Post on 28-Dec-2015
New Insights into Substance Use Disorders (SUD) From Brain Imaging
Iliyan Ivanov. MD
Mount Sinai School of Medicine
Alcohol Medical Scholars Program
1©AMSP 2012
Substance Use Disorders (SUD)
They are:
• Prevalent Lifetime risk ~ 20% Past year ~8%
• Expensive ↓ Work ↑ Health care ↑ Crime
• Can be difficult to treat 25-50% relapse in 3-6 month Handful of FDA approved Tx
2©AMSP 2012
SUD Biology & New Tx
• SUDs → changes in brain networks
• Understanding changes → new Tx
• Neuroimaging may ↑ insights for:
Brain regions/networks related to SUD
Neurochemicals mediating drug effects 3©AMSP 2012
This Lecture Will Review
• Definitions & backgrounds
• Biological systems relevant to SUDs
• Visualizing brain systems with neuroimaging
• Clinical & Tx applications
4©AMSP 2012
Dependence (DSM-IV)• Repeated problems in same 12 months; 3+ of:
Tolerance: ↓Effects with same amount, or ↑Use for same effects Withdrawal: physiological symptoms ↑ Amount or longer use than intended Inability to stop or cut down use ↑ Time spend obtaining, using or recovering Important activities given up or reduced Use despite problems
5©AMSP 2012
Abuse (DSM-IV)
• 1+ in same 12 mo of:
Role interference Hazardous use Legal problems Social/interpersonal problems
Not dependent
6©AMSP 2012
Clinical Course
• Trajectory for alcohol dependence by age:First drink 12-14 First intoxication 14-18 First minor problems 18-25DSM Dx of dependence 25-35Enter Tx 40s
• ↑ Morbidity for: Heart disease (↑ cholesterol and BP)
Cancer (↓ immune function)Accidents Major depression (acute fx of alcohol)Suicide: 3-10% lifetime risk
7©AMSP 2012
Clinical Course –con’t
• Age of death: 55-60
~10 years earlier than general population
11-25% of premature deaths
• Fluctuating course
Abstinence → temporary control→ misuse
Average of 4 months abstinence in 1-2 years
Long term “controlled” use – 1-5%
Spontaneous remissions: ~20%
8©AMSP 2012
Imaging Can Show Functioning
• Acute drug effects Opioids stimulate opioid receptors Amphet/cocaine ↑ dopamine (DA) Depressants
↑ γ-Aminobutyric acid (GABA) ↓ Glutamate
• Positive reinforces→ ↑ acute DA release Natural rewards (e.g. food) → bursts of DA Most drugs ↑ DA 10 fold over natural rewards
11©AMSP 2012
Stopping Drugs → Opposite Effects
• Chronic use may cause
↓ Number of DA receptors in striatum
↓ Blood circulation throughout brain
• Stopping use may result in
↑ Number receptors ↓ by chronic use
Blood circulation normalizes 12©AMSP 2012
Regional Drug Effects • Mostly in regions rich in DA (e.g. Striatum) Consist of Caudate Putamen Globus pallidus
Divided into Ventral striatum/nucleus accumbens (NAcc) - Motivation - Experience of rewards Dorsal striatum (caudate & putamen) - Decision making - Initiation of action
13©AMSP 2012
1-2 Min 3-4 5-6
6-7 7-8 8-9
9-10 10-20 20-30
6416 32 48 800
0,008
0,006
0,004
0,002
0,000
0,010
% D
OS
E /
cc
Time (mins)
[11C] COCAINE UPTAKE IN HUMAN STRIATUM
STRIATUM
Drug Effects on the Brain
• Drugs target the striatum
14
2 Neurosystems Key to Drug Effects
• Behavioral Activation System (BAS)
Functions – ↑ person’s actions
BAS includes: NAcc, orbito-frontal cortex
Activity affects sensitivity to rewards
15©AMSP 2012
Behavioral Inhibition System (BIS) • Modulate person’s actions
- ↑ BIS activity = ↑ inhibition of action
- ↓ Activity = ↓ inhibition of action = impulsivity
Consists of - Dorso-lateral prefrontal cortex (DLPC)
- Inferior frontal cortex (IFC)
- Anterior cingulate cortex (ACC)
• Changed activity results in ↑ or ↓ impulsivity
16©AMSP 2012
SUD Relates to BAS/BIS
Mismatch
• When well-matched → adaptive behaviors
• Mismatch → problem behaviors → drug problems
18©AMSP 2012
Functional Neuroimaging of BAS/ BIS• Methods with radioactive chemicals
Positron Emission-Tomography (PET)
Single Proton Emission Computer Tomography (SPECT)
• Visualize Changes in blood flow
Distribution of nutrients (glucose)
Chemicals binding to brain receptors e.g. DA
• Short comings Low resolution (fuzzy brain pix)
Expensive
Radiation exposure to subjects/staff
19©AMSP 2012
PET Visualization of BAS Changes in brain structures = different behaviors
*
***
.003 .01 .03 .1
0.0
0.5
1.0
1.5
2.0
S.003 .01 .03 .1
0
10
20
30
40
50 REINFORCERS(per session)
INTAKE (mg/kg/session)
Morgan et al. (2002) 20©AMSP 2012
MORE
LESS
Control SUD
PET visualization of BAS in SUD
• SUD = ↓receptors in the striatum
21©AMSP 2012
PET visualization of BAS in SUD• Blood circulation changes in: Normal subjects
Cocaine dependence 10 day abstinence
Cocaine dependence 100 day abstinence
22©AMSP 2012
Functional Neuroimaging of BAS/BIS• Functional Magnetic Resonance Imaging (fMRI), detects changes in blood flow changes in blood flow = changes in neural activity
Artery Vein
Arterioles VenulesCapillary Bed
Neurons
23
Functional Neuroimaging of BAS/BIS
• Other methods
Magnetic Resonance Spectroscopy (MRS) - Uses “magnetic signature” of brain molecules - Detect ↑ vs.↓ concentration of the molecules - ↕ in concentration = cellular dysfunctions
MR shows both structure & function - High resolution - Show differences in brain activity during tasks - No radiation exposure
• Short comings → expensive
24©AMSP 2012
fMRI Best Image of BIS Function
• Is best because:
Inhibition best studied in “real time”
Inhibitory tasks engage cortical-structures
PET NOT in real time
• Show functions during cognitive task
Motor : e.g. don’t press button
Cognitive : e.g. name color vs. read word
Drug related images (drug vs. neutral cues) 25©AMSP 2012
fMRI Findings in SUD
• ↓ Inhibition when at risk
Adolescents with SUD parents = ↓ motor inhibition
- ↓ Motor inhibition = ↓ activity in ACC, striatum
- Possibly reflect genetics
Adults with SUD have ↓ motor/cognitive inhibition
- ↓ Activity in ACC, DLPC, IFG
- Could be due to genetics and/or drug effects
27©AMSP 2012
fMRI Findings in SUD
• Adults who quit drugs show motor inhibition ↑ Activity in DLPC & ACC May be important for Tx effects
• ↑ Inhibition after Tx ↑ Cognitive inhibition after Tx with stims ↑ Cognitive inhibition =↑ activity in ACC,
OFC28©AMSP 2012
New Insights in SUD from Neuroimaging
• Functional model for SUD
• Biological basis of recovery
• Visualizing Tx effects
29©AMSP 2012
SUD Functional Model
• ↑ BAS and ↓ BIS high drive & low inhibition
• High drive and low inhibition = ↑substance use
• ↑ Substance use may lead to SUD
• SUD may be related to BAS/BIS mismatch
• Mismatch might predate SUD = biological risk30©AMSP 2012
Neuroimaging and SUD Recovery
• Drug induced physiological symptoms last 48-72hrs
• Low BAS activity lasts ~ 30 days
• Full recovery of BAS activity occurs > 1 year
• Even in late sobriety perform worse on tasks
• Prescription drugs may “speed up” recovery
31©AMSP 2012
DA Transporters in Early/Late Detoxin METH Abuse
1
1.2
1.4
1.6
1.8
2
Early Late
Caudate
DA
Tra
nsp
ort
ers
(Bm
ax/K
d)
1.51.61.71.81.92
2.12.22.3
Early Late
Putamen
p < 0.003 p < 0.05
32©AMSP 2012
Cognitive Function in Early/Late DetoxIn METH Abuse
6789
10111213
Early Late
Timed gate
Tim
e (
sec
on
ds
)
p = 0.14
4550556065707580
Early Late
Pegboard
Tim
e (
sec
on
ds
) p = 0.73
6
8
10
12
14
16
Early Late
Delayed RecallN
um
be
r o
f W
ord
sp = 0.11
6
8
10
12
14
16
Early Late
Immediate Recall
Nu
mb
er
of
wo
rds
p = 0.47
Motor
Memory
33©AMSP 2012
Neuroimaging and Tx Effects on BAS/BIS
• Tx may affect brain activity by
Meds affect brain function = fMRI detects changes
Behavioral Tx = ↑ cognition
↑ Cognition = ↑ brain activity = detected by fMRI
34©AMSP 2012
Med Effects on Brain Functions in SUD
• Stims ↑ cognitive inhibition in cocaine dependence
• ↑ Cognitive inhibition = ↑ activity in ACC1, OFC2.
35©AMSP 2012
Neuroimaging and Behavioral Tx
• Mesial (m)PFC → ↕ inhibition with drug cues
↓ Activity in mPFCR =↓ inhibition = ↑ relapse risk
Cognitive Tx → cognitive control
Cognitive control → “normalizes” mPFC activity
“Normalized” mPFC activity = ↓ relapse risk
These changes can be tracked by fMRI
36©AMSP 2012