Sleep onset is a creative sweet spot

Sleep onset is a creative sweet spot

The ability to think creatively is paramount to facing new challenges, but how creativity arises remains mysterious. Here, we show that brain activity common to the twilight zone between sleep and wakefulness (nonrapid eye movement sleep stage 1 or N1) ignites creative sparks. However, hitting the creative sweet spot requires individuals balancing falling asleep easily against falling asleep too deeply.

Behavioral task

Participants were presented with eight-digit strings, composed of three possible numbers (1, 4, and 9), and given a task to find the final solution of each string.

Key Findings

The discovery of a hidden rule is 2.7 times more likely after spending only 1 min of N1 during an incubation period, compared to a similar period of quiet rest including only wakefulness.

Participants

103 healthy participants (73 females, age 23.23 ± 3.58 years) recruited, screened out for exclusion criteria such as excessive daytime sleepiness, history of sleep, and neurological or psychiatric disorders

Hypnagogic Experiences

To account for the time factor, we also compared the amount of reported hypnagogia at the bottle drop with the one obtained in an additional control experiment, in which subjects took a 30-min break in a dark bedroom; they were regularly awakened by a sound and asked to describe their mental content.

The Eureka moment

To detect sudden changes in solving time (taken here as a marker of insight), we used an algorithm provided by MATLAB named “findchangepts”, which detects abrupt changes in signals.

Results

We scored each participant’s break using standard sleep scoring criteria (34) and divided participants into three groups based on their vigilance state during the break (see demographic and sleep parameters in table S1): the “Wake” group, the “N1” group (subjects with at least one 30-s epoch of N1 but without any signs of deeper sleep stages, N = 24), and the “N2” group, including three who directly fell into N2 without passing by N1.

A single minute of N1 inspires insight

There was a significant effect of the group (wake versus N1 versus N2) on the percentage of participants who found the hidden rule after the break (Fisher’s test, P < 0.001)

Neurophysiology of the sweet spot

Sleep onset is a complex, dynamic process (35, 36), potentially encompassing multiple transitions between different substages (31), each with subtle variations in physiological activity (e.g., alpha/theta, muscle relaxation).

The first stage of non-REM sleep (N1) has received little attention, and its cognitive role is largely unknown.

However, a recent study showed that 10 min of “awake quiescence” (i.e., a quiet rest spent in a dimly lit room with reduced sensory stimulation) more than doubled the number of subjects who discovered a hidden rule compared to ten min of active wake (12).

EEG spectral analyses

extracted power spectrum over contiguous epochs of 30 s

Acknowledgments: We thank S. Leu, P. Dodet, J. Maranci, B. Dudoignon, and M. A. Paller for help with sleep scoring.

Funding: This work was supported by Doctoral School ED3C (to C.L.), a research grant from Société Française de Recherche et Médecine du Sommeil (C.O.), and INSERM research endowment (to D.O.).

Experimental procedure

The protocol was subdivided into four main phases: training, pre- and post-training phases

Object

The ideal object needed to meet the following criteria: makes a noise when falling, is light weight to avoid cramped arms, is slippery to facilitate the fall, is large enough so that the fist cannot close on it, and prevents the object from falling

A reliable marker of sleep onset

Holding an object while napping is propitious to capturing creative sparks

A delayed Eureka moment

The “Eureka” moment did not occur immediately following the resting period, but rather after 94 trials on average, regardless of the group [mean Wake= 82.67, N1 = 101.55, N2 = 106.73, Wilcoxon signed-rank test, z = −6.33, P < 0.001]

EEG recordings

Subjects were continuously monitored with video polysomnography during the experiment. The montage included three EEG channels (FP1, C3, and O1), EOG with electrodes placed on the outer canthi of the eyes, chin EMG, a microphone, and infrared video recordings (Brainet, Medatec Ltd., France).

Sleep scoring

Two scoring methods were applied: The standard sleep scoring guidelines from the American Academy of Sleep Medicine (AASM) (34) and a microsleep scoring method, similar to the one recently developed by Hertig-Godeschalk et al. (42).

Statistical Analysis

Interjudges’ agreement was evaluated with the Cohen’s Κ test.

Source

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