N-methyl-D-aspartate receptor (5)
Receptor for the neurotransmitter glutamate
- Glutamate being the primary excitatory neurotransmitter in the brain
- Receptor found throughout the brain
- Highly concentrated in the hippocampus
- Important receptor participating the physiological basis of learning and memory - long-term potentiation - LTP
Early Study of Memory (3+3)
Suggested widely distributed encoding and storage of information
- identify locations of learned habits
- Lesions to neocortex
- Severing neural pathways
Examine:
- Maze way finding
- Puzzle manipulation (door opening)
- Visual discriminations
Early Study of Memory: Conclusions from this research… (3)
No one part of the brain on the neocortex damage cause issue to learning and memory
Seemed to be more widespread damage was: the more issues/ impairments exist
- supports the notion that learning and memory happen over distributed systems
1953 - Patient HM - Surprising Result (5)
Great surprise, when following the removal of a particular region of the brain, the result was
- elimination of the patient’s ability to complete his own autobiography
- Lost the ability to lay down new memories
- Generalised epileptic seizures
- Growing progressively worse in severity and frequency
- High doses of medication not helping
Was seen by Dr. William Scoville
Lobectomies
Take off the medial temporal lobes bilaterally (on both sides)
Retrograde memory impairment
forgetting memories in the past
Anterograde memory impairment
inability to form new memory
Consequence of HM’s surgeries
- As a treatment for epilepsy, quite effective
- However, severe anterograde memory impairment was presented
Quite alarming to Scoville, who contacted neurosurgeon, Dr. Wilder
Dr. Brenda Milner and HM (3)
• Examined HMs memory deficits resulting from bilateral removal of his medial temporal lobes
• Global Anterograde Amnesia - numerous aspects of his ability to learn and remember are affected
• Impaired in spatial/topographical learning about the events occurring
Traumatic brain injury (TBI) and Retrograde Amnesia (2)
Time-dependent retrograde amnesia
- Severity of injury determines how far back in time amnesia extends
Theories of Retrograde Amnesia (3)
- System Consolidation Theory
- Multiple-trace Theory
- Reconsolidation Theory
System Consolidation Theory (3)
- Role of the hippocampus is to consolidate memories and then send them to be stored elsewhere in the brain
- Accounts for preservation of old memories
- As more damage occurs, the more old memories will be lost
Multiple-trace Theory (Cabeza & Moscovitch) (5)
Three kinds of memory for events:
- Autobiographic memory: Hippocampus
- Factual semantic memory: Temporal Lobe
- General semantic memory: other cortical areas
- Each type is dependent on a different brain area
- Old memories are more resistant to amnesia because they change location in the brain as they are recalled
Autobiographic Memory Might be re-transcribed
eg. Autobiographic mem is actually in temporal lobe into semantic
- Like when ur fam tells you about what you’ve done in the past
Reconsolidation Theory (Haubrich & Nader) (2)
- A memory reenters a labile phase when it is recalled and is then restored as a new memory
- Results in many different traces for the same event
Not all memory was obliterated following HMs surgery (2)
- Skills (motor learning)
- Mirror drawing task
Priming and a task example (2)
- A stimulus is used to sensitize the nervous system to a later presentation of the same or a similar stimulus
- The Gollin Incomplete- Figures Test
Multiple Memory Systems (Brenda Milner)
based on evidence that different kinds of information are processed and stored in different parts of the brain:
Short term
Long term:
- Declarative
- episodic
- semantic
- Non-declarative
- Procedural
- Priming, conceptual learning
- simple classical conditioning
- non-associative learning
Impairments in Implicit Memory
J.K. - Born 1914 (4)
Petroleum engineer 45 yrs
Mid 70s Parkinson’s symptoms
- Implicit memory deficits
- Forgot how to turn on lights
- Tried to use tv remote to turn off the radio
- Preserved memory for events and new experiences
Explicit Memory - HM (3) Residual, and brain part
HM - had some residual memory
(Letting ppl in faster)
- People around him, researchers become familiar
- His own reflection as an older man becomes familiar
- Familiarity encoding in a remaining part of his medial temporal lobe- Parahippocampal gyrus
Neural Substrates of Explicit Memory: Where? (1)
Herbert Petri and Mortimer Mishkin
- Temporal-frontal lobe: neural basis for explicit memory
Anatomy of the Hippocampus: Ammon’s horn
1st C:
Dentate gyrus: projects to Ammon’s horn
2nd C:
Ammon’s horn
Anatomy of Hippocampus: Granule Cells (3)
- Stellate cells of the dentate gyrus
- “sensory” cells
Star shaped: stellate cells, afferent info
Anatomy of Hippocampus: Pyramidal Cells
- Cells of Ammon’s horn
- “Motor” cells
Ammon’s horn: big pyramidal cells
