CHIMe lab

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Task Design

General

  • Applied cognitive psych experiment to see how the brains of heavy multitaskers are different than the brains of light multitaskers
  • 2 tasks: event-related design for Vogel, block-design for N-back
  • Protocol
    • N-back practice ~4 min
    • 2-back block 3min20s
    • 3-back block 3min20s
    • 2-back block 3min20s
    • 3-back block 3min20s
    • Vogel practice ~2 min
    • Vogel task 9min36s
    • = 30 minutes of task time
    • Diffuser 13min
    • Total approx min of task time


Vogel task

  • See Vogel paper
  • Red/blue rectangles, detect orientation change in red rectangles, ignore blue rectangles
  • FOUR conditions: 0,2,4,6 distractors
  • 2 red rectangles in all 4 conditions
  • Length: approximate 2 min practice, 9min36s test
  • Trial timing
  • All slides and input updated to thumb/index button presses, except for start of real task, which is set to keyboard and triggers the MRI.
  • Note there is a concern with removing trials with 4, 6 and 8 red rectangles (as these require more cognitive load, and do not allow the participant to 'expect' two red rectangles), but due to timing constraints, we are not able to include them.



N-back task

  • See Jaeggi paper
  • Block desgin, alternating between two difficulty levels (2-back and 3-back)
  • Length: total 20 min (plus break time, in between blocks. No breaks within blocks.)
    • ~4 min practice: 2 min 2-back practice + 2 min 3-back practice
    • 3 min 20s 2-back test
    • 3 min 20s 3-back test
    • 3 min 20s 2-back test
    • 3 min 20s 3-back test
    • triggers at the beginning of each block
    • Block length of 3 min 20s was chosen because it is exactly double the block length in the PNAS article
    • no triggers for practice because practice length can vary
  • All slides and input updated to thumb/index button presses, except for start of real task, which is set to keyboard and triggers the MRI.
  • UNRESOLVED: In the practice files, the accuracy message box needs a <spacebar> press to continue. How to change it to THUMB/"1"
  • Scan script needs to be added to 2-back and 3-back practice files


Methods

Hypotheses

Working Memory in Vogel Task

HMMs will have less effective working memory use than LMMs, ie. HMMs will resemble lower-capacity individuals in they will allow distractors into working memory. ROI: Prefrontal cortex. Vogel paper found EPR differences in the lateral occipital posterior parietal electrode sites.

Possibly make the retention interval longer? Do a behavioural pilot?

Working Memory in N-back task

HMMs will have less effective working memory than LMMs. ventrolateral PFC (BA 44/45/47) is concerned with active maintenance and updating of information dorselateral PFC (BA 9/46) is concerned with active manipulation and monitoring WM also been associated to dorselateral PFC, Broca’s area and parietal cortex anterior cingulated associated to task difficulty See Table 1 in N-back paper for ROI Note: N-back paper found single and dual task differences in the precentral gyrus and the superior parietal lobule.

Approach Response in Sensation seeking

HMMs will have more sensation seeking characteristics. HSSs showed stronger fMRI responses to high-arousal stimuli in brain regions associated with arousal and reinforcement (right insula, posterior medial orbitofrontal cortex), whereas LSSs showed greater activation and earlier onset of fMRI responses to high-arousal stimuli in regions involved in emotional regulation (anterior medial orbitofrontal cortex, anterior cingulate). Furthermore, fMRI response in anterior medial orbitofrontal cortex and anterior cingulate was negatively correlated with urgency. Finally, LSSs showed greater sensitivity to the valence of the stimuli than did HSSs. These distinct neurobiological profiles suggest that HSSs exhibit neural responses consistent with an overactive approach system, whereas LSSs exhibit responses consistent with a stronger inhibitory system.

Characteristics of ADHD

HMMs will have more ADHD characteristics, i.e. we expect to see hypoactivation of the PFC/caudate/ant. Cingulate circuit and/or the posterior circuit in HMMs during the N-Back and Vogel tasks, compared to LMMs. Summary: PFC – role in suppressing irrelevant stimuli during task. Caudate – role in inhibition. Anterior cingulate – role in attention and reward-based decision making.

The most popular theory in terms of the neurobiological substrate of ADHD is dysfunction in the frontostriatal circuits. The three essential components of the executive functions that present with ADHD diagnoses are related to adequate functioning of the prefrontal cortex (PFC); temporal integration, working memory and inhibition (inhibition has been studied the most in ADHD). fMRI has revelealed:

  • hypoactivation of the PFC and caudate nucleus during an inhibiton task in ADHD sufferers (Teicher et al 2000, Nat Med 6:470)
  • hypoactivation of the anterior cingulate nucleus during a Stroop test, a stop signal test, and a Go-NoGo test in ADHD sufferers(Bush et al 1999, Biol Psychiatry 45:1542; Rubia et al 1999, Am J Psychaitry 156:891; Durston 2003, Ment Retard Dev Disabil Res Rev 9:184)

ADHD includes:

There is also a second theory of the neurobiological substrate of ADHD which implicates a posterior cortical circuit, including the posterior superior temporal cortex, and the inferior parietal cortex (both these regions play a role in focus of attention and ignoring distraction) – stop signal and Go/NoGo tasks (Mulligan et al 2011, Psychaitry Res 194:119.

Interestingly there is a theory that the frontostriatal dysfunction underlies the inattentive subtype of ADHD, while the posterior dysfunction may underlie the hyperactive/impulsive subtype of ADHD, or the combined type. We could narrow our hypothesis regarding which of the 2 circuits (anterior vs. posterior) is most likely to differ in HMMs by looking at the literature of ADHD subtypes doing our tests (i.e. the N-Back) and seeing whether the performance of one subtype or the other more closely mirrors the performance of HMMs.

Structural MRI has revealed: Decreased volume of PFC subregions in ADHD sufferers (Reviewed in Quintero et al 2009, Actas Esp Psiquiatr 37:352) Conflicting reports on volume changes in the caudate, cerebellum and basal ganglia.

Explore/Exploit

HMMs will exhibit more exploratory activation. The explore/exploit model proposes that information about cost (calculated by the anterior cingulate cortex (ACC)) and reward (calculated by the ventromedial prefrontal cortex (vmPFC) and orbitofrontal cortex (OFC)) converge on both the ventral tegmental area (VTA) and the locus coeruleus (LC). This information is used by the VTA to implement a reinforcement learning algorithm that adjusts the weights in the decision network. In the LC, evaluative information sets the mode of responding (phasic or tonic), which, through norepinephrine (NE) release and gain modulation of units in the decision network, regulates the balance between exploration and exploitation.




Participants

  • Aim to run n = 20, 10 heavy multitaskers, 10 light multitaskers
  • Must run before July 31 (end of grant)


Input Details

  • we will use the 1-handed cylinder with the thumb and index button in the dominant hand -> "HHSC l5"
  • setting is USB, input in numbers from the participants (1=thumb, 2=index), input in keyboard to start the stimulus
  • respiration and pulse osimeter included


Project Timeline and Notes

Timeline

  • IRB submitted. Revisions submitted. Waiting for approval.
  • Outline specific hypotheses. DONE
  • Complete Level 3 MRI training: test DONE. Practical exam: June 6, 9-10am. DONE
  • CPR training: May 31. DONE
  • update e-prime files. DONE
  • Coordinate with Nanna to add triggers to e-prime tasks, synch/test with scanner. June 6, 8-9am. DONE
  • run pilot participant. Goal: Friday June 8. DONE


ANALYSIS

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