“…A second objective of the study was to determine whether sleep may play a role in the formation of clusters or perhaps their maintenance. Numerous studies have now provided evidence that sleep plays a significant role in memory consolidation—the amount of sleep (mainly rapid eye movement sleep, REM) is augmented following a learning experience (Destrade et al, 1978; Fishbein et al, 1974; Hennevin et al, 1995; Lucero, 1970; Portell‐Cortés et al, 1989; Smith et al, 1977; Smith & Rose, 1997; Smith & Wong, 1991), while sleep deprivation following learning produces an impairment of long‐term memory (Alvarenga et al, 2008; Binder et al, 2012; Chen et al, 2006; Cho et al, 2018; Fishbein, 1971; Graves et al, 2003; Hagewoud et al, 2010; Ishikawa et al, 2014; Palchykova et al, 2006; Pearlman, 1973; Prince et al, 2014; Ravassard et al, 2016; Silva et al, 2004; Smith et al, 1998; Smith & Butler, 1982; Smith & Rose, 1996). Sleep or the lack of, has also been shown to suppress synaptic plasticity (i.e., long‐term potentiation), which is a model of learning and memory (Campbell et al, 2002; Chen et al, 2006; Kopp et al, 2006; Ravassard et al, 2009; Romcy‐Pereira & Pavlides, 2004; Vecsey et al, 2009) (for review, see Rasch & Born, 2013).…”