Neural Oscillations, 40 Hz, and Near-Infrared Light: A Research Overview

Neural oscillations are measurable patterns of electrical activity produced by groups of neurons. They are associated with processes such as sensory perception, attention, movement, learning, and sleep. However, these associations do not mean that a particular frequency functions as a simple “brain mode,” or that delivering light at the same frequency will automatically produce a corresponding cognitive effect.

This distinction is especially important when discussing 40 Hz light. A device that pulses light 40 times per second is producing a 40 Hz optical output. Whether the brain responds at the same frequency—and whether that response has any meaningful behavioral effect—must be tested separately with appropriate measurements.

What Are Neural Oscillations?

Neural oscillations reflect recurring changes in the electrical activity of neuronal populations. Researchers often organize them into frequency bands such as delta, theta, alpha, beta, and gamma.

These bands are useful analytical categories, but their boundaries are approximate. They are not independent switches that turn specific mental functions on or off. The same frequency range may be involved in different processes depending on the brain region, task, timing, and physiological state.

Gamma activity is commonly described as oscillatory activity beginning around 30 Hz and extending to approximately 90 Hz or higher. Gamma-band activity has been observed during perception, attention, working memory, and communication between neural populations. Its function, however, remains an active area of research.

Importantly, researchers distinguish among:

• Increased electrical activity within the gamma-frequency range
• A true rhythmic gamma oscillation
• Synchronization between different brain regions
• Entrainment to an external 40 Hz stimulus

These measurements are related, but they are not interchangeable. An increase in gamma-band power, for example, does not necessarily demonstrate that the brain has become entrained to a 40 Hz input. Reviews by Buzsáki and Wang and Bosman and colleagues emphasize the diversity and complexity of gamma activity across neural systems.

What Does “40 Hz Entrainment” Mean?

In neuroscience, entrainment generally refers to a reliable temporal relationship between an external rhythm and neural activity. Researchers may examine whether neural responses align in frequency and phase with a repeating stimulus.

Demonstrating entrainment normally requires electrophysiological measurements such as electroencephalography (EEG) or magnetoencephalography (MEG), along with appropriate control conditions. A stimulus frequency alone is not evidence of a neural response.

For example, a 40 Hz setting means that the device’s output is modulated approximately 40 times per second. It does not, by itself, establish that:

• The cortex produces a sustained 40 Hz oscillation
• Brain regions become synchronized at 40 Hz
• Attention or memory improves
• A specific neural network has been activated or “reset”

Pulse width, duty cycle, irradiance, exposure duration, treatment location, tissue penetration, and individual physiology can all influence the biological response. Two devices using the same nominal pulse frequency may therefore deliver substantially different exposures.

Three Different Forms of Light Research

Discussions of light and neural oscillations frequently combine evidence from methods that are scientifically distinct.

Visual rhythmic stimulation

Visible flickering light directly stimulates the visual system through the retina. EEG studies have demonstrated that rhythmic visual stimulation can produce frequency-specific responses under certain experimental conditions.

A study by Notbohm, Kurths, and Herrmann, for example, found evidence of neural entrainment during rhythmic visual stimulation. The response depended on factors including stimulus intensity and the relationship between the stimulation frequency and the participant’s intrinsic neural rhythm.

This does not establish that near-infrared light applied to the scalp produces the same response. Visual flicker and transcranial photobiomodulation involve different routes of exposure and should not be treated as equivalent interventions.

Transcranial near-infrared photobiomodulation

Near-infrared photobiomodulation does not primarily depend on visible stimulation of the retina. Proposed mechanisms include interactions between absorbed light and cellular metabolism, circulation, and redox signaling. These mechanisms remain under investigation and may vary considerably with the exposure parameters.

One small randomized, sham-controlled crossover study examined an 810 nm, 40 Hz photobiomodulation protocol in 20 healthy participants. The study used four transcranial light modules together with an intranasal applicator and reported changes in several EEG frequency bands and network measurements following a single session.

The authors characterized the results as preliminary and called for confirmatory research. The study did not establish improved attention or memory, and its protocol differed from Brainlume’s design. Because the EEG comparison focused on activity before and after the session, the findings should be interpreted as possible post-session electrophysiological modulation—not direct proof that the brain became phase-locked to the device’s 40 Hz output. The paper also disclosed relationships between several authors and the device company, which should be considered when evaluating the evidence. See Zomorrodi et al., 2019.

A later scoping review of human electrophysiological studies concluded that transcranial photobiomodulation may affect measured brain activity, but also noted the small number of studies and substantial differences among protocols. The current evidence is therefore better described as exploratory than conclusive.

Optogenetic research

Some laboratory studies use optogenetics to activate specific neurons—including parvalbumin-positive inhibitory interneurons—and investigate how those cells contribute to gamma oscillations.

Optogenetics requires neurons to be genetically modified so that they respond to light. Light is then delivered with high spatial and temporal precision, often through implanted optical equipment. This is fundamentally different from applying near-infrared light noninvasively through the scalp.

Optogenetic findings can help explain how neural circuits generate oscillations. They do not demonstrate that a consumer near-infrared device directly activates the same neurons, ion channels, or circuit pathways.

Does Gamma Activity Equal Better Cognition?

Gamma synchronization has been associated with selective neural communication and multiple cognitive processes. The “communication through coherence” framework proposed by Fries, for example, describes how coordinated oscillatory timing may help neural populations exchange information efficiently.

However, an association between gamma activity and cognition does not establish that externally producing more gamma activity—or applying a stimulus at 40 Hz—will improve focus or memory.

Neural oscillations are context-dependent. More activity is not necessarily better, and no single frequency represents a universal setting for optimal cognition. A meaningful conclusion would require controlled human studies that measure both the neural response and a predefined cognitive outcome.

Available human photobiomodulation research does not adequately support claims that near-infrared light:

• Directly activates parvalbumin-positive neurons through Nav1.1 channels
• Narrows the spike-timing-dependent plasticity window to a specific number of milliseconds
• Creates “smarter” dendrites or new neural wiring
• Switches off the default mode network
• Resets thalamocortical rhythms
• Promotes sleep spindles
• Improves focus or memory by inducing 40 Hz gamma entrainment

Such statements combine hypotheses and findings from different experimental models and should not be presented as established Brainlume mechanisms.

What Brainlume’s Pulse Settings Mean

Brainlume offers near-infrared light with defined pulse settings. Labels such as 40 Hz and 10 Hz describe the timing of the emitted light:

• 40 Hz: the light output is modulated approximately 40 times per second.
• 10 Hz: the light output is modulated approximately 10 times per second.

Although 40 Hz falls within commonly used definitions of the gamma band and 10 Hz falls within the alpha range, this numerical correspondence does not demonstrate that the brain enters a gamma or alpha state.

Brainlume does not measure EEG activity during ordinary use. It therefore cannot determine whether an individual user’s neural oscillations have changed or become synchronized with the selected pulse frequency.

The scientifically appropriate interpretation is that these settings are light-delivery parameters informed by areas of ongoing research. They should not be described as confirmed methods for generating a specific brain rhythm, improving cognitive performance, repairing neural circuits, or addressing a medical or psychological condition.

A Responsible Reading of the Evidence

Current research supports several cautious conclusions:

1. Neural oscillations are genuine and measurable features of brain activity.
2. Gamma activity participates in complex neural processes, but 40 Hz is not a universal “focus frequency.”
3. Visual flicker, transcranial near-infrared photobiomodulation, and optogenetics are different research methods.
4. A 40 Hz optical pulse does not automatically produce 40 Hz neural entrainment.
5. Preliminary studies suggest that some photobiomodulation protocols may influence EEG measurements, but the evidence base remains small and device-specific.
6. Research has not established that Brainlume’s pulse settings improve attention, memory, sleep, mood, or any clinical condition.

The most accurate way to discuss this field is to separate established neuroscience from experimental findings and from product-specific conclusions. Neural oscillations offer a valuable framework for studying brain activity, but the relationship between pulsed near-infrared light, electrophysiological measurements, and everyday cognitive performance requires substantially more controlled human research.

References

1. Buzsáki G, Wang XJ. Mechanisms of Gamma Oscillations. Annual Review of Neuroscience. 2012;35:203–225.
2. Bosman CA, Lansink CS, Pennartz CMA. Functions of Gamma-Band Synchronization in Cognition. European Journal of Neuroscience. 2014;39(11):1982–1999.
3. Fries P. Rhythms for Cognition: Communication Through Coherence. Neuron. 2015;88(1):220–235.
4. Notbohm A, Kurths J, Herrmann CS. Modification of Brain Oscillations via Rhythmic Light Stimulation Provides Evidence for Entrainment. Frontiers in Human Neuroscience. 2016;10:10.
5. Zomorrodi R, et al. Pulsed Near-Infrared Transcranial and Intranasal Photobiomodulation Significantly Modulates Neural Oscillations: A Pilot Exploratory Study. Scientific Reports. 2019;9:6309.
6. Shetty SJ, et al. Effect of Transcranial Photobiomodulation on Electrophysiological Activity of the Brain in Healthy Individuals: A Scoping Review. Journal of Clinical Neuroscience. 2023;117:156–167.

Important Notice

This article is provided for general educational purposes. The cited studies used different stimulation methods, devices, exposure parameters, participant groups, and outcome measures. Their findings should not be interpreted as evidence that Brainlume entrains neural oscillations or produces the same experimental outcomes.

Brainlume is a general wellness device. It is not intended to diagnose, treat, cure, or prevent any disease or medical or psychological condition.