Neurosciences John Evenden Varieties of Impulsivity: Evidence from Animal Studies John Evenden Dept...

NeurosciencesJohn Evenden

Varieties of Impulsivity: Evidence from Animal Studies

John Evenden

Dept of Neurosciences

AstraZeneca R & D Wilmington

Wilmington, DE, USA


What’s in this talkFour Questions• What is Meant by Different Varieties of Impulsivity?• Do Biologically Important Factors Influence the

Different Varieties of Impulsivity in Different Ways?• How does “personality” (or trait impulsivity)

interact with state impulsivity?• Does it make a difference whether impulsive

behaviour leads to loss of rewards or punishment?


Question 1

What is Meant by Different

Varieties of Impulsivity?


Varieties of ImpulsivityExamples from Personality Research

Dickman (1990) Dysfunctional Dickman (1993) AttentionalFunctional “Reflection-impulsivity”

Disinhibition

Buss & Plomin (1975) Inhibitory control Eysenck (1993) ImpulsivenessDecision time VenturesomenessLack of PersistenceBoredom/Sensation seeking BIS-10 motor

(Patton et al, 1995) cognitivenon-planning

Tridemensional Personality Questionnaire Novelty seekingCloninger (1987) Harm avoidance

Reward dependence


Impulsive Decision Making and the 3-term Contingency

Stimulus UCS/Reinforcer

Response

What are the CONSEQUENCES of

different contingencies?

What do I need to know in

PREPARATION to act?

Classical Conditioning

Instrumental ConditioningHow should I

EXECUTE my act to ensure predicted

outcome?


Three types of impulsive decision making

PREPARATION Not all relevant information Uncertain

is taken into account before Discrimination

making a decision

EXECUTION The necessary behaviour is Fixed Consecutive

ended before the goal is Number Test

attained

CONSEQUENCES A quick, but less valuable Delayed

outcome is chosen rather Reinforcement Test

than a later but more valuable


Three tests of impulsive decision making

PREPARATION Not all relevant information Uncertain

is taken into account before Discrimination

making a decision

EXECUTION The necessary behaviour is Fixed Consecutive

ended before the goal is Number Test

attained

CONSEQUENCES A quick, but less valuable Delayed

outcome is chosen rather Reinforcement Test

than a later but more valuable


Question 2

Do Biologically Important Factors

Influence the Different Varieties

of Impulsivity in Different Ways?


Fixed Consecutive Number Schedule

L.L.L.R = 3 No Food L.L.L.L.L.L.L.R = 7 No Food L.L.L.L.L.L.L.L.R = 8 Food L.L.L.L.L.L.L.L.L.L.R = 10 Food

Count up how many times

each length occurs and plot it

in a histogram (distribution

analysis)

NumberofChainsendingat eachlength

0 1 2 3 4 5 6 7 8 9 10 11 12 1314.....

More impulsive Less impulsive


Paced Fixed Consecutive Number Test Trained to press left and right lever to obtain small food

pellets

After this the levers are retracted for either 2 or 5 seconds

every time the rats presses

Trained press first the left lever then the right lever to get

food

Trained to press the left lever several times before pressing

the right lever to get food.

This way the experimenter has control over how fast the

rat can press the lever and the minimum time to complete a chain of responses

Lever LeverFood


Fast Component

% C

hai

ns

at le

ast

n lo

ng

0

20

40

60

80

100

Slow Component

0 5 10 15 20

0

20

40

60

80

100

% C

hai

ns

at le

ast

n lo

ng

Chain Length

saline0.03 mg/kg 8-OH-DPAT0.1 mg/kg 8-OH-DPAT0.3 mg/kg 8-OH-DPAT

Fast Component

% C

ha

ins

at

lea

st

n l

on

g

0

20

40

60

80

100

Slow Component

0 5 10 15 20

0

20

40

60

80

100

% C

ha

ins

at

lea

st

n l

on

gChain Length

saline0.1 mg/kg DOI0.3 mg/kg DOI1.0 mg/kg DOI

Paced Fixed Consecutive Number Schedule - 8-OH-DPAT, DOI - survival plot

8-OH-DPAT reduces impulsivity, DOI increases impulsivity


Uncertain DiscriminationRats are first trained that a lit lampsignals lever which gives food

When they have been trained to 95 - 100% correctthe test procedure is started in which the signalis made uncertain.

First one of the levers is chosen as “correct”.

Then one of the three lights is turned on at random.

After 0.1 s that light is turned of, and again one of the lights is turned on at random

...and so on...

Each time one of the lights is chosen, the probability that it is the one over the correct leverincreases by a small amount until after about 5 s it is on nearly all the time.

Lamps


Uncertain Discrimination - 8-OH-DPAT, DOI

Reaction Time (s)

0 to 1 1 to 2 2 to 3 3 to 4 >4

Per

cent

Cor

rect

Res

pons

es

50

60

70

80

90

Num

ber

of R

espo

nses

5

10

15

20

25

30

35

40

45

50

Vehicle

0.3 mg/kg DOI1.0 mg/kg DOI

0.1 mg/kg DOI

**

**

*

*

Reaction Time (s)

0 to 1 1 to 2 2 to 3 3 to 4 >4

Per

cent

Cor

rect

Res

pons

es

50

60

70

80

90

Num

ber

of R

espo

nses

5

10

15

20

25

30

35

40

45

Vehicle

0.03 mg/kg 8-OH-DPAT0.1 mg/kg 8-OH-DPAT

0.01 mg/kg 8-OH-DPAT

**

*

**

*


Impulsivity - Trait and State

We usually think of impulsivity as an aspect of personality

• DSM personality disorders are essentially lifelong

• Most personality questionnaires are designed to look for the personality trait of impulsivity

But

• Drugs change the state of the subject, not his/her underlying personality


Question 3

How does “personality” (or trait

impulsivity) interact with state

impulsivity?


State and Trait interactions

• Acutely administered drugs are a model of “state”

• Different strains of rats are models of different patterns of “traits”

Question

• Do the drugs have the same effects in different rat strains with different levels of “trait impulsivity”?


Paced Fixed Consecutive Number Schedule

- amphetamine, haloperidol - AA/ANA rats

Chain length (CL)

5 10 15 20

% c

ha

ins

lon

ger

tha

n C

L

0

20

40

60

80

100AA Saline

AA 0.2 mg/kg amphetamine

AA 0.4 mg/kg amphetamine

ANA Saline

ANA 0.2 mg/kg amphetamine

ANA 0.4 mg/kg amphetamine

Key comparison

Haloperidol FCN8

Chain length (CL)

5 10 15 20

Pe

rce

nt c

ha

ins

long

er

tha

n C

L

0

20

40

60

80

100AA Saline

AA 0.01 mg/kg haloperidol

AA 0.03 mg/kg haloperidol

ANA Saline

ANA 0.01 mg/kg haloperidol

ANA 0.03 mg/kg haloperidol


Question 4

Does it make a difference

whether impulsive behaviour

leads to loss of rewards or threat

of punishment?


Motivation and impulsivity

• Most non-human impulsive behaviour results in loss of positive reinforcers

• Much human impulsive behaviour results in delivery of punishers

Question

• Is it possible to model self control using avoidance of punishment in rats?


Fixed Consecutive Number Shock

Avoidance

• Basic schedule is two-lever paced fixed consecutive number (FCN6)

• Option 1: make 6 or more consecutive responses on left lever and then press right lever for delivery of one food pellet

• Option 2: make less than 6 consecutive responses on left lever and then press right lever for delivery of one food pellet + 0.5s footshock (0.45 - 0.9 mA)


Paced FCN Shock Avoidance

Rat 1 (Shock Avoidance)Rat 3 (Shock Avoidance)Rat 10 (Positive Reinforcer)Rat 17 (Positive Reinforcer)

1 3 5 7 9 11 13 15 17 190

20

40

60

80

100

Chain Length (CL)

Per

cen

t C

hain

s lo

nger

tha

n C

L

Amphetamine increases impulsivity if the outcome is loss of reward, but reduces impulsivity is the outcome is punishment


Summary• Different aspects of impulsivity are differentially sensitive to the various

drugs– dopaminergic drugs primarily seem to affect EXECUTION of behaviour– “traditional” serotonergic deficit may fit best with a deficit in

PREPARATION

• Effects of the drugs don’t always fit with expectations• The effects of the drugs depend (in part) on the strain of rat used.

Impulsive behaviour is modulated by trait factors (genetics, “personality”), and state factors (in this case, drug treatment). These factors interact with one another. This interaction is complex and not obvious

• Positive reinforcement schedule and punishment schedule can maintain the same pattern of self control/impulsivity

• The effects of drugs can be dramatically different if self-control is brought about by negative reinforcement (loss of reward) or punishment.

Neurosciences John Evenden Varieties of Impulsivity: Evidence from Animal Studies John Evenden Dept...

Documents

Transcript of Neurosciences John Evenden Varieties of Impulsivity: Evidence from Animal Studies John Evenden Dept...