Science Section 4 Flashcards
What is synaptic plasticity?
the ability of synapses to strengthen
or weaken over time in response to changes in their
inputs
True or false. Synaptic strength is fixed.
False
What are monocular deprivation experiments?
an experimental manipulation that deprives one eye of normal vision in order to study changes in development
Can a short period of monocular deprivation change the structure of the synapses and dendrites seen in layer 4C of V1?
Yes
Critical period
limited periods of time when an aspect of brain development is particularly sensitive to inputs from the external environment
What is whisking?
When rodent whiskers are moved back and forth via little muscles in the skin to scan the environment
Barrel field
an area of a rodent’s primary somatosensory cortex representing the touch or somatosensory inputs of each of their whiskers
Phantom limb syndrome
a condition in which patients experience sensations in a limb that does not exist due to the connections from the periphery to the brain remaining in place after amputation
Phantom sensation is a result of ____
The sensations often result from the stimulation of the skin regions whose cortical representations border that of the missing body part.
What is the storage of information over time called?
Memory
According to Santiago Ramon what does learning require?
the formation of new connections between neurons
What is habituation?
learning to ignore stimulus that has no meaning
True or False? The brain stops changing and adjusting to the environment after the critical period.
False. The brain never stops changing but it does become less plastic as the result of aging
Describe Eric Kandel’s experiment to study memory using a sea slug (Aplysia californica)
He primed the sea slug to not react to a stimulus poking its underbelly as it no longer saw the stimulus as harmful. He found that the neurons would still fire the same action potential as they did prior to learning but it had a smaller impact on the postsynaptic cell (aka synaptic weakening, less responsive). When the situation was reversed, the neurons has a larger response (increase on neurotransmitter release and expansion of the synapse surface area was responsible)
What is sensitization?
strengthening of the behavioral response in response to stimulation that is harmful
What do scientists use to record electrical activity
electrophysiological recordings
What is LTP? (long term potentiation)
strengthening of a synapse that is usually based on changes in the postsynaptic receptors.
How long does LTP last
for weeks in living mammals and can potentially last for an entire lifetime.
What is responsible for condensing and consolidating memories
the hippocampus
what is the signal that can cause AMPA receptors to be removed from the postsynaptic membrane,
called long-term depression or LTD
What is the mechanism (process) for the short term sensitization of the gill withdrawal reflex, in regards to Kandel’s experiment with sea slugs?
1). Sensory neuron receives the shock stimulus 2). Interneurons bringing that signal to the next siphon sensory neuron releases serotonin 3). The serotonin binds to GPCRs in the axon terminal to stimulate the production of cAMP (second messenger) 4). Activated by cAMP, protein kinase A (PKA) phosphorylates several proteins and potassium channels 5). The K+ channels now have much more delayed time to open during action potentials which allows there to be a greater amount of Ca+ channels to open in the terminal 6). This extends exocytosis and increases amount of glutamate that is released onto the motor neuron
Under normal synaptic transmission what is released
Glutamate it binds to postsynaptic AMPA receptors
LTP is linked to?
Memory storage, especially with the hippocampus
How do researchers use electrophysiological recordings to measure the strength of a synapse and how it changes based on experiment?
They record the membrane potential of the presynaptic and postsynaptic neurons before and after a learning event
What changes to morphology often accompany electrophysiological changes?
Changes in the synaptic spine shape and structure
Increasing long term potentiation (LTP) in the hippocampus can cause what?
A super memory
If there is too little LTP in the hippocampus this can cause?
Difficulty storing new memories
In a mammal’s hippocampus, when is LTP induced?
when both the presynaptic and postsynaptic cell are depolarized at the same time
The presynaptic cell for LTP releases what neurotransmitter when it fires an action potential?
Glutamate
What are the two receptors the postsynaptic cell for LTP has for glutamate to bind to?
AMPA and NMDA
What are AMPA receptors?
ionotropic receptors that allow sodium to flow through the cell which depolarizes the cell
What NMDA receptors?
Have a pore (that is typically blocked by a positively charged magnesium molecule but can be removed if there is enough depolarization caused by the influx of sodium via AMPA receptors as positive repels positive) that allows sodium and calcium into the cell
True or False? NMDA receptors are ion channels
False. The brain never stops changing but it does become less plastic as the result of aging
Calcium influx into the postsynaptic cell triggers the activation of what? (still regarding LTP)
Calcium calmodulin-dependent protein kinase (CaMKII)
What is CaMKII?
a second messenger enzyme that allows AMPA receptors to be inserted into the postsynaptic neuronal membrane
More postsynaptic AMPA receptors means what?
A strengthened response to the same stimulus
When CaMKII adds a phosphate group to AMPA receptors, it makes them?
Work more efficiently
What second messenger, in regards to LTP, causes changes to the dendritic spine shape?
CaMKII
What is the function of CREB?
as a transcription factor it is critical for producing new proteins to maintain structural changes, in LTP, long term and to strengthen the synaptic connection
CREB is phosphorylated by what second messenger enzyme?
CaMKII
What mechanism weakens the synaptic connection?
LTD (long-term depression)
Which part of the brain decides which memories to store and preserve?
Hippocampus
What are the neighboring areas to the hippocampus?
The rhinal and entorhinal cortexes.
What happens before memory is stored in the cortex related to its content?
It’s consolidated by the hippocampus and becomes stable for long term.
How many layers does the entorhinal cortex have?
6
Where does most input to the hippocampus come from?
the entorhinal cortex
What does damage to the hippocampus on both sides of the brain do?
It prevents new long-term memories from forming, but does not erase those encoded before the injury.
What is special about the dentate gyrus?
It is the one of the few locations where neurogenesis happens
How many layers does the hippocampus itself have?
Only three, but it’s no less critical.
What is the bundle of axons the entorhinal cortex sends called?
The perforant path
What is neurogenesis and where can it be found in adults?
Neurogenesis is the birth of new neurons and one of the few locations it can be seen in the adult human brain is in the dentate gyrus.
What is the main part of the hippocampus called?
Ammon’s Horn, or Cornu Ammonis in Latin.
What are the axons that the granule cells send called?
Mossy fibers
Are Schaffer collaterals axons or cells?
Axons help project the other pyramidal cells in the CA1 subregion.
What are Schaffer collaterals thought to be crucial for?
The consolidation of short-term memory to long-term memory.
the hippocampus…
picks what memories to keep and helps to properly store them
What is short-term memory?
Short lived memory, and requires constant attention.
There are also memory inputs in the hippocampus from…
limbic or emotional regions
What are the three main processes involved with long-term memory?
Encoding, storage, and retrieval of information.
regions considered “emotional regions” include?
The amygdala, hypothalamus, and cingulate gyrus
Memory related to a particular song would be stored close to the…
auditory cortex
memory for a particular face would likely be stored near the…
visual cortex
the entorhinal cortex helps process…
perceptual and sensory inputs
the dentate gyrus is one of the few locations where there is evidence of ___ in adults
Neurogenesis, the birth of new neurons
fornix
the axons of pyramidal cells projecting out of the hippocampus, brings information from the hippocampus a range of deep brain regions
Short term memory goes away after…
it is no longer being focused on
The average person can retain __ to __ items in their short term memory
5, 9
What part of the brain is crucial for maintaining short term memory?
the prefrontal cortex, especially the top and side regions
3 main processes of long term memory?
encoding, storage, and retrieval (recall)
Encoding
the act of learning or acquiring new information
Storage
the ability of the brain to file away new information even when you aren’t paying attention to it or consciously thinking about it
Retrieve or recall
remembering something, getting information so that your conscious mind can work with it
Long term memory can be divided into two groups called?
explicit and implicit
explicit memory
the usual type of memory mentioned, any memory that can be consciously recalled
explicit memory can also be divided into two subcategories called?
sematic and episodic
semantic memories
facts without context or emotions involved
episodic memories
memories that relate to experiences or “episodes” in life
what type of long term memory does not use the hippocampus
implicit
implicit memory
unconscious and unrehearsed, slower to encode and take longer to learn but stick around for a lifetime
Subtypes of implicit memory include
procedural memory, priming, classical conditioning
procedural memory
learned motor skills, memory of how to ride a bike or learning a musical instrument. involves motor regions of the brain such as the cerebellum
Plasticity
is the ability of the brain to change and adapt
What is the purpose of the Human Connectome Project?
to create the world’s largest map of neural circuit structure and function
It is common to evoke the phantom sensation in a missing hand or arm by touching the ____
Face. The face representation in the S1 homunculus is immediately next to the representation for the hand.
What happens to the area of the cerebral cortex that is dedicated to a part of the body that is now missing?
It is taken over by neighboring cortex representation areas of the neighboring body part that is missing.
what is an analogy of synaptic strength
the strength of the connection between two synapses can be turned up or down like a stereo volume control, some shout and some whisper
ocular dominance columns
there are stripes of tissue across layer 4C that get their input from one eye only (next to another stripe getting input from the other eye only).
Downsides of perturbing and recording from the brain
they are invasive techniques
what animal did David Hubel and Torsten use in discovering ocular dominance columns?
cats :)
monocular deprivation
one eye is sealed at birth that way no light is never let into the eye ever in the animals development (a cat or monkey)
dose a few days of Monocular deprivation affect the eye’s function of ocular dominance?
yes just a few days change the structure of the synapses and dendrites
plastic changes
Plastic changes are learning and storing memories this is important to our brains
What gives rise to ocular dominance columns?
The separate inputs from the eyes target separate neurons in layer 4C, giving rise to ocular dominance columns.
critical periods
a time of development that the person can form incorrectly based off the environment, not just seen in the eyes but also in auditory language development
Phantom limb syndrome
a time of development that the person can form incorrectly based off the environment, not just seen in the eyes but also in auditory language development
priming
exposure to a stimulus. for example remembering a list of foods after being shown pictures of kitchen appliances
classical conditioning
getting a subject to form an association between a meaningful stimulus and a neutral item
