Learning and Memory
What is an engram?
An engram is a physical representation of learning
Lashley's Engram
Thompson's Engram
Lashley looked for a physical representation of learning in the cerebral cortex.
He didn't find an actual physical representation of learning but he found that overall when more brain areas were working, the brain was more effective in learning
Thompson came after Lashley and looked for learning in the cerebellum.
He found that learning occurred in a kind of linear way. From there he discovered that the LIP (lateral interpositus nucleus) was responsible for learning because it played a big role in the linear process of learning. It was kind of the end-all-be-all.
Types of Memory
Sensory
Short-Term/Working
Long-Term
Implicit Memory
Explicit Memory
Kind of like a passive learning
Ex. That exercise you did where you listened to the story and then had to fill in the words with missing letters and you usually ended up spelling words that were in the story
You often don't remember when you learned the thing
You can say the fact
These two kind of go back and forth
Why do different types of long-term memory exist?
Shows that many different areas of the brain are responsible for learning
Long Term Potentiation
How is it involved in memory?
What receptors are involved?
How does it occur?
Protein synthesis?
The Hippocampus
Limited capacity
Limited duration
Encoding
Shortest type of memory
Comes from the senses
Visuospatial Sketchpad
Phronological Loop
Viewing images in the mind
Storage of verbal information
Episodic Buffer
Draws info from what you sense/stores info in long-term memory
Ex. Remembering a phone number after someone said it to you
Ex. Remembering the layout of a bedroom
You're consciously aware
Types
Semantic
Episodic
ideas and concepts not drawn from personal experience
Ex. names of colors, capitals of countries
the collection of past personal experiences that occurred in specific settings
Ex. your skiing vacation last winter, the first time you traveled by airplane
Types
Priming
Procedural
Associative
Non-Associative
Connecting two things together but not knowing why they're connected
Habitualization
creating habits based off of stimulation in the environment
Sensitization
learning through repeated exposure to a particular stimulus
Ex. dog initially likes riding in the car but after a couple of rides to the vet, it stops because it associates the car with bad vet experiences
Types
Classical Conditioning
Operant Condition
They exist because there are different types of things that need to be remembered
Explicit (Episodic) Memory
Semantic Dementia
loss of semantic memory
Ex. holding a closed umbrella over your head, bringing wife a lawnmower when she asked for a stepladder
associative memory is still there
occurs in anterior temporal cortex
Delayed matching-to-sample and Delayed nonmatching-to-sample
Spatial Memory
Context
Consolidation
Test declarative memory
When there was hippocampal damage, memory was impaired
Basal ganglia can take over when hippocampus is gone
Types of cells
Place cells
Spatial View cells
Ex. when you're figuring out the best route to a friend's house (hippocampal activity increases)
Ex. PET and MRI scans of London taxi drivers show really active (or large?) hippocampi
Damage
Radial Arm Task
Morris Water Maze Task
The rats with damage would re-enter paths of the maze where they should have known there was no food there anymore because they already ate it
The rats with damage had a hard time finding the platform
describes the process of strengthening a memory
Damage shows that in rats if the hippocampus is damaged, the rat can learn a new task but it'll forget it quickly
Drugs that block protein synthesis in hippocampus (before learning or right after) doesn’t prevent learning but prevents remembering task 2 days later
H.M. had an issue with consolidating short-term/working memory into long-term memory
Recent memories include more details/context and relies heavily on hippcampus
Taking tests in the same place you learned the material helps you do better on the test
Recalling recent memories activates hippocampus (episodic memories that have a lot of contextual details also activates hippocampus)
Because it involves persistent strengthening of the synapse and the consolidation of memories, it allows memories to be made in long-term memory
Creation of LTP
It all starts with a baseline: delivers a single perforant path; measure response in dentate gyrus
Then it goes to LTP induction: deliver high frequency stimulation (of moderate strength)
Lastly, it goes to test: delivers a single impulse and measure response
Glutamate receptors
NMDA
AMPA
Kainate
Metabotropic Receptors
CaMKII
CREB
The glutamate goes to the glutamate receptor (AMPA) and opens that which activates Na+ to be let into the dendrite
If it is enough glutamate that will activate the Mg to be pushed away from the NMDA receptor. Now, Ca- can enter
Now the Ca- can attach to proteins and essentially make proteins (CREB and CaMKII) that create new AMPA receptors
ionobotropic receptor
Korsakoff's Syndrome
It is a chronic memory disorder
What is the cause?
A thiamine deficieny
Usually found in excessive alcoholics
What are the symptoms?
apathy
memory loss
confusion
confabulation
What's the area that is the problem?
dorsomedial thalamus
What is Alzheimer's Disorder?
memory loss (procedural memory is better than declarative memory
caused by build up of amyloid-B
causes damage to dendritic spines
causes decreased synaptic input
causes decreased plasticity
biological factors
hippocampus
cerebral cortex
other areas
Types of Amnesia
Retrograde
Anterograde
not being able to remember things from before brain injury
not being able to remember things from after the brain injury
Who was H.M.?
Damage
part of temporal lobe was missing especially hippocampus
Issues
some impaired LTP
weak (new) semantic memory for repeated facts
was not able to imagine a future because that requires you to remember past events to use as a basis
severely impaired episodic memory
Things that stayed intact
short-term memory
intelligence
implicit/procedural memory