Characteristics of Brain Signals in Response to Audiovisual Stimulation Using the Electrical Capacitance Volume Tomography (ECVT) Principle

Abstract

The human brain continuously generates electrical activity that changes measurably when it processes external stimuli. Electrical Capacitance Volume Tomography (ECVT) is a non-invasive, radiation-free volumetric sensing technique that has been adapted, as a helmet-shaped capacitive sensor, to monitor human brain electrical activity in real time. This study characterizes the ECVT-based brain signal response to audiovisual stimulation and identifies the measurement frequency and sensor-channel combination most sensitive to stimulus-related change. A single healthy male subject (21 years old) was measured using a 16-sensor ECVT helmet connected to an Arbitrary Function Generator and an oscilloscope. Peak-to-peak voltage (Vpp) was recorded for six representative sensor-channel pairs at three carrier frequencies (500 kHz, 1 MHz, and 5 MHz) under three conditions – audiovisual (video and music) stimulation, a water-filled helmet reference, and an empty (air-filled) helmet reference – with six repeated measurements per combination. Across the three frequencies, the 500 kHz measurements showed the most pronounced differences between channels and between conditions, while the 1 MHz and 5 MHz measurements showed comparatively little variation. At 500 kHz, channel responses during audiovisual stimulation were visibly more variable than during the water-filled or empty reference conditions. Among the tested frequencies, 500 kHz was the most sensitive for detecting ECVT signal changes associated with audiovisual stimulation, indicating that both operating frequency and channel selection are important considerations for ECVT-based studies of brain responses to sensory stimulation.