[2] Hallucinatory palinopsia, usually due to seizures or posterior cortical lesions, describes afterimages that are formed, long-lasting, and high resolution.
Illusory palinopsia, usually due to migraines, head trauma, prescription drugs, visual snow syndrome or hallucinogen persisting perception disorder (HPPD), describes afterimages that are affected by ambient light and motion and are unformed, indistinct, or low resolution.
cause focal cortical hyperactivity or hyperexcitability, resulting in inappropriate, persistent activation of a visual memory circuit.
Illusory palinopsia consists of afterimages that are short-lived or unformed, occur in the same location in the visual field as the original stimulus, and are continuous or predictable.
Hallucinatory palinopsia describes formed afterimages and scenes that are lifelike, high-resolution, long-lasting, occur anywhere in the visual field, and are unpredictable.
[citation needed] The clinical characteristics that separate illusory from hallucinatory palinopsia also help differentiate and assess risk in visual illusions and hallucinations.
Increased accuracy in fMRI might also allow for the observation of subtle metabolic or perfusional changes in illusory palinopsia, without the use of ionizing radiation present in CT scans and radioactive isotopes.