Part 1

This excellent review (1) covers many of the brain regions we have discussed as being implicated in all the addictive behaviours.

We have previously suggested also  that these brain regions are connected in impaired  decision making deficits and that these deficits in decision making are prompted by an impaired ability to process emotion. In fact this Literary Review does mention briefly the role of emotion  in decision making .

This is a very good review of how maladaptive decision making is common to all addictive behaviours, substance and behaviour addictions and may need to be considered part of the pathomechanism of these disorders?

This blog will be in three parts. First the components of decision making and how they may be impaired in substance addiction before, in parts 2 and 3, looking at decision making deficits in a variety of behavioural addictions.

“We reviewed the cognitive and neurobiological commonalities between chemical and behavioral addictions. Poor impulse control, limited executive function and abnormalities in reward processing are seen in both group of entities. Brain imaging shows consistent abnormalities in frontoparietal regions and the limbic system. In drug addiction, exaggerated risk taking behavior and temporal discounting may reflect an imbalance between a hyperactive mesolimbic and hypoactive executive systems. Several cognitive distortions are found in pathological gambling that seems to harness the brain reward system that has evolved to face situations related to skill…Abnormalities in risk assessment and impulsivity are found in variety of eating disorders, in particularly related to eating behavior. Corresponding findings in eating disorder patients include abnormalities in the limbic system, i.e. orbitofrontal cortex (OFC), striatum and insula.

Similarly, internet addiction disorder is associated with risky decision making and increased choice impulsivity with corresponding discrepant activation in the dorsolateral prefrontal cortex, OFC, anterior cingulate cortex, caudate and insula. Sexual addictions are in turn associated with exaggerated impulsive choice and suggestive evidence of abnormalities in reward processing. In sum, exploration of executive function and decision making abnormalities in chemical and behavioral addictions may increase understanding in their psychopathology and yield valuable targets for therapeutic interventions.”

…Behavioral addictions which include but are not limited to pathological gambling, internet addiction, sexual addiction, pathological buying, compulsive eating resemble chemical addictions in many domains: natural history, phenomenology, tolerance, craving, comorbidity, overlapping genetic contribution, and neurobiological mechanisms [7-9]. For instance, Griffith using a biopsychosocial model posited that both chemical and behavioral addictions consist of a number of distinct common components, i.e. salience, mood modification, tolerance, withdrawal, conflict and relapse [10]. Behavioral addictions also may share some core features with impulse control disorders. However, the heavier impact on the lives of the patients with substance use disorder (SUD) or behavioral addictions is blatantly related to pervasively making poor decisions.

These decisions revolve around being continuously engaged in self-harming behaviors despite ongoing negative consequences. Poor decision making compounded with mental illness enhances the existing potential for bad outcomes. Thus, addressing impaired decision making processes might provide a valuable strategy to improve health indicators and quality of life in many patients. Here, we will review how concepts used to characterize decision making and their known neural underpinnings may provide a practical approach to understanding the psychopathology and generation of therapeutic alternatives for substance abuse disorders and behavioral addictive disorders.

PubMed database searching was used to extract articles for our review. The search was conducted using the terms: “addiction”, “decision making”, “cognitive control”, “reward”, “temporal discounting”, “behavioral addictions”.

DECISION MAKING CONCEPTS AND BRAIN IMAGING

Decision making is a complex multidimensional process involving motivation and drive, giving subjective value to different options, identifying and choosing alternatives based on the values and preferences, assessing consequences of our choices, taking risk, and seeking reward. A recent model by Redish et al. of the genesis of decision making posits that decisions represent the outcome of three interacting systems: planning, habit, and a situation-recognition systems.

Furthermore, challenges or vulnerabilities to these systems are proposed to be associated with the natural course of addiction and to provide potential for therapeutic intervention [11]. Several brain structures, including dorsolateral prefrontal cortex (DLPFC), anterior cingulate cortex (ACC), ventromedial prefrontal cortex (VMPFC), ventral striatum, amygdala and insula are involved in decision making process.

Cognitive Control

Cognitive control is essential to the ability to flexibly direct our behavior in response to constantly changing environment and tasks and includes but is not limited to: working memory, response inhibition, conflict monitoring, error detection, and task-switching…a distinct functional-anatomical network associated with cognitive control – DLPFC and ACC [12]. This finding supports the conclusion that the rostral ACC plays an essential role in flexibility, shifting between cognitive tasks and response sets, whereas lateral structures in the DLPFC are essential when competing responses need to be inhibited [13, 14]…

…examples of the clinical relevance of cognitive control deficits in addiction disorders are poor impulse control and error monitoring that are associated with relapse and inability to stop addictive behaviors [17].

Reward and Value

We direct our actions to satisfy our needs, based on assessments of the immediate environment. In the psychological and psychoanalysis literature this has been described as motivation and drive [18]…

Schultz et al. showed increased phasic responses in the ventral tegmental area dopaminergic neurons in primates when presented with an unexpected pleasurable stimuli …Thus, dopamine neurons seem to encode the likelihood of a rewarding outcome and its continuous update (prediction error). Dopamine is therefore believed to provide a teaching signal to parts of the brain responsible for acquiring new behaviors. Neuroimaging experiments have identified dopaminergic regions, the OFC and striatum, mainly its ventral portion, as sites active during reward processing [21]…

… the striatum and the VMPFC…constitute the brain reward valuation system…the anterior mPFC and posterior cingulate cortex (PCC) also intervene in the computation of expected value [24, 31, 32]…The ventral striatum is also active in response to reward anticipation [35] and saliency [36]…

Emotions and Feedback

…the Somatic Marker Hypothesis proposes that emotions play a critical role in the ability to make fast, rational decisions in complex and uncertain situations [38]. The term “somatic“ refers to associations between reinforcing stimuli that induce an associated physiological affective state. As it postulated by Damasio: emotions, are changes in both body and brain states in response to different stimuli. Physiological changes (e.g., muscle tone, heart rate, endocrine release, posture, facial expression, etc.) occur in the body and are relayed to the brain where they are transformed into an emotion that tells the individual something about the stimulus encountered. Over time, emotions and their corresponding bodily change(s) become associated with particular situations and their past outcomes. When making decisions, these physiological signals (or ‘somatic markers’) and their evoked emotion are consciously or unconsciously associated with their past outcomes and bias decision-making towards certain behaviors while avoiding others.

Both the VMPC and amygdala are critical to triggering somatic states, except amygdala is responsible for processing events that occurs in the immediate environment, where VMPC triggers somatic states from memories, knowledge and cognition. A major source of supporting evidence for this theory was provided by experiments using the Iowa Gambling Task: a computerized task, assessing decision making under ambiguous conditions [39]. In this task individuals are challenged with four decks of cards, each with a different potential payoff, to maximize their monetary gain. Performing well on this task requires particularly learning from feedback.

Temporal discounting

…Temporal discounting refers to the decrease in the subjective value of a commodity as a function of its amount and the delay to receive it [40]. For instance, if someone would prefer $10 now, instead of $100 in one month, it could be said that the temporally distant $100 are discounted to an immediate lesser value of $10. This phenomenon is found in humans, primates, rodents and even pigeons.

…Temporal discounting can be studied in the laboratory, by systematically adjusting choices of how much of a reward now is comparable to a full reward in some point in the future.

Temporal or delay discounting is an operational measure of delayed gratification and has been equated to impulsivity. Mischel and collaborators explored this extensively in the 1970s. In a hallmark experiment, preschool children were offered the choice of one treat (cookie or candy) immediately, or to wait several minutes for two treats. This task was remarkably predictive of children’s future life achievements. including higher cognitive and academic performance and more stable emotional regulation [42].

Later follow up showed that the ability to wait as a preschooler predicted less risk for crack cocaine use [43]. This capacity to delay gratification has been associated with effective self-regulation through the use of abstract rather than consummatory strategies, as well as the use of attention shifting. Temporal discounting is the outcome of opposing trends. On one hand, an instinctive response of craving immediate satisfaction of desires or needs, is linked to activation of VMPFC and subcortical structures, mainly the ventral striatum [44-47]. On the other hand, executive function (i.e. reasoning and planning) is associated with the activity of the right DLPFC and posterior parietal cortex [44]. Activity in the mPFC, ventral striatum and PCC is directly proportional to a reward magnitude, but inversely to the delay in time in which it is expected [48]. Processing of risk element in temporal decision making seems to be associated with activation in DLPFC and posterior parietal cortex, whereas temporal computation is linked to activation of the PCC and the striatum [49, 50]. These results suggest that cognitive processing of temporal discounting needs to integrate an element of risk and visualization of the future.

DRUG ADDICTION

Drug addiction is characterized by loss of control and compulsive drug use, despite obvious detrimental consequences [51]. It involves repeated exposure to drugs over time, which induces permanent changes in the brain that increase the risk of relapse even after many drug-free years. It has been proposed that drug abuse may involve ‘‘hijacking’’ of normal learning processes in the mesocorticolimbic system. This system has evolved as part of a motivational system that regulates responses to natural reinforcers and is not equipped to handle the overwhelming stimulation associated with drugs of abuse [52]. Accruing evidence also supports involvement of two cognitive processes in drug abuse: temporal discounting and risk taking behavior. Both depend on the balance between executive function (DLPFC and posterior parietal cortex) and the instinctual reward valuation system (VMPFC and ventral striatum).

It is likely that this balance might be broken in drug addiction due to abnormal PFC function, namely DLPFC and VMPFC. Proneness to risk taking behavior in drug addiction is linked to abnormalities in the frontoparietal circuitry. Behavior of patients with drug abuse resembles that of patients with lesions in the VMPFC in their poor performance in risk taking and temporal discounting tasks [53]. Drug dependent individuals often prefer riskier less yielding options, which correlates with PFC alterations, specifically, VMPFC overactivation and decreased right DLPFC activation [54-59].

In 2005 Bechara proposed that drug addiction is the product of an imbalance between two opposing neural systems that control decision making: an impulsive, amygdala based system, and a reflective, PFC system [39]. To support this idea author referred to the similarities in behavior between individuals with VMPC damage and drug addicts: unawareness of the problem, being oblivious to the consequences of their actions, making choices that would eventually lead to financial and personal losses. In terms of implications for treatment and prognosis, Bechara proposed dividing addicted individuals based on their physiological responses as match or no match to VMPC patients, where addicts who match VMPC patients display insensitivity to future consequences, are guided by immediate prospects and have a harder time recovering from addiction and abstaining.

Furthermore, one of the most influential models of drug addiction, the somatic marker hypothesis proposes that decision-making depends on neural substrates that regulate homeostasis, emotion and feeling. One of the central issues in drug addiction would be a disruption of emotional influence on decision making processes with underlying abnormalities in the limbic system leading to hyperactivity of the amygdala and PFC hypoactivity [60]. This line of thought is closely related to a role of intertemporal choice in addiction.

The ability to delay gratification of needs has been shown to be the outcome of a cognitive control (DLPFC and posterior parietal cortex) and limbic systems [44]. Moreover, a consistent finding in dependence to several substances (i.e. opioids, cocaine, amphetamine, nicotine and alcohol) is exaggerated impulsive choice seen as exaggerated temporal discounting [61-64]. This means drug addiction is associated with a tendency to prefer smaller rewards here and now. Neuroimaging experiments with methamphetamine [61, 62] and alcohol abusers [63] have shown an unbalance between limbic and the frontoparietal systems.

Temporal discounting and executive function abnormalities are found in addiction to several substances [66-68]. Further, working memory training in stimulant users normalized temporal discounting alterations [66]. This finding is quite promising because it sets the groundwork to test whether executive function training may be a viable therapeutic target for drug addiction [69]. Moreover, distinct findings in cocaine users show more frequent self-serving behavior in the distribution and Dictator games in addition of temporal discounting and risky choice abnormalities [70]. On the Game of Dice Task, a gambling task with explicit rules for gains and losses and fix winning probabilities, patients with opioid dependence showed lower executive functioning and chose the risky alternatives more frequently than the healthy controls [71].”

Tomorrow in Part 2 we look at decision making and their correlation to neural correlates (brain mechanisms) in behaviour addictions.

Reference

1. Engel, A., & Cáceda, R. (2015). Can Decision Making Research Provide a Better Understanding of Chemical and Behavioral Addictions?. Current drug abuse reviews, 8(2), 75-85.