Sleep Fragments

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What is the F4 artifact?

Contributed by James A. Rowley, MD, Wayne State University School of Medicine

In the 30 second epoch presented, what is the artifact noted in the F4 EEG lead?

note: chin lead malfunctioning so not included)


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Blink Artifact

–The artifact is a blink artifact.  Note that the artifacts correlate with the rapid eye movement activity seen in the E1 and E2 leads.

–The patient is awake as evidenced by the alpha rhythm seen in the O2 EEG lead.  Given the patient is awake, the frequent rapid eye movements indicate blinking.

–As the F4 lead is positioned above the eye, eye movements can occasionally be recorded in this lead, leading to the artifact seen in this fragment.

–Usually, blink artifact is not recorded in the central and occipital leads as they are located too far away from the electrical activity to record it.  However, in this particular fragment, some artifact can also be seen in the C4 lead.


–Chokroverty S, Thomas RJ, Bhatt M. Atlas of Sleep Medicine. Philadelphia: Elsevier, 2005, pages 21-22.

Images Legend:

–E1-M2 and E2-M2, left and respectively right outer cantus electro-oculography electrodes; chin2-chin 1, submental electromyography signal; F4-M1, C4-M1 and O2-M1, right frontal, central and respectively, occipital electroencephalography electrodes; L LEG and R LEG, left and respectively right lower limbs electromyography electrodes; PFLOW, nasal pressure signal; TFLO, the airflow via nasal/oral thermocouples; THORAX and ABDM, chest and respectively abdominal walls motion via inductive plethysmography; EKG, one standard electrocardiogram lead; SAO2, the pulse oximetry by finger probe.

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