Beatriz Luna, PhD

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Vulnerabilities in Neurocognitive Processes in
Adolescence

• Beatriz Luna, PhD
• Laboratory of Neurocognitive Development
• University of Pittsburgh

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Control of Behavior

• Exogenous
• Elicited by external guides
• External Stimuli, Emotional States
• Not guided by a planned response
• Reflexive Behavior
• Endogenous
• Voluntary
• Guided by internal plans
• Overrides exogenously-guided behavior
• Cognitive Control of Behavior / Decision Making
• Can be adult like in adolescence

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Conclusions Adolescence

• Adolescents can demonstrate adult-level cognitive
  control of behavior
• Behavioral Studies
• Brain mechanisms that support adult-level
  behavior in adolescence are immature
• fMRI studies
• Adolescent cognitive control of behavior is
  immature and vulnerable to error
• Conclusions

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Brain Maturation in Adolescence
Synaptic Pruning
Myelination

• Improved Brain Function
• Increased efficiency of local computations
• Increased speed of neuronal transmission

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Cognitive Development Core Processes

• Voluntary Response Inhibition (Paus 1990, Levin
  1991, Ridderinkhof 1997, Fischer 1997, Munoz
  1998, Luna 2004)
• Working Memory (Zald 1998, Demetriou 2002, Luna
  2004)

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Oculomotor Studies of Cognition

• Direct Measure of Cognitive Control
• Minimal strategy formation
• Well-delineated Neural System
• Anatomically Physiologically
• Simple Cognitive Tasks
• Appropriate for Developmental Studies

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• Behavioral Studies

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Methods

• 245 subjects
• 8-30 yo (93 Female/152 Males)
• Tasks
• Speed of Processing
• Response Inhibition
• Working Memory

Child Development 2004
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Direct current electro-oculography (EOG)
-24 deg
-16 deg
-8 deg
1 meter
0 deg
8 deg
16 deg
24 deg
Darkened Room
20
10
Visually Guided Saccades
Central Fixation (1.5-2.5s)
Saccade
Saccade to Target (1.5s)
-30 -20 -10 0 10
20 30
Degrees of Visual Angle
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Antisaccade Task
3 - 5 sec
Central Fixation
Saccade away from
1.5 sec
Peripheral Target
Feedback
1.5 sec
-24 -16 -
8 0 8 16 24
Illuminated Targets
Degrees of Visual Angle
Correct Gaze Location
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12
ODR/ Memory Guided Saccade Task
1.5-2.5s
Central Fixation
0.1 s
Target Location to be Remembered
1,2,4,8 s
Delay Period
Saccade to Remembered Location
1.5 s
2.0 s
Feedback
Illuminated Targets
-27 -18 - 9 0 9 18 27
Correct Gaze Location
Degrees of Visual Angle
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Speed of Processing
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Voluntary Response Inhibition
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Working Memory Accuracy
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Conclusions

• Cognitive control of behavior matures in
  adolescence
• What develops is the sophistication of responses
  not the appearance of an ability

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• Brain Imaging Studies

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fMRI
Capillary Bed
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baseline
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activation
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Response Inhibition
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MR Imaging Methods

• Subjects (N36)
• 8-13y (N11)
• 14-17y (N15)
• 18-30y (N10)
• fMRI Studies
• 3.0 Tesla GEMS scanner
• Gradient-Echo EPI, TR 5000
• In-plane resolution 3.125 mm2
• 23 - 3 mm slices, 2 mm gap
• Standard anatomic imaging (SPGR)

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Antisaccade Block Design
Prosaccade Trial
Antisaccade Trial
Fixation
Fixation
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Adults gt Adolescents and Children
Adults
Children
Adolescents
R
L
FEF
PEF
Sup Coll
Lat Cer
14
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Adolescents and Children gt Adults
Adults
Children
Adolescents
PPC
R
L
DLPFC
13
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Response Inhibition Planning
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Event Related Antisaccades
Prosaccade Trials
Antisaccade Trials

Cue


10
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Preparation to Inhibit a Response
Adults
Children
Adolescents
FEF
R
L
9
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Antisaccade Preparation FEF

• Adolescents, like children, do not reach
  adult-level activation for correct responses.
• Adolescents, like adults, do show a second peak
  of activation.

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Preparation to Inhibit a Response
Adults
Children
Adolescents
DLPFC
VLPFC
R
L
9
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Antisaccade Preparation DLPFC

• Adolescents, like children, show a delayed peak
  of activation.
• Adolescents, like adults, show a similar
  magnitude of activation.

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Conclusions Response Inhibition

• Maturation is characterized by the emergence of
  an integrated collaborative brain system.
• Adolescents are not as efficient at activating
  brain regions supporting response planning
• Adolescents compensate for immature brain systems
  by recruiting PFC

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Working Memory
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Methods ODR task
Working Memory Trials
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Working Memory
Children
Adolescents
Adults
Basal Ganglia Caudate Putamen
DLPFC
Superior Temporal Gyrus
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Working Memory Encoding and Maintenance
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Methods ODR task
Spatial Working Memory Trials
Saccade
Delay 2.5 or 10
time

VGS Trials
Saccade
Cue 75 ms
Baseline
Fix 1250 ms
Jittered 2.5-12.5s
Fix 2425 ms
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Prefrontal Cortex Maintenance
Children 8-12yo
Adolescents 13-17yo
Adults 18-30yo
2.5s Delay
BA9
10s Delay
BA10
BA9
PFC supports WM maintenance and is on line at all
ages
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Hippocampus Encoding
Children 8-12yo
Adolescents 13-17yo
Adults 18-30yo
2.5s Delay
10s Delay

• The hippocampus supports encoding and is only
  recruited by adults

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Conclusions Working Memory

• Adolescents are not efficient at recruiting
  regions that support encoding information in
  working memory.

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Take Home Message

• While adolescents behave similarly to adults the
  brain processes supporting cognitive control of
  behavior are not mature
• Adolescence is a still unstable stage that is
  vulnerable to immature processing

2
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Why?

• Adolescence is a crucial and necessary period of
  plasticity when brain circuitry and behavior is
  beginning to be established.
• Risk-taking behavior and novelty seeking may
  provide a mechanism for increasing exposure to
  the environment necessary for successful
  sculpting of the system.

end
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Laboratory of Neurocognitive Development
Dr. Bea Luna PI
Dr. Miya Asato
Dr. Suzy Scherf
Matt Costello MA
Krista Garver BA
Chuck Geier MA
Emi Yasui BA
Melanie Wilds BA