[Abstract Title]. - Society for Neuroscience

Abstract: Central fatigue is a subjective phenomenon which can be examined using transcranial
magnetic stimulation (TMS). Motor Evoked Potentials (MEPs) are shown to be reduced up to 15
min after a fatiguing exercise. Similarly, repetitive finger movements performed at maximal
velocity for 1 min are capable to induce a long lasting depression of MEP. In literature there are
no studies comparing data from corticospinal excitability and motor behavior during and after a
fatiguing exercise. Aim of this study was therefore to compare changes in corticospinal
excitability and motor behavior parameters in normal subjects during and after a fatiguing motor
task based on repetitive finger opposition movements.
Seven normal subjects (5 females and 2 males, mean age 27.5) participated in this study after
giving their informed consent. Subjects wore a sensor-engineered glove on their right hand and
performed a repetitive finger motor sequence (opposition of thumb to index, medium, ring and
little fingers) at a metronome rate of 2Hz.
Subjects were asked to perform for two times the finger motor sequence lasting 5 min (1st (1S)
and 2nd SEQUENCE (2S)) with an interval of 1 min during which the MEP recording was
performed. MEPs were recorded from the right opponens pollicis muscle. The stimulus intensity
producing MEP amplitudes of 1 mV (SI1mV) at rest was established. Then, 10 responses at
SI1mV have been collected before 1S, immediately after 1S and 2S and every 5 min for 20 min
after 2S.
Further, we considered as motor behavior parameters the time between the touch onset and the
corresponding tone in its absolute value (ABSTE) and the percentage of advanced and delayed
finger movements with respect to the tone occurrence.
When subjects performed a fatiguing exercise MEP amplitude was significantly reduced
immediately after the 1S and still remained around this value up to 10 minutes after 2S after that
it recovered to its initial value. Regarding motor behavior data, the percentage of sequences with
advanced onset significantly decreased from the 1st minutes to the 5th. Similarly, ABSTE value
significantly increased during the performance of the task from the 1st minutes to the 5th.
Interestingly, differently from corticospinal excitability, at the beginning of 2S motor behavior
parameters completely recovered to their initial values (1st minute of 1S).
We showed that fatiguing exercises based on repetitive finger opposition movements can
influence corticospinal excitability and motor behavior. However, since the time course of these
two phenomena is different we suggest that fatigue influences them through two different neural
mechanisms.
Disclosures: M. Bove, None; L. Avanzino, None; A. Tacchino, None; A. Giannini, None; M.
Ghilardi, None; A. Quartarone, None; G. Abbruzzese, None.
Poster
277. Voluntary Movement: Cortical Planning and Execution II
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 277.13/LL5