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ADHD (Chacko et al. (2014) (RCT of Cogged working memory training in…

- - - - Parent + teacher questionnaire ratings of everyday behaviour
      - Parent/teacher interview
      - School and clinical observations
    - - Castellanos et al (2005)
      - Reliance on multiple observations, rather than merely performance on a task
  - - - Ritalin blocks DA and epinephrine reabsorption and improves ADHD symptoms
      - Evidence also from molecular
      - Increased activity of DA transporters in key brain areas in ADHD
  - - - 316 kids; medicated and combined groups perform better on cognitive tests of attention
      - Medicated groups regress to other groups 10 months and 2 years post-treatmeat
- - - - Difficulty following instructions
      - Often appear "spaced out", easily confused, lethargic
      - Difficulty processing information quickly - will make frequent mistakes with work
      - Inattentive, problems keeping mind on one topic, distracted by irrelevant sights and sounds
    - - May blurt out things, including improper comments
      - Display emotions without restraint
      - Fidget and squirm while seated
      - Struggle to stay sitting in class
      - Will often prefer to do things that have small but immediate payoff than what for large payoff
      - Always "on the go", constantly moving and talking
- - - - Garon et al (2008) - EFs are adaptive, goal-directed behaviours that enable individuals to override more automatic or established thoughts and responses
      - Refs are strongly associated with the PFC
      - EF = three separable components (Miyake et al, 2000)
        
        Working memory
        
        Inhibition
        
        Ability to override or suppress automatic, dominant, or prepotent (previously reinforced) responses that would otherwise interfere w/ the efficient attainment of a goal, Christ et al (2007)
        
        Stop-Signal Task
        
        Primary task = speeded visual choice
        
        Use response keys to indicate which of two letters appeared on screen
        
        30% of trails, immediately after stimulus, a time signals ps should not respond
        
        Tone can appear at different intervals after the stimulus
        
        Number of times response made when stimulus followed by stop signal
        
        Stop-signal reaction time (SSRT): key measure of stopping speed)
        
        Mental set shifting
      - EFs + ADHD
        
        Frontal lobe patients display impulsive behaviour similar to that seen in hyperactive-impulsive subtype
        
        Claim here: ADHD is the result of cog deficit in (one or more) EFs
        
        Suggestion that executive dysfunction a cause of ADHD stems from study of neuropsychological patients
    - - Oosterlaan et al (1998)
        
        ADHD (n=121) vs control (n=133): average d for difference in SSRT = 0.64 (moderate)
        
        Meta-analysis of 8 studies using Stop task
        
        But: Inhibitory deficits not confined to ADHD
        
        Conduct disorder (n=40) vs controls (n=58): d = 0.51
        
        ADHD vs conduction disorder: d =0.07
      - Pennington & Ozonoff (1996)
        
        67% of all EF measures used in the studies showed group differences
        
        Only 35% non-EF measures (e.g. of verbal ability) showed differences
        
        Significant differences between ADHD and control participants in 15/18 EF studies overall
        
        Deficits in response inhibition uniquely distinguished ADHD group
        
        Meta-analysis
      - Wilcutt et al. (2005)
        
        ADHD deficits in all EFs (ds = 0.4-0.7)
        
        So, not specific to inhibitory problems
        
        But, of course, aspects of EF correlated at around .3/.4 in adults (Miyake et al., 2000) and children Lehto et al., 2003)
        
        Meta-analysis of 83 studies involving 6700 ps
    - - High variability on EF tasks in ADHD
        
        Overall group differences are consistently moderate in size
        
        But, how many children could be considered "impaired"?
      - Nigg et al. (2005)
        
        Reanalysed results from 3 large-scale, independent studies of ADHD (> 800 ps)
        
        Sig overlap between ADHD ad neurotypical samples on EF tasks
  - - - Delay aversion hyp:
        
        Impulsivity in ADHD not the result of an inability to inhibit, but a choice to avoid delay
      - Theory rooted in animal learning research
        
        Importance of reinforcers (rewards) in shaping behaviour
        
        Rewards = more effective in shaping behaviour if they occur soon after response
      - Hypothesis: kids with ADHD show faster decline of effectiveness of reinforcer across time
      - Contingency between present action and future rewards is not signalled as strongly as in TD
      - Recognising that reward is linked to behaviour only occurs if reward follows behaviour immediately
      - Aversion to delay occurs as a natural (rational) consequence
      - Hyperactivity a tactic to reduce perceived passing of time
    - - Sonuga-Barke et al. (1992)
        
        Task involves choosing a reward of either 1/2 points under different conditions (repeated measures)
        
        Complete 4 conditions in counterbalanced order, across two sessions
        
        Boys w/ ADHD, and age- and IQ- matched controls
      - No post choice delay condition
        
        Small reward delivered 2 seconds after choice
        
        Large reward 30 seconds after choice
        
        Next choice immediately after reward delivered
        
        Best strategy = choose small reward (in 1 min, can have received 30 points choosing small reward, but on 4 on large
        
        Found: both groups choose small reward
      - Post-choice delay condition
        
        30 seconds delay after small reward before next choice
        
        Only 2 seconds delay after receiving large reward before next choice
        
        Thus: both associated with delay of 32 seconds
        
        Best choice = large reward (4 pnts in 1 min 4 secs vs. 2 pnts in that time)
        
        Found: Both groups choose large reward
      - Thoughts
        
        Kids with ADHD can choose large rewards if overall delay is held constant
        
        Not just impulsively choosing immediate small reward (waited 30 seconds in post-choice) - can inhibition circumstances
        
        If ADHD = delay aversion, then should choose small reward (worse outcome), short delay
      - Time constraint condition (2s/30l) only 10 mins to win
        
        Trials constraint condition (2s/30l) only 20 trails
      - Found
        
        Only sig diff in the constraint condition
        
        Kids w/ ADHD choose small rewards sig
        
        Thus: ADHD kids won less money
        
        Key motivation for impulsive responding is to reduce overall delay
        
        They chose small rewards not because immediacy, or efficiency but because they dislike delay
        
        Replicated (small reward in constrained)
      - Solanto et al (2001)
        
        EF and motivation theorists collaborate
        
        Rigorously-diagnosed combined-type ADHD ps and age matched controls
        
        Stop task and choice task, plus questionnaires
        
        Found
        
        Group difference in choice task (only 1/3 of ADHD, compared to nearly 2/3 of controls chose large reward): d= 0.90
        
        Choice task correlated with: teacher ratings of hyperactivity & impulsivity, independent ratings of class interference & aggression
        
        Group difference in SSRT and probability of inhibition: d = 0.68 and 0.89, respectively
        
        SSRT correlated with observations of classroom interference & aggression
        
        No influence of secondary difficulties
        
        Important: Stop and Choice tasks not correlated, discriminant function analysis
        
        Stop accuracy 68%
        
        Choice accuracy 71%
        
        Combined 87.5%
        
        Measures tap (partially) separable aspects of ADHD
        
        Replicated in pre-school children