Learning: Acquisition of new information

Memory: Retention of Learned information

Karl Lashley

task may have depended on many different sensing and motor capabilities. Large lesions, may have impacted areas responsible for these and not memory and learning. Only cortex explored.

Many neurons are reciprocally connected.

A stimulus activates a network of neurons

Activity continues while stimulus is removed.

Neuronal connections that are activated at the same time are strengthened. (Learning)

Partial stimuli can now activate the entire network.

Henry Molaison

Seizures required removal of temporal lobe.

Could learn motor and perception skills, but could not form new memories.

Procedural (implicit, unconscious): Tuning and modification of networks that support skilled performance

Declarative(explicit, conscious): encoding, storage and retrieval of memories for specific facts

Procedural

Repetition Priming

Associative Learning (Classical Conditioning)

Non-Associatve learning (Habits, sensitization)

Basal Ganglia (acquired habitual activity, bike riding, piano playing)

Cerebellum (sensory-motor adaptations, VOR plasticity)

Activity and firing patterns change as behavior is learned.

In the rat, the primary activity experienced moves further back from the point at which the decision must be made to do a behavioral task as it is learned.

Parkinson's, Huntington's showed deficits

Amnesia patients were fine!

amygdala (emotional responses -> fear conditioning)

cerebellum (muscle learning ->blink reflex)

Altered response to a stimulus, given repeated presentation of the stimulus

organism learns about benign stimulus, elimintates inappropriate defensive response

Mediates preferences and aversions (unconsciously)

Develops biases toward rewarded stimuli

Fear conditioning

Rats habituate to the chamber

Tone is played -> shock rats as CS

Tone played alone -> cause rats to freeze, blood pressure to rise

Learn how to discriminate between alike stimuli

Improves with training.

Early processing stages in the visual cortex.

Learning did not transfer between eyes or different quadrants of the same eye, implying a retinotopic map.

Short-term memory (immediate and working)

Long-term memory

Short term -> Temporary, limited capacity, requires rehearsal (immediate)

Long term -> more permanent, greater capacity, characteristic of declarative memory, doesn't require rehearsal.

Active retention of information when it isnt available from the environement ("keep in mind")

Immediate -> actively held in mind, <30 sec lifetime (no rehearsal), disruption-prone, 7 items

Working -> retention of information to guide behavior (notice car, calc speed and direction, forget when car is gone), manipulations of information to protect interference

the same brain regions where precise sensory information is encoded.

IT for object recognition, S1 for recognizing textures

Often active during memory delay period, carrying task-relevant information (i.e. maintaining stimulus location)

Not totally responsible for it, damage to prefrontal cortex does not eliminate working memory.

PFC-destroyed monkey could not do a remembering task in the light, but could in the dark -> attention based?

Reverberating neural activity -> short-term memory

Stabilizing the reverberating neural activity -> long-term memory

Use it or lose it.

cerebral trauma induces recent memory loss (car accident amnesia)

Stimulants administered after learning enhance memory

Protein synthesis inhibitors do not prevent learning, but disrupt memory of training

Memory requires protein synthesis

No.

Hippocampus deals with early fragile memory, reactivation of a memory can be disrupted through electroconvulsive shock, inhibition of protein synthesis.

Memories are rewritten every time they are activated

Ansiomyocin injection into fear conditioned animals immediately after the conditioned stimulus prevents them from becoming afraid.

Fear still works if the protein inhibitor is injected later after the critical period.

Semantic -> Factual

Episodic -> autobiographical

Facts about objects, words, concepts

depends on associations between objects and facts based on experience

affected by damage to posterior parietal cortex

Knowledge about time and place

depends on prefrontal cortex

separate from semantic memory

frontal lobe damage produces people who forget how they acquired information

Medial temporal lobe consisting of:

Hippocampus, Perirhinal cortex, parahippocampal cortex

Provides main input to hippocampus from polymodal association areas

Major output stage of the hippocampus.

Henry Molaison, fell off bike age 7, removed MTL to improve epillepsy symptoms. 

Can't form new memory! Brenda Millner studied him.

Amnesia doesn't impair any other motor, intellectual functions

Amnesia is temporally selective, but can still have normal short-term memory capability

Deficits in making new long-term memories.

Severe Memory impairments in all sensory modalities

(input/output stage to the hippocampus)

greater deficits in object recognition, compared to damage in the hippocampus

this is hard to know, given the specificity of the lesions is not very good.

1 object is shown once, after a delay, the object and a new one are shown together, rewards choosing the new object

Can study amnesia

occurs in 3 branches of the hippocampus

rapidly induced

stable over hours/days

Rats learned how to find their way to a hidden platform.

NMDA inhibitors injected into hippocampus drastically reduced performance given different starting locations (didn't learn as trials increased)

Could do the task they learned initially from a constant start position

Hippocampus and associated areas bind together sequences of events and places to form episodic memories

(rats could do same starting location, but screwed up when having to go from different starting locations)

High number of corticosteroid receptors in the hippocampus

PTSD patients have atrophied hippocampal regions

Cortisol affects declarative memory, not procedural

Rats show spatial memory deficits when confronted with cats (water maze errors up 300%)

Stress increases eyeblink responses (fear based learning)