Introduction
Memory is defined as the storage of a learned item and evidence suggests
that a brain region called the hippocampus is active during its
consolidation (Tulving and Markowitsch, 1998; Duff et al., 2020).
Several biomarkers for cognitive operations in the hippocampus have been
studied, including altered structure, functional connectivity, and
volume of hippocampus (Feng et al., 2019); however, in this review; we
concentrate on Sharp Wave-Ripple complexes (SWRs). SWRs are brief
(50-100 ms), high-frequency (120-250 Hz), synchronous events that occur
during non-rapid-eye movement sleep and “off-line” states of the brain
associated with consummatory behaviors and memory consolidation
(Buzsáki, 2015; Cowen et al., 2020; Oliva et al., 2020; Zhen et al.,
2021; García-Pérez et al., 2022). In addition, the effect of alcohol on
memory has been studied previously (Abrahao et al., 2017; Miyake et al.,
2020; Hamel et al., 2022), however, to the authors’ knowledge, SWRs have
not been evaluated in association with memory impairment by chronic
alcohol administration.
Moreover, effective identification of ripples may be performed visually
by an expert, although it is a laborious and time-consuming work.
Methodologies for facilitation or automatic identification of ripples
and their analysis are more commonly reported for epilepsy than for
SWRs. Epileptic patients present High Frequency Oscillations (HFOs),
which are events with frequencies of 80-600 Hz (Burnos et al., 2014). As
the bandwidth of SWRs is 120-250 Hz, which is in between the bandwidth
of HFOs, the reported methodologies for HFOs may be used for the
identification of SWRs. Different approaches for automatic detection of
ripples are also reviewed in this article.
This review intends to communicate the state-of-the art about the
relationship between alcohol, memory consolidation, and ripple activity,
as well as the use of the main methodologies to identify SWRs
automatically.