A Study of the Relationships between the Ratio of 2nd to 4th Digit Length and Cerebral Laterality

ABSTRACT

OBJECTIVES: Cerebral laterality is thought to be an important marker for neurodevelopment. Prenatal testosterone could influence both cerebral laterality and 2nd to 4th finger length ratio(2D4D). EEG coherence and 2D4D were examined to investigate the relationship between prenatal testosterone level and cerebral laterality. METHODS: EEG was recorded in 24 healthy subjects in the eyes closed resting state. Differences in 2D4D finger ratio were used to discriminate "masculine finger type" and "feminine finger type" groups. The 2D4D ratio was lower and greater than one for the "masculine finger type" group and "feminine finger type" group, respectively. We used coherence analysis to estimate the cortical functional connectivity. RESULTS: There were statistically meaningful relationships among cerebral functional connectivity, sex and finger ratio. Man and masculine finger type group showed higher intra-hemispheric coherence than those of woman and feminine finger type group. Woman and feminine finger type group showed higher inter-hemispheric coherence than those of man and masculine finger type group. CONCLUSIONS: These results imply that prenatal testosterone might act as important determinants of cerebral laterality. Further examination of the relationship between 2D4D and EEG coherence in schizophrenia could give some clues for the neurodevelopmental hypothesis of schizophrenia genesis.