Item Details

abstract

Dopamine signaling is thought to play a critical role in reward-related learning, and the predominant hypothesis proposes that dopamine neurons signal the expected reward values of sensory stimuli in the form of a short-latency phasic burst. Thus, the reward prediction hypothesis assumes that information relevant to determining stimulus identity informs dopamine neuron firing. Recently, this critical assumption has been questioned and given rise to an alternative hypothetical framework proposing that dopamine activity represents a more generic signal of stimulus salience. Proponents of this competing hypothesis note that the requisite feature-based discrimination would not be possible in a period short enough to inform the dopamine response. Instead, the "saliency hypothesis" proposes that short-latency dopamine activity reflects the relative salience of stimuli (independent of their reward value) and that this signal likely derives from the superior colliculus (SC), a subcortical structure lacking the capacity for fine feature discrimination but specializes in detecting and locating salient sensory events. Support for this latter view comes from recent anatomical evidence for a projection from the SC to substantia nigra pars compacta and physiological findings showing that SC activity can drive phasic dopamine activity. This dissertation provides a critical test of these competing hypotheses through in vivo recording from dopamine neurons in the context of behavioral tasks capable of dissociating activity relating to stimulus salience from that which predicts reward value. Results from these studies reveal a biphasic neural response and suggest that dopamine neurons both encode the occurrence of salient events and predict reward at distinct temporal latencies.

subject

phasic dopamine

associative learning

reward prediction

salience

substantia nigra pars compacta

in vivo electrophysiology

contributor

Hudgins, Eric (author)

Deadwyler, Sam (committee chair)

Stanford, Terrence (committee member)

McHaffie, John (committee member)

Redgrave, Pete (committee member)

Salinas, Emilio (committee member)

date

2010-05-05T12:42:24Z (accessioned)

2010-06-18T18:59:08Z (accessioned)

2010-05-05T12:42:24Z (available)

2010-06-18T18:59:08Z (available)

2010-05-05T12:42:24Z (issued)

degree

Neuroscience (discipline)

identifier

http://hdl.handle.net/10339/14829 (uri)

language

en_US (iso)

publisher

Wake Forest University

rights

Release the entire work for access only to the Wake Forest University system for one year from the date below. After one year, release the entire work for access worldwide. (accessRights)

title

FUNCTIONAL ROLES OF MIDBRAIN DOPAMINE NEURONS IN ASSOCIATIVE LEARNING

type

Dissertation