Long-Term Memory
- Declarative
- explicit memory
- knowledge that we have conscious access to (personal and world knowledge)
Long-Term Memory
- Declarative
- Episodic
- ‘How’
- memory for a specific autobiographical event; information about spatial and temporal context: where and when the event occurred
- information we ‘remember’
Long-Term Memory
- Declarative
- Semantic
- ‘What’
- facts or general knowledge about the world
- information we ‘know’
Long-Term Memory
- Nondeclarative
- implicit memory
- knowledge that we have no conscious access to (procedural knowledge, perceptual priming, etc.)
Long-Term Memory
- Nondeclarative
- Skill Learning
- Priming
- Conditioning
- Skill learning = e.g. knowing how to ride a bicycle
- Priming = eg. being more likely to use a word you heard recently
- Conditioning = e.g. salivating when you see a favorite food
Differences of episodic and semantic memories
- episodic: must have autobiographical content; acquired in a single exposure (event itself)
- semantic: does not need autobiographical content; can be acquired in single exposure, but generally needs few additional exposures before being fully acquired
Which one comes first? Episodic or semantic
- episodic memory grows out of semantic memory
- semantic memory is information we have encountered repeatedly, often enough that the actual learning episodes are blurred and only the semantic “fact” content remains
Acquiring and Using Episodic and Semantic Memories
- depth of processing
- affects recognition later –> the deeper, the more likely to be remembered
Acquiring and Using Episodic and Semantic Memories
- consolidation period
= length of time during which new memories are vulnerable and easily lost
- predictions:
- older memories relatively stable and difficult to disrupt
- more recent memories vulnerable to disruption
Acquiring and Using Episodic and Semantic Memories
- cues in recall and recognition
- more cues = better recall
- free recall = generate information from memory
- cued recall = some kind of information given
- recognition = pick out correct answer from list of possible options
When Memory Fails
- Interference
- proactive and retroactive interference
- Interference –> episodic memory (=when two memories overlap in content, the strength of either or both memories may be reduced)
When Memory Fails
- Source amnesia
- cryptomnesia
Source amnesia = we remember a fact or event but attribute it to the wrong source
Cryptomnesia = person mistakenly thinks that his current thoughts are novel or original; personalize idea
When Memory Fails
- False Memory
= memories of events that never actually happened
- tend to occur when people are prompted to aging missing details
- eyewitness memory –> more prone to error than most people realize
Brain Substrates - Hippocampus and Frontal Cortex
- hippocampus (and nearby brain structures): critical for forming new episodic memories; also: spatial learning and classical conditioning
- frontal cortex and some subcortical areas: help determine what gets stored and when
Cerebral Cortex and Semantic Memory
- areas of sensory cortex: involved in processing sensory information
- association cortex: involved in associating information within and across modalities
- agnosia = selective disruption of the ability to process a particular kind of information
- semantic networks are organized by object properties including visual properties, functional properties, and so on
Medial Temporal Lobes and Memory Storage
- damage in medial temporal lobe: associated with inability to learn new information
- anterograde amnesia = inability to form new episodic memories
- retrograde amnesia = loss of memories for events that occurred before the injury
- damage to hippocampal region:
- could cause memory failure because region is needed to encode information, retain or consolidate it, to receive it when needed, or any combination of these factors
- hippocampal region critical for transfer of short-term memories into long-term ones
Medial Temporal Lobes and Memory Storage
- Theories about hippocampal role in memory
- standard consolidation theory
- hippocampus and related medial temporal lobe structures are initially required for episodic memory storage and retrieval but their contribution diminishes over time until the cortex is capable fo retrieving the memory without hippocampal help
Medial Temporal Lobes and Memory Storage
- Theories about hippocampal role in memory
- multiple memory trace theory
- episodic (and possibly semantic) memories are encoded by an ensemble of hippocampal and cortical neurons, and the cortical neurons never, in normal circumstances, become fully independent of the hippocampal neurons
Clinical Perspectives
- Patient H.M.
- amnesia –> inability to retain new material for more than a brief period
- both retrograde & anterograde amnesia
- hippocampus: still intact but no connection to other structures
- showed that:
- memory can be separated from other cognitive functions
- short-term memory differs from long-term memory
- impairment did not hold for motor learning
Clinical Perspectives
- Korsakoff’s Syndrome
- symptoms:
- impaired memory
- fail to recall many items or events of the past
- often deny that anything is wrong with them
- often show disorientation to time and place
- may confabulate
- causes:
- lack of vitamin thiamine –> long-term alcohol abuse can lead to vitamin deficiencies
- mammillary bodies shrink
Clinical Perspectives
- Alzheimer’s Disease
- three principal features:
(1) collections of intraneuronal filaments called neurofibraillary tangles
(2) extra cellular deposits of an abnormal protein in a matrix called amyloid in so-called senile plaques
(3) diffuse loss of neurons - changes mostly in neocortex, limbic structures and selected brainstem nuclei
Systems Consolidation
= second form of memory consolidation
- reorganization process in which memories from the hippocampal region (where memories are first encoded) are moved to the Neo-cortex in a more permanent form of storage
Systems Consolidation
- Standard Model
- H.M. predicts this
- novel information is originally encoded and registered –> memory of these new stimuli becomes retained in both the hippocampus and cortical regions
- with time –> some memories become consolidated & don’t need hippocampus anymore
- predicts Ribot gradient
Systems Consolidation
- Multiple Trace Theory
- argues that hippocampus is always involved in the retrieval and storage of episodic memories
- states that both episodic and semantic memories rely on the hippocampus and the latter becomes somewhat independent of the hippocampus during consolidation
- hippocampus always important
- episodic memory depends on hippocampus
- semantic memory can also be stored in neocortex
- does not predict Ribot gradient
