[Abstract Title]. - Society for Neuroscience

with altered performance of tasks requiring interhemispheric integration of sensory and motor
information. Here we investigated the CC functional role in bimanual coordination combining
motor behavioral with Magnetic Resonance Diffusion Tensor Imaging (DTI) data in MS
patients.
We asked 14 MS patients to perform repetitive finger opposition movements of thumb to index,
medium, ring and little fingers with the two hands simultaneously, paced with a metronome set
at 1, 1.5 and 2Hz. We defined the Inter Hand Interval (IHI) as the absolute time difference
between the corresponding touch onsets occurring in the two hands: the larger is the IHI, the
more severe is the impairment in bimanual coordination. Sub-regions were selected in the CC:
CC1 included the genu and the rostrum, CC5 covered the splenium; CC2, CC3, CC4 were
identified in the remaining portion of the CC, subdividing the “anterior to posterior” distance
into 3 parts. Fractional Anisotropy (FA) values were obtained by DTI data to quantify damage in
each CC area.
In a first series of experiments, an eyes closed paradigm was chosen to exclude confounding
effects due to the integration of acoustic and visual information. Interestingly, a correlation
between mean IHI and FA values was found only in CC1 and CC2 for all the rates.
To investigate the role of posterior CC in bimanual coordination, a sub-group of 5 MS patients
underwent a new experimental paradigm where a visual cue substituted the acoustic cue as
metronome. In addition, a visual input was given to the patient in correspondence of the finger
touch for the two hands separately, providing real-time feedback about the bimanual
performance. After a phase of motor task execution at a specific rate set by the visual cue, the
patient continued the task trying to preserve the same rhythm as before, always with the signals
representing the two hands but without the visual metronome. Results showed a trend to a
correlation between mean IHI and FA values in the posterior CC.
We showed that anterior and body callosal connections are essential to perform simultaneous
bimanual finger opposition movements, while the posterior CC seems to be involved only when
a visual paradigm is adopted. These findings suggest that bimanual coordination relies on
communication through CC in different sub-regions according to the specific motor task
modality.
Disclosures: L. Bonzano, None; A. Tacchino, None; L. Roccatagliata, None; G. Abbruzzese,
None; G.L. Mancardi, None; M. Bove, None.
Poster
251. Demyelinating Disorders: Animal Models and Human Studies I
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 251.5/V32
Topic: C.08.b. Animal models