Nicotinic acetylcholine receptors (nAChRs) are widely expressed throughout the
central nervous system and modulate neuronal function in most mammalian brain
structures. The contribution of defined nAChR subunits to a specific behavior is
thus difficult to assess. Mice deleted for ß2-containing nAChRs
(ß2−/−) have been shown to be hyperactive in an
open-field paradigm, without determining the origin of this hyperactivity. We
here develop a quantitative description of mouse behavior in the open field
based upon first order Markov and variable length Markov chain analysis focusing
on the time-organized sequence that behaviors are composed of. This description
reveals that this hyperactivity is the consequence of the absence of specific
inactive states or “stops”. These stops are associated with
a scanning of the environment in wild-type mice (WT), and they affect the way
that animals organize their sequence of behaviors when compared with stops
without scanning. They characterize a specific “decision
moment” that is reduced in ß2−/− mutant
mice, suggesting an important role of ß2-nAChRs in the strategy used
by animals to explore an environment and collect information in order to
organize their behavior. This integrated analysis of the displacement of an
animal in a simple environment offers new insights, specifically into the
contribution of nAChRs to higher brain functions and more generally into the
principles that organize sequences of behaviors in animals