Functional maturation of neocortex: a base of viability

Abstract

The term "viability" is not simply a synonymous with being "born alive," but is closely related to the capability of having a "meaningful life" and having a reasonable period of survival. The definition of "viability" is generally based on two major criteria: the biological, which takes into consideration the maturity of the foetus, and the epidemiological, which is based on the survival rates reported in literature. The neuromaturation of the cerebral cortex is a dynamic process promoted by the subplate, a transient population of neurons that guides the development of cortical and thalamocortical connections. These connections are for example fundamental for cortical processing of sensory information and mental processes. The first thalamocortical and cortico-cortical connections grows at 23-24 postconceptional weeks, which coincides with the age limit for premature baby survival.

PREMM: preterm early massage by the mother: protocol of a randomised controlled trial of massage therapy in very preterm infants

“…The neuromaturation of the cerebral cortex, initially laid down in cortical layers prior to 20 weeks gestation, is a dynamic process from 30 to 40 weeks gestation. It is during this time, the subplate, a transient population of neurons, guides the development of cortical and thalamocortical connections [8], maturing from its maximal prominence to almost complete regression. These connections are fundamental for cortical processing and cognition [8].…”

“…It is during this time, the subplate, a transient population of neurons, guides the development of cortical and thalamocortical connections [8], maturing from its maximal prominence to almost complete regression. These connections are fundamental for cortical processing and cognition [8]. Between 29 and 41 weeks, total brain volume is increased nearly 3-fold, cortical gray matter volume is increased 4-fold and cerebellar volume is increased 4-fold [7].…”

Physiology of Human Birth and Mental Disease

“…Clinical experience and publications have shown that from the 23rd to 24th PCW, the fetus is capable of surviving without any developmental harm if adequately assisted with medical intensive treatment. This is what is defined as viability, a condition that implies not only being born alive but it is closely related to the concepts of capability of meaningful life and of reasonable period of survival [11]. Viability appears to be strictly related to the subplate zone which plays a major role in the structural development of connectivity and cerebral cortex neuromaturation [11].…”

“…This is what is defined as viability, a condition that implies not only being born alive but it is closely related to the concepts of capability of meaningful life and of reasonable period of survival [11]. Viability appears to be strictly related to the subplate zone which plays a major role in the structural development of connectivity and cerebral cortex neuromaturation [11]. The subplate is a transient compartment of the fetal telencephalic wall, placed under the cortical plate.…”

Defining pain in newborns: need for a uniform taxonomy?

“…The question of conscious pain perception in the early preterm newborn (or foetus) has been hotly debated , mainly because of its social, ethical and legal implications . Consciousness was widely believed to reside in the cerebral cortex, thus putatively being absent or rudimentary in those without functional thalamocortical connections , although mechanisms underlying the subcortical control of consciousness and functionality of the subplate zone appear to challenge that default. Attempting to set forth criteria for early human consciousness would create the difficulties of ‘measuring’ consciousness and the conundrums of trying to prove or disprove whether consciousness is present at different stages of development .…”