cost-benefit decision making in heavy drinking men

Neuroeconomics integrates concepts and methods from psychology, economics, and cognitive neuroscience to understand how the brain makes decisions. In economics, demand refers to the relationship between a commodity’s consumption and its cost, and, in behavioral studies, high alcohol demand has been consistently associated with greater alcohol misuse. Relatively little is known about how the brain processes demand decision making, and the current study is an initial investigation of the neural correlates of alcohol demand among heavy drinkers. Using an event-related functional magnetic resonance imaging (fMRI) paradigm, participants (N=24) selected how much they would drink under varying levels of price. These choices determined access to alcohol during a subsequent bar laboratory self-administration period. During decisions to drink in general, greater activity was present in multiple distinct subunits of the prefrontal and parietal cortices. In contrast, during decisions to drink that were demonstrably affected by the cost of alcohol, significantly greater activation was evident in frontostriatal regions, suggesting an active interplay between cognitive deliberation and subjective reward value. These choices were also characterized by significant deactivation in default mode network regions, suggesting suppression resulting from greater cognitive load. Across choice types, the anterior insula was notably recruited in diverse roles, further implicating the importance of interoceptive processing in decision-making behavior. These findings reveal the neural signatures subserving alcohol cost–benefit decision making, providing a foundation for future clinical applications of this paradigm and extending this approach to understanding the neural correlates of demand for other addictive commodities.

Activities of Daily Living Are Associated With Older Adult Cognitive Status: Caregiver Versus Self-Reports

We compared the extent to which subjective report of activities of daily living (ADLs) by caregivers and older adults were associated with objective measures of older adults’ cognition. In independent studies (Study 1 N = 238; Study 2 N = 295), bivariate correlations and multiple regression analyses examined the association of caregiver and self-rated reports of older adult basic, instrumental, and total ADLs and older adult cognition. We examined the magnitude of the caregiver/self-report discrepancy and older adult cognition. In both studies, caregiver reports more accurately accounted for older adult cognitive differences. Older adult visuospatial/constructional deficits were uniquely related to caregiver basic ADL reports. Results indicate that caregiver reports of older adult ADLs are more reliable indicators of older adult cognition than self-reports, and this difference grows as older adult cognition decreases. Thus, older adult ADL assessment may be useful in providing information on potential cognitive decline.

Functional Impairment in Mild Cognitive Impairment Evidenced Using Performance-Based Measurement:

Older adults (OAs) with mild cognitive impairment (MCI) are traditionally thought to have preservation of activities of daily living (ADLs). However, recent evidence suggests OAs with MCI may have difficulty completing ADLs and specifically instrumental ADLs (IADLs). The ADLs are frequently evaluated through self- or collateral report questionnaires, while performance-based measures are infrequently utilized, despite the decreased bias and increased accuracy and sensitivity associated with these instruments. This investigation compared ADLs between community-dwelling OAs with (n = 20) and without MCI (n = 30) using a self-report questionnaire (Older American Resources and Services Activities of Daily Living Scale; OARS), a collateral report questionnaire (OARS), and a performance-based measure (the Direct Assessment of Functional Status–Revised). Consistent with our hypothesis, OAs with MCI had decreased ADLs and IADLs on the performance-based measure compared to cognitively intact OAs, while there were no differences in ADLs or IADLs on self-report questionnaires or collateral report questionnaires. Our results suggest OAs with MCI have decreased ability to complete IADLs. However, this investigation suggests these deficits may not be detected by questionnaires and are more likely to be found with performance-based testing.

Lateral temporal hyper-activation as a novel biomarker of mild cognitive impairment.

Memory dysfunction in mild cognitive impairment (MCI) due to Alzheimers pathology is primarily associated with episodic memory deficits linked to deterioration of the medial temporal lobes (MTLs). Currently, there is a call to discover novel biomarkers of MCI in order to improve research criteria. Functional activation differences in MCI during episodic memory-task performance are often evidenced in the MTLs, and frontal and parietal lobes, but it has been suggested that examination of working memory (WM) differences may be more useful in detecting MCI. In the current study, MCI and control participants performed a complex WM span (CWMS) task while functional magnetic resonance imaging (fMRI) data were acquired. Results indicated hyper-activation of the lateral temporal lobes, MTLs, and frontal and parietal regions during encoding and maintenance, and hyper-activation of the lateral temporal, frontal, and parietal lobes during CWMS recall for the MCI participants. Medial and lateral temporal differences during encoding and maintenance are consistent with previous findings, but lateral temporal differences are often not elaborated upon. Hyper-activation of the lateral temporal lobes during WM encoding and maintenance, and also during recall, suggests that this region may provide valuable information regarding WM impairment in MCI and Alzheimers. Given that whole-brain functional imaging of the MTLs is often limited due to artifact and partial voluming of sub-fields, examination of lateral temporal differences may provide a novel biomarker related to WM impairment in MCI.

Openness to experience is related to better memory ability in older adults with questionable dementia

The personality traits Openness to experience and Neuroticism of the five-factor model have previously been associated with memory performance in nondemented older adults, but this relationship has not been investigated in samples with memory impairment. Our examination of 50 community-dwelling older adults (29 cognitively intact; 21 with questionable dementia as determined by the Clinical Dementia Rating Scale) showed that demographic variables (age, years of education, gender, and estimated premorbid IQ) and current depressive symptoms explained a significant amount of variance of Repeatable Battery of Neuropsychological Status Delayed Memory (adjusted R 2 = 0.23). After controlling for these variables, a measure of global cognitive status further explained a significant portion of variance in memory performance (ΔR2  = 0.13; adjusted R 2 = 0.36; p < .01). Finally, adding Openness to this hierarchical linear regression model explained a significant additional portion of variance (ΔR2  = 0.08; adjusted R 2 = 0.44; p < .01) but adding Neuroticism did not explain any additional variance. This significant relationship between Openness and better memory performance above and beyond ones cognitive status and demographic variables may suggest that a lifelong pattern of involvement in new cognitive activities could be preserved in old age or protect from memory decline. This study suggests that personality may be a powerful predictor of memory ability and clinically useful in this heterogeneous population.

Clarifying the neural basis for incentive salience of tobacco cues in smokers.

In functional magnetic resonance imaging (fMRI) studies, smoking cues have been found to elicit increases in brain activity in regions associated with processing rewarding and emotional stimuli. However, most smoking cue studies to date have reported effects relative to neutral control stimuli with no incentive properties, making it unclear whether the observed activation pertains to value in general or the value of cigarettes in particular. The current fMRI study sought to clarify the neural activity reflecting tobacco-specific incentive value versus domain-general incentive value by examining smoking cues, neutral cues, and a third set of cues, monetary cues, which served as an active control condition. Participants were 42 male daily smokers. Compared to neutral cues, significantly greater activation was found in the left ventral striatum in response to tobacco and money cues. Monetary cues also elicited significantly increased activation in the right inferior frontal gyrus and cuneus compared to the other two cue types. Overall, the results suggest that the salience of monetary cues was the highest and, as a result, might have reduced the incentive salience of tobacco cues.

Minimal functional brain differences between older adults with and without mild cognitive impairment during the stroop

ABSTRACT This investigation compared the neural correlates of inhibition in normal older adults (OAs) and OAs with mild cognitive impairment (MCI). It was hypothesized the MCI group would require a greater amount of resources for inhibition, and therefore display greater functional activation in specific regions of interest (ROIs). Twenty-six OAs without and 17 with MCI completed the Stroop task during functional neuroimaging, and completed additional out-of-scanner neuropsychological measures. During inhibition, there were minimal functional Magnetic Resonance Imaging (fMRI) differences found between groups in a priori specified ROIs and with post-hoc multiple regression analyses. However, these minimal differences did not survive corrected thresholds. Robust differences were found with several tasks of a neuropsychological screening battery. The results of this study suggest only very minimal group differences in fMRI activation during inhibition which may not reliably identify MCI, and this condition may be best detected by traditional neuropsychological techniques.

The Neuroeconomics of Tobacco Demand: An Initial Investigation of the Neural Correlates of Cigarette Cost-Benefit Decision Making in Male Smokers

How the brain processes cigarette cost-benefit decision making remains largely unknown. Using functional magnetic resonance imaging (fMRI), this study investigated the neural correlates of decisions for cigarettes (0–10 cigarettes) at varying levels of price during a Cigarette Purchase Task (CPT) in male regular smokers (N = 35). Differential neural activity was examined between choices classified as inelastic, elastic, and suppressed demand, operationalized as consumption unaffected by cost, partially suppressed by cost, and entirely suppressed by cost, respectively. Decisions reflecting elastic demand, putatively the most effortful decisions, elicited greater activation in regions associated with inhibition and planning (e.g., middle frontal gyrus and inferior frontal gyrus), craving and interoceptive processing (anterior insula), and conflict monitoring (e.g., anterior cingulate cortex). Exploratory examination in a harmonized dataset of both cigarette and alcohol demand (N = 59) suggested common neural activation patterns across commodities, particularly in the anterior insula, caudate, anterior cingulate, medial frontal gyrus, and dorsolateral prefrontal cortex. Collectively, these findings provide initial validation of a CPT fMRI paradigm; reveal the interplay of brain regions associated with executive functioning, incentive salience, and interoceptive processing in cigarette decision making; and add to the literature implicating the insula as a key brain region in addiction.