Chapter 18- Basal Ganglia Flashcards
(47 cards)
what are the 6 functions of basal ganglia ?
1) regulation of muscle contraction and force
2) initiation and termination of mvmt
3) regulate multi-joint mvmt
4) control movement sequencing
5) oculomotor control
6) habit learning
what parts of the basal ganglia are for input ? where is the input usually from ?
caudate nucleus and putamen
input usually from cortex
what parts of the basal ganglia are for output ?
globus pallidus
what parts of the basal ganglia have the information “bounce around” ? where does it connect to ?
substantia nigra
connected to striatum and also projects to thalamus
does the basal ganglia communicate with the spinal cord ?
nope
which part of the basal ganglia goes wrong in Parkinson’s ?
substantia nigra
which neurotransmitter is involved in basal ganglia ?
dopamine
what does the basal ganglia like ? what drives it ?
reward (dopaminergic)
therefore, will favor motor programs that lead to reward
what are the input parts of the basal ganglia involved in ? 3 names and roles
putamen and caudate nucleus
1- some related to movement (phasic cells)
2- some related to movement but only with reward (tonic cells)
3- some related to movement only in right context, like in sequences (phasic cells)
what are the cells in the substantia nigra involved in ?
reward itself or cues to reward (guide for which movement to encode)
what is the majority of cells in striatum
phasic cells (80%)
what do the spines of the phasic cells do ?
they seem to support movement production
when do phasic cells fire ?
only when movement is going to be produced
therefore they are quasi-silent
when do tonic cells fire ?
more perpetually
always firing AP
how can the tonic cells firing pattern be modified ?
they can be conditioned to modulate firing pattern in relation to movement. tonic cell modulates firing in relation to learned behavior (with reward)
how exactly will tonic cells fire after they’ve been conditioned to associate a “click” with a reward ?
tonic cells continuously fire for a fact. however, after the click reward, there is a pause and then a rebound in the firing AP. this indicates that they need to pause in order to increase firing after.
in the substantia nigra, when will the cells fire ?
to predict reward
with classical conditioning, how will the firing pattern in the substantia nigra change ?
at first, the SN will only fire when the reward is presented.
however, when it is learned that the light is the trigger for reward, they will fire during the trigger, and then, after more time, will learn to fire even before the trigger.
how do striatum cells preferentially fire ? how is this demonstrated
inside a sequence.
if a rat cleans itself, it does so in a natural sequence of events. neurons will fire preferentially in different phases of this sequence, and will fire more in a sequence.
what kind of movement is the basal ganglia best suited to represent ?
representation of SUCCESSFUL motor programs
do we need the basal ganglia to move ?
nope
what does the striatum consist of ?
caudate and putamen
what happens when the striatum is at rest ?
since the striatum inhibits the globus pallidus, the globus pallidus is tonically active. this inhibits the VA/VL complex of the thalamus which then cannot excite the upper motor neurons in the cortex.
what happens when the striatum is transiently excited ?
this transiently inhibits the globus pallidus, which means that we’re inhibiting the inhibition effect the globus pallidus has on the VA/VL complex of the thalamus, meaning the frontal cortex can be excited
