Levels of Interference in Long and Short-Term Memory Differentially Modulate Non-REM and REM Sleep

Abstract

Study Objectives: It is commonly accepted that sleep is beneficial to memory processes, but it is still unclear if this benefit originates from improved memory consolidation or enhanced information processing. It has thus been proposed that sleep may also promote forgetting of undesirable and non-essential memories, a process required for optimization of cognitive resources. We tested the hypothesis that non-rapid eye movement sleep (NREMS) promotes forgetting of irrelevant information, more specifically when processing information in working memory (WM), while REM sleep (REMS) facilitates the consolidation of important information. Methods: We recorded sleep patterns of rats trained in a radial maze in three different tasks engaging either the long-term or short-term storage of information, as well as a gradual level of interference. Results: We observed a transient increase in REMS amount on the day the animal learned the rule of a long-term/reference memory task (RM), and, in contrast, a positive correlation between the performance of rats trained in a WM task involving an important processing of interference and the amount of NREMS or slow wave activity. Various oscillatory events were also differentially modulated by the type of training involved. Notably, NREMS spindles and REMS rapid theta increase with RM training, while sharp-wave ripples increase with all types of training. Conclusions: These results suggest that REMS, but also rapid oscillations occurring during NREMS would be specifically implicated in the long-term memory in RM, whereas NREMS and slow oscillations could be involved in the forgetting of irrelevant information required for WM.

Long-term effects of interference on short-term memory performance in the rat

“…In the present study, we showed that information supposedly forgotten after each trial during HIWM training were stored from one trial to another (during a delay longer than 15 seconds) and even from one day to the next, building PI and impairing rats' performance as we have previously shown [28,35,36]. In HIWM training, the use of cognitive resources in WM is thus no longer optimal because adaptive forgetting of information may not be sufficient to erase PI after a trial in this very repetitive task.…”

“…The role of sleep occurring during this 24h delay may be of fundamental relevance in the consolidation of PI given that much evidence points towards a role of sleep, and in particular REM sleep, in memory consolidation [61–63]. Recently however, we have shown that performance of rats trained in a spaced HIWM task was positively correlated to an increase in slow wave sleep amount and slow wave activity [35], a result in agreement with theories attributing to these sleep stage and oscillations a role in the weakening of synaptic transmission [64]. While memory is supposed to depend on the strengthening of synapses involved in learning processes [65–67], spatial forms of forgetting have been shown to rely on the weakening (downscaling or depression) of hippocampal synaptic transmission [68].…”

“…Here, we question the duration capacity of WM, and therefore the possibility to discriminate it from long-term memory, by showing that WM can persist in time, or alternatively that WM content can be transferred into an intermediary memory form between WM and long-term memory. We used two delayed-non-match-to-place WM radial maze tasks designed in our laboratory [ 28 , 35 , 36 ], and we showed that when the repetitiveness of the task is increased (compared to the task used by Roberts and Dale), the content of WM can be kept in memory for days (either in WM or another form of memory), impairing rats' performance after several days of training by generating long-term PI. In fact, we show that after several days of training, WM reset is no longer possible.…”

Decreased Information Replacement of Working Memory After Sleep Deprivation: Evidence From an Event-Related Potential Study

“…However, other reports have indicated a decrease in the activation of the parietal cortex after sleep deprivation (Almklov et al, 2015). Moreover, the results revealed that the decrease in activation was significantly correlated with a decrease in short-term memory after sleep deprivation (Adrienne, 2013; Xie et al, 2015; Nicolas et al, 2016; Julien et al, 2017). Previous study using an n-back task to test WM in participants who had been sleep-deprived for 24 h found that sleep deprivation leads to a reduction in metabolic activity in the brain’s regional network (prefrontal cortex, anterior cingulate gyrus, thalamus, and cerebellum) mainly involved in information processing and executive control (Choo et al, 2005).…”

Prenatal Ozone Exposure Induces Memory Deficiencies in Newborns Rats

“…Several studies have reported that children exposed to air pollutants, including fine particles and O 3 , develop systemic inflammation, attention deficit and memory deterioration (Calderón-Garcidueñas et al, 2008, 2016). Memory processes depend on the sleep-wake cycle (Fraize et al, 2016). It is widely known that sleep disorders affect both memory and learning.…”