In electroencephalography (EEG), artifacts refer to any signals that are not generated by the brain itself. These extraneous signals can originate from various sources and are classified into three main categories:

  • Physiologic artifacts: These are caused by the body’s natural processes, such as muscle activity (e.g., eye movements, blinking, or facial muscle contractions).
  • Electric artifacts: These arise from external electrical equipment, including power lines or the EEG machine itself.
  • Environmental artifacts: These result from factors in the surrounding environment, like electrical noise or electromagnetic interference.

Challenges in Identifying EEG Artifacts

Identifying artifacts on EEG can be difficult due to several reasons:

  • Ubiquity of artifacts: Artifacts are commonly present and can appear anywhere on the EEG. Unlike cerebral signals, they don't follow predictable localization patterns, making them harder to differentiate.
  • Disorganization: Artifacts are often chaotic and unpredictable in their patterns, sometimes overlapping with actual brain activity, which complicates their identification.
  • Similarity to cerebral signals: Some artifacts can mimic brain signals, even taking on rhythmic patterns that may look like seizures. This resemblance can lead to misinterpretation of the data.

Differentiating Artifacts from Brain Activity

Despite these challenges, certain characteristics of artifacts help in distinguishing them from actual brain signals:

  • Predictability: While artifacts can appear disorganized, true brain activity tends to follow more predictable patterns based on neurophysiological principles.
  • Behavior of cerebral signals: Real brain activity has more consistent properties (e.g., specific waveforms and locations), which allows for differentiation from the chaotic nature of artifacts.

In summary, although identifying EEG artifacts can be challenging due to their widespread occurrence and resemblance to brain activity, understanding their sources and behavior helps clinicians differentiate them from actual cerebral signals.