Photic Driving Response

A 24-year-old woman undergoes routine EEG following a single unprovoked generalized tonic-clonic seizure. MRI brain and neurological examination are normal. During intermittent photic stimulation (IPS) with a strobe at 30 cm from closed eyes, the occipital leads (O1, O2) show rhythmic waveforms that are **time-locked to the flash frequency** (marked **B** in the diagram), most prominent between 8–15 Hz, bilaterally symmetric, and restricted to posterior head regions. The response disappears promptly when the strobe stops, with no spread to central or frontal channels and no spike-and-wave discharge. Which of the following best characterizes this finding and its clinical significance in this patient?