sign in sign up
<<
Home , Anterograde amnesia, Confabulation, Echoic memory, Encoding (memory), Explicit memory, Iconic memory

Overview PSY393 Cognitive Neuroscience • Introduction •H.M.

• Short-term memory • • Short-term memory store

• Long-term memory Donna Rose Addis • The model of long term memory 13 Nov 2003 • Neuroanatomy of long term memory

Introduction H.M.: Who is he?

• The most famous case of • What is and memory • Case details: • Learning = acquisition • Memory = persistence of learning • Absence started at 10 yrs old • Generalized seizures started at 16 • Stages of learning and memory • Medication were not controlling seizures • – study phase • At 27 yrs: Surgery to remove his medial temporal • – retention interval lobe bilaterally • Retrieval – test phase

H.M.: Areas of damage H.M.: Areas of brain damage

• Removal of bilateral medial • Removal of bilateral medial temporal lobe

Hippocampus (1) (1) (2) Parahippocampal gyrus (2)

1 H.M.: Areas of brain damage H.M.: Who is he?

• Removal of bilateral medial temporal lobe • Result of this surgery: Global amnesia • : - unable to form new long-term • : - unable to retrieve any memories from the 11 yrs before his surgery - Because of his seizures?

Hippocampus & • BUT other aspects of memory are preserved, parahippocampal • e.g., short term memory gyrus removed • Dissociation indicates separate memory systems

Short-term memory STM: Sensory Memory

MEMORY • Very short duration (seconds) Short-term memory Long-term memory • Decays rapidly – tested by partial report • Capacity: ~ 12 items Sensory memory Short-term / working • : memory Echoic memory Visuospatial sketchpad - Sensory memory for auditory information (echo) Phonological Loop Central Executive • Iconic memory: - Sensory memory for visual information ()

STM: STM store STM: STM store

• Short-term Memory • Ways of testing short-term memory • Duration: seconds to minutes - : Rey Complex Figure COPY • Capacity: Magic number 7 ± 2 chunks • Ways of testing short-term memory - Visual memory: geometric figures that are difficult to verbalize

2 STM: STM store STM: STM store

• Ways of testing short-term memory • Ways of testing short-term memory - Visual memory: Rey Complex Figure - : stories, word pairs, word lists

• Serial position effect: - Primacy vs. Recency effects

Primacy Recency

STM: Serial Position effect STM: Modal model

•Primacy effect • (Atkinson & Shiffrin, 1968) - more rehearsal, enters LTM - Faster presentation rate = Ð primacy Sensory Inputs • Recency effect - Info still in STM, so dumped out - Distractor at end of list = Ð recency Sensory memory

Primacy Short-term storage Recency REHEARSAL

Long-term storage

STM: Levels of Processing STM: Lesion evidence

• (Craik and Lockhart, 1972) • Patient H.M.: Spared STM, Impaired LTM • Effectiveness of different encoding strategies • Can repeat and remember 5 digits as long as he isn’t distracted from rehearsing • Deeper encoding more effective • BUT this information doesn’t get into LTM - e.g., Is it living? • Described as “marooned in the moment” - Elaborative – relate info to previous knowledge • Patient E.E.: Impaired STM, Spared LTM • Shallow encoding not as effective • Tumour in inferior parietal/superior temporal cortex - (e.g., font size) • Impaired STM, preserved LTM - Processing only surface features • Not consistent with modal model Double • Getting info into LTM not just about how long you hold Dissociation it in STM, but how you process it

3 Long-term memory: LTM: Explicit Memory

MEMORY • (Tulving, 1972) - Personally experienced events Short-term memory Long-term memory - Specific time and place – context - Conscious that it is our personal past, Explicit memory we remember that we did that, we can recollect (Declarative memory) details about the context - e.g., remembering when you first held your Episodic Semantic (events) (facts) baby sister

• Specific personal • General Knowledge experiences from particular time & place

LTM: Explicit Memory LTM: Explicit Memory

• (Tulving, 1972) • Patient K.C. (Rosenbaum et al., 2000) - Facts we know about the world - Damage to his hippocampus bilaterally (motorbike - Lacks contextual information accident) - Even if we remember the episode we acquired the - Spared semantic memory, e.g., defining words fact, the fact itself is distinct - Spared personal semantic memory, e.g., names of - e.g., knowing that Mr. Tim Hortons was a hockey work friends player for the Leafs - Impaired episodic memory: e.g., cannot recall any specific episodes at work or with those friends

LTM: Explicit Memory LTM: Testing Explicit Memory

• Semantic • Recall versus Recognition - Damage to the anterior inferior temporal cortex - Impaired semantic memory: Impaired at naming - Recall: e.g., tell me what words were on the list objects, can’t tell you about famous people or - If a patient can’t recall a memory, it could mean events either they just can’t retrieve it, or there is no - Spared episodic memory memory there to retrieve - Recognition: e.g., was DEFINE on the list? Y/N • Consider these patients and K.C.: - We are providing direct cues to the information - Even if their retrieval processes are not working effectively, if the information is there, they will be Double able to recognize it Dissociation

4 LTM: Testing Explicit Memory LTM: Testing Explicit Memory

• The Remember-Know paradigm • The Remember-Know paradigm: Patient Jon - Can test whether someone has an episodic or - Hippocampal damage as a baby semantic memory of some information - Some personal events he could remember - “I remember when ….” vs. “I know that ……” - Some he was only knew about - Greater activation of his residual hippocampus - E.g., a famous name such as “Princess Diana” or when retrieving “remembered” events versus “Margaret Thatcher” “known” events - Answer Remember if you can actually remember a personal episode connected to her - Answer Know if you know who this person is, but can’t remember a specific episode

LTM: Testing Explicit Memory LTM: Testing Explicit Memory

• Verbal and Visual memory • Verbal & visual memory (encoding & retrieval) - Verbal memory: word-pairs and stories after - Verbal memory: supported by the left MTL a delay - Visual memory: supported by the right MTL - Visual memory: Rey complex figure after - e.g., patients with damage delay to : - Left medial temporal lobe = difficulties mainly with verbal memory TRY IT!! - Right medial temporal lobe = difficulties mainly with visual memory

Double Dissociation

LTM: Explicit Memory LTM: Explicit Memory

• Anterograde memory • Anterograde memory - Memory for information since the brain injury - Memory for information since the brain injury - Represents ability to form new LTMs - Represents ability to form new LTMs • Retrograde memory • Retrograde memory - Memory for information presented before the brain - Memory for information presented before the brain injury injury - Represents ability to retrieve older LTMs - Represents ability to retrieve older LTMs - Temporally graded or flat gradient - Temporally graded or flat gradient

Retrograde Anterograde Retrograde Anterograde INJURY INJURY Amnesia Amnesia Amnesia Amnesia

temporal gradient time flat gradient time

5 LTM: Explicit Memory Long-term memory:

• Often get some degree of both, e.g., H.M. MEMORY • Why? Depend to some extent on the same brain structures (e.g., hippocampus) Short-term memory Long-term memory

• Patient M.L.: Isolated retrograde amnesia Explicit memory Implicit memory - Severe retrograde amnesia (declarative memory) (non-declarative memory) - Initially had anterograde amnesia but this resolved quickly Procedural Perceptual Classical Non-associative Memory Representation Conditioning learning System

Dissociation

LTM: Implicit Memory LTM: Implicit Memory

• Implicit memory typically outside of awareness • Perceptual • - Being primed to use certain information - Learning skills; e.g., riding a bike, mirror-drawing - Shown a list of words such as DEFINE

1st day 2nd day 3rd day - Later given stems and asked to complete it with the first word that comes to : - e.g., DEF Î Most likely to give DEFINE even if you can’t explicitly remember that word being on the list Number of errors

Attempts each day

LTM: Implicit Memory LTM: Implicit Memory

• Is implicit memory impaired in amnesia? • - Often when explicit memory is impaired, implicit - Pavlovian conditioning memory remains intact - conditioned paired with an unconditioned • Patient H.M.: Mirror drawing stimulus - Got faster each time, made less errors - Indicates he was “learning” this task • Non-associative learning - BUT each time, he had no explicit memory that he - e.g., habituation or sensitization had ever seen this task before • Patient H.M.: Priming - Completed word stems with words from the list even though he had no explicit memory for them being on the list

6 LTM: Implicit Memory LTM: Neuroanatomy

• Are there patients showing the opposite? • Patient M.S.: Priming • What regions of the brain support LTM? - Damage to the right - Impaired on priming tasks, but spared explicit • What role do they play? memory • Parkinson’s disease: Procedural memory • What’s the evidence? - Damage to the basal ganglia - Impaired on skill learning; also habituation • Lesion cases •

Double Dissociation

LTM: Role of the medial temporal lobes LTM: Role of the medial temporal lobes

• Medial temporal lobes • Medial temporal lobes and encoding:

- H.M. was the first case to highlight the importance - Forms links between information (Eichenbaum, 1991) of the MTL in forming new memories and - e.g., between items (banana – dog) retrieving old memories - e.g., between an item and its context (the word - Anterograde amnesia DEFINE was in list 2) - Retrograde amnesia (temporal gradient) - Detects novel stimuli (Tulving et al., 1994) So, the MTL is important in LTM … - Activates more when encoding information we ... But what does it do? haven’t seen before

- Continuously records experience (Moscovitch, 1992)

LTM: Role of the medial temporal lobes LTM: Role of the medial temporal lobes

• fMRI: MTL is active during successful encoding • What is the role of the MTL in LTM? Wagner et al., 1998 1. Consolidation hypothesis (Squire) - When just encoded, memories are dependent on the hippocampus for retrieval - After a while, they become “consolidated”, i.e., independent of the MTL, dependent on the cortex - Explains temporal gradients: information not yet consolidated cannot be retrieved once hippocampus is damaged

Retrograde Anterograde INJURY Amnesia Amnesia

7 LTM: Role of the medial temporal lobes LTM: Role of the medial temporal lobes

• What is the role of the MTL in LTM? • fMRI: Retrieving details of episodic memories 1. Consolidation hypothesis - The hippocampus is an integrator of context and 2. Multiple Trace Theory (Nadel and Moscovitch, 1997) recollective details of episodic memories - When we retrieve memories with more details, - Hippocampus important in retrieval of ALL the hippocampus is more active truly episodic memories R - Explains flat retrograde amnesia - What about temporal gradients? - Older episodic memories often become semantic and so don’t need the hippocampus for retrieval

Addis et al. (in press)

LTM: Role of the LTM: Role of the Prefrontal Cortex

• MTL not the only region involved in LTM • Encoding: Left Prefrontal Cortex • Prefrontal cortex also play important role - Supports the use of encoding strategies • Summarized in the HERA model (Cabeza et al) - Impaired frontal functioning: e.g., older adults: - Hemispheric Encoding/Retrieval Asymmetry - Tend to use shallow encoding strategies - Show poorer performance on encoding tasks - Successful encoding shows greater activation of left PFC (Wagner et al., 1998)

LTM: Role of the Prefrontal Cortex LTM: Role of the Diencephalon

• Retrieval: Right Prefrontal Cortex • Damage to regions such as dorsomedial - Important in processing supporting retrieval and mammillary bodies causes amnesia - e.g., strategies used to search for a memory - Similar to MTL amnesia - Impaired explicit / spared implicit memory - Post-retrieval processing, e.g., verification

- Right PFC damage: (“honest lying”) • Causes of damage: - Often produce “memories” that are actually - and : composites of different real events and Korsakoff’s syndrome aspects of semantic memory -Strokes -WHY? - Fencing foils (case N.A.) and snooker cues - Compensation for lack of episodic detail (case B.J.) entering the brain via the nostril - Lack of verification - Inability to inhibit responses

8 LTM: Role of the Diencephalon Summary: Important memory dissociations

• What role does the diencephalon play? (Hodges and McCarthy, 1993) • Short-term vs. long-term memory - Case P.S.: Stroke in DM thalamus • Explicit vs. implicit memory - Severe retrograde amnesia - Link between frontal lobes (search strategies) • Semantic vs. episodic memory and posterior (stored memory traces) - Damage = disconnection syndrome • Anterograde vs. retrograde memory - Can’t use search strategies to search through memory traces • Verbal vs. non-verbal memory

9