Psych202 - Foundations of Cognitive Neuroscience
Lecture 3 - Episodic Memory and the Medial Temporal Lobe
Multiple Memory Systems
Decide memory into subsystems divided by their capacity
Declarative memory - stuff you can talk about
Non- declarative - motor skills hard to describe
Events - episodic memory
Amnesia
● A deficit in memory (due to brain damage, disease, drugs)
● Different levels of retrograde and/or antrograde memory damage - ‘live in the present’ (declarative
memories)
● Procedural memory tends to be intact - they know how to survive and fight, etc
Types of amnesia
● Retrograde amnesia - memory impairment for information acquired
prior to the cause of amnesia
● Anterograde amnesia - deficit in learning new information after the
onset of amnesia
A Neuropsychological Approach
● How a person’s cognition and behaviour are related to the brain (and the whole nervous system)
● Often focuses on how brain injuries or diseases affect cognitive and behavioural functions
The case of H.M. (Henry Molaison)
What Happened?
● Suffered from severe, intractable epilepsy
○ Epilepsy: a neurological disorder marked by sudden recurrent episodes of sensory
disturbance, loss of consciousness, or convulsions, associated with abnormal electrical
activity in the brain.
● Foci in bilateral Medial Temporal Lobes
● Treated with bilateral medial temporal lobectomy - surgical removal
● Removal of the hippocampus and amygdala
Medial Temporal Lobectomy
The extent of surgical removal is displayed by the
black holes
, Did H.M. Get Better?
● Reduced convulsions (severity and frequency)
● Improved IQ from 104 to 118
● Minor retrograde amnesia for events within 2 years before the surgery
● Profound anterograde amnesia: could not form long-term memories for events after surgery
H.M.’s Anterograde Amnesia
● Could not form new long-term memories
● Global amnesia: affecting all sensory modalities - everything is impaired - lived his life as he was
always 16
● Specificity (and implications)
○ Largely preserved memory of the past
○ Normal short-term/working memory
○ Normal procedural/implicit memory
H.M.’s Working Memory: Digit Span +1 Test
● 56791
● 567914
● 5679142
● People without amnesia -> up to 18 digits
● H.M. -> can only repeat up to 7 digits
● H.M.’s main deficit was that he couldn't code STM into LTM -canno longer expand the digits
H.M.’s Implicit Memory: Mirror Drawing Task
● Learning of mirrored visual feedback as a result of manual movement is retained
● After each trial, the number of errors made was reduced and over several days the
errors have decreased
✅
● Able to learn the muscle pattern to draw the star - learnt a procedural memory
● Procedural/ implicit memory
Summary: Amnesia and MTL
• Two types: anterograde / retrograde
• Damage in MTL
-> anterograde amnesia
❌
-> some retrograde amnesia
✅
explicit memory impaired
short-term and implicit memory are normal
Our conclusions
1. MTL critical for -> making new memories ->retrieving old memories (partially?)
2. Explicit memory is governed by a different system than short-term memory or implicit memory
Memory processes
Encoding and retrieval -> what part of the MTL does what
Encoding - learning new associations
Lecture 3 - Episodic Memory and the Medial Temporal Lobe
Multiple Memory Systems
Decide memory into subsystems divided by their capacity
Declarative memory - stuff you can talk about
Non- declarative - motor skills hard to describe
Events - episodic memory
Amnesia
● A deficit in memory (due to brain damage, disease, drugs)
● Different levels of retrograde and/or antrograde memory damage - ‘live in the present’ (declarative
memories)
● Procedural memory tends to be intact - they know how to survive and fight, etc
Types of amnesia
● Retrograde amnesia - memory impairment for information acquired
prior to the cause of amnesia
● Anterograde amnesia - deficit in learning new information after the
onset of amnesia
A Neuropsychological Approach
● How a person’s cognition and behaviour are related to the brain (and the whole nervous system)
● Often focuses on how brain injuries or diseases affect cognitive and behavioural functions
The case of H.M. (Henry Molaison)
What Happened?
● Suffered from severe, intractable epilepsy
○ Epilepsy: a neurological disorder marked by sudden recurrent episodes of sensory
disturbance, loss of consciousness, or convulsions, associated with abnormal electrical
activity in the brain.
● Foci in bilateral Medial Temporal Lobes
● Treated with bilateral medial temporal lobectomy - surgical removal
● Removal of the hippocampus and amygdala
Medial Temporal Lobectomy
The extent of surgical removal is displayed by the
black holes
, Did H.M. Get Better?
● Reduced convulsions (severity and frequency)
● Improved IQ from 104 to 118
● Minor retrograde amnesia for events within 2 years before the surgery
● Profound anterograde amnesia: could not form long-term memories for events after surgery
H.M.’s Anterograde Amnesia
● Could not form new long-term memories
● Global amnesia: affecting all sensory modalities - everything is impaired - lived his life as he was
always 16
● Specificity (and implications)
○ Largely preserved memory of the past
○ Normal short-term/working memory
○ Normal procedural/implicit memory
H.M.’s Working Memory: Digit Span +1 Test
● 56791
● 567914
● 5679142
● People without amnesia -> up to 18 digits
● H.M. -> can only repeat up to 7 digits
● H.M.’s main deficit was that he couldn't code STM into LTM -canno longer expand the digits
H.M.’s Implicit Memory: Mirror Drawing Task
● Learning of mirrored visual feedback as a result of manual movement is retained
● After each trial, the number of errors made was reduced and over several days the
errors have decreased
✅
● Able to learn the muscle pattern to draw the star - learnt a procedural memory
● Procedural/ implicit memory
Summary: Amnesia and MTL
• Two types: anterograde / retrograde
• Damage in MTL
-> anterograde amnesia
❌
-> some retrograde amnesia
✅
explicit memory impaired
short-term and implicit memory are normal
Our conclusions
1. MTL critical for -> making new memories ->retrieving old memories (partially?)
2. Explicit memory is governed by a different system than short-term memory or implicit memory
Memory processes
Encoding and retrieval -> what part of the MTL does what
Encoding - learning new associations
