Infra-slow fluctuation (ISF) training focuses on the brain’s lowest frequencies (below 0.1 Hz), captured using specialized DC amplifiers. Unlike classical neurofeedback, which trains toward specific targets, ISF training simply reflects these ultra-slow oscillations back to you in real time. There’s no goal to achieve – the act of perceiving your own infra-slow activity triggers autonomic state shifts, which we monitor and optimize throughout the session.

WHAT ARE INFRA-SLOW OSCILLATIONS?

Infra-slow oscillations (ISOs) are electrical rhythms with periodicities ranging from tens of seconds to several minutes. First discovered by Russian scientist Nina Aladjalova in 1957, ISOs reflect the intrinsic excitability of neuronal populations and demonstrate phase-amplitude coupling with faster EEG frequencies – meaning they modulate and organize higher-frequency brain activity.

Research by Valentina Ilyukhina at the Bechtereva Institute expanded this work, introducing the concept of Ultra-Slow Bioelectric Potentials (USBP) – a universal bioelectrical communication system within and between brain and body systems. Ilyukhina proposed that USBP determine an individual’s “level of optimal wakefulness,” the efficiency of compensatory mechanisms, and overall adaptive capacity.

Modern neuroimaging has validated these early insights. With the discovery of intrinsic network dynamics in the resting brain and advances in fMRI, researchers have correlated infra-slow electrical oscillations with BOLD signal changes, suggesting ISOs act as a modulatory mechanism coordinating interaction among key brain networks. Current research at institutions including the University of Helsinki and Technical University of Graz continues to refine our understanding of how these slow rhythms organize brain-body communication and neural network dynamics.

GERT PFURTSCHELLER AND WOLFGANG KLIMESCH

Pfurtscheller was fascinated by biological pace-makers and their inter-dependance via phase-coupling, as demonstrated by the neuro-physiological relationship between heart and brain. Klimesch’s prolific research culminated in a theoretical framework known as the Binary Hierarchy Brain Body Oscillation Theory. 

INFRA-SLOW OSCILLATION- CLINICAL APPLICATIONS

The Othmers developed bipolar infra-low frequency training in 2006, establishing a process-oriented approach that tracks symptoms along an arousal continuum from low to high activation states.

Mark Smith refined this method by adding referential channel monitoring to overcome the limitations of purely bipolar recordings, shifting the training frequency range to approximately 0.0010-0.0075 Hz, and integrating physiological monitoring with systematic within-session and between-session symptom tracking.

Building on the understanding that brain network interactions are modulated by infra-slow oscillations, Smith and Dr. DeRidder developed ISF LORETA training. This approach targets the three core networks governing human cognition and self-regulation: the Default Mode Network, Salience Network, and Central Executive Network – a framework established by neuroscientist Vinod Menon in 2011.

WHAT HAPPENS DURING YOUR INFRA-SLOW FLUCTUATION TRAINING SESSION?

ISF training is fundamentally different from traditional neurofeedback. Rather than operantly conditioning your brain to increase or decrease specific frequencies, we’re working at a more foundational level. Traditional neurofeedback assumes the brain is ready and interested in learning; ISF works beneath that – by simply mirroring your brain’s infra-slow activity back to you, we create the conditions for your nervous system to naturally synchronize and self-regulate. The goal is to identify your optimal training frequency (OF) – the specific frequency at which your nervous system achieves its most regulated, balanced state.

FINDING YOUR OPTIMAL FREQUENCY

Your first session begins at a predetermined starting frequency. After a few minutes, we ask targeted questions about emerging sensations – any discomfort, agitation, drowsiness, or shifts in your state. Frequency adjustments have direct effects on arousal: higher frequencies tend to increase activation (and can produce agitation or motor restlessness), while lower frequencies reduce arousal (and can induce drowsiness or depressed states). This is why we don’t follow a “plug-and-go” approach – we remain closely attuned to your responses and adjust in real time until you experience calm alertness and physiological ease. Once identified, this optimal frequency becomes the foundation for your subsequent sessions.

THE MIRROR, NOT THE DIRECTOR

Unlike traditional neurofeedback that rewards increases or inhibits decreases, ISF training works as a mirror. You receive auditory feedback through a two-tone system: a higher tone when your infra-slow amplitude increases by more than 15% relative to a running average, and a lower tone when it decreases by more than 15%.

Think of it like a room full of tuning forks – when one tuning fork is struck, the others begin to resonate in sympathy. Similarly, your nervous system naturally synchronizes with the movement of the ISF signal reflected in the auditory tones. The mirroring process itself triggers the regulatory effect. As you perceive these ultra-slow rhythms, your brain recognizes and organizes around this “organizing rhythm,” promoting fluid, timely brain function and global system regulation.

IMMEDIATE STATE SHIFTS

One of ISF’s distinctive characteristics is its capacity for immediate state change. Many clients experience significant shifts within a single 30-minute session – walking in rating their anxiety at 7/10 and leaving at 2/10 or lower. This happens because infra-slow frequencies coordinate the autonomic nervous system and help separate emotional processing networks from autonomic distress signals. The training increases your window of tolerance for uncomfortable emotions and helps you identify physiological cues from a more regulated “witness” perspective rather than from within the activation itself.

This immediate relief isn’t just symptomatically valuable – it demonstrates to your nervous system that regulation is achievable, building confidence in your brain’s natural capacity for self-regulation.

The shifts in autonomic nervous system state persist, and/or enfold in the 24 hours following the training session. It is therefore very important to get feedback from the client within 24 hours. They have to focus on any changes that occur with regards to sleep, pain, apetite, alertness or drowsiness, emotionality or mood, arousal or relaxation.

INFRA-SLOW FLUCTUATION TRAINING- BIBLIOGRAPHY

Infra-Slow Fluctuations Training bibliography, courtesy of Neurofeedback Services of New York, can be found here