Perceptual Learning

• Involves learning about things, not what to do when they are present.

• Simple perceptual learning, recognizing stimuli, takes place in appropriate regions of sensory association cortex.

Visual Learning

Inferior temporal cortex - necessary for visual pattern discrimination, receives info from visual cortex.

Ventral/dorsal streams - what and where.

Delayed matching-to-sample task - requires that stimulus be remembered for a period of time.

- "Remembering" the stimulus involves a neuronal circuit; it is the circuits, not the individual neurons that recognize particular stimuli.

- Lesions of inferior temporal cortex disrupts an animal's ability to remember what it has just seen.

- Electrical stimulation of the inferior temporal cortex during the delay causes forgetting.

• Responses of single neurons in inferior temporal cortex recorded when pairs of stimuli shown.

- Found that when stimuli are paired, the neural circuits responsible for recognizing them become linked together.

- Perception of either stimulus activates both circuits.

• Visual long-term memory involves the establishment of new circuits in the inferior temporal cortex by means of synaptic changes.

Auditory Learning

Auditory learning tasks modify response characteristics of neurons in various parts of the auditory system

• Study pairing tones with shock

- pretraining, neuron responds best to 9.5 Hz tone

- CS is 9-Hz tone, paired with shock

- after training, neuron now responds best to 9-Hz tone and less to 9.5 Hz.

Medial Division of the Medial Geniculate Nucleus (MGm): Important for classically conditioned emotional responses

- Receives info from auditory and somatosensory systems.

- Directly connected to the central nucleus of the amygdala.

- Which activates the nucleus basalis.

- Nucleus basalis contains acetylcholine neurons which innervate auditory cortex, telling it to pay particular attention to the ventral division of the medial geniculate nucleus (conveys auditory information).

S-R Learning

(1) Classical Conditioning

• Central nucleus of the amygdala involved in classically-conditioned emotional responses.

• Pairing of tone and footshock increases responses to CS.

Extinction - somehow, NMDA receptors again involved - most likely due to long-term depression.

(2) Instrumental Conditioning and Motor Learning

Two pathways exist between sensory association cortex and motor association cortex:

(a) Direct trascortical connections: Short-term memory and with hippocampus involved in episodic memory.

(b) Via basal ganglia and thalamus: Used once no longer "new" learning; Parkinson's example

premotor cortex - monkeys raising arms for food; humans learning motor task.

Reinforcement - reinforcing brain stimulation discovered by Olds and Milner in 1954.

medial forebrain bundle - best place for self-stimulation; also involved in natural reinforcers, such as food, water, or sex.

dopamine - likely serves as a neuromodulator, involved in reinforcement-receptors in nucleus accumbens.

conditioned place preference - animals prefer to be where they have encountered a reinforcing stimulus.

• this process used to test influence of dopamine on reinforcement.

• if given dopamine antagonist during place training, do not develop conditioned place preference.

• also involved in negative reinforcement - dopamine antagonists prevent avoidance learning.

• amphetamine is a dopamine agonist - animals will work to get injections of it.

- drug discrimination procedure - train animals to press a certain lever to receive food after it has been given a drug and to press another lever after it has been given saline.

- found that rats would press drug lever only if amphetamine put directly into nucleus accumbens, rather than other brain structure.

- they pushed the saline lever if they also had been given a dopamine receptor blocker with the amphetamine into the nucleus accumbens.

 
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