Formed visual hallucinations are seen in a lesion of -
Unformed (elementary) visual hallucination:- ocular disorders, disorders of the occipital lobe, migraine.
Formed visual hallucination:- Disorders of Temporal lobe, diseases of upper brain stem or thalamus (peduncular hallucinosis).
Note:- Temporal lobe lesions can cause → Auditory, visual (formed) and olfactory hallucinations.
Frontal
Occipital
Temporal
Arcuate fasciculus