This study aims to explore the potential of binaural beats, adjusted in real-time via EEG feedback, to positively influence brain states related to relaxation, focus, and cognitive performance. The investigators are examining how these auditory techniques can improve memory, attention, and overall subjective well-being.

With the existence of a strong evidence base regarding audio-assisted relaxation, audio products are widely used globally to achieve relaxed and focused mental states. The utility of audio for achieving relaxed mental states has revolutionized with the advent of the concept of binaural beats, an auditory phenomenon that is induced by separately presenting two tones of different frequencies to each ear. The superior olivary nucleus of the midbrain computes the difference between the two tones, and with time, the brain state is expected to synchronize with the difference in the frequencies presented to the two ears. Binaural beats are widely used to achieve relaxed mental states for applications including improved memory, enhanced relaxation, augmented hypnotherapy, improved sleep quality, creating and breaking habits, addiction therapy, and enhanced cognitive performance with limited empirical support.

Electroencephalography (EEG) is a well-established technique for recording the electrical activity of the brain. This is conventionally achieved through the placement of multiple electrodes across the scalp, allowing for the detection of the brain's spontaneous electrical activity over a period of time. EEG measures voltage fluctuations resulting from ionic current flows within the neurons of the brain. Single-electrode electroencephalography simplifies the conventional approach by using one electrode placed at a strategic location on the scalp. When recorded over the pre-frontal cortex, this method allows for capturing the electrical activity of the brain's frontal lobe, which is responsible for high-level cognitive functions and behavior. EEG waves are typically divided into bandwidths known as frequency bands. These are characterized based on their frequency, which is measured in cycles per second (Hz), and include:

Delta waves (0 to 4 Hz): Associated with deep sleep and certain pathological conditions.

Theta waves (4.1 to 8 Hz): Linked to drowsiness, early stages of sleep, and meditation.

Low Alpha waves (8.1 to 10 Hz): Related to relaxed, calm, and resting states. High Alpha waves (10.1 to 14 Hz): Often associated with a state of wakeful relaxation.

Low beta waves (14.1-20 Hz): Associated with arousal, active thought, concentration, complex thought High beta waves (20.1-32 Hz): Associated with heightened arousal, hyperactive thought, hypervigilance, and states of anxiety/panic While the brain produces all of these wave types simultaneously, typically, one frequency band is dominant at any given time, reflecting the predominant brain state. For instance, during deep sleep, delta waves predominate, while during active concentration, beta waves are more prominent.

The Frequency-Following Response (FFR) is a neurophysiological mechanism where brain EEG activity synchronizes with auditory frequency stimuli. This synchronization is particularly evident with binaural beats. While many studies have supported the notion that binaural beats, via FFR, can induce desired brain states that are particularly for relaxation (e.g., increased high alpha activity), increased receptivity for hypnotic suggestions (e.g., heightened low alpha or theta activity), as well as induce sleep and improve the quality of sleep. However, other studies have challenged this notion, supported by not observing a significant FFR when the brains were stimulated for a duration of < 5 minutes with one binaural beat frequency falling within a particular band at a given time. In fact, delivering binaural beats to participants, regardless of their current brain state, could result in discomfort, headaches, and dizziness.

The proposed study aims to overcome this limited efficacy of a static binaural beat frequency in eliciting an FFR by guiding the delivered binaural beat frequency with real-time feedback obtained from a single-electrode EEG. Based on the current biological understanding of FFR, the investigators propose to conduct a randomized, double-blinded, sham-controlled repeated-measures crossover trial to answer the following research questions:

1. Can a dynamic binaural beat frequency implemented with single-electrode EEG guidance elicit an FFR to guide the predominant EEG frequency of an individual to a target low alpha state?

2. Can a target low-alpha state achieved with the EEG feedback be sustained while the binaural beats are delivered at the target low-alpha frequency?

3. Will guiding the brain to the low-alpha state and maintaining it for up to 15 minutes in the target low-alpha state be associated with improvements in

   1. subjective perception of relaxation, sleepiness, focus, performance on cognitive tasks, and overall well-being
   2. objectively measured speed of reacting to stimuli, attention, inhibitory control (i.e., decreased impulsivity), and better memory encoding in a stop-signal reaction task
   3. objective performance in a Go-No-Go task
   4. objective performance in a graded novelty encoding task

Inclusion Criteria:

• Male and female adults (age > 18 years)

Exclusion Criteria:

• Cognitive impairment (self-reported)
• Gross visual, auditory, or motor impairments; severe physical, psychiatric, or neurological impairments
• History of epilepsy, seizures, or seizure-like episodes
• History of intracranial lesions, stroke, traumatic brain injury, neoplasms, cranial surgery, or foreign bodies
• Current daily alcohol or substance abuse
• Current daily use of medications affecting EEG activity (e.g., anti-epileptics, opioids) or lowering seizure threshold
• Self-reported auditory hypersensitivity or prior adverse effects from audio stimulation

De-identified individual participant data may be shared with qualified researchers upon a reasonable request and after obtaining institutional approval.

Both participants and research staff will be blinded to condition; randomization and condition assignment are automated within the PsychoPy script.