Imaging the Normative Development of
Motivated Inhibitory Control and the Effects of Daily Smoking
Adolescence
Charles Geier, Ph.D.
Department of Human Development and Family Studies
Pennsylvania State University
•  Period of transition from childhood to adulthood
–  Focus in this talk: 13-17 years
Health Paradox of Adolescence
•  Improvements in physical health
and in the cognitive control of
behavior Risk-taking
–  WM, reasoning, problem solving
Decision making
•  Increased risk taking –  Negative consequences
contribute to a nearly 200%
increase in mortality rates
during adolescence –  Health paradox of adolescence
Reward
Inhibitory
Control
Geier & Luna (2009), Pharm., Biochem., & Beh.
Mature Reward System
Adolescent Brain Development
•  Extensive literature
characterizing mature reward
system
–  e.g., Orbitofrontal cortex
(OFC), dorsal/ventral
striatum, medial prefrontal
cortex
P >.25
•  The adolescent brain, including primary regions of
the reward circuitry, shows persistent immaturities
through adolescence:
–  Microstructural changes:
•  Continued thinning of gray matter in basal ganglia and OFC OFC (BA 10, 11, 47)
•  Dissociable component
signals –  Dopamine (DA) system changes:
Sowell et al. (1999)
–  Anticipatory - detection,
anticipation/expectation
–  Consummatory - feedback
(prediction error signaling)
•  Increased density of dopaminergic inputs to PFC (layer 3)
•  Increased number of D1 and D2 receptors in striatum during
adolescence vs. adulthood •  Dopamine transporter (DAT) levels peak during adolescence
in striatum Ventral Striatum
Probability Maps Overlaid on MNI brain (FSL)
Schultz (1998)
1
Adolescent Reward System
Adolescent Reward System
•  Evidence from developmental functional magnetic
resonance imaging (fMRI) studies investigating differences
in reward processing: –  Prior to reward delivery - ANTICIPATORY
–  After reward is delivered - CONSUMMATORY
–  Similar basic circuitry –  Immature recruitment ANTICIPATORY
CONSUMMATORY
}
•  Discrepancy may be related to phase studied:
•  The directionality of adolescent “immature” reward
responses is still not clear:
Detection
–  Ventral Striatum
•  Under-active VS (Bjork et al., 2004) •  Over-active VS (Ernst et al., 2005; Galvan et al.,2006): Anticipation
Feedback
Ernst et al., 2005
Galvan et al., 2006
Bjork et al., 2004
Response Inhibition Response Inhibition: Stopping inappropriate responses
Risk-taking
ANTISACCADE TASK
Decision making
Reward
+
Inhibitory
Control
TIME
Hallett (1978)
Geier & Luna (2009), Pharm., Biochem., & Beh.
Sample Behavioral Responses
During Antisaccade Task
CORRECT RESPONSE
Response Inhibition ERROR
EYE POSITION
LEFT
•  Response inhibition
continues to mature
into adolescence
RIGHT
TIME
Stimulus Appears
Luna et al. (2004)
2
C EYE MOVEMENT
ye movement (with
up to 800 degrees per
hat brings the point of
visual acuity — the
o the image of interest.
Response Inhibition REVIEWS
•  A distributed circuitry supports antisaccade performance
Box 1 | Neural circuitry controlling saccadic eye movements
Retino-geniculo-cortical pathway
Direct pathway
Indirect pathway
An extensive body of literature
Frontal cortex
a
describing lesion studies,
SEF
Parietal cortex (LIP)
human behavioural testing,
DLPFC
functional neuroimaging,
FEF
animal neurophysiology and
Visual cortex
detailed anatomy has
identified several brain areas
CN
Thalamus
LGN
that are involved in controlling
GPe
visual fixation and saccadic eye
movements, including regions
Retina
STN
SNpr
SCi SCs
in the cerebral cortex, basal
Basal ganglia
ganglia, thalamus, superior
Retinotectal pathway
colliculus (SC), brainstem
reticular formation and
Cerebellum
Reticular
Saccade
cerebellum48,49,56,96,114–116
formation
(see panels a and b).Visual
inputs to the system arise from
the retino-geniculo-cortical
Munoz & Everling (2004)
Voluntary
b
pathway to the primary visual
(frontal cortex, basal ganglia)
cortex and from the
retinotectal pathway to the
Visual reflexive
Suppression
superficial layers of the SC.
(parietal/occipital cortex)
(frontal cortex, basal ganglia)
Visual information is
processed through several
extrastriate visual areas117
Oculomotor behaviour (SC)
before it impinges on motor
structures to affect action. The
Excitatory connection
lateral intraparietal area (LIP)
Premotor circuit (RF)
in the posterior parietal cortex
Inhibitory connection
is at the interface between
sensory and motor processing118,119. The LIP projects to both the intermediate layers of the SC120 and the frontal cortical
121,122
, including the frontal eye fields (FEF), the supplementary eye fields (SEF) and the dorsolateral
oculomotor areas
prefrontal cortex (DLPFC). The FEF has a crucial role in executing voluntary saccades98,123–125. The SEF is important for
internally guided decision-making and sequencing of saccades126,127. The DLPFC is involved in executive function, spatial
working memory and suppressing automatic, reflexive responses91–93. All of these frontal regions project to the
SC28,59,62,128–130, which is a vital node in the premotor circuit where cortical and subcortical signals converge and are
integrated56,131. The FEF, SEF and SC project directly to the paramedian pontine reticular formation to provide the (Duka & Lupp,
59,132,133
necessary input to the saccadic premotor
circuit et
soal.,
that
a saccade
suppressed
1997; Blaukopf
2006;
Jazbecisetinitiated
al., 2006;orHardin
et al., 2007)
.
Frontal cortical oculomotor areas also project to the caudate nucleus (CN)66,134,135. GABA (!-aminobutyric acid) neurons
in the CN project through the direct pathway to the substantia nigra pars reticulata (SNpr). Neurons in the SNpr form the
main output of the basal ganglia circuit: they contain GABA and project to the intermediate layers of the SC and to nuclei in
the thalamus that project to the frontal cortex. Cortical inputs to the direct pathway lead to disinhibition of the SC and
thalamus because these signals pass through two inhibitory synapses. There is also an indirect pathway through the basal
ganglia, in which a separate set of GABA neurons in the CN project to the external segment of the globus pallidus (GPe).
GABA neurons in GPe then project to the subthalamic nucleus (STN). Neurons in the STN send excitatory projections to
neurons in the SNpr, which in turn project to the SC and thalamus. Cortical inputs to the indirect pathway lead to inhibition
of the SC and thalamus because these signals pass through three inhibitory synapses134,136. LGN, lateral geniculate nucleus;
SCi, superior colliculus intermediate layers; SCs, superior colliculus superficial layers.
Rewards and Response Inhibition
•  Few studies have directly examined the influence
of reward on response inhibition behavior
to these two processes: suppression of the automatic
response and vector inversion.
Monkeys can be trained to perform the anti-saccade
task and therefore provide an important animal model2,3
in which to investigate neural processing related to saccadic suppression and sensory–motor transformation.
Pro-saccade and anti-saccade trials can be randomly
interleaved in a block of trials and the instruction as to
which type of movement to generate can be conveyed by
the colour or shape of the initial fixation marker. In this
configuration, human4–6 and monkey 2,3 subjects produce
E REVIEWS | NEUROSCIENCE
a qualitatively similar pattern of behaviour. FIGURE 1b
illustrates the distribution of reaction times obtained
from a monkey generating correct pro- and antisaccades and the reaction times of direction errors
(saccades triggered in the wrong direction: towards the
target in the anti-saccade task; away from the target in
the pro-saccade task). There are two important observations. First, if the peripheral target appears suddenly and
participants are allowed to move immediately, correct
pro-saccades are initiated earlier than correct antisaccades. Second, most direction errors are confined to
Response Inhibition •  Cortical Eye Fields: –  Frontal Eye Field (FEF)
–  Supplementary Eye Field
(SEF) –  Intraparietal Sulcus (IPS)
-  Superior Colliculus
-  Inferior Frontal Gyrus
-  Dorsolateral PFC
Adolescents
FUNCTIONAL BRAIN MATURATION
789
Adults
Luna et al. (2001)
Objectives
•  Characterize normative adolescent reward processing
and influence of rewards on response inhibition
behavior and circuitry
FIG. 2. Group activation maps (t ! 4.0) during an antisaccade task relative to a visually guided prosaccade task superimposed on the
structural anatomic image of a representative subject (26 y.o. F) warped into Talairach space. Columns show the average activation for each
age group. Rows depict the orientation (rows 1 and 2 ! sagittal; 3 and 4 ! axial; 5 and 6 ! coronal) that optimally illustrate activation in
brain regions of interest. Ant-Cing, anterior cingulate; DM-TH, dorsomedial thalamus; Pre-SMA, presupplementary motor area; SEF,
supplementary eye fields; Prec, precuneus; SC, superior colliculus; sFEF, superior precentral sulcus aspect of the frontal eye field; IPS,
intraparietal sulcus; BG, basal ganglia; DLPFC, dorsolateral prefrontal cortex; SMG, supramarginal sulcus; Lat Cer, lateral cerebellum; and
DN, dentate nucleus.
Today’s Talk:
analyses were
to compare
the percentage
We response
used Analysis
of Functional
Partperformed
1: Examine
rewards
and effects on
inhibition
signal change in ROI between groups. We also explored
circuitry in adolescents and young
the associations between age as a continuous variable
and activation
through curve-fitting
regression
PartinII:ROIExamine
function of
these
analyses. The threshold value of 4.0 for the t statistic
was used because it has yielded a reasonable empirical
error rate over many studies that our group, as well
as other investigators, have performed with our particular scanner and single-shot echoplanar pulse sequence.
NeuroImages
(AFNI) software (Cox, 1996) to overlay the functional
adults
data onto co-planar anatomic images. Each individual
subject’s in
data
were smoothed with a 5.6-mm fullsystems
smokers
width– half-maximum filter and transformed into Talairach space. Then data were averaged across subjects
in each age group. AFNI was also used for defining
ROIs, as described above, and for 3-D motion correction. AFNI was used to perform voxelwise group comparisons at a t value ! 3.0. This analysis yielded the
VOLUME 5 | FEBRUARY 2004 | 2 1 9
Study 1: Reward and Effects on Response Inhibition in
Adolescents and Young Adults
©2004 Nature Publishing Group
Ring Reward AS: Task Design
•  Rewarded AS task
has multiple
components –  Cue (assessment)
–  Response prep
(anticipation)
–  Response
REWARD or NEUTRAL
$
$
$
$ + $
$ $ $
###
# + #
###
Cue (1.5 sec)
(Reward Assessment)
Response Preparation (1.5sec)
(Reward Anticipation)
Saccade Response (1.5sec)
+
+
ITI (1.5, 3, or 4.5 sec)
Are there developmental
differences in these
components?
Catch Trial 1
(no response)
$
$
$
$ + $
$ $ $
{
+
+
{
Catch Trial 2
(no preparation,
no response)
$
$
$
$ + $
$ $ $
+
Geier et al. (2010) Cerebral Cortex
3
Behavioral Results: Error Rate
Study 1: Methods
p<0.001
*
•  Participants (N=34)
–  18 Adolescents, 13-17 years
–  16 Young Adults, 18-26 years
More Errors
•  fMRI Studies –
–
–
–
–
–
–
Gray = Reward
White = Neutral
3.0 Tesla Siemens scanner (BIRC)
Gradient-Echo EPI, TR = 1.5
In-plane resolution 3.125 mm2 29 - 4 mm slices, no gap
Standard anatomic imaging (MPRAGE)
Simultaneous Eye tracking: ASL (Bedford, MA) LRO 504
Did not assume a HDR shape in analysis
p=0.07
#
•  Software
–  FSL (preprocessing) (Smith et al., 2004; Jenkinson & Smith, 2001; Smith, 2002)
–  AFNI (deconvolution, statistical analyses, images) (Cox, 1996; Ward, 1998)
–  CARET (PALS atlas) (Van Essen et al., 2001; Van Essen, 2002;
$
#
$
http://brainmap.wustl.edu/caret )
–  ILAB (Gitelman, 2002)
Adolescents generated more errors overall
Error rates dropped for both age groups on reward trials
Behavioral Results: Latency
p < 0.005
p < 0.05
*
*
Slower
Responses
#
Gray = Reward
White = Neutral
Ventral Striatum Activation
During Cue and Preparation
+
$
#
$
Adolescents and adults generated faster responses on
reward trials
Right VS
(8, -58, 53)
(-28, -1, 35)
(-7, 29, 35)
Right Precuneus
RESPONSE PREPARATION
(11, 8, -7)
Adult Reward
Adult Neutral
Adolescent Reward
Adolescent Neutral
RESPONSE
Left FEF
Left InfPCS
L DMPFC
y=4
z = 51
(-31, -10, 44)
Left FEF
Left FEF
(-25, -13, 56)
RED = Adolescent Reward
Adult Reward
Adult Neutral
Adolescent Reward
Adolescent Neutral
4
Study 1: Summary
Study 2: Addressing Reward Value Across Age Groups (Behavioral)
•  Delayed, then heightened adolescent reward response in
ventral striatum
–  Results support both over- and under-active reward system
accounts
•  Increased preparatory activity in oculomotor circuitry
(e.g., FEF) during reward trials suggests a potential process
for how rewards improve behavior in adolescents
Geier & Luna (2012), Child Development
Study 2: Reward Value •  Minimizing age differences in reward value :
Study 2: Reward Value
•  Minimizing age differences in reward value :
1.  Participants choose their own reward (e.g., iTunes,
Home Depot, pre-paid Visa card)
Study 2: Reward Value
•  Minimizing age differences in reward value :
Study 2: Reward Value
•  Minimizing age differences in reward value :
1.  Participants choose their own reward (e.g., iTunes,
Home Depot, pre-paid Visa card)
2.  Win or lose points on each trial rather than money
1.  Participants choose their own reward (e.g., iTunes,
Home Depot, pre-paid Visa card)
2.  Win or lose points on each trial rather than money
3.  Set range of points available ( fixed-economy )
5
Study 2: Bars Reward Antisaccade Task
Cue
(Reward Assessment)
1.5 sec
NEUTRAL
LOSS
+
+
+
•  Participants (N=110)
Saccade Response
(Reward Feedback)
1.5 sec
+
+
Inter-trial Fixation
1.5 sec
+
–  64 Adolescents (13-17 years, 34 Females)
–  46 Young Adults (18-26yrs, 25 Females)
•  Subjects eye data scored (correct/error) during the
experiment; received immediate, auditory feedback based
on performance
+
Response Preparation
(Reward Anticipation)
1.5 sec
+
Study 2: Methods
REWARD
CORRECT!
ERROR!
60 trials per run, 2 runs per session:
40 reward, 40 punish, 40 neutral trials
Error Rates Across Reward and Loss Magnitudes
Study 2: Summary
Adults
•  Adolescents can show mature levels of inhibitory
control when enhancing reward salience and minimizing
reward value differences
Adolescents
*
*
–  5-point (highest magnitude) trials
–  Choosing own reward, fixed-economy point system
*
Adolescents reach adult-levels of inhibitory control on trials
with higher incentive magnitudes
*p<0.05
Error bars +/- 1 SE
Bars Reward AS Task (fMRI)
Study 3: Addressing Age Differences in
Reward Value (fMRI)
1.5 sec
REWARD
NEUTRAL
LOSS
+
+
+
1.5 sec
Cue
(Incentive Assessment, Detection)
Response Preparation
(Incentive Anticipation)
Saccade Response
(Auditory Feedback)
+
1.5 sec
Jittered ITI (1.5, 3, or 4.5 sec)
+
+
{
+
Catch Trial 1
(no saccade response)
+
+
{
Catch Trial 2
(no preparation,
no saccade response)
+
Geier et al. (in preparation)
6
Study 3: Methods
•  Subjects (N=69)
–  44 Adolescents
•  13-17 years
•  21 Females
–  25 Adults
•  18-26 years
•  16 Females
•  fMRI –  Parameters identical to Study 1
–  3.0 Tesla Siemens scanner –  Gradient-Echo EPI, TR = 1.5
–  Deconvolution – no assumed HDR shape –  Simultaneous Eye tracking
+
+
+
+
Time
•
Incentive Cue
(Incentive Assessment, Detection)
+
+
+
Main Effect of Time
Cue
Incentive
Assessment
Visual
cortex
+
+
Medial PFC
BA 10/32
+
Cingulate
FEF
+
Time
Inferior PCS
•
180.76
Ventral
Striatum
F
Inferior
parietal lobule
6.08
p<1 x10-10
+
+
+
Main Effect of Time
Cue
Incentive
Assessment
CUE
+
+
Solid = Adults
Dashed = Adolescents
+
Left Ventral Striatum
(-4, 7, 1)
REW
NS
Cingulate
FEF
180.76
F
6.08
p<1 x10-10
Ventral
Striatum
Inferior
parietal lobule
NEUT
LOSS
NS
NS
NS = Not Significant
7
LOSS CUE
*
+
Cue/Assessment
Left FEF
(-1, 4, 46)
•  In the context of this task, adolescents and adults show
similar responses in ventral striatum suggesting similar
initial assessment of incentives •  Adults show heightened responses to loss cues in
oculomotor, inhibitory control regions (FEF, IPL)
p<0.05
*
Right Inferior
Parietal Lobule
–  Suggests that adults may be initially more motivated by
potential loss cues (Roesch & Olson, 2004)
p<0.001
(32, -58, 37)
*
Right Cingulate
p<0.05
(5, 7, 43)
Solid = Adults
Dashed = Adolescents
sPCS
Response Preparation
(Incentive Anticipation)
Main Effect of Time
Response Preparation
Anticipation
+
Anterior cingulate
+
+
Precuneus
+
Inferior
PCS / FEF
Superior colliculus
+
Time
Insula
•
Ventral
Striatum
64.85
Inferior
parietal lobule
F
6.08
p<1 x10-10
sPCS
+
Response Preparation
Anticipation
Main Effect of Time
PREP
+
Solid = Adults
Dashed = Adolescents
Right Ventral Striatum
(17, 16, 1)
REW
Anterior cingulate
Inferior
PCS / FEF
NS
64.85
F
Ventral
Striatum
Inferior
parietal lobule
NEUT
LOSS
NS
NS
6.08
p<1 x10-10
NS = Not Significant
8
LOSS PREP
*
+
Preparation/Anticipation
Left FEF
*
Right Inferior
Parietal Lobule
p<0.01
(38, -59, 34)
–  Suggests that motivation to avoid potential losses might be
delayed in adolescence relative to adults
*
Right
Anterior
Cingulate
p<0.05
(2, 7, 34)
Solid = Adults
Dashed = Adolescents
•  In the context of this task, adolescents and adults show
similar responses in ventral striatum during reward
anticipation
•  Adolescents show heightened activation during
anticipation of potential losses in anterior cingulate and
cortical eye fields (FEF, SEF, IPL)
p<0.05
(-25, -8, 43)
Saccade Response
Feedback
Saccade Response
(Feedback)
Cingulate
+
+
Main Effect of Time
SEF
Visual Cortex
+
FEF
Superior
Colliculus
+
Time
•
335.47
Ventral striatum
Inferior
parietal lobule
F
7.93
p<1 x10-15
Saccade Response
Feedback
Main Effect of Time
Solid = Adults
Dashed = Adolescents
SACCADE
SEF
Right Ventral Striatum
(10, 15, -4)
Cingulate
*
REW
FEF
p<0.05
335.47
F
Ventral striatum
Inferior
parietal lobule
7.93
p<1 x10-15
NEUT
LOSS
NS
NS
NS = Not Significant
9
SACCADE
REWARD TRIALS
Solid = Adults
Dashed = Adolescents
Right Inferior
Parietal Lobule
Left FEF
(-25, -11, 46)
(29, -47, 40)
Left SEF
(29, -47, 40)
Right Cingulate
Left SEF
Right Cingulate
*
*
(-4, -8, 52)
Right Inferior
Parietal Lobule
Left FEF
*
*
(-25, -11, 46)
Solid = Adults
Dashed = Adolescents
NEUTRAL TRIALS
SACCADE
(8, 7, 31)
(-4, -8, 52)
(8, 7, 31)
all p<0.05
• CEF = cortical eye field
• VS = ventral striatum
Saccade/Feedback
OVERALL SUMMARY
STUDY 1 - RINGS
• Adult VS (rew cue)
•  Adults: heightened responses in VS, FEF, SEF, PPC, and
cingulate, suggesting that they invest more in processing of
reward feedback
RELATIVE ACTIVATION
STUDY 3 - BARS
• Adult CEF (loss cue)
–  May reflect mature process of monitoring the context and
consequences of eye movements during reward trials (Schall et al.,
2002)
STUDY 3 - BARS
• Adult CEF (rew feedback)
• Adult VS (rew feedback)
STUDY 1 - RINGS
• Teen VS (rew prep)
• Teen CEF (rew prep)
STUDY 3 - BARS
• Teen CEF (loss prep)
T
A
A
A
T
T
Cue/
Assessment
Preparation/
Anticipation
Saccade/
Feedback
STAGE OF PROCESSING
Take Home: Studies 1-3
1.  Adolescents show distinct brain responses when
making inhibitory responses in the context of
incentives
–  True even when value differences were minimized and
overt behavior was equivalent
2.  Results indicate that basic processes supporting
more complex decision-making are still immature
during adolescence Part II. Effects of Smoking
Decision making
Reward
Inhibitory
Control
10
Background
P >.25
•  Smoking remains a leading, preventable cause of morbidity and
mortality worldwide •  Large fraction of smokers report wanting to quit, but few (less
than 7%) are able to maintain prolonged abstinence Nicotine and reward
P >.25
•  Nicotine activates reward
pathways
•  Abstinence after chronic use
results in a decrement in the
sensitivity to non-drug rewards
(e.g., money)
•  Anhedonia P >.25
Nucleus
Accumbens
Ventral
Striatum
Nicotine
Nicotine and reward
Study 4: Methods
•  A reduced sensitivity to non-drug rewards may contribute
to continued smoking following quit attempts (relapse):
–  Smoking >> alternatives, leading to biased decisions
•  Altered responses to non-drug reward – key to several
theories of dependence
•  Quantifying these changes may provide a neurobiological
marker of nicotine dependence •  Participants (N=33)
–  23 Daily Smokers (18-65 years)
•  5+ CPD for more than 1 year
•  Low , Middle , High Dependence (NDSS)
–  11 Non-Smokers (18-65 years)
REWARD or NEUTRAL
•  fMRI session
–  “Ring” reward antisaccade task
–  Simultaneous eye tracking
–  Tested after 12-hours of abstinence (biochemically verified)
$
$
$
$ + $
$ $ $
###
# + #
###
+
Geier et al. (in preparation)
Ventral Striatum Activation During Reward
Cue in Non-Smokers and Abstinent Smokers
+
Study 4: Behavior
Reward
More errors
Visual Cortex
(Control)
Ventral Striatum
*
% MR Signal Change
*
Cue Neutral
% MR Signal Change
p < 0.01
TR
* Group by Time, p < 0.01
All participants show improved performance with reward;
Abstinent smokers vs. non-smokers generate more errors overall
TR
Non-Smokers
Smokers
Abstinent adult daily smokers vs. non-smokers
show a reduced sensitivity to reward cues
11
Ventral Striatum Activation During Reward
Cue in Non-Smokers and Abstinent Smokers
+
+
Prepara)on Cue % MR Signal Change
Ventral Striatum
*
Right FEF
TR
Right Sup. Parietal
Non-smokers
Non-smokers
TR
* Group by Time, p < 0.01
Non-Smokers
Non-Smokers
Low Dependence
Smokers
Middle Dependence
High Dependence
Response Right Inf. PCS
Non-smokers
Reward Neutral
Non-smokers show a robust response when anticipating responding for reward
Next step: Adolescent smoking •  Almost invariably, adult smokers
start during adolescence
Posterior
Parietal
•  Daily smoking typically by age 18
•  Little is known about the
neurobiological effects of adolescent
smoking and links to emerging
dependence
Anterior
Cingulate
Posterior
Cingulate
Thank you!
Research Questions
•  Will adolescent smokers show greater abstinence-related
reward deficits compared to adults?
•  Or, will hyper-active reward systems ‘compensate’ during
periods of withdrawal? RELATIVE ACTIVATION
Penn State Hershey Cancer Institute
Social Science Research Institute
Clinical Translational Science Institute
Collaborators
T
A
A
T
Cue/
Assessment
A
T
Preparation/
Anticipation
Saccade/
Feedback
Penn State :
Steve Branstetter, Ph.D.
Jonathan Foulds, Ph.D.
Mark Greenberg, Ph.D.
Steve Wilson, Ph.D.
University of Pittsburgh:
Eric Donny, Ph.D.
Bea Luna, Ph.D.
Aarthi Padmanabhan
Michael Hallquist, Ph.D.
Maggie Sweitzer
Matt Weaver, Ph.D.
Rachel Denlinger
Gina Sparacino
STAGE OF PROCESSING
12