Association between problematic smartphone use, sleep quality, and chronotype among Sudanese medical students during armed conflict: a cross-sectional study.

Neurofeedback training (NFT) is a prominent technique used by researchers across many different fields—from educational to clinical settings—to investigate neurophysiological substrates of human behavior (; ; ). NFT can be described as a closed-loop system that combines the measurement of brain activity with real-time sensory (e.g., visual, auditory, tactile) feedback of specific components of neural activation, allowing a person the voluntary manipulation of their own brain activity. Through NFT paradigms, researchers aim to develop new applications for the improvement of various cognitive functions. For that electroencephalography (EEG) has emerged as the de facto standard measurement modality in NFT research, thanks to its high temporal resolution, broad spectrum of neural modulation capabilities, as well as easy and flexible application (). Through EEG-based NFT, it is possible to self-regulate oscillatory fluctuations in specific brain frequency bands, such as the theta (4–7 Hz) or alpha (8–12 Hz) bands, which stem from synchronous neuronal activity that can be recorded non-invasively from a person’s scalp (). Different frequency bands are associated with different mental processes, but certain mental processes can also generate complementary patterns across multiple frequency bands. Moreover, the spectral power level (i.e., signal intensity) of each frequency band is differently distributed across the cortical surface (), as well as influenced by psychological () and anatomical factors (). Also, substantial interindividual differences exist, regarding the ability and strategies used to successfully control one’s own brain activity using NFT (; ). Besides clinical applications, training programs aimed at the improvement of cognitive abilities are one of the most investigated research subjects involving NFT (). One major area in this regard concerns learning and memory, where it was found that the EEG theta band plays a crucial role in information consolidation and retrieval processes (; ; ; ). first described an interconnection between task−/event-related theta and alpha activity, which is characterized by a phasic increase in theta power accompanied by a simultaneous decrease in alpha power during the memorization of visually presented words. argues that—while attentional and semantic memory demands are related to phasic suppression of alpha—phasic increases of theta may reflect memory consolidation processes originating from hippocampo-cortical feedback loops (note that from this point onward when referring to theta activity, we generally refer to task−/event-related, i.e., phasic, changes of theta, except when explicitly indicated otherwise). demonstrated a positive relationship between increased memory load and frontal midline theta (Fm theta) power—so named due to its occurrence over the frontal midline cortical area (; )—further suggesting that Fm theta power indexes the engagement of memory-related processes. Studies utilizing signal source-localization revealed the medial prefrontal cortex and dorsal anterior cingulate cortex (ACC) as the main sources of the Fm theta rhythm (; ; ; ). Being part of the Papez circuit, the ACC shows interconnections with brain regions involved in learning and memory, such as the amygdala and hippocampus. More recently, Fm theta was identified as a potential key mechanism of cognitive control and attention (; ; ). Given its multifaceted involvement in learning, memory, and cognitive control processes, Fm theta has become a promising target frequency for NFT interventions (). In a recent meta-analysis on Fm theta NFT () it has been reported that previous studies primarily utilized NFT protocols aiming at Fm theta upregulation, to elicit positive effects on performance measures related to memory (; ; ), as well as motoric and executive functions (; ). conclude that although current research shows promising results on the efficacy of Fm theta NFT for memory enhancement, substantial heterogeneity across studies prevents firm conclusions regarding its true effect size.