Measuring Pain-Evoked Brain Activity in Neonates Using a Flat-Tip Probe Coupled to EEG

Begin with a settled infant wearing an electroencephalography, or EEG cap, with electrodes contacting the scalp.

The active electrode is positioned at the skull vertex, the reference electrode behind the left ear, and the ground electrode on the right forehead.

Hold the infant's right hand horizontally.

Record the background EEG to establish a baseline.

Next, take a flat-tip probe connected to a contact trigger device fixed to the EEG recording system and apply a mild pain stimulus to the hand.

The probe sends a signal to the computer, marking the stimulus trigger time.

The stimulus activates nociceptors  — the skin's pain-sensitive sensory neurons — opening ion channels.

This allows positive ion influx, generating action potentials.

These action potentials propagate from the nociceptors through the Aδ fibers and project to the spinal cord, from where they reach the brain.

The active electrode captures the brain signals, generating the EEG that identifies the pain response.

Begin by choosing a new work file. Set the sampling rate to 2,000 Hertz. Set the low cutoff filter to a frequency of 1 Hertz. Set the high cutoff filter to 70 Hertz, and the notch filter to 50 Hertz. Select a study name to store the data.

Start the EEG and the video recording. Whilst the neonate's right hand is held in a horizontal position, record background EEG activity. Annotate the EEG recording manually to record periods where no stimuli are applied and the infant is resting. Once the background EEG is stable, administer the required amount of flat-tip probe stimuli to the neonate's right hand.

Be careful to use the flat-tip probe perpendicularly to the neonate's hand so the tip does not bend and the correct force is applied. When the flat tip probe reaches the nominal force on the skin, a trigger signal is generated by the contact trigger device. This signal is sent to the computer, tagging the EEG recording with a trigger mark.

After the stimuli are administered, stop all the recordings and document the experimental setting details. After taking off the electrodes of the infant's head, clean the scalp with a wet towel to remove any residuals.