lecture 20 - stuart baker Flashcards
air puff is given to the eye and that causes a blink
if the air path is paired with a tone which predicts the appearance of the ait path over trails the rabbit starts to blink before the stimulus
this is cerebellar dependant
when there’s a large lesion in the cerebellum the learning is abolished and cannot be re learned
he lesioned the cerebellar cortex instead of the whole cerebellum
results were that
in the rabbits that learnt for 5 days learning was abolished but they can relearn the task
in the rabbits that learn for 7 days, learning was un effected
so leaving the deep cerebellar nuclei in tact changed the results
cerebellum has multiple sites for learning
for example
the projection down from the purkinje fibres to the deep cerebellar nuclei
the cerebellum is learning things initially in the cerebellar cortex and then its downloading that learnt motor programme in someway down to the deep cerebellar nuclei
so eventually in a highly trained motor task, if the cerebellar cortex is lost and the deep cerebellar nuclei the learning memory is still preserved
the goal of control of posture is to…
maintain centre of mass over base of support
strategy I: move COM (centre of mass)
if the surface moves backwards (e.g standing on the metro)
the body will sway forwards and that’s now an unstable posture as the COM has now moved outside the centre of support
recovery: activate leg muscles that will make the body sway back and compensate for the sway forwards and restore the COM above base of support
strategy II: enlarge base of support
recovery: increase base of support by taking a step forward
sensory systems that allow us to have stable control of posture is the
vestibular system
what is the vestibular system
an organ which gives us information about the movement of the head
2 components to the vestibular system
1 = the semicircular canals
there are 3 of them
they tell us about angular rotation and angular acceleration
2 = otolith organs
2 of them (utricle and saccule)
they sense linear acceleration
utricle and saccule
hair cells with the cilia of them embedded into gelatinous matrix
on top of the gelatinous matric are otoliths which are small crystals of calcium carbonate
when there’s a linear accelerations this causes deformation of the gelatinous matrix and a sway of the hair cells and then that acceleration can be detected
also detects acceleration due to gravity
semicurcular canals
the ampulla is a bulge in the canal
which contains a cupula (fluid filled) which has hair cells attached to it which will sway as the fluid moves with angular acceleration and activates the hair cells
vestibular gives us the angle of the head relative to gravity
can have a severe head angle but be stable
so postural control also needs the body angle
cullen (2012)
monkey is being swivelled back and forth which causes firing in vestibular afferents
she then took the animal and fixed the head and just moved the body, there was no discharge in the vestibular afferent
she then recorded from the fastigial nucleus in the cerebellum and she found cells that responded to the activation of rotating the whole monkey but they also responded to when just the body was rotated and not the head
the two signals are combined together to give an unambiguous signals that says the body is moving
measuring responses to self generated movement
somebody held a balloon with a weight on it
someone else pops the balloon and the weight dropped
the person sways and then compensate for the sway and that happens after the bursting of the balloon
when the subject bursts the balloon, the change in centre of pressure occurs before the balloon is bursts (anticipatory postural adjustment)
basal ganglia
are nuclei which in the midbrain
