Why do we have memory?
- Simpler and more flexible way of learning than hard-wiring at birth; allows neurons to self-modify based on their experience
- Memory is the best way to upgrade prediction
T/F: There is a dedicated region for memory
False. There is no such thing as a dedicated memory organ; memory is distributed!
(Lashley experiment trained rats on a maze and lesioned brain to see where memory was stored)
What disorder/symptoms did HM have?
First grand mal seizure at 16, becoming more frequent until ~11 fits/week.
Treated with bilateral removal of medial temporal lobe (hippocampus and associated structures)
Effect of bilateral medial temporal lobectomy (esp on HM)?
- Seizures dramatically reduced
- Short term memory was fine
- Long term memory was fine
- But couldn't form new long term memories
(e.g. Memento, pianist with herpes)
Thus, short and long term memory are separate and the medial temporal lobe is somehow involved
Anterograde amnesia (def)?
- Unable to form new memories
Retrograde amnesia (def)?
- Unable to remember the past
What is explicit memory? Implicit?
What did we learn about them from HM?
Explicit- conscious memory
Implicit- unconscious memory; habitual
HM's case revealed that explicit and implicit memories are separate as well
(Could improve drawing in a mirror although could not remember practicing)
How do explicit and implicit memories fit within long and short term memories?
Explicit and implicit memories are long term memory
Short term memory is held where?
Held in neuronal firing
Long term memory is held where?
Cemented into brain structure; physical changes in structure of brain that remain there for an extended amount of time; memories undergo consolidation through time
What is a concussion (def)?
Concussion- a temporary disturbance of consciousness from a non-penetrating blow to the head
How can a concussion affect memory?
Concussions may cause retrograde amnesia for a period (loss of memory held in neuronal firing before it can be cemented) before the blow and a period of anterograde amnesia after (lasting about the same length of time as the person was unconscious)
Concussions disrupt consolidation (storage) of recent memories
What kind of amnesia is seen in comas?
Same kind of amnesias as concussions; severity of amnesia correlates with duration of brain coma
Why/how is the hippocampus necessary for short term memory being converted to long term structural changes?
How long does this take?
The hippocampus runs the cortex through practice routines (of the specific neuronal pattern/network representing a certain experience/memory)
Takes ~ 15 minutes
What structural changes occur for long term memory?
Long term strengthening and weakening of synapses (cells that fire together wire together); results in associative neural network
- LTP- long term potentiation
- LTD- long term depression
What is a major NT in brain plasticity?
What are the memory components/symptoms of Alzheimer's Disease (AD)?
- Progressive brain deterioration
- Begins with slight loss of memory and progresses to dementia
- Major anterograde and retrograde amnesia
- Also deficits in short term memory
What is the underlying mechanism for amnesia in Alzheimer's?
Alzheimer's amnesia is partially related to acetylcholine depletion
Treatment for Alzheimer's?
Drugs that boost acetylcholine transmission by preventing breakdown (4 on the market)
- Provide modest relief in mild cases
- Little use in advanced cases
Also Memantine (Namenda) to prevent neuron loss from excess glutamate/excitotoxicity by decreasing neuronal sensitivity to glutamate
What is Scopolamine's mechanism?
Affect on memory?
Scopolamine has antiocholinergic effects; may disrupt memory (higher doses)
- Nausea and motion sickness
- Intestinal cramping
- Ophthalmic purposes
Also used as a date rape drug/aid for rubbery because it induces anterograde amnesia (50% of ER admissions for poisonings in Bogota)
How come some adults have Alzheimer's but no one can tell?
Cognitive reserve in adult plasticity
- Education and intelligence may permit cognitive tasks to be accomplished in new ways
- Even as brain degenerated, could find/establish new ways from point a to point b
- Ex) nuns who had many tasks and much social interaction each day
- Important to maintain cognitive fitness in old age!
What is Ribot's law?
Older memories are more stable; recent memories are more like to be lost (first in-last out)
- Through time, memories get more cemented into structure (memories get stronger with time)
What is re-consolidation? Effects?
When memory is retrieved from long term memory, it is temporarily held in short term
- Recalling a memory makes it susceptible to erasure (e.g. posttraumatic amnesia) until reconsolidation
- Unfortunately, doesn't work in traumatic memories...these are stored in a secondary system in the amygdala
What is anisomycin?
How does it effect memory?
A protein synthesis inhibitor
- Can prevent reconsolidation of memory
Where are memories stored?
Each memory is stored diffusely throughout the brain structures that were involved in its formation
Damage to ____ results in memory deficits?
Damage to a variety of structures results in memory deficits. However, certain structures are more involved in certain memory types...
What sort of memory is stored in the hippocampus?
What sort of memory is stored in the inferotemporal cortex?
What sort of memory is stored in the amygdala?
What sort of memory is stored in the prefrontal cortex?
Temporal ordering of events, tasks involving a series of steps
What sort of memory is stored in the cerebellum?
Sensorimotor tasks (remembering how to ride a bike)
What are the (3) ways that the brain stores changes related to memory?
- Changes in neuronal connection (synapses)
- Growth of new neurons (neurogenesis)
- Changes in gene expression (epigenetics- experience can change gene expression permanently, as in rat pups licked by their mothers)
What is the problem of eyewitness testimony?
Memory is constructed
What are two different methods underlying extraordinary memories?
- Larger cortical area devoted to one task (savantism)
What is synesthesia?
Information hooking into other things
- Ex) people who see numbers with color
- Ex) easier to memorize poetry to music (song lyrics)
What does retrograde amnesia prove about the consolidation of memory?
Retrograde amnesia shows that memories are consolidated over time