Using ADHD as a model for
understanding neural networks
Dr. Laura Jansons
02/22/2014
ADHD
• Diagnosis made by behavior observation:
DSM-V
– 18 symptoms of ADHD, need to meet a
percentage of them to be diagno...
– Old: ADHD is dysfunction of frontal lobe
– New: abnormally functioning brain circuitry
– New: Several etiological influe...
• Based on what we’ve learned from neuroimaging, we should
be thinking in terms of loops and connections, and not land
mar...
7 brain networks involved in ADHD
Yeo and colleagues (2011)
• Frontal Parietal network: effortful cognitive tasks, esp. no...
• What this means for neuropsychologists is
that it is no longer appropriate to think of
ADHD as a simple ‘‘frontal-lobe d...
Functionally mapping ONE symptom of
ADHD using one type of test
• Stevens and colleagues, 2007, provided the first descrip...
• There is not one region in the brain
responsible for inhibiting response.
• There are “loops” of communication that
lead...
Withholding response
These loops can be mapped on the brain via
fMRI.
The following is the “blue”, “yellow” and “red”
circ...
13
Stevens, et al, 2007
Blue: pay attention there’s something unique
going on here, what do I do?
Yellow: transforming sen...
Fig. 1. Brain regions in each component
associated with successful response inhibition.
(A) Fronto-striatal-thalamic indir...
Summary Stevens 2007
• Causal relationships among ensembles of
different brain regions.
• May help understand that there i...
Stevens 2009
• Network dynamics supporting correct
responses and errors of commission
• NCs between 11 and 37
• Go/No-Go t...
Stevens 2009
• The analysis found five distinct functional
networks related to correct hits and errors.
Go
XRapidly presented
(1000 ms intervals)
85% Go stimuli
right index finger taps
Go
X
Go
X
No Go
K
Correct Button Pushes
A: a motor-execution neural circuit integrated with frontal, parietal, and
striatal regions (Orange)...
Errors A
A: a motor-
execution neural
circuit showing
absent or decreased
activity in brain
regions engaged for
higher-ord...
Errors B
B: a low-probability
stimulus processing
functional circuit that
has a greater response
amplitude to errors
Errors C
C: the pregenual
cingulate-temporal
lobe network
possibly reflecting an
affective response to
errors
(bilateral a...
• Why are NP task so inadequate?
Behaviorally defined criteria in ADHD
do not easily ‘‘map’’ on to functional
brain networ...
• assessment instruments were never designed
to evaluate the networks and interactions in
question.
• CPT’S are not ADHD t...
• the challenge to functional neuroimaging is to
find a way to effectively ‘‘diagnose’’ ADHD.
• Neuropsychology can establish itself at the
‘‘ground floor’’ in developing methodologies
to explore these different dime...
ADHD as a model for understanding neural network dynamics
ADHD as a model for understanding neural network dynamics
ADHD as a model for understanding neural network dynamics
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ADHD as a model for understanding neural network dynamics

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  • Blue: pay attention there’s something unique going on here, what do I do?
    Yellow: transforming senses into actions
    Red: Executive Control and Working Memory
  • motor system activation was functionally integrated with prefrontal and parietal
    regions frequently observed during goal-directed behavior involving motor attention and working memory.
  • Striatal regions typically recruited in response execution were not engaged
    This may reflect a breakdown of higher-order control on error trials.
    functional interpretation of mesiotemporal activity is that it could represent internal speech [Ryding et al., 1996], a literal or figurative sub-vocal ‘whoops!’ response made to errors.
  • which likely contributes affective salience to No-Go target stimuli [Holroyd and
    Coles, 2002]. Activity in these frontotemporal areas has been linked to internally-generated emotional response
    [Reiman et al., 1997], awareness of errors [Hester et al., 2005], and self-referential thinking [Vogeley et al., 2001],
    suggesting these regions may underlie awareness of and emotional reaction to errors.

    Specifically, affective responses might signal the failure to reinforce stimulus-action-reward associations.
  • ADHD as a model for understanding neural network dynamics

    1. 1. Using ADHD as a model for understanding neural networks Dr. Laura Jansons 02/22/2014
    2. 2. ADHD • Diagnosis made by behavior observation: DSM-V – 18 symptoms of ADHD, need to meet a percentage of them to be diagnosed – Diagnosed using behavioral checklists – Problem for neuropsychologists: • DSM-V is not based on NP test data • DSM-V not based on Neuroanatomy • DSM-V is based on “lesion” or disease model.
    3. 3. – Old: ADHD is dysfunction of frontal lobe – New: abnormally functioning brain circuitry – New: Several etiological influences, “common disease- common variant model” – New: ADHD is not one thing, there is not one place on the brain we can map.
    4. 4. • Based on what we’ve learned from neuroimaging, we should be thinking in terms of loops and connections, and not land marks. • Those loops recruited in ADHD: –Cerebro-cortical –Cortical-basal ganglia –Cerebo-cerebellar –Basal ganglia-cerebellar
    5. 5. 7 brain networks involved in ADHD Yeo and colleagues (2011) • Frontal Parietal network: effortful cognitive tasks, esp. novel. • Ventral attentional network : directs attn. to salient objects. “What” you are seeing or “what” an object is used for. • Dorsal attentional network : Where and How of spatial attn. “Where” is object located and “how” do I use it. • Visual Network: interacts with dorsal and ventral route • Limbic network: anticipation of rewards, monitors errors and conflict resolution. • Sensory-motor network: motor skills • Default mode network: What you are imagining at rest.
    6. 6. • What this means for neuropsychologists is that it is no longer appropriate to think of ADHD as a simple ‘‘frontal-lobe disorder’’ • Need to replace the localizationist view, ADHD is not just one thing from one place in the brain with one trajectory. • This is why there is no NP test available, ADHD is heterogeneous, the symptoms are heterogeneous.
    7. 7. Functionally mapping ONE symptom of ADHD using one type of test • Stevens and colleagues, 2007, provided the first description of how multiple neural network dynamics are associated with response inhibition in normal control adolescent and adult subjects in the performance of a “Go-No-Go” task.
    8. 8. • There is not one region in the brain responsible for inhibiting response. • There are “loops” of communication that leads to disinhibition, in fact there are three. • We are always “idling” and anticipating. When the light is red, the car is not “off”. • There is a lot going on when you inhibit a response.
    9. 9. Withholding response These loops can be mapped on the brain via fMRI. The following is the “blue”, “yellow” and “red” circuit. Correctly rejected No-Go stimuli involved with successful response inhibition:
    10. 10. 13 Stevens, et al, 2007 Blue: pay attention there’s something unique going on here, what do I do? Yellow: transforming senses into actions. Object recognition, salience/reward value Red: Executive Control and Working Memory
    11. 11. Fig. 1. Brain regions in each component associated with successful response inhibition. (A) Fronto-striatal-thalamic indirect pathway engagement consistent with modulation of motor function (Blue); (B) precentral gyri deactivation concurrent with prefrontal and inferotemporal activation (Yellow); (C) frontoparietal circuit activity consistent with higher-order presentations of No-Go’ response contingencies (Red). Statistical results are thresholded at a low of p < .001, corrected for searching the whole brain.
    12. 12. Summary Stevens 2007 • Causal relationships among ensembles of different brain regions. • May help understand that there is no one linear cause for disinhibition, alterations in specific connections or brain region could impact psychopathological conditions.
    13. 13. Stevens 2009 • Network dynamics supporting correct responses and errors of commission • NCs between 11 and 37 • Go/No-Go task
    14. 14. Stevens 2009 • The analysis found five distinct functional networks related to correct hits and errors.
    15. 15. Go XRapidly presented (1000 ms intervals) 85% Go stimuli right index finger taps
    16. 16. Go X
    17. 17. Go X
    18. 18. No Go K
    19. 19. Correct Button Pushes A: a motor-execution neural circuit integrated with frontal, parietal, and striatal regions (Orange), B: the ‘default mode’ neural network (imagining a task as if you were doing it)
    20. 20. Errors A A: a motor- execution neural circuit showing absent or decreased activity in brain regions engaged for higher-order control (things are going on implicitly—without thought) “whoops” Car’s going down the road without a driver, disturbance in intention program, start, stay stop. Connection between working memory and Impulsivity—environment , stimulus, triggers behavior not thought
    21. 21. Errors B B: a low-probability stimulus processing functional circuit that has a greater response amplitude to errors
    22. 22. Errors C C: the pregenual cingulate-temporal lobe network possibly reflecting an affective response to errors (bilateral amygdala activation)
    23. 23. • Why are NP task so inadequate? Behaviorally defined criteria in ADHD do not easily ‘‘map’’ on to functional brain networks. • With the advent of functional neuroimaging, it was seen conclusively that these sorting and planning tasks should not fairly be considered ‘‘frontal’’ tests.
    24. 24. • assessment instruments were never designed to evaluate the networks and interactions in question. • CPT’S are not ADHD tests: they measure a range of impulses and don’t correlate with one another. • Current: widely accepted belief of causal heterogeneity in ADHD. ADHD is not one thing with one cause.
    25. 25. • the challenge to functional neuroimaging is to find a way to effectively ‘‘diagnose’’ ADHD.
    26. 26. • Neuropsychology can establish itself at the ‘‘ground floor’’ in developing methodologies to explore these different dimensions of behavior. • Challenge in the field today seems to need a way to bring these two worlds together.
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