Hallucinations

Sensory deprivation hallucination

Hallucinations can be caused by sensory deprivation when it occurs for prolonged periods of time, and almost always occurs in the modality being deprived (visual for blindfolded/darkness, auditory for muffled conditions, etc.). Though, some researchers found that in some people hallucinations can be induced after just 15 minutes of sensory deprivation. Research on hallucinations after involuntary sensory deprivation - such as in the cases of vision (Charles Bonnet syndrome) or hearing loss (Musical ear syndrome)- hypothesizes that they are caused by the brain's need to receive sensory input for processing. Loss of sensory input causes sudden neural firings in the regions responsible for processing them. The brain then misattributes the source of these internal neural firings as coming from external sensory source, which manifest themselves as hallucinations. Though, no definitive cause for these type of hallucinations has been found. These hallucinations usually resolve or reduce in frequency once sensory input is either restored or increased (e.g. after getting hearing aids) or after some time has passed and the brain is able to reorganize itself.