Transcript Lecture 3 - Joe Francis Lab

Kinematics in the CNS
From Chapter 10: Vibration of the biceps causes activation of the muscle
spindles. This is perceived as a lengthening of that muscle, that is in the
direction opposite to its normal active movement direction.
Sensory Integration is used to estimate the hand or end effectors position.
When the subject holds a light in their hand there is
a difference in the perceived hand position of 4°
between when the hand held light is on or off.
Likewise, if the subjects held a small speaker in
their hand a similar illusion would occur that is they
believed the auditory source was moving as was
their hand.
Thus, you do not appear to have separate
estimates of where your hand is, but rather the
CNS uses information from the different sensory
systems to produce one estimate of hand position.
The gain on each sensory system can be changed.
Muscle vs. Movements
M1 neurons
influence several
motor pools
and often
synergistic muscles.
Consider addressing
to be of the
movement. The
controlled variable
question is open,
but there is good
evidence for control
of the dynamics, but
as in many cases
it is probably a bit
of both and
depends on the
situation at hand.
Encoding limb configuration
There is a large degree of
correlation that occurs
naturally when we move our
limbs. Bosco and Poppele got
around this by fixing the knee
joint angle. They found that
about 50% of the activity did
not change from when the
joint was fixed to when it was
free, and concluded that the
activity in half of the cells in
the dorsal spinocerebellar
tract reflect end effector
position and the other half the
limbs configuration.
S1 neurons and limb configuration
Helms-Tillery et al found that
neurons in S1 (areas 1,2 3b), had
a preferred axis that they
represented. The coding could be
fit to the function
f  co  c1x  c2 y  c3z
For a majority of cells the y axis
dominates the rate change. This
would indicate that perhaps the
representation for movements
along this axis are heightened.
This was tested on humans by
Van Beers et al (pg 170). They
found results that agreed with this
notion. Others have seen such
a preferance in M1 activity as well.
A. Somatosensory mapping and B. Motor mapping. From Nolte pg 75