When adjusting the high-frequency filter (HFF), which frequency range is typically targeted?

When adjusting the high-frequency filter (HFF) in an EEG system, the focus is specifically on high frequencies, typically in the range of 30 Hz and above. The purpose of the high-frequency filter is to reduce or eliminate high-frequency noise and artifacts that can interfere with the interpretation of EEG waves. By targeting these high frequencies, the filter helps in clarifying the signal by allowing the lower-frequency brain activity to be more prominent and discernible.

In this context, adjusting the high-frequency filter is crucial to ensure that the recorded brain waves, such as alpha, beta, and gamma rhythms, are accurately represented without distortion from irrelevant high-frequency signals. This is particularly important in clinical settings where precision in neurological monitoring can significantly impact patient assessments.

The other choices refer to different aspects of frequency ranges. Low frequencies pertain to brain activity such as delta waves, while medium frequencies relate to theta activity. Subsonic frequencies are not typically relevant in EEG monitoring since EEG primarily measures electrical activity in the brain within the specified frequency bands. Thus, targeting high frequencies with the HFF ensures the signal is clear and clinically useful.