Transcript Neurobiological Substrates of Play Behavior

CH2CH2NH2
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The Playful Mind
Play Behavior and the Neurobiology
of Having Fun
References to “fun” in the scientific literature are
few and far between
Is play fun?
• Ask any kid
• Rats will run a maze when the opportunity
to play is the reward
• Rats will prefer an environment where
they’ve played over an environment where
they haven’t played
The questions of the day
• What exactly is play and how do we study it in a rat?
• Is there a neural circuit for play?
• Since dopamine is involved in everything else, is it
also involved in play?
• Are there genes for playfulness?
• Can studying play in rats tell us anything about
psychiatric conditions in human children?
• Is this the “fountain of youth”?
What exactly is play
and how do we
study it in rats?
What exactly is play?
Play is repeated, incompletely functional
behavior differing from more adaptive
versions structurally, contextually, or
ontogenetically, and initiated voluntarily
when the animal is in a relaxed or unstressed
state.
Burghardt (2001)
The many faces of play
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Imaginative play
Symbolic play
Sensorimotor play
Object play
Rough-and-tumble play
Dependent Measures for
Studying Play in the Rat
• Contacts directed to nape
• Responses to nape contacts
– Responses which tend to continue
the play bout
– Responses which either stop the bout
or put the bout “on hold”
• Frequency of pins
Contact directed
to nape
Response to
nape contact
Complete rotation
(pin)
The Fun House
Inside the Fun House
Is there a neural circuit for play?
• Experimental
approaches
– Lesions
– Metabolic markers
– Administration of
neurochemicals
What do we know?
• Cerebral cortex not that important
• Multiple subcortical circuits
– Thalamic / Somatosensory circuit
– Basal ganglia circuit
– Limbic circuit
Thalamic – somatosensory circuitry
• Responsiveness to
playful solicitation
• Specificity to
stimulus type
• “tickling” and
“laughter”
Thalamic – somatosensory circuitry
• Responsiveness to
playful solicitation
• Specificity to
stimulus type
• “tickling” and
“laughter”
Basal ganglia circuitry
• Motor patterning
• Motivational
component
• “sensitized” by lack
of stimulation
(boredom)
Basal ganglia circuitry
• Motor patterning
• Motivational
component
• “sensitized” by lack
of stimulation
(boredom)
Primary motor pathway
Limbic circuitry
• Evolution of
mammals and the
emergence of limbic
system
• Importance of the
social bond
Limbic circuitry
• Evolution of
mammals and the
emergence of limbic
system
• Importance of the
social bond
Is there a neural circuit for play?
• Multiple circuits
• Cortical
development may
inhibit subcortical
“play circuitry”
Since dopamine seems to be
involved in everything else, is it
also involved in play?
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“Dopamine, how do I love thee? Let me count
the ways”, jokes George Koob, Ph.D., from the
Scripps Institute. Excitement about dopamine
is now so high that the danger is not
underestimating its reach, but exaggerating it:
“Today’s gig is that dopamine is a kind of
everyman’s neurotransmitter because it does
everything. And the fact is, it doesn’t.
“The Plunge of Pleasure”
Psychology Today
September/October 1997
Brain Dopamine Systems
PFC
CPu
NAc
SN
VTA
Nigrostriatal system
Mesolimbic/Mesocortical system
“Tweeking” receptors with neurochemicals
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Agonists
Antagonists
Reuptake inhibitors
Reverse-reuptake
(release)
Administer drug
Observe behavior
Dopamine and play
• Psychomotor stimulants (amphetamine,
methyphenidate) potently reduce play
• D1 dopamine agonists and antagonists uniformly
reduce play
• D2 dopamine agonists reduce play
– Low doses may increase play
• D2 dopamine antagonists uniformly reduce play
• Extensive dopamine lesions alter the patterning of
play
Breaking up play
Anticipatory/Preparatory
Behaviors
Consummatory
Behaviors
Anticipatory/Preparatory Behaviors
Stimuli predictive of reinforcer
Increased release of dopamine in
mesolimbic terminal regions
Increased anticipatory or preparatory
responding
Anticipatory Response for Play
5 minutes
5 minutes
Control
alone
alone
Play
alone
play
partner
Dependent measure:
tunnel crosses
Play experience yields an
anticipatory response
Tunnel Crosses
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Control (n= 9)
Play (n= 9)
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Day of Testing
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Blockade of dopamine receptors with
haloperidol
disrupts anticipatory activity
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Anticipatory Behavior and Play
Stimuli predictive of play
Increased release of dopamine in
mesolimbic terminal regions
Anticipatory eagerness
Ultrasonic vocalizations as measure of
anticipatory eagerness
Acquisition of 55 kHz vocalizations
• Control animals placed
in chamber for 2
minutes
• Experimental animals
placed in chamber for 2
minutes prior to a 5
minute opportunity to
play
Haloperidol reduces vocalizations
Effects of haloperidol on play
• Nape contacts reduced
in rats allowed to play
with same partner
every day
• No effects on
responsiveness to nape
contacts
Since dopamine seems to be
involved in everything else, is it
also involved in play?
• Important for actual
execution of the behavior
patterns
• Anticipatory eagerness
• Mesolimbic vs.
nigrostriatal involvement
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Are there genes for
playfulness?
Use of inbred strains
• Known behavioral and neurobiological
differences between selected strains
• Fischer-344 and Lewis strains
• Groundwork for studying genetics of play
• Increased understanding of disorders with
genetic origins
Fischer-344 and Lewis strains
• Responsiveness to stress
• Fischer > Lewis
• Reactivity to handling and novelty
• Fischer > Lewis
• Susceptibility to inflammatory disease
• Lewis > Fischer
• Self-administration of abused drugs
• Lewis > Fischer
• Play behavior
• Lewis > Fischer
Play
solicitation
Playful
responsiveness
Does isolation affect sensitivity to
amphetamine?
60 minutes baseline
Fischer
or
Lewis
Social
vs.
1 day isolation
Amphetamine (2 mg/kg)
Social
vs.
3 days Isolation
90 minutes post-injection
Amphetamine has comparable effect after
1 day of isolation
3 days of isolation results in sensitized response
in Lewis rats, but not Fischer rats
Is there a parallel with drug use and abuse?
Isolation-induced sensitization
Chronic, intermittent
bouts of play
isolation
Sensitized response
to amphetamine
Drug-induced sensitization
Chronic, intermittent
drug taking
withdrawal
Sensitized response
to amphetamine
Are there genes for
playfulness?
• Strain differences
• Independence of
maternal influence
• Individual
differences?
• Personality traits?
Can studying play in rats tell us
anything about psychiatric conditions
in human children?
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Attention deficit disorder (ADHD)
Autism
Childhood depression
Anti-social behaviors and violent
tendencies
Is this the
“fountain of youth”
Why is it important for your child to play?
When children play, they exercise their senses, their
intellect, their emotions, their imagination - keenly and
energetically…to play is to explore, to discover and to
experiment. Playing helps children develop ideas and gain
experience. It gives them a wealth of knowledge and
information about the world in which they live - and
about themselves. So to play is also to learn. Play is fun
for children. But it’s much more than that - it’s good for
them, and it’s necessary…play gives children the opportunity
to develop and use the many talents they were born with.
Why is it important for your child to play?
When children play, they exercise their senses, their
intellect, their emotions, their imagination - keenly and
energetically…to play is to explore, to discover and to
experiment. Playing helps children develop ideas and gain
experience. It gives them a wealth of knowledge and
information about the world in which they live - and
about themselves. So to play is also to learn. Play is fun
for children. But it’s much more than that - it’s good for
them, and it’s necessary…play gives children the opportunity
to develop and use the many talents they were born with.
Lego’s Building Set