Tactile hallucinations

Tactile hallucination is the false perception of tactile sensory input that creates a hallucinatory sensation of physical contact with an imaginary object. It is caused by the faulty integration of the tactile sensory neural signals generated in the spinal cord and the thalamus and sent to the primary somatosensory cortex (SI) and secondary somatosensory cortex (SII). Tactile hallucinations are recurrent symptoms of neurological diseases such as schizophrenia, Parkinson's disease, Ekbom's syndrome and delerium tremens. Patients who experience phantom limb pains also experience a type of tactile hallucination. Tactile hallucinations are also caused by drugs such as cocaine and alcohol.

During ancient Greek times, touch was considered to be an unrefined perceptual system because it differed from the other senses on the basis of the distance and timing of perception of the stimulus. Unlike vision and audition, one perceives touch simultaneously with the medium and the stimulus is always proximal and not distal. By 17th century, the British empiricist John Locke attributed the word “feeling” with two types of sensation.Weber distinctly identified these two types of sensation as the sense of touch and common bodily sensibility. This distinction further helped 19th century psychiatrists to distinguish between tactile hallucinations and cenesthopathy. During the 19th century, tactile hallucinations were classified as symptoms associated with insanity, organic and toxic syndromes and delusional parasitosis yet there was no identification on how such hallucinations were caused. Currently, neuroscientists such as Dr. Oliver Sacks and Dr. V.S. Ramachandran have analyzed and attributed tactile hallucinations as a dysfunctional perception of the brain as opposed to just a symptom related to insanity. They have contributed significantly to propose tactile hallucinations as the false perception of tactile sensory input creating a sensation of touch with an imaginary object.

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