Ein interessante Studie zu Geschlechterunterschieden im Gehirn bei Säuglingen:
The developing brain undergoes systematic changes that occur at successive stages of maturation. Deviations from the typical neurodevelopmental trajectory are hypothesized to underlie many early childhood disorders; thus, characterizing the earliest patterns of normative brain development is essential. Recent neuroimaging research provides insight into brain structure during late childhood and adolescence; however, few studies have examined the infant brain, particularly in infants under 3 months of age. Using high-resolution structural MRI, we measured subcortical gray and white matter brain volumes in a cohort (N = 143) of 1-month infants and examined characteristics of these volumetric measures throughout this early period of neurodevelopment. We show that brain volumes undergo age-related changes during the first month of life, with the corresponding patterns of regional asymmetry and sexual dimorphism. Specifically, males have larger total brain volume and volumes differ by sex in regionally specific brain regions, after correcting for total brain volume. Consistent with findings from studies of later childhood and adolescence, subcortical regions appear more rightward asymmetric. Neither sex differences nor regional asymmetries changed with gestation-corrected age. Our results complement a growing body of work investigating the earliest neurobiological changes associated with development and suggest that asymmetry and sexual dimorphism are present at birth.
Quelle: Investigation of brain structure in the 1-month infant (Scihub Volltext Link)
Aus der Studie:
Unterschiede Gehirn Mann Frau 1 Monat
Da geht es um die
- Größe des Gehirns von männlichen und weiblichen Babies nach Geburt.
- Das Volumen der weißen Substanz im Gehirn
- Das Volumen der grauen Substanz im Gehirn
Wie man sieht ist das Gehirn der männlichen Babies im Durchschnitt zB größer, und zwar über die hier erfassten Alter hinweg, auch wenn es einzelne männliche Babies mit relativ kleinen und einige Mädchen mit relativ großen Gehirnvolumen gibt. Der Trend ist aber recht deutlich.
Auch die Daten zu den verschiedenen Bereichen zeigen deutliche Unterschiede:
Unterschiede Gehirn Mann Frau 1 Monat
Es wird schwer das mit einer unterschiedlichen Sozialisiation zu erklären. Sie müsste dann wohl bereits im Mutterleib ansetzen. Was allerdings pränatale Hormone in der Tat machen, wie man beispielsweise an dem Testosteronspiegel sieht:
Testosteron Maenner Frauen
Aus einer Besprechung der Studie:
Dean’s team found that the boys’ brains were 8.3 per cent bigger, in line with the sex difference in brain volume found in adults and the few other available infant studies. Also as seen in adults, male brains had relatively more white matter (connecting tissue) and female brains more grey matter, relative to total brain size.
A number of specific neural areas were larger in males, such as parts of the limbic system involved in emotions, including the amygdala, insula, thalamus and putamen. The researchers also found evidence for relatively larger hippocampi, an area involved in memory, which has more commonly been found to be larger in females, although not universally so. Meanwhile female brains were relatively larger in other limbic areas such as parts of the cingulate gyrus, caudate and parahippocampal gyrus, and they had a few white-matter structures that were relatively larger.
These sex differences were smaller than has been observed in adults, which suggests that maturation continues this differentiation, likely through the high volume of sex steroid receptors in these brain areas. The alternative suggestion is that the subsequent differentiation is due to socialisation, but for the forces of socialisation to work along the same lines as pre-existing biological forces would suggest that socialisation is at most a feedback loop between biology and society.
There were a lot of brain areas that differed structurally between the sexes, but it would be irresponsible to draw any firm conclusions about what they might mean for function and behaviour. For instance, what could differences in overall insula size possibly mean psychologically when the area is associated with “compassion and empathy, perception, motor control, self-awareness, cognitive functioning”, “interpersonal experience” and “psychopathology”?
Insofern liegt noch viel Arbeit vor den Forschern, bis sie die Unterschiede wirklich verstehen. Aber dennoch entzieht diese Studie vielen, die auf einen Blank Slate abstellen und annehmen, dass Geschlechterunterschiede nur auf Sozialisiation zurück gehen können einiges an Boden bzw. erfordert, dass diese ihre Thesen kritisch hinterfragen.