At approximately day 1

Hippocampus is curved, multilayered and infolded.

Reference

O’Rahilly R, Muller F. 1999. The embryonic human brain. An atlas of developmental stages. Second edition. New York: Wiley-Liss.

At approximately day 1

Rapid eye movements.

Duration: 3 weeks

Reference

DiPietro JA. 2001. Fetal neurobehavioral assessment. In: Singer LT, Zeskind PS, eds. Biobehavioral assessment of the infant. New York: The Guilford Press. p 43-80. Citing Als, H. 1982. Toward a synactive theory of development: Promise for the assessment and support of infant individuality. Infant Mental Health J 3:229-243.