From the article:

ProBDNF is the precursor form of mature brain-derived neurotrophic growth factor (BDNF), and both are active in the hippocampus and cortex – areas key to learning, memory and higher thinking. Intriguingly, proBDNF and BDNF encourage different actions; BDNF promotes the differentiation of new neurons and their constituent parts (axons, dendrites and synapses), and proBDNF the pruning of synapses – a process that occurs particularly in the early stages of life.

“Our results suggest that the nervous system plays an active role in both potentiating and dampening its own activity as necessary,”