BDNF Val 66

33 Recent data suggest that the Val66Met polymorphism of the BDNF gene can alter cortical 34 plasticity within the motor cortex of carriers, which exhibits abnormally low rates of cortical 35 reorganization following repetitive motor tasks. To verify if long-term retention of a motor skill 36 is also modulated by the presence of the polymorphism, 20 participants (10 Val66Val; 10 37 Val66Met) were tested twice at a one week interval. During each visit, excitability of the motor 38 cortex was measured by transcranial magnetic stimulations (TMS) before and after performing a 39 procedural motor learning task (Serial Reaction Time Task) designed to study sequence-specific 40 learning of the right hand and sequence-specific transfer from the right to the left hand. 41 Behavioral results showed a motor learning effect that persisted for at least a week and task42 related increases in corticospinal excitability identical for both sessions and without distinction 43 for genetic group. Sequence-specific transfer of the motor skill from the right hand to the left 44 hand was greater in session 2 than session 1 only in the Val66Met genetic group. Further 45 analysis revealed that the sequence-specific transfer occurred equally at both sessions in the 46 Val66Val genotype group. In the Val66Met genotype group, sequence-specific transfer did not 47 occur at session 1, but did at session 2. These data suggest a limited impact of Val66Met 48 polymorphism on the learning and retention of a complex motor skill and its associated changes 49 in corticospinal excitability over time, and a possible modulation of the interhemispheric transfer 50 of procedural learning. 51