40 Hz, Brain Synchrony, and the Sound of Neurodegeneration

2 days ago
4 min read

Scene from the I Jornada Académica de Neuromúsica, Educación y Salud (NUS Agency), where a live piano performance is accompanied by real-time recording and visualization of the musician’s brain activity. The setup illustrates how neural signals can be synchronized with and displayed alongside the produced audio, highlighting the interaction between music and brain dynamics. — Scene from the *I Jornada Académica de Neuromúsica, Educación y Salud* (NUS Agency), where a live piano performance is accompanied by real-time recording and visualization of the musician’s brain activity. The setup illustrates how neural signals can be synchronized with and displayed alongside the produced audio, highlighting the interaction between music and brain dynamics.

In recent years, 40 Hz has emerged as a frequency of growing interest in neuroscience. What was once just a point in the gamma band of brain oscillations is now at the center of research spanning cognition, perception, and even neurodegenerative disease.

At Starlab, we are exploring how this frequency—whether delivered through electrical stimulation or sound—can reveal and potentially influence brain health.

Why 40 Hz matters

Gamma-band activity, particularly around 40 Hz, has long been associated with higher-order cognitive functions such as attention, perception, and memory. But its relevance has taken a new turn with findings linking disrupted gamma activity to Alzheimer’s disease (AD).

A number of preclinical and clinical studies have shown that stimulating the brain at 40 Hz—using light, sound, or non-invasive brain stimulation—can entrain neural activity and may reduce pathological markers associated with AD. This has sparked a wave of clinical trials exploring whether 40 Hz stimulation could slow cognitive decline or modulate disease progression.

Technologies such as transcranial electrical stimulation, including systems like Starstim from Neuroelectrics, are being investigated as tools to deliver controlled stimulation at this frequency. While the field is still evolving, the idea is compelling: restoring or enhancing gamma synchrony could support neural communication in brains affected by neurodegeneration.

From stimulation to natural synchrony

But the brain does not only respond to externally applied electrical currents—it also naturally synchronizes to sensory input, especially sound.

A powerful example of this comes from auditory neuroscience. If you listen to a familiar riff like Smoke on the Water, your brain doesn’t just passively receive the sound—it actively tracks it. This tracking can be measured using EEG through responses such as the Frequency-Following Response (FFR).

Pioneering work by researchers like Nina Kraus (Auditory Neuroscience Laboratory) has shown that the FFR can reconstruct key features of sound, including pitch and timing. In healthy individuals, this neural representation closely resembles the original acoustic signal. In contrast, in conditions such as concussion, this representation becomes degraded—highlighting how sensitive these measures are to brain health.

Reconstruction of a musical piece from EEG-derived Frequency-Following Responses (FFR) in a healthy individual (left) and in a participant with a history of concussion (right). The degraded fidelity in the latter reflects impaired neural encoding of sound. Adapted from the Auditory Neuroscience Lab (Nina Kraus, Northwestern University). Video source: https://www.youtube.com/watch?v=N5pRHmCDVUw — Reconstruction of a musical piece from EEG-derived **Frequency-Following Responses (FFR)** in a healthy individual (left) and in a participant with a history of concussion (right). The degraded fidelity in the latter reflects impaired neural encoding of sound. Adapted from the Auditory Neuroscience Lab (Nina Kraus, Northwestern University). Video source: https://www.youtube.com/watch?v=N5pRHmCDVUw

ASSR and the 40 Hz brain

Closely related to the FFR is another EEG measure: the Auditory Steady-State Response (ASSR). While the FFR reflects fine-grained encoding of complex sounds, the ASSR captures how well the brain synchronizes to rhythmic auditory stimulation at specific frequencies—such as 40 Hz.

This makes ASSR particularly well suited to studying gamma-band entrainment.

At Starlab, we use ASSR paradigms to probe how the brain responds to 40 Hz auditory stimulation. This allows us to measure neural synchrony in a precise and non-invasive way.

Our recent findings in collaboration with ACE Alzheimer Center suggest that this synchrony is not uniform across populations. In particular, individuals with Mild Cognitive Impairment (MCI) who also present positive Alzheimer’s disease biomarkers show reduced neural synchronization at 40 Hz compared to healthy controls.

This reduction in ASSR strength may reflect early disruptions in neural circuitry—potentially offering a functional biomarker of disease progression.

Comparison of neural synchronization at 40 Hz, measured Auditory Steady-State Responses (ASSR), between individuals with Mild Cognitive Impairment without Alzheimer’s disease biomarkers (MCI−) and with positive biomarkers (MCI+). Reduced synchronization in the MCI+ group suggests early disruption of gamma-band neural activity associated with neurodegenerative processes. — Comparison of neural synchronization at 40 Hz, measured **Auditory Steady-State Responses (ASSR)**, between individuals with Mild Cognitive Impairment without Alzheimer’s disease biomarkers (MCI−) and with positive biomarkers (MCI+). Reduced synchronization in the MCI+ group suggests early disruption of gamma-band neural activity associated with neurodegenerative processes.

Music, neuroscience, and 40 Hz: the NES project

These questions were at the heart of our recent participation in the I Jornada Académica de Neuromúsica, Educación y Salud coordinated by NUS AGENCY, an interdisciplinary event exploring the intersection of music, brain science, and wellbeing.

During the event, the Proyecto NES – 40 Hz was presented—an initiative investigating how music-based stimulation can modulate brain activity. By embedding 40 Hz structure within musical experiences, the project aims to bridge scientific rigor with ecological, engaging stimuli.

This approach opens an exciting avenue: instead of delivering abstract stimulation, we can explore how meaningful auditory experiences—like music—can drive neural entrainment.

Expert panel at the I Jornada Académica de Neuromúsica, Educación y Salud (NUS Agency), where interdisciplinary specialists discussed the scientific, clinical, and technological implications of music–brain interactions. Topics included neural entrainment, 40 Hz stimulation, and the role of music-based approaches in cognitive health and wellbeing. — Expert panel at the *I Jornada Académica de Neuromúsica, Educación y Salud* (NUS Agency), where interdisciplinary specialists discussed the scientific, clinical, and technological implications of music–brain interactions. Topics included neural entrainment, 40 Hz stimulation, and the role of music-based approaches in cognitive health and wellbeing.

Towards new biomarkers and interventions

Taken together, these lines of research point toward a converging idea:

The brain’s ability to synchronize at 40 Hz is functionally meaningful
This synchrony can be externally modulated
And its disruption may signal early stages of neurodegeneration

By combining approaches—electrical stimulation, auditory paradigms, and EEG measures like FFR and ASSR—we move closer to objective, signal-based biomarkers of brain health.

At Starlab, our goal is not only to understand these mechanisms but also to translate them into practical tools for early detection, monitoring, and potentially intervention in conditions like Alzheimer’s disease.

Conclusion

40 Hz is more than just a frequency—it is a window into how the brain coordinates activity across networks, processes the world, and maintains cognitive function.

Whether through direct stimulation or through sound, studying how the brain entrains to this rhythm offers a promising path forward. From reconstructing music in neural signals to detecting subtle disruptions in cognitive decline, the convergence of neuroscience, technology, and auditory research is opening new frontiers in brain health.

And in this emerging landscape, listening to the brain—quite literally—may be one of our most powerful tools.

Interested in collaborating?

If you want to explore how this technology could support patient stratification, biomarker discovery, or early detection, we’d love to hear from you.

📩 Reach out to us at: info@starlab.es