The last stage of development: The restructuring and plasticity of the cortex during adolescence especially at puberty

Abstract

There is considerable evidence of reorganization in the prefrontal cortex during adolescence in humans, as well as in rodents, where the cellular basis can be explored. Studies from my laboratory in the rat medial prefrontal cortex are reviewed here. In general, growth predominates before puberty. Pruning mainly occurs at puberty and after with decreases in the number of synapses, dendrites, and neurons. Perineuronal nets, extracellular structures that control plasticity, are pruned peripubertally only in female rats, which may further open the adolescent prefrontal cortex to environmental influences. This is supported by our recent evidence that exposure to mild stress early, but not late, in adolescence decreases prepulse inhibition. Additionally, exposure to methamphetamine in females early in adolescence increases the number of a major class of inhibitory interneurons, parvalbumin neurons, while the opposite occurs late in adolescence. In females, even estrogen receptor beta mRNA decreases at puberty in the prefrontal cortex. Interestingly, rats of both sexes perform better after puberty on a test of cognitive flexibility in the water maze. Thus, evidence is accruing that adolescence is not a single entity but rather an ongoing set of processes, and environmental effects will differ depending on timing and sex.

Effects of early life adversity and adolescent basolateral amygdala activity on corticolimbic connectivity and anxiety behaviors

“…The copyright holder for this preprint this version posted March 29, 2024. ; https://doi.org/10.1101/2024.03.26.586708 doi: bioRxiv preprint adult levels by p55 when histology was performed (Juraska, 2024). Additionally, previous work from our group showed increases in female BLA-PFC innervation that were already apparent by p28, therefore if BLA activity does provoke innervation to the PFC in females, inhibition from p33-39 may have been too late to affect any MS-evoked changes.…”

“…Additionally, no increases in innervation were seen in females, indicating that by late adolescence, any previously observed increases in BLA-PFC connectivity may have pruned back to control levels. Both males and females exhibit significant pruning within the PFC between adolescence and adulthood, however females display greater losses than males (Koss et al, 2014) It is unknown at what age male and female PFC pruning spikes, which allows for the possibility that inhibition of BLA activity from p33-39 had differential effects on PFC innervation, and that innervation in female controls reached adult levels by p55 when histology was performed (Juraska, 2024). Additionally, previous work from our group showed increases in female BLA-PFC innervation that were already apparent by p28, therefore if BLA activity does provoke innervation to the PFC in females, inhibition from p33-39 may have been too late to affect any MS-evoked changes.…”