Characteristics of the memory sources of dreams: A new version of the content-matching paradigm to take mundane and remote memories into account

Several studies have demonstrated that dream content is related to the waking life of the dreamer. However, the characteristics of the memory sources incorporated into dreams are still unclear. We designed a new protocol to investigate remote memories and memories of trivial experiences, both relatively unexplored in dream content until now. Upon awakening, for 7 days, participants identified the waking life elements (WLEs) related to their dream content and characterized them and their dream content on several scales to assess notably emotional valence. Thanks to this procedure, they could report WLEs from the whole lifespan, and mundane ones before they had been forgotten. Participants (N = 40, 14 males, age = 25.2 ± 7.6) reported 6.2 ± 2.0 dreams on average. For each participant, 83.4% ± 17.8 of the dream reports were related to one or more WLEs. Among all the WLEs incorporated into dreams dated by the participants (79.3 ± 19%), 40.2 ± 30% happened the day before the dream, 26.1 ± 26% the month before (the day before excluded), 15.8 ± 21% the year before the dream (the month before excluded), and 17.9 ± 24% happened more than one year before the dream. As could be expected from previous studies, the majority of the WLEs incorporated into dreams were scored as important by the dreamers. However, this was not true for incorporated WLEs dating from the day before the dream. In agreement with Freud’s observations, the majority of the day residues were scored as mundane. Finally, for both positive and negative WLEs incorporated into dreams, the dreamt version of the WLE was rated as emotionally less intense than the original WLE. This result, showing that dreams tend to attenuate the emotional tone of waking-life memories towards a more neutral one, argues in favor of the emotional regulation hypothesis of dreaming

Correction: Characteristics of the memory sources of dreams: A new version of the content-matching paradigm to take mundane and remote memories into account.

[This corrects the article DOI: 10.1371/journal.pone.0185262.]

Neural shape mediation analysis

Abstract Neural signal shapes convey significant information about their generating processes. In this study, we introduce a data-driven methodology to identify sensory and behaviourally-relevant traces within neural responses. We present a phenomenological model that characterises temporal variations in intracranial EEG using eight interpretable parameters: peak time, peak intensity, initial and final baselines, accumulation and depletion period, and their respective concavities. This model effectively captures subtle signal variations, especially in sensory decision-making tasks. By decomposing the signals in this manner, we then conduct a comprehensive brain mediation analysis on iEEG data’s shape, pinpointing regions that mediate behavioural processes. Importantly, we can determine which signal dynamics specifically reflect underlying behavioural processes, enhancing the depth of analysis and critique of their role in behaviour. Preliminary applications on a cohort of epileptic patients reveal that our model explains over a third of the signal variance at the trial level across all brain regions. We identified four key regions—encompassing sensory, associative, frontal, and premotor areas—that mediate the impact of task difficulty on reaction time. Notably, in these regions, it was the depletion period, rather than signal amplitude, that correlated with behavioural speed. This study highlights the potential of our approach in providing detailed insights into the neural mechanisms linking stimuli to behaviour

Characteristics of waking life elements incorporated into dreams.

<p>All waking life elements (black) and day residues only (grey). Error bars represent standard error of the mean. *<i>p<</i>.<i>05</i>.</p

Characters and places of the dreams.

<p>Error bars represent standard error of the mean. **<i>p<</i>.<i>01</i> ***<i>p<</i>.<i>001</i>.</p

Percentage of the dated WLEs incorporated into dreams as a function of their temporal remoteness.

<p>Percentage of the dated WLEs incorporated into dreams as a function of their temporal remoteness.</p

Rating (Mean+SD) of the dated WLEs incorporated into dreams as a function of their remoteness.

<p>Rating (Mean+SD) of the dated WLEs incorporated into dreams as a function of their remoteness.</p

Examples of concerned incorporated into a dream.

<p>Examples of concerned incorporated into a dream.</p

Averaged scores given by the dreamers at awakening to describe the WLEs incorporated into their dreams.

<p>Averaged scores given by the dreamers at awakening to describe the WLEs incorporated into their dreams.</p

Distribution of the dated WLEs incorporated into dreams as a function of their remoteness.

<p>(A) Distribution of all the WLEs incorporated into dreams when 3 categories of remoteness are considered. (B) Distribution of the WLEs incorporated into dreams which happened between 1 day to 14 days when 4 categories of remoteness are considered. Error bars represent standard error of the mean. ***<i>p <</i>.<i>001</i>.</p