Fundamental analysis of relationships between hearing and cognition in maternal brain function

For elucidating the mechanism of brain activations with the maternal five senses, we propose investigating the connection between cognitive functions and prefrontal hemodynamics in a women's brain during a time of pregnancy and child raising. As a proof-of-concept of the proposal, we examined the prefrontal hemodynamics corresponding to functional changes in maternal hearing, which is one of the maternal five senses during pregnancy and child raising. Based on the progress of our subjects' child raising, we divided them into four female groups: postnatal: group-I, within only a year; group-II, approximately 2 years; group-III, more than 10 years, and nonpregnant: group-IV. We instructed them to carry out five kinds of tests: simple reaction, SR; choice reaction, CR; working memory, WM; one card learning, OC; and divided attention, DA using card games through a cognitive function test called “CogHealth”. Hemodynamic changes at the prefrontal areas were measured using a multi-channel functional near-infrared spectroscopy (fNIRS) apparatus equipped with 3×5 probes (22 ch). And we used two hearing tasks: the sound of baby crying, and the Chopin's nocturne as a control. According to the results of the four groups in connection with the hemispheric asymmetry in their prefrontal hemodynamics, there were noticeable asymmetries in each group in the hemodynamics with the two hearing tasks. The most significant asymmetry in the hemodynamics was observed in the postnatal group-I (within only a year). Concerning the time flame of changes in the CogHealth scores, we took notice of the fact that the response time for DA task temporarily failed at a point of twelve months after childbearing. An increase in the response time was observed just after the twelve months interval; however, the accuracy of the response tended to be gradually declined after the interval. We assumed that these transient fails might occur due to postnatal changes in a women's brain cultivated during their child raising with a strong emotional response; quick, appropriate and adaptable to a child's capability. As it turned out, our findings confirm the close connection between cognitive functions and prefrontal hemodynamics in a women's brain during their child raising.