Formed visual hallucinations such as people, animals, or complex scenes, arise from the inferior temporo-occipital visual association
cortex. Common causes of formed visual hallucinations include toxic or metabolic disturbances (especially hallucinogens, anticholinergics, and cyclosporin), withdrawal from alcohol or sedatives, focal seizures, complex migraine, neurodegenerative conditions such as Creutzfeldt-Jakob disease
or Lewy body disease, narcolepsy, midbrain ischemia (peduncular hallucinosis or psychiatric disorders. Of note, in psychiatric disorders
visual hallucinations are less common than auditory hallucinations, and they usually occur with accompanying sound. Formed visual hallucinations
can also appear as a release phenomenon. Thus, patients with visual deprivation in part or all of their visual fields caused by either ocular or central
nervous system lesions may occasionally see objects, people, or animals in the region of vision loss, especially during the early stages of the deticit.
Visual hallucinations that occur in elderly patients as a resuh of impaired vision have been called Bonnet syndrome.
source: Neuroanatomy Through Clinical Cases
