Sleep-dependent upscaled excitability, saturated neuroplasticity, and modulated cognition in the human brain

Abstract

Sleep strongly affects synaptic strength, making it critical for cognition, especially learning, and memory formation. Whether and how sleep deprivation modulates human brain physiology and cognition is not well understood. Here we examined how overnight sleep deprivation vs overnight sufficient sleep affects (a) cortical excitability, measured by transcranial magnetic stimulation (TMS), (b) inducibility of LTP- and-LTD-like plasticity via transcranial direct current stimulation (tDCS), and (c) learning, memory and attention. The results suggest that sleep deprivation upscales cortical excitability due to enhanced glutamate-related cortical facilitation and decreased and/or reversed GABAergic cortical inhibition. Furthermore, tDCS-induced LTP-like plasticity abolishes while the inhibitory LTD-like plasticity converts to excitatory LTP-like plasticity under sleep deprivation. This is associated with increased EEG theta oscillations due to sleep pressure. Finally, we show that learning and memory formation, behavioral counterparts of plasticity, and working memory and attention, which rely on cortical excitability, are impaired during sleep deprivation. Our data suggest that upscaled brain excitability, and altered plasticity, due to sleep deprivation, are associated with impaired cognitive performance.

A systematic review of randomized controlled trials on efficacy and safety of transcranial direct current stimulation in major neurodevelopmental disorders: ADHD, autism, and dyslexia

“…Furthermore, ADHD is related to sleep difficulties and the majority of children with ADHD have late chronotypes (i.e., eveningness) (Bijlenga et al., 2019 ; Coogan & Mcgowan, 2017 ). Recent works also show applying tDCS on circadian non‐preferred time (Salehinejad et al., 2021 ) and under sleep pressure (Salehinejad et al., 2022 ) can abolish the expected effect on cortical excitability, tDCS‐induced neuroplasticity, and cognitive functions. This should be considered especially for the therapeutic application of tDCS in ADHD that is associated with a more evening oriented circadian preference and sleep difficulties.…”

The Impact of Bilateral Anodal tDCS over Left and Right DLPFC on Executive Functions in Children with ADHD

“…Moreover, and related to this, our results are limited to behavioral performance and cannot deliver information about the physiological and neural effects of this protocol on the parameters of brain physiology. Last but not least, there are other external factors with a huge impact on tDCS-induced plasticity and cognitive function such as the time of the day that stimulation is delivered [ 54 ] and sleep [ 55 ]. These factors are also impaired in the ADHD population [ 56 ] and need to be controlled in order to see the real effects of the stimulation.…”

The Impact of Bilateral Anodal tDCS over Left and Right DLPFC on Executive Functions in Children with ADHD

“…Moreover, and related to this, our results are limited to behavioral performance and cannot deliver information about the physiological and neural effects of this protocol on parameters of brain physiology. Last but not the least, there are other external factors with a huge impact on tDCS-induced plasticity and cognitive function such as the time of the day that stimulation is delivered (Salehinejad, Wischnewski, et al, 2021) and sleep (Salehinejad, Ghanavati, Reinders, et al, 2022). These factors are also impaired in ADHD population (Bondopadhyay et al, 2022) and need to be controlled in order to see real effects of the stimulation.…”