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.
Granule Cells
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.
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