Sleeping brains can process and recognize very brief auditory stimuli
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INSUFFICIENT LEANING
refutedsupported
the weight of evidence
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Retrieved evidence confirms that the sleeping brain can process auditory inputs via active auditory pathways, but lacks specific documentation regarding the recognition and processing of very brief auditory stimuli.
Abstract
This study investigated the morphology of the functional near-infrared spectroscopy (fNIRS) response to speech sounds measured from 16 sleeping infants and how it changes with repeated stimulus presentation. We observed a positive peak followed by a wide negative trough, with the latter being most evident in early epochs. We argue that the overall response morphology captures the effects of two simultaneous, but independent, response mechanisms that are both activated at the stimulus onset: one being the obligatory response to a sound stimulus by the auditory system, and the other being a neural suppression effect induced by the arousal system. Because the two effects behave differently with repeated epochs, it is possible to mathematically separate them and use fNIRS to study factors that affect the development and activation of the arousal system in infants. The results also imply that standard fNIRS analysis techniques need to be adjusted to take into account the possibilities of multiple simultaneous brain systems being activated and that the response to a stimulus is not necessarily stationary.
, Niethard, & Born, 2023 ).
Although the sleeping brain is generally considered to be in an “offline” state, dedicated to processing internally generated activity patterns such as SWRs, the brain is not fully disconnected from the environment in this state. In particular, sounds heard during sleep are processed by a fully functional and highly active auditory system ( Edeline, Dutrieux, Manunta, & Hennevin, 2001 ; Hayat et al., 2022 ; Issa & Wang, 2008 ; Nir, Vyazovskiy, Cirelli, Banks, & Tononi, 2015 ; Pena, Perez-Perera, Bouvier, & Velluti, 1999 ; Sela, Krom, Bergman, Regev, & Nir, 2020 ). The ability of the auditory system and the circuits it communicates with to process sounds during sleep is evolutionarily adaptive, as it supports rapid awakening in response to sounds of approaching predators or offspring calls ( Velluti, 1997 ). However, many sounds processed by the brain during sleep are not behaviorally relevant. In particular, it is estimated that more than 20% of people living in major urban environments are regularly exposed during nighttime to the sounds of household appliances, outdoor traffic or other neighborhood noise ( Brink, Omlin, Muller, Pieren, & Basner, 2011 ; Chepesiuk, 2005 ; Europe, World Health Organization, Hurtley, & World Health Organization. Regional Office for, 2009 ; Fiedler & Zannin, 2015 ; Fritschi & World health Organization. Regional Office for, 2011 ; Jarosinska et al., 2018 ). Yet, whether ongoing processing of sounds during sleep interferes with sleep-dependent cognitive processes and may therefore come at a cost for the process of memory consolidation, remains largely unexplored.
Direct projections from the auditory system to major hippocampal input regions, namely the perirhinal cortex and the lateral entorhinal cortex ( Budinger & Scheich, 2009 ; Furtak, Wei, Agster, & Burwell, 2007 ; Insausti, Herrero, & Witter, 1997 ; Kerr, Agster, Furtak, & Burwell, 2007 ; Mascagni, McDonald, & Coleman, 1993 ; Steward, 1976 ), form an ana
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