Biology subjects

Salehinejad, M. A.

Publications and source records attributed to Salehinejad, M. A..

3 recordsLinked to original sources

bioRxiv2023

Enhancement of neurophysiological signatures of working memory by combined yoga and tDCS

Transcranial direct current stimulation (tDCS) is a non-invasive neuromodulation technology that can modulate cortical excitability. Similarly, yoga has been found to influence neuronal activity and cognition. The aim of this study was to investigate the impact of combined yoga and tDCS on event-related potential (ERP) components during an N-Back working memory task. In a randomized, double-blind, cross-over design study, 22 healthy participants underwent a yoga/active tDCS session (2mA; 20min; anode on F3, cathode on F4) or a yoga/sham tDCS session on two different days. During the N-Back task, ERP components were obtained before and after each intervention. Results show that active tDCS plus yoga was associated with significant changes in the amplitude of the P200 component for the 2-Back in Fz and F3 channels and P300 for 3-Back in F3 and Pz electrodes. These results suggest that combining behavioral and electrical neuromodulation techniques may have the potential to enhance cognition and neurophysiological effects.

neuroscience↗

bioRxiv2021

Cognitive functions and respective parameters of human brain physiology are chronotype-dependent

Circadian rhythms have natural relative variations among humans known as chronotype. Chronotype or being a morning or evening person, has a specific physiological, behavioural, and also genetic manifestation. Whether and how chronotype modulates human brain physiology and cognition is, however, not well understood. Here we examine how cortical excitability, neuroplasticity, and cognition are associated with chronotype in early and late chronotype individuals. We monitor motor cortical excitability, brain stimulation-induced neuroplasticity, and examine motor learning and cognitive functions at circadian-preferred and non-preferred times of day in 32 individuals. Motor learning and cognitive performance (working memory, and attention) along with their electrophysiological components are significantly enhanced at the circadian-preferred, compared to the non-preferred time. This outperformance is associated with enhanced cortical excitability (prominent cortical facilitation, diminished cortical inhibition), and long-term potentiation/depression-like plasticity. Our data show convergent findings of chronotype can modulate human brain functions from basic physiological mechanisms to behaviour and higher cognitive functions.

neuroscience↗

bioRxiv2021

Sleep-dependent upscaled excitability and saturated neuroplasticity in the human brain: From brain physiology to cognition

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 sufficient sleep affects (a) cortical excitability, as 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 LTD-like plasticity converts to excitatory LTP-like plasticity under sleep deprivation. This is associated with increased EEG theta activity, which is related 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.

neuroscience↗