Lecture 11 - The Remembering Brain 1 Flashcards
What is Episodic Memory?
What, where and who of an episode. Mental time travel, ability to re-experience. Involves relational memory and context (placing past experience within a particular time and place)
What is relational memory?
Ability to create links between unrelated bits of info - making a coherent episode (episodic memory)
What is autobiographical memory?
Personal memories, episodic such as birthday party last year, semantic such as old address
How does information flow within the Medial Temporal Lobe system?
- Hierarchical organisation
- Info collected through perirhinal and parahippocampal cortices
- Passes to the entorhinal cortex and reaches hippocampus
What is anterograde amnesia?
Difficulty acquiring new memories
What is retrograde amnesia?
Difficulty remembering past memories (prior to amnesia onset)
What is the case study of Patient HM?
Had bilateral medial temporal lobectomy (both sides removed)
Included removal of hippocampus and amygdala
- Had minor retrograde amnesia (couldn’t recall events within the 2 years preceding the surgery)
- PROFOUND anterograde amnesia - could not form LTM for events after surgery
What did HM’s anterograde amnesia entail?
- Preserved some memories of the past and had a functioning STM / Working memory (could retain numbers and names for 15 mins)
- Could not form new long term memories
- Every time he woke up he thought it was 1953 and expected to see faces from this year
How was HM impaired on the digit span test?
When a list is increased by 1 digit each time, normal subjects can recall up to 18 digits
HM could not successfully repeat more than 7 digits - UNABLE TO TRANSFER FROM STM TO LTM
How did HM perform in the mirror drawing task?
- Task requires tracing a star without crossing the lines (seen through a mirror)
- Over time performance increases - motor skills
- HM showed improvement over 3 days but no recollection of ever doing the task
- Motor functions and performance improved showing some elements of LTM preserved
What is the Medial Temporal Lobe system critical for?
Making new memories and retrieving old memories
What is the subsequent memory paradigm?
Aims to evaluate how encoding-phase activity leads to successful VS unsuccessful memory
Time 1 - encoding, collect neural data
Time 2 - memory test - classify as remembered or forgotten events
Are there differences in brain activation that discriminate remembered vs forgotten stimuli?
Does the brain activity at encoding predict which items are later going to be recognised and which will be forgotten? - Wagner et al. (1998)
Activity in the left ventrolateral prefrontal cortex and left medial temporal lobe was predictive of later remembered vs forgotten stimuli
What does familiarity mean?
Context-free memory where recognised items feel familiar
What does recollection mean?
Context-dependent memory involving specific info
What is the role of the perihinal cortex?
Processes item representations - important for familiarity
What is the parahippocampal cortex?
Process context - scene perception
What was Ranganath et al. (2004) study?
PPTs shown face / place and asked to keep it in mind followed by a test stimulus (either matching sample or paired / different)
Activates FFA and parahippocampal area
Holding in mind during delay sustains activity in region
Retrieving a different associate flips the activity to be consistent with new stimulus
Holding in mind sustains activity in parts of ventral system
Found subsequent memory effects for familiarity and recollection
What brain area is important for recollection?
Hippocampus - binds items in context
- Important for memory involving names with faces
- Location of objects / people within a scene
What is consolidation?
Formation of memories. Moment-to-moment changes in brain activity that translates to permanent structural changes in the brain- forms neural connections
What is synaptic consolidation?
Increases the probability that a post synaptic neuron will fire in response to neurotransmitters released from presynaptic neuron. FASTER, structural changes in synaptic connections - takes hours / days
What is system consolidation?
Slower, gradual shift of memory from the hippocampus to the cortex
What is the standard consolidation model?
Hippocampus links together different kinds of info in many regions of the brain - active role in binding activity
Overtime hippocampus plays less of a role
Patients with hippocampal damage - Alzheimers (memories lost)
What is evidence for the standard consolidation model
Semantic dementia patients with lesions to the anterior temporal lobes but spared hippocampus have impaired episodic memory. Showed reversed temporal gradient - memories for recent events not yet transferred from hippocampus to neocortex so are intact.
