Sleep Strengthens Memory in Infancy

From birth and across the lifespan, sleep in critical for gradually building memories into a robust state termed consolidation.

The repetition of practice as well as sleep both play integral roles in gradually building sensory-perceptual-motor memory for the acquisition of infant breastfeeding skills. Clinicians commonly observe increases in the infant’s speed and accuracy for achieving and sustaining the oral grasp of the nipple-areolar complex in subsequent feedings, as well as improvements in organized, effective suckling when a nursing session is followed by a long or short nap, in the absence of any interference in the infant’s learning to feed, and in the absence of significant learning constraints, i.e., task constraints (such as inverted nipple anatomy) and/or individual constraints (such as complete cleft of the lip and palate).

Interference is a theory that forgetting is caused by other learned information. Interference is heavily studied in the cognitive sciences, including the role of sleep in supporting the consolidation and reconsolidation of labile memories.

Newly formed memories are fragile, including motor memories. For example, the earliest memory for a newly created computer password is fragile until we perform enough repetition of that specific new password. In addition, we must have rest and sleep between practice sessions in order to further process these fragile new memories into an increasingly robust state of memory, termed consolidation.

In their 1995 seminal paper providing the first formal definition for the phenomenon of “nipple confusion,” Neifert et al. cited interference as a factor in the observable breastfeeding difficulties displayed by many infants following a learning experience with an artificial nipple, reflecting the fragility of early motor memories for the oral grasp and/or effective suckling for adequate transfer of milk.

Neifert M, Lawrence R, Seacat J.  Nipple confusion: Toward a formal definition.  The Journal of Pediatrics June 1995;126(6):S125-S129

Some new studies from 2018 and 2019 on sleep’s role in building memory:

Title: Sleep-dependent selective imitation in infants.

In: Journal of Sleep Research 2019 Feb;28(1):e12777. doi: 10.1111/jsr.12777.

Authors: Konrad C, Dirks ND, Warmuth A, Herbert JS, Schneider S, Seehagen S.

Open access:

From the summary: “Sleep might help infants selectively ‘discard’ aspects of a learning experience that they identify as being not useful or relevant in the future.”

Title: Sleep accelerates re-stabilization of human declarative memories.

In: Neurobiology of Learning and Memory 2019 Apr 25;162:1-8. doi: 10.1016/j.nlm.2019.04.012.

Authors: Moyano MD, Diekelmann S, Pedreira ME, Forcato C.

Abstract only:

From the summary: “Consolidated memories can return to a labile state upon presentation of a reminder, followed by a period of re-stabilization known as reconsolidation . . . . Sleep plays a fundamental role in the consolidation and integration of new memories, and recently sleep has also been implicated in memory reconsolidation . . . . These findings suggest that 90 min of sleep accelerate memory re-stabilization after reminder presentation, shortening the reconsolidation time window and protecting the memory against subsequent interference. This rapid memory re-stabilization may depend on slow oscillation activity during NREM sleep.”

Title: Memory in 3-month-old infants benefits from a short nap.

In: Developmental Science 2018 May;21(3):e12587. DOI: 10.1111/desc.12587.

Authors: Horváth K, Hannon B, Ujma PP, Gombos F, Plunkett K.

Abstract only:

The abstract: “A broad range of studies demonstrate that sleep has a facilitating role in memory consolidation (see Rasch & Born, 2013). Whether sleep-dependent memory consolidation is also apparent in infants in their first few months of life has not been investigated. We demonstrate that 3-month-old infants only remember a cartoon face approximately 1.5-2 hours after its first presentation when a period of sleep followed learning. Furthermore, habituation time, that is, the time to become bored with a stimulus shown repetitively, correlated negatively with the density of infant sleep spindles, implying that processing speed is linked to specific electroencephalographic components of sleep. Our findings show that without a short period of sleep infants have problems remembering a newly seen face, that sleep enhances memory consolidation from a very early age, highlighting the importance of napping in infancy, and that infant sleep spindles may be associated with some aspects of cognitive ability.”