Complex sentence: Certain forms of the gene are associated with a mild form of epilepsy and, though by no means a certainty, déjà vu occurs often enough during seizures that researchers have reason to suspect a link.
Split into simpler sentences: Certain forms of the gene are associated with a mild form of epilepsy. Though by no means a certainty, déjà vu occurs often enough during seizures that researchers have reason to suspect a link.