What factor is most likely to cause a 60-Hz artifact?

A 60-Hz artifact typically arises from electrical interference, often related to the frequency of the power supply in many regions, which is 60 Hz. High and unequal electrode impedances can amplify the effects of this interference. When electrodes have varying impedances, they can pick up different levels of noise from the environment, particularly from electrical sources, leading to distortions in the recorded signal. This makes it more likely for the artifact to manifest prominently in the data captured during sleep studies.

In the context of the other factors, while incorrect placement of reference electrodes can lead to signal issues, it is not necessarily linked to a 60-Hz artifact specifically. Similarly, direct pressure on an electrode might cause localized artifacts rather than a consistent frequency disturbance. Lastly, incorrect filter settings can also impact the signal, but they would more likely affect the overall frequency range captured rather than introduce a distinct 60-Hz artifact per se. Thus, focusing on high and unequal electrode impedances provides the most direct connection to the emergence of a 60-Hz artifact in sleep data recordings.