Are centrioles really absent in human neurons?
You asked for "latest studies/info"... Funnily enough, mature neurons with centrioles were described by Cajal (who needs no introduction) in 1911.

If you want a more modern source, you can see Jacobson (1978):


  Microtubules associated with the cilia and centriole are present in all young neurons and many mature neurons and glia. Neuronal cilia and centrioles can be seen very easily by light microscopy in sections impregnated with silver by the Nauta method (H. A. Dahl, 1963). Centrioles can also be shown by light microscopy in neurons stained by other histological methods. (emphasis mine)




Sources:


CAJAL, S. RAMON Y. (1911). Histologie du système nerveux de l'Homme et des Vertébrés (trans. L. Azoulay, 1952), vol. i. Madrid: Consejo Superior de Investigaciones Cientificas.
Jacobson, M. (1978). Developmental Neurobiology. Boston, MA: Springer US.