Page 17 - UNIT 3

direction of movement and stimulate the semicircular ducts. This suggests that the
vestibulocerebellum is especially important in controlling balance between agonist and antagonist
muscle contractions of the spine, hips and shoulders during rapid changes in body positions as
required by the vestibular apparatus.

 One of the major problems in controlling balance is: the amount of time required to transmit
position signals and velocity of movement signals from the different parts of the body to the
brain. Even when the most rapidly conducting sensory pathways are used, the delay for
transmission from the feet to the brain is still 15 to 20 ms. (Ex: the feet of a person running
rapidly can move as much as 25.4 cm during that time; therefore, it’s impossible for signals
from the body to reach de brain at the same time that the movements actually occur).

The signals from the periphery tell
the brain how rapidly and in which
directions the body parts are moving
Then, how is it possible for the brain to know and then the vestibulocerebellum
when to stop a movement and to perform calculates in advance from these
the next sequential act, especially when the where the different parts will be
movements are performed rapidly? during the next few ms. The results
of these speculations are the key to
the brain’s progression to the next
sequential movement.

So, during control of equilibrium, it’s presumed that information from both the body periphery and the
vestibular apparatus is used in a typical feedback control circuit to provide anticipatory correction of
postural motor signals necessary for maintaining equilibrium even during extremely rapid motion,
including rapidly changing directions of motion.

5.2. Spinocerebellum feedback control.

(1) The intermediate zone of each cerebellar hemisphere
receives information during a movement performance of
two sources:

1. from the cerebral motor cortex and from the
midbrain red nucleus, about the intended
sequential plan of movement, and
2. from the peripheral parts of the body, especially
from the distal proprioceptors of the limbs, about
what actual movements result.

(2) Then, the intermediate zone of the cerebellum
compares both information and the deep nuclear cells send
corrective output signals to:

1. the cerebral motor cortex through nuclei in the
thalamus and
2. to the magnocellular
portion (lower portion) of the
red nucleus that originates the rubrospinal tract.

17