Plasticity, Memory and Transmission: Week 4 Flashcards
synapse
connection between 2 neurons
3 types of synapses
axo-dendritic synapse
axo-somatic synapse
axo-axonic synapse
what is the most common type of synapse
axo-dendritic synapse
axo-dendritic synapse
pre synpactic axon to post synaptic dendrite
axo-somatic synapse
pre synaptic axon to post synaptic some
axo-axonic synapse
pre synaptic axon to post synaptic axon; can influence/ regulate release of post synaptic cell transmitters
synaptic clef
small space between pre and post synaptic neuron
how small is the synaptic clef
20 nm wide
synaptic vesicle function
contain neurotransmitters and release when action potential fired
3 types of neurotransmitters
amino acids, amines, peptides
amino acid neurotransmitters
Glutamate (excitatory), GABA (inhibitory), Glycine
amine neurotransmitters
norephedrine, acetylcholine, dompaine, serotonin, etc.; modulate amino acid transmitters
peptide neurotransmitters
Enkephalins (Enk) and Substance P; combination of amino acids
how many different types of neurotrasmotters does a neuron contain
1 type of either amino acid or amine neurotransmitters and neuropeptides
formation of peptide neurotransmitter mechanism
-rough ER: synthesis precursor peptide
-golgi: form active neurotransmitter peptide
-secretory granules ready to release neurotransmitters
neurotransmitter release mechanism
1)synaptic vesicle docked at presynaptic active zone
2)action potential -> increase Ca2+ in pre synaptic cell
3)Ca2+ increase depolarize cell and signals neurotransmitter release
4) synaptic vesicles are recycled
synaptotagmin 1 function
Ca2+ ion sensor that leads to triggering neurotransmitter release
SNARE protien complex function
aids in docking and fusing vesicle to membrane
how does Ca2+ influence neural processes
Ca triggers vesicle fusion with cell membrane -> neurotransmitters released
what are the 2 classes of post synaptic receptors
ligand gated ion channels and G protein couples receptors
ligand gated ion channels mechanism
neurotransmitter binds, structural change, channel opens, ion flow with conc gradient
what is another name for ligand gated ion channel
ionotropic receptor
G-protien coupled receptor pathway
neurotransmitter binds, g protein activated, g protein subunits or intracellular messanges communicate with ion channel, ion channel opens, ion flow across membrane
what is another name for g-protien coupled receptor
metabotropic receptor
is the ligand gated ion channel or the g protein coupled receptor pathway faster
ligand gated ion channel
how does glutamate binding to a receptor impact the cell
positive ions into the cell to depolarize it
how does GABA binding to a receptor impact the cell
negative ions into the cell to hyperpolarize it
which type of ion channels produce “rapid post synaptic effects” and how long is the effect
transmitter/ligand gated ion channels: membrane potential change in 1-2 milliseconds that lasts ~10 milliseconds
Glutumate receptor subtypes
AMPA, NMDA, kainate
what type of receptor is AMPA
ionotropic: ligand gated
what type of receptor is NMDA
ionotropic: ligand gated and voltage gated
GABA receptor subtypes
GABA a and GABA b
what type of receptor is GABA a
ionotropic
what type of receptor is GABA b
metabotropic
why is the NMDA different than the other glutamate receptors (Kaiate and AMPA)
only opens when glutamate binds AND cell is already depolarized since Mg or Zn cations block it at rest
how do drugs act on GABA gated Cl- channel (GABA a receptor)
many different compounds binding to receptor can enhance or change GABA’s effect
ex. ethanol increases inhibition (enhances GABA)
what are the 2 types of post-synaptic potentials (PSP)
excitatory and inhibitory
EPSP
excitatory post synaptic potentials: cells action potential becomes less negative -> depolarization -> activate
ex. glutamate acting on AMPA receptors
IPSP
Inhibitory Post synaptic potential: cell potential gets more negative -. hyperpolarize cell -> inhibition
ex. GABA acting on GABA a receptors
synaptic integration: spacial summation
multiple presynaptic neurons simultaneously stimulate a postsynaptic neuron, leading to a combined effect on the postsynaptic neuron
synaptic integration: temporal summation
neuron processes signals arriving at the same synapse in rapid succession
-> eventually reach high enough potential for action potential to fire
synaptic plasticity
change in how effectively information is transmitted acorss synapse
*synaptic strength
how to larger/increased EPSP influence synaptic strength
increased synaptic stength
how do smaller/ decreased EPSP influence synaptic strength
decreased synaptic strength
short term facilitation
temporary increase in synaptic strength
short term depression
temporary decrease in synaptic strength
long term potentiation and long term depression
long-lasting changes in synaptic strength that are thought to be the basis of associative learning and memory
synaptic strength specificity
specific to only synapses where presynaptic neuron was active (for LTD and LTP)
*ex) only change memory at specific synapse not all memories
3 mechanisms for long term potentiation (LTP)
- increase effectiveness of AMPA receptor/ increased channel opening
-more AMPA receptors inserted into synapse (so more neurotransmitters can bind)
-increased neurotransmitter release via retrograde messenger
retrograde messenger
sends message from post synaptic cell to pre synaptic cell (backwards) -> increase pre synapic Ca2+ and transmitter release
what determines if LTP or LTD occurs
Ca levels
what does a large increase in post synaptic Ca 2+ induce
LTP
what does small increase in post synaptic Ca 2 induce
LTD
what concept is synaptic plasticity an important mechanism for
learning and memory
what are the different types of memory
long term/short term memory and declarative/ nondeclarative memory
declarative memory
long term memory involving consciously recalling facts and events
nondeclarative memory
long term memories of skills, habits, and dispositions that are not consciously recalled
2 types of declarative memory
semantic memory and episodic memory
semantic memory
consciously recalled long term memories about facts about the world/ general facts
episodic memory
consciously recalled long term memories about personal experiences/ personal life (autobiographical memory)
2 types of amnesia
retrograde and anterograde
retrograde amnesia
forget things before the trauma
*may remember things from long long ago (childhood)
anterograde amnesia
inability to form new memories after trauma
what happened to patient HM
he had a severe seizure condition due to traumatic brain injury so they did a surgery to remove 8 cm of tissue from the medial temporal lobe including the hippocampus
results of HM surgery
-seizures got better
-anterograde amnesia
-procedural memory still in tact
HM conclusions
hippocampus/ surroundings area in medial temporal lobe have a role in long term memory/ anterograde amnesia
what other tissues (besides hippocampus) were cut out of HM
parahippocampal areas: parahippocampal cortex, perirhinal cortex, rhinal sulcus, entorhinal cortex
what is the hippocampus main role in memory thought to be
consolidation and retrieval of memories; not necessarily stored long term in the hippocampus
where are declarative memories thought to be stored mainly
neocortex (6 layered part of cerebral cortex)
2 main areas of hippocampus function
-episodic memory(mental time travel; remembering past events of own life)
-spatial navigation
what is episodic memory
ca[acoty to consciously remember personally experienced events (mental time travel)
what is the goal of episodic memory
to guide future actions to result in more efficient behavior and better rewards
pattern seperation
the ability to distinguish similar patterns and experience; kep similar memories distinct
pattern completion
the ability to retrieve full past experiences from partial input (ex. cake reminds you of your bday party event)
main input to hippocampus episodic memory pathway
entorhinal cortex (EC)
what part of hippocampus episodic memory pathway is responsible for pattern separation
dentate gyrus (DG)
what part of hippocampus episodic memory pathway is responsible for pattern completion and why
Cornu ammonis 3 (CA3) because this area is very interconnected; autoassociative network between C3 neurons
main outputs to hippocampus episodic memory pathway
Subiculum or EC
hippocampus episodic memory pathway mechanism
info from cerebral cortex and sensory system inputs -> Entorhinal cortex -> Dentate gyrus for pattern separation -> Cornu ammonis 3 for pattern completion -> exit
how would pattern completion be affected if there was no hippocampus (only neocortex representations)
no separate hippocampus spot where cerebra; cortex inputs all go to, overlapping inputs -> confusing similar memories
semantic memory
acquired knowledge about the world
what brain regions are activated by general semantic processes
many central hubs of the brain; not localized to one brain area
2 possible models of semantic knowledge
distributed only view and distributed plus hub view
distributed only view of semantic memoery
distributed representations of different aspects of semantic memory (shapes, motion, color etc.) working in parallel with no hierarchy
distributed plus hub view of semantic memory
Amodal hub in anterior temporal lobe modulates specific regions of distributed representations communication
category selective cells
cells that respond selectively to particular categories of information; commently visual
ex. face selective cells
concept cells
cells that respond to a certain concept across many domains of sensory input (reading, picture, audio, etc)
concept cells and consciousness
concept cells only respond to designated concept if subject is consciously aware of what they are seeing; conscious recognition
concept cells topography/ orginization
no obvious topography in medial temporal lobe; sparse coding
