Electroencephalogram theta-beta ratio (TBR)

The Electroencephalogram theta-beta ratio (TBR) is an electrophysiological metric calculated by dividing the power of the theta frequency band (typically 4–8 Hz) by the power of the beta frequency band (typically 13–30 Hz), usually measured at the vertex (Cz electrode) during a resting state (Monastra et al., 1999). It is widely conceptualized as a biomarker for cortical arousal and executive control, with higher ratios indicating lower levels of arousal and decreased attentional capacity (Arns et al., 2013). Historically, the TBR gained significant attention as a putative diagnostic marker for attention-deficit/hyperactivity disorder (ADHD), following observations that children with ADHD often exhibit elevated theta power and reduced beta power (Snyder & Hall, 2006). In 2013, the U.S. FDA cleared the first medical device, the NEBA System, which utilizes the TBR to aid in the clinical evaluation of ADHD in children and adolescents (FDA, 2013). While not a molecular target itself, the TBR serves as a pharmacodynamic endpoint in neuropsychiatric research, as psychostimulant medications like methylphenidate and amphetamines typically normalize the ratio by suppressing theta activity and enhancing beta activity (Loo et al., 1999). Despite its clinical utility, the status of TBR as a standalone diagnostic tool remains controversial due to inconsistent findings regarding its sensitivity and specificity across diverse patient populations (Loo & Makeig, 2012).

Other names

TBRTheta/beta ratioTheta-beta power ratioEEG theta-beta power ratio

Drugs targeting this ratio typically work by modulating catecholaminergic (dopamine and norepinephrine) neurotransmission in the prefrontal cortex, thereby increasing cortical arousal and reducing the relative power of slow-wave theta activity while increasing fast-wave beta activity (Loo et al., 1999; Arns et al., 2013).