Transcript Document 208848

motivation, reward
& addiction
Feb 20, 2009
..or why we play the lottery
anticipation, outcome
and experience
Breiter et al, 2001
what motivates us to eat?
escape from hunger
pleasurable (olfactory) experience
boredom
etc…..
drive-states:
hypothalamus, limbic system
and beyond…
influence of learning and emotion on goaldirected behavior - motivation by pleasure?
Kelley 2004
addiction
hijacking of the natural reward processes
movie time
how do we become addicted?
DEPENDENCE
need for continued exposure to a drug so
as to avoid withdrawal symptoms
dependence occurs as a result of adaptive
changes in the body (homeostasis?)
“cravings” (induction of a drive-state?)
does dependence = addiction?
(Nestler 1992)
simple homeostasis
molecular / cellular models of
tolerance & dependence
from dependence to addiction
why are some abused drugs not addictive?
is there a common “addiction mechanism”?
electrical self-stimulation
drugs kill
“a hungry animal often
ignored available food
in favor of the pleasure
of stimulating itself
electrically .... 2000
times per hour for 24
consecutive hours”
(Olds 1956)
“pleasure centers”
DA neurons and reward
VTA
(Schultz et al, 1993)
does DA signal reward?
displacement of [11C]raclopride binding by DA release
(Volkow et al, 1997)
PET scan
MP = methylphenidate
“RITALIN”
learned associations
not so fast……
DA activity is
altered by
experience
prediction errors
novelty
VTA DA response is
associated with
sensory cues
i.e., DA response
predicts reward
drive is to correct error
(Schultz et al 1997)