Impulsivity Mgr et. Mgr Pavlína Hlavatá Brno FSS MU 5. 10. 2018 Syllabus  What is impulsivity?  Impulsivity in clinical context, motivation  Subtypes of impulsive behaviour  Impulsivity as a personal dimension  Behavioural models of impulsivity  Behavioural tasks  Neurobiology of impulsivity  Treatment What is impulsivity? What is impulsivity?  Heterogenous concept – consists of several dimensions?  A tendency to act without thinking  Acting without evaluation of consequences  Inability to suppress irrelevant or unfavourable behaviour  Impulsivity manifests in personality traits, cognitive and emotional processes or behaviour control  Personality traits: high sensation seeking, lack of perseverance, positive and negative urgency, high reward sensitivity Impulsivity in clinical context  Disruptive forms of behaviour  Aggressive behaviour, self-destructive behaviour, binge eating, suicide, drug abuse, alcoholism, gambling, risk sexual behaviour, property destruction  High negative impact on life  ADHD, borderline personality disorder, mania, substance use disorders, kleptomania, Parkinson disease, bulimia  Inhibitory control deficit present in the close relatives of patients - ? Inheritable Motivation for research • Impulsivity is present in many neuropsychiatric disorders, • Significant negative influence on patient‘s life, • No effective treatment, • Inconsistent terminology. • After subjective distress, impulsivity is the most common diagnostic criteria in the DSM-IV. → Prevention, prediction (addiction) – identification of the risk factors, → Treatment, → Improving the quality of life, → Better diagnostics, → Better description, improving of terminology,..  Impulsivity as a personality dimension  Impulsivity as a consequence of some neurobiological impairment Impulsivity as a personality dimension  Buss and Plomin (1975): temperament dimension (impulsivity, emotionality, activity, sociability ) – inhibitory control, decision time, persistence, sensation seeking  Eysenck – venturesomeness (aware risky behaviour)  Cloninger (1991) – impulsivity as an aspect of novelty seeking (terms related to thrill seeking and acting on feelings of the moment without regard for rules and regulations.)  Zuckerman (1991) – impulsive sensation seeking (a lack of planning and the tendency to act impulsively, experience seeking, or willingness to take risks for the sake of excitement or novel experiences) Impulsivity as a personality dimension  Measured by self-assessment questionnaires  Barrat scale (Patton, Stanford and Barrat, 1995) - 3 factors – attentional impulsiveness, motor impulsiveness, nonplanning impulsiveness  UPPS-P (Whiteside and Lynam, 2001, Cyders and Smith, 2007) – negative and positive urgency, lack of premeditation, lack of perseverance, sensation seeking - based on previous questionnaires and concepts - Includes aspect of emotional impulsivity Behavioural impulsivity models  Impulsivity as a consequence of abnormal functions of neural system  Measured by behavioural tasks  Motor impulsivity - waiting impulsivity - stopping impulsivity  Impulsive decision making  Nigg‘s taxonomy (2000)  Behavioural inhibition: prepotent response inhibition, interference control (distractibility) Behavioural impulsivity models Motor impulsivity  Ability to inhibit preplanned, dominant or unwanted action (waiting impulsivity).  Ability to stop ongoing action (Stopping impulsivity)  Measured by choice reaction time tasks  Tasks: Go/No-Go task, Stop signal task, Continuous performance task Impulsive decision making  …preference for smaller, more immediate rewards over larger, more delayed rewards  The value of delayed reward is discounted in inverse proportion to its delay.  Tasks: delay discounting, probability discounting, Iowa gambling task Interference control  …ability to ignore irrelevant information while processing the target stimulus.  In the interference control tasks, a person has to react quickly to the stimulus ignoring distractors presented at the same time.  Tasks: Stroop Color-Word test, Flanker task, Simon test, the Opposite World task,.. Behavioural impulsivity models Motor impulsivity (inhibitory control, response inhibition) Interference control Impulsive decision making Waiting impulsivity (action restraint) Stopping impulsivity (action cancellation) Impulsivity Behavioural inhibition Impulsivity tasks Go/No-Go task  Measures the ability to inhibit preplanned, dominant or unwanted action. Go stimulus – target → react No-Go stimulus – inhibition → don´t react Go: No-Go ratio 50:50 or less No-Go stimuli  Variables – reaction time, accuracy - commission errors, omission errors Slow reaction time + more commission errors - impulsivity vs. Fast RT + more omission errors – attention problems Continuous performance task  The GNG task with a predominance of No-Go stimuli – sustained attention Impulsivity tasks - Go/No-Go task  Simple GNG tasks  Complex GNG tasks (more types of No-Go stimuli, variable No–Go stimuli,..)  Modifications: Stimuli – letters, pictures, symbols,.. Emotional GNG tasks Impulsivity tasks - Go/No-Go task - Behavioural version low frequency of No-Go stimuli – high inhibitory load - fMRI – low cognitive load, low working memory demands - equal Go:No-Go ratio is better. Unequal Go:No-Go ratio makes interpretation difficult Impulsivity tasks Stop signal task  Ability to stop an ongoing action Go-stimulus No-Go signal (visual or acoustic) – after this signal Go stimulus turns to No-Go, subject has to cancel his reaction  Variables – SST reaction time – time needed to stop reaction Longer SSRT = inhibitory problems - accuracy, reaction time Impulsivity tasks - Stop signal task  Stop signal delay = delay between the onset of Go stimulus and the stop signal - Fixed or variable delay - Variable delay → high inhibitory load  Stop signal reaction time can not be measured directly  Estimated from reaction time and stop signal delay and probability of making error after the stop signal Impulsivity tasks Stroop Color-Word test  Variables - Interference score, number of items made in time, number of errors, time needed to complete condition  Variants – picture, wrapped words, emotional Impulsivity tasks Flanker task  Target stimulus – arrow pointing to the left or right  Incongruent stimuli  Congruent stimuli  Neutral stimuli  Variables – number of errors, reaction time Impulsivity tasks Simon task  Central fixation point  Target stimulus in some position from the central fixation point  React according to the type of stimulus, ignore the position of the stimulus Impulsivity tasks Delay discounting  Choice – two options – smaller immediate reward or bigger but delayed reward  How fast declines the worth of money in time?  As the delay of a reward increases, the subjective value of this delayed reward decreases. Impulsivity tasks - Delay discounting indifference points – subjective value for immediate and delayed reward is the same. value =A/(1 + k*D)  A is the amount of the reward, D is the delay to reward, and k is a free parameter (discounting parameter).  Larger values of k indicate steeper decline of subjective value (=steeper curve in graph) → greater impulsivity.  Variables – k, AUC (area under curve).  Impulsive = big k, small AUC Impulsivity tasks - Delay discounting  Variants: different time delays (days →decades), commodity (money, drugs, alcohol,..), immediate rewards decline (regular, random).  Value of money is more stable than other commodities  Good marker for addiction risk Impulsivity tasks Probability discounting task Immediate reward x bigger probabilistic reward As the probability of receiving a specific gain decreases, the subjective value of that gain decreases. The value of a probabilistic reward decreases as its probability decreases, so it becomes less likely that the probabilistic gain will be chosen from among alternatives Indifference points → k A lower degree of probability discounting (higher subjective values) is associated with risk-seeking choices. When the degree of discounting is steeper than the expected value, data points fall below the EV line. A higher degree of probability discounting (lower subjective values) → risk-averse choices. Probabilistic looses: Someone who is risk-seeking is more likely to choose the possibility of losing nothing, while taking the risk of possibly losing the entire larger amount, rather than incur a smaller, certain loss. Impulsivity tasks Iowa gambling task  4 decks of cards containing winning and loosing cards  Good decks and bad decks  IGT involves probabilistic learning via monetary rewards and punishments, where advantageous task performance requires subjects to forego potential large immediate rewards for small longer-term rewards to avoid larger losses. A – bad deck, high immediate rewards, frequent looses B – bad deck, high immediate rewards, infrequent but very high looses C – good deck, small immediate rewards, frequent but low looses D – good deck, small immediate rewards, infrequent looses Impulsivity tasks – Iowa gambling task  Impulsive people prefer large immediate rewards with risk of large looses in the future  or prefer low probable but large looses over certain but small looses.  Brain activity – ventromedial prefrontal cortex, orbitofrontal cortex dysfunctions Neural substrates of impulsivity Neurotransmitter systems  Dopaminergic, serotoninergic and noradrenergic systems  Specific reactions during tasks – for example gamblers dopamine IGT Treatment Bari and Robbins (2013):  Prefrontal noradrenergic neurotransmission – important for stopping impulsivity  Dopamine – motor readiness for inhibition and activation in striatum  Norepinephrine and dopamine – error monitoring  5HT – more affective forms of inhibition and waiting inhibition Treatment  SSRI (Lieb et al., 2010)  Mood stabilizers (Huband et al., 2010)  Olanzapine (Lieb et al., 2010), quetiapine 5HT2A receptor (Van de Eynde et al., 2008), aripiprazole and lamotrigine (Lieb at al., 2010).  ADHD – stimulants (Moeller et al., 2010)  Mechanism is not well understood yet.  Different drugs improve performance in different impulsivity tasks.  Different groups of patients/patients have problems in different tasks. Brain structures involved in inhibition  ACC, insula, preSMA, SMA, pre-motor cortex, parietal cortex, inferior frontal gyrus, subcortical structures  Most important – prefrontal and pre-motor areas Brain structures involved in ihibition  Inferior frontal gyrus (IGG) – most important for response inhibition  Pre-motor region – controls motor excitability  SMA – stopping response, more active in people with fast SSRT – response initiation, selection  Parietal cortex – visuospatial attention?  DLPFC – working memory, task rules maintaining, executive control in motivational and emotional behaviours  ACC – response selection, conflict monitoring, error detection, working memory Brain structures involved in inhibition  Subcortical structures: Thalamus, Basal ganglia  Fronto-striatal network – indirect pathway - Proactive inhibition, selective inhibition  Hyperdirect pathway Cortical regions (stop command) → basal ganglia pre-SMA and inferior frontal gyrus– subthalamic nucleus (STN)Globus pallidus - Fast inhibition of ongoing actions a) Aron et al. 2007, b) Poldrack et al. 2011 Selective x non-selective inhibition in fMRI Is inhibitory activity present in GNG task selective (present only when NoGo stimlus appears)? Vs. Is inhibition context-dependent and present during the whole GNG condition (after red cross)? Control condition – after green cross – only Go stimulus follows Go/No-Go condition – after red cross can appear both Go and No-Go stimulus No inhibition Inhibition after both stimuli Albares et al. 2014 Thank you for your attention Literature  Bari A, Robbins T. 2013. Inhibition and impulsivity: behavioral and neural basis of response control. Prog Neurobiol. 108:44-79.  Brevers, D., Bechara, A., Cleeremans, A., & Noël, X. 2013. Iowa Gambling Task (IGT): twenty years after–gambling disorder and IGT. Frontiers in psychology. 4, 665.  MacKillop, J., Amlung, M. T., Few, L. R., Ray, L. A., Sweet, L. H., & Munafò, M. R. 2011. Delayed reward discounting and addictive behavior: a metaanalysis. Psychopharmacology. 216(3): 305-321.  Nieuwenhuis S, Yeung N, Van Den Wildenberg W, et al. 2003. Electrophysiological correlates of anterior cingulate function in a go/no-go task: effects of response conflict and trial type frequency. Cogn Affect Behav Neurosci. 3(1): 17-26.  Stahl C, Voss A, Schmitz F, et al. 2014. Behavioral components of impulsivity. J Exp Psychol Gen. 143(2): 850.