The learning process that proceeds within the adult human brain has long been an intense interest of study for neuroscientists especially in regards to the events that unfold on a cellular and molecular level. It has been shown that physical activity as well as the experience that comes with being in novel environments triggers the production, development and eventual connectivity of newly-formed neurons within the adult human brain.
Diego D. Alvarez and his colleagues (Laboratorio de Plasticidad Neuronal, Fundación Instituto Leloir–Instituto de Investigaciones Bioquímicas de Buenos Aires–Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Av. Patricias Argentinas 435, Buenos Aires C1405BWE, Argentina) focused their studies on the mechanism through which the experience of an enriched environment (EE) impacts the incorporation of newly-formed adult neurons into the hippocampal network – an area of the human brain involved in retaining declarative (explicit) memory. Declarative memory refers to the memory of facts and events.
The cells of interest are referred to as granule cells (GCs) (see image below). In the investigators’ study of newly-formed GCs using the mouse animal model, they found that exposing the test animal subjects to EE accelerated the incorporation of these neurons into the microcircuits of the dentate gyrus – the apparent site for the establishment of new memories.
In addition, further study demonstrated that in order for this incorporation of new GCs to proceed, the process required the participation of parvalbumin y-aminobutyric acid-releasing interneurons (PV-INs). Inactivation of PV-INs effectively prevented the effects of EE. Neuronal stem cells (NSC) of the adult hippocampus are the precursors of GCs of the dentate gyrus.
These results further our understanding of the complex cellular and molecular mechanisms involved in incorporating new memories in the adult human brain.