The Sex-Related Differences of Relationships between 2D : 4D Ratio and Electroencephalographic Coherence in Patients with Schizophrenia Compared with Controls

OBJECTIVES: Prenatal testosterone is known to influence both cerebral laterality and 2nd to 4th digit ratio (2D : 4D). Epigenetic changes are thought to play some role in it. We studied sex-related differences between 2D : 4D and cerebral laterality in patients with schizophrenia and controls to examine the effects of prenatal testosterone in the development of schizophrenia. METHODS: Forty one men (18 schizophrenic patients and 23 controls) and 40 women (17 schizophrenic patients and 23 controls) were recruited from one psychiatric hospital in Korea. The 2D : 4D and electroencephalographic (EEG) coherence in 19 channels (66 pairs of interhemispheric coherence and 54 pairs of intrahemispheric coherence) were measured. The sex-related statistical analyses between 2D : 4D and EEG coherence in controls and patients with schizophrenia were performed using multiple regression. RESULTS: In male patients, the relationship between 2D : 4D and right intrahemispheric EEG coherence showed mainly positive correlation in delta and theta frequency bands, while it showed negative correlation in male controls. In female patients, the relationship between 2D : 4D and interhemispheric EEG coherence showed stronger positive correlation in alpha and beta frequency bands, while it showed weaker positive correlation in female controls. CONCLUSIONS: Low prenatal testosterone may play certain roles in altered correlation between 2D : 4D and cerebral laterality in schizophrenia and the development of schizophrenia by epigenetic mechanism.

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

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(2D:4D). EEG coherence and 2D:4D 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 2D:4D finger ratio were used to discriminate "masculine finger type" and "feminine finger type" groups. The 2D:4D 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 2D:4D and EEG coherence in schizophrenia could give some clues for the neurodevelopmental hypothesis of schizophrenia genesis.

Relationship between eye dominance and handedness in two different methods among university students / 国际眼科杂志(Guoji Yanke Zazhi)

AIM: To evaluate the relationship between eye dominance and hand preference among university students with respect to dominant hemisphere. METHODS: A total of 179 university students (mean age ±SD was 19.4±1.6 years) were included in the study. The subject population was composed of 110 females (61.5%) and 69 males (38.5%) volunteered for examina-tion. Eye dominance was determined by two different methods named Gündoan and McManus tests. Handed-ness was also determined by two different methods as Edinburgh Handedness Inventory Oldfield (1971) and McManus tests. The reliability of the survey was examin-ed using a test-retest method.RESULTS: Without gender difference right/left eye dominance were found respectively for 110 (61.5%), 69 (38.5%) subjects by Gündoan test. When the same subjects were re-tested by McManus method the right/left eye dominance was found respectively for 128 (71.5%), 51 (28.5 %). The results of these two methods were related significantly, with an agreement score κ=0.256 (P<0.01). In females the right/left eye dominance were found respectively as 62 (56.4%), 48 (43.6%) by Gündoan test as it was found respectively 74 (67.3%), 36 (32.7%) for the same subjects when re-tested by McManus test method. The results of these two tests for females were related significantly by Fisher exact test (P<0.05), with agreement score κ=0.239 (P<0.01). In males the right/left eye dominance were found respectively as 48 (69.6%), 21 (30.3%) in Gündoan test method as it was found 54 (78.3%), 15(21.7%) for the same subjects when re-tested by McManus test (P>0.05). Right handedness ratios were 91.6% (n=164) and 91.1% (n=163) in Oldfield and McManus tests, respec-tively. Statistical agreement between these two methods was also represented with a high score (κ=0.753, P<0.01). The statistical relationship correlation between eye dominance and throwing hand was found significant by McManus test methods (Fisher exact test P<0.017) with an agreement score phi=0.193, P<0.05.CONCLUSION: The marked right handedness was observed among university students in both two hand preference tests. According to McManus test the throwing hand seems to have more consistent relation with the right eye dominance. Throwing hand and dominant eye seems to be a most reliable way for detecting functional asymmetry and cerebral laterality.