Antenatal study of the Heschl's gyrus: The first step to understanding prenatal learning

We located Heschl's gyrus (HG) in utero during antenatal development. The antenatal location of the HG will allow us to evaluate adaptations of the human foetal cortex in response to auditory stimuli.

We classified 244 human foetuses between 18 and 41 weeks' gestation using two-dimensional (2D) and three-dimensional (3D) ultrasounds according to foetal neurological development: Foetal Stage, Extremely Preterm, Very Preterm, Moderate to Late Preterm, and Term. We considered two HG shapes: single gyrus (SG) and duplicated gyrus (DG). We studied two subtypes of the DG shape: partial and complete duplicated gyrus.

We found 156 cases (63.9%) of single gyrus and 88 cases (36.1%) of duplicated gyrus, of which 39 (44.3%) showed a partial duplication and 49 (55.7%) showed complete duplication. SG appeared in 93.5% of cases in the Foetal Stage and represented 75% of the Term group. DG increased during foetal life. In the Very Preterm group, the relation between SG and DG was detected in 50%, so that DG (59.1%) was more prevalent than SG (40.9%) in the Moderate to Late Preterm group, and the majority of foetuses were found to exhibit SG (75%) in the Term group. The observed increase in DG was due to the complete duplicated gyrus subtype. We did not find differences between hemispheres in any of the groups.

We located the foetal Heschl's gyrus and the SG and DG shapes. The peculiar pattern in each foetal neurological stage could show a functional sign in a cortical area with a remarkable adaptation capacity.