My son got an EEG where they put probes on his head while he slept for 30min. Do the probes have lights on them and flash when something happens?

Normal stimulation. Bright lights flashing at different frequencies are used as a standard part of the eeg. Referred to as "photic stimulation, " the flashes cause discharges in the visual region of the brain. In some patients, the evoked responses are asymmetric or excessively large, which can indicate an abnormality.