Brain oscillations, rhythmic
stimulation and non-Invasive sensory
entrainment
The functional architecture of perception is supported by distinct
neurophysiological rhythms organized across different spatial scales
\cite{buzsaki2004large}. This essential function -potentially supporting all
cognitive activity- has its basis that start from a single neuron
\cite{Hutcheon_2000} passing through different neural
circuits \cite{Whittington_1997} to thalamo-cortical and
cortico-cortical networks \cite{L_rincz_2009}. Thus, different brain
rhythms occur at distinct frequency bands as a function of micro- and
macro-network architecture \cite{buzsaki2004large}. Different aspects of
cognitive activity can thus be described in terms of neuronal
oscillators, hierarchically organized interacting at different
frequencies \cite{buzsaki2004large}. A biological mechanism
named synchronization of neuronal elements enables the dynamic
perceptual framing of sensory information (Varela 1981); a
neurophysiological process derived from oscillatory coordination \cite{Jensen_2010,Salinas_2001,fries2005mechanism}. Within this
neural mechanism, temporal segmentation serves to reduce the problem of
information overload because sensory stimuli can be processed serially.
In this context synchronous voltage variations that occurring within
8-13 Hz in adults and within 6-9 Hz in children, known as alpha
oscillations are thought to be a crucial element or these processes \cite{Palva2007}. Furthermore, these lower frequency rhythms (theta 4-8 Hz, alpha 8-13 Hz)
have been related to long-distance brain communication dynamics, while
higher frequency bands like gamma (>30 Hz) have been
associated with local neuronal interaction \cite{von_Stein_2000}. It
has been proposed that low- and high-frequency oscillatory systems
belong to a larger multi-band coordination system, enacting an
informational multiplexing mechanism \cite{Akam_2014} through
cross-frequency interactions \cite{Palva2007,Jensen_2007,Canolty_2010}.
Activity in different frequencies across brain structures may also
provide important clues to these functions, for instance posterior
alpha-band oscillations (8–12 Hz) are related to the sensory input
regulation \cite{L_rincz_2009}, and attentional selection \cite{Thut_2009,Worden_2000,Sauseng_2005,Kelly_2006}.
Hence, when perception unfolds during driving activities, also
relies on processes that enable effective selection and integration of
relevant information from the vast amount of sensory inputs on the road,
that is constantly bombarding the driver's brain.
Sensory function improvements could be therefore made by a natural property
of oscillations. This is, oscillatory activity is self-sustained and dynamic
(e.g. \cite{pikovsky2003synchronization,Glass_2001}), implying that brain
rhythms could be modulated by an external sources. For instance, if the
modulation is carried out periodically by an external stimulus, the ongoing waves may then become synchronized to the external patterns. In other words, brain rhythms will synchronously
cycle with the same period as the external sensory input, becoming “entrained ” and
coordinated to the rhythm of external incoming events \cite{Lakatos_2008}. Within this context,
synchronization and entrainment are synonymous \cite{pikovsky2003synchronization}.
Thus, in this perspective we will use the term entrainment to refers
synchronization to a natural brain rhythmic with rhythm of external
(sensory) incoming events.
RE-ESCRIBIR, NO SE ENTIENDE --> [Therefore, generating non-invasive stimulation of a coordinated nature
pulsed sensory stimulation appear as key tool for simultaneously entrain
many primary sensory structures and input pathways including
sub-cortically and cortical structures. In this context pulsed form of
rhythmic stimulation is steady-state sensory stimuli presentation.] For
instance, transient visual events that are repeated at fixed frequency
\cite{Herrmann_2001}, in order to entrain the natural brain frequencies to
the rhythm of the presentation. With this non-invasive approach to sensory stimulation, stimuli can be presented in a wide range of
repetition frequencies, covering the physiological range of brain
oscillations from slow-waves to high-frequencies bands \cite{Herrmann_2001,Thut_2009}, allowing non-invasive brain stimulation at appropriate frequencies
and temporal scales. Likewise, inducing sensory entrainment
on drivers' brains appear as a perfect candidate to generate non-invasive
safety tools for prevention of automobile accident. In addition, note the possibility of generating a tool in road
infrastructure to modify and improve the perceptual and behavioral
performance of drivers appears as a neuroergonomic challenge in urban
design, as well also opening a new path in the way the concept of road
safety is constructed, designed from and for the human brain.