neuronal plasticity Flashcards
memory
simply describes stored information about past (recent or distant) experiences
what are 3 main types of memory
1.Sensory
2.Working
3.Long-term
2 categories of long term memory
1.declarative memory
2.procedural memory
what is declarative memory
memory that can be expressed in language – facts or information that have been learnt
what is procedural memory
are ones that involve the learning of skills – riding a bicycle, playing a musical instrument
what are 2 things declarative memory are divided into?
1.semantic memory
2.episodic memory
semantic memory
which is material learnt independent of its context. An example would be knowing the names of colors.
Episodic memory
particular context, such as memory of a particular event
in memory what is explicit
where information is consciously held and actively fed into long-term memory storage
in memory what is implicit
where information is integrated into long-term memory without our conscious recollection
why is memory important?
provides a template/framework for your responses to different situations
the limbic system
hippocampus is involved in many forms of memory but particularly spatial and long-term explicit memory
the limbic system-amygdala
link to negative emotional memory, learned fear.
the pre-frontal cortex
plays a key role in working memory and integration of information for transfer to long-term memory
the striatum
plays a key role in learning of skills and habits (this also links to it’s role in the control of movement and procedural learning)
the cerebellum
plays a key role in procedural learning
neocortex
developmentally newer regions of the cortex that have all six layers of cells present
-includes most of the prefrontal cortex and also the cortical association areas in the temporal and parietal regions
engram
describe the ‘memory trace,’ that allows a memory to be stored
what are the 2 ways memory is stored in engram?
1.electrically
2.physically
what is the electrical way in engram
as a pattern of activity within neuronal circuits
what is the physical way in engram
through changes in the cellular make-up, this could be morphological or metabolic/functional
what 3 locations can memory be located at?
1.The engram
2.The engram cell
3.the engram circuit
The engram(location)
resulting from subcellular changes
The engram cell
changes at the single neuron level
engram circuit
seen as changes at a network level
papez ciruit
the cyclical circuitry
what happens in papez circuit?
1.electrical activity passes from hippocampus through limbic system
2.then back to the limbic system
3.this type of activity holds information in working memory
4.can also contribute to emotional processing
Neuroplasticity
describes the ability for a neuron or neuronal network to alter its activity, to increase/decrease it’s response to certain stimuli or inpu
what 4 routes can occur in neuroplasticity?
1.rewiring
2.reconnecting
3.retracting
4.regenerating
rewiring
changing activity at the level of the single neuron
Reconnecting
changing the connectivity of neurons
Retracting
pruning connections to streamline activity
Regenerating
growth of new neurons (neogenesis)
what do the 4rs lead to?
enhancement of reduction in the likelihood of a particular neuron and/circuit being activated
what 2 modals are in the 4rs?
1.Long-term potentiation
2.Long-term depression
long term potentiation(Tim Bliss and Tereje Lamo 1973)
1.they found that when they recorded in the hippocampus (a key area for learning and memory) of rabbits
2.if they applied a brief period of high frequency stimuli and then went back to the regular stimulation levels
3.activity in the stimulated population of neurons was increased
4.increase lasted for hours!
how did the induction of rapid onset occur
LTP was dependent on activation of the NMDA
NMDA
glutamate receptor
what is NMDA dependent on?
voltage dependent due to the channel being blocked by magnesium (Mg2+), this block is removed by the high frequency stimulation and this allows the channel to open.
what do NMDA channels allow?
allow entry of Ca2+ into the post synaptic terminal, and this calcium entry triggers second messenger cascades that can induce plastic changes within the cell
2 what plastic changes are made in NDMA channels
1.structural (e.g. changing the synapse shape)
2.functional (e.g. changing receptor sensitivity or number)
what changes occur in NDMA channels?
pre-synaptically that leads to an increase in transmitter release. Overall this leads to an increased response to later stimulation
what happens when there is increased response to later stimulation in NDMA channels
NMDA-receptor dependent LTP
what can NMDA-receptor dependent LTP be induced by?
metabotropic glutamate receptors
long term depression
model that would allow information to be deleted from the circuitry
-is induced by low level activation of the receptors.
what 2 forms does long term depression have ?
1.NMDA- dependent
2.Non-NMDA dependent
how can In-vitro LTD be induced?
low frequency stimulation (1Hz) for an extended period of time (15 mins)
what does in-vitro cause ?
causes enough depolarisation to open some NMDA receptors, but not enough to activate LTP
what happens when there is depolarisation of NMDA receptors but not enough to activate LTP?
leads to low-level calcium entry a reduced level of activation of the second messenger cascades, internalisation of the AMPA receptors from the post-synaptic membrane and retraction of spine morphology
what happens after retraction of spine morphology?
Pre-synaptically, this results in decreased transmitter release. All of these reduce the likelihood of the neuron firing again.
depotentiation
possible to reset LTP using LTD
what does LDT play a role in?
thought to play a role in procedural/skills learning, and also in conditioned learning (such as fear conditioning), where improved performance and responsiveness is dependant on removing errors
what happens during induction of LTP and LTD
range of second messenger cascades are activated.
what do NMDA receptors activation allow?
allows Ca2+ entry, which triggers intracelllular signalling cascades.
Type 1 mGluR
metabotropic glutamate receptors) activates PLC (phospholipase C) which can trigger many kinase cascades activating genes that increase protein synthesis
what else do type 1 mGlurR activate?
trigger Ca2+ release from intracellular stores
Type 2 mGLuR
modulate cAMP levels.
what can activation of cascades in MGLuR lead to?
upregulation of receptors, with new AMPA receptors being inserted into the membrane, which increases the amount of depolarisation when the next stimulus arrives.
what do metabotropic glutamate receptor change?
shape of the synapse or the number of synapses linked to the potentiated synapse, increasing the surface area of the connection, increasing the likelihood of transmission.
synaptic pruning
reduction in spines (the points of connection, where the synapses are located
memory loss
associated with cognitive decline associated with dementia, or as a result of stroke or traumatic brain injury.
2 main forms of amnesia
1.anterograde
2.retrograde
anterograde
loss of memory of events following the trauma
