IN-PHASE CODİNG AND HAND PREFERENCE

ABSTRACT
Aim: Bimanual in-phase movement, which is frequently seen in infancy, disappears in the first decade of life with central nervous system maturation. Hand dominance becomes evident and interhemispheric inhibition is initiated to suppress the opposite hand. However, in-phase movements are frequently used in our daily lives.
Materials and methods: Thirty students (14 female, 16 male) with right hand dominance were included in the study. Two screw assemblies placed on a wooden plane were designed to perform tightening or loosening orders. Test 1: ordered to tighten screws at the same time with both hands.  Test 2: ordered to tighten the screw with only left hand. Fisher's exact test was used to compare the ratios between the sex. P <0.05 was considered significant.
Results: Test 1: In the bimanual tightening test, the left hand performed mirror symmetrical movement instead of voluntary correct antiphase movement in 11 persons (78.6%) in females, and the left hand unwantedly loosened the screw. This rate was 37.5% in males (6 persons). The error rate was higher in female gender (χ2: 0.021, p: 0.033). Test 2: In the unimanual left hand tightening test, mirror symmetric movement instead of antiphase movement was seen in 7 female persons (50%) and in 5 male persons (31.3%). The left hand therefore made a loosening motion instead of tightening the screw. The difference between the two groups was not found for this test (chi-square: 0.295, p: 0.457).
Conclusion: The relatively higher error in the female gender in the bimanual task, which is more otomatic movement, may be due to the fact that the male gender knows the use of this device in advance. There was no difference in the unimanual task with more voluntary attention between genders. It is discussed in the light of the literature that the cause of left-hand errors may be in confliction with visomotor information on the real trajectory of movement of the nondominant hand.
Key words: Hand preference, Motor learning, İn-Phase movement