Transmissions of the efference copy signal and re-afference signal during active and passive hand movements: a Somatosensory Evoked Potential study

Contemporary theories of motor control suggest intensive crosstalk between
motor and somatosensory regions. Each motor command is assumed to go not only
to the body but also to other brain regions, the somatosensory cortices such as
BA2 in particular. The motor signal sent from the central nervous system to the
peripheral system is called efference signal. A copy of this signal sent to
somatosensory area is called efference copy. In one fMRI study (Study Title:
Measuring the Mirror Neuron System: A Combined EEG/fMRI Study, METC number:
2009/056, ABR number: 29796 / NL29796.042.09) we did last year we found that
the enhancement of activation in somatosensory area BA2 during active action
compared to passive action may be due to an efference copy sent from SMA to BA2
using Dynamic causal modeling (DCM) analysis. But the methods constrained us
from precisely quantifying the timing and strength of this influence. In the
present study we want to confirm the finding and quantify the contribution of
the efference copy in the difference between active action and passive action
using somatosneory evoked potentials (SEP).

In this study we want to quantify the contribution of the efference copy in the
difference between active action and passive action using somatosneory evoked
potentials (SEP).
Our first hypothesis is that during the motor planning stage, the difference in
SEP between active and passive task is caused only by efference copy sending
from SMA to BA2. According to the nature of SEPs, the early components reflect
subcortical activation and later components are believed to be associated with
higher levels of cortical processing. We suppose that the SEPs during the motor
planning state will be only differentiating in later (after 45ms) components.
Our second hypothesis is that during the squeezing action stage, the difference
in SEP between active and passive is caused by the combination of efference
copy and re-afference signal sending from the sensory system back to the
somatosensory area in the cortical system. So the SEP differences may show on
both earlier and later components.

The participants will wear a thin latex glove on their right hand which
attached to an identical glove worn by experimenter. There are three tasks in
this study: Active; Passive and Relax.
During the active task, participants will be instructed to squeeze gently with
their right hand for 2 seconds in each trial.
During the passive task, participants will keep their hands relaxed and the
experimenter will squeeze the particpant's hand.
During the relax task, participants will keep their hands relax through the
session.
We will apply electrical stimuli on the median nerve on the participants* wrist
during their performing of the task and record the SEP signal on their scalp.
The electrical stimuli will be applied twice in each trail. One is during the
motor planning stage the other one is during the squeezing action stage.

A small electrical current is sent through a probe to the skin near a nerve on
participant's wrist. This may be done several times. This makes a twitching or
pulsating feeling in the wrist. Participant's thumb may twitch during the test.
While the sensation may be unusual or slightly uncomfortable, this test is not
harmful and most people don't consider this test painful.