What is full band Electroencephalogram (EEG)?

What is Full Band EEG?

Full band EEG (fbEEG) is an electroencephalographic recording technique that captures the complete physiological frequency spectrum of brain electrical activity, ranging from infraslow frequencies (0.01 Hz) to ultrafast frequencies (up to 500 Hz or higher), rather than the conventional clinical EEG bandwidth of approximately 0.5-50 Hz. 1, 2

Technical Requirements and Recording Parameters

Full band EEG requires specific technical components that differ from conventional EEG:

• Direct-current (DC) coupled amplifiers with wide dynamic range and high sampling rates are essential for capturing the full frequency spectrum 1, 2
• DC-stable electrode-skin interface must be used to maintain signal integrity across the entire frequency range 1, 2
• The standard 19 electrodes of the 10-20 International System should be used for diagnostic purposes, with recording durations of 20-30 minutes to capture variations in vigilance levels 3

Frequency Bands Captured

Full band EEG encompasses multiple frequency ranges that extend beyond conventional clinical EEG:

• Infraslow activity (<0.1 Hz) that is typically filtered out in standard EEG 4
• Traditional frequency bands including delta (<4 Hz), theta (4-7 Hz), alpha (8-13 Hz), and beta (>13 Hz) 3
• High-frequency oscillations (HFOs) including gamma (40-80 Hz), ripple (80-200 Hz), and fast ripple (>200/250 Hz) bands 4
• Ultrafast frequencies extending to several hundred Hz 1, 2

Clinical Significance and Applications

The expanded bandwidth of full band EEG captures physiologically and pathologically meaningful brain activity that conventional EEG misses:

• Epilepsy evaluation: High-frequency oscillations, particularly ripple and fast ripple bands, show very close relationship to epileptogenicity and may function as surrogate biomarkers of epileptic activity 4
• Cognitive function assessment: Physiological high-frequency activity plays important roles in higher brain functions 4
• Encephalopathy monitoring: Full spectrum recording allows detection of subtle changes in brain function across all frequency bands 5
• Immature brain assessment: Spontaneous activity in the preterm human brain includes frequencies outside the conventional bandwidth 1, 2

Critical Advantages Over Conventional EEG

Elimination of the lower (infraslow) or higher (ultrafast) bands in routine EEG leads to situations where salient and physiologically meaningful features of brain activity remain undetected or become seriously attenuated and distorted. 1, 2

Key advantages include:

• No frequency-dependent trade-offs: Full band EEG does not favor any frequency band at the expense of another 1, 2
• Faithful, non-distorted recording: Captures brain activity without attenuation or distortion across the entire physiological spectrum 2
• Detection of previously missed activity: Reveals epileptic seizures, sleep phenomena, and cognitive task-related activity that occur outside conventional bandwidth 1, 2

Common Pitfalls to Avoid

• Using conventional AC-coupled amplifiers will filter out infraslow activity and may distort signals at frequency band edges 1, 2
• Inadequate electrode-skin interface stability can introduce artifacts, particularly in the DC and infraslow ranges 1, 2
• Confusing pathological and physiological HFOs: Differentiation between epileptic and physiological high-frequency oscillations is critical, especially in epilepsy surgery planning 4
• Insufficient sampling rates will fail to capture ultrafast frequencies adequately 2

Current Status and Future Direction

With currently available electrode, amplifier, and data acquisition technology, full band EEG is expected to become the standard approach in both clinical practice and basic science, replacing the conventional limited-bandwidth EEG that has remained essentially unchanged for over 50 years 1, 2. The technique is readily attainable with commercially available equipment and does not require specialized or experimental technology 1, 2.