A gustatory hallucination is the perception of taste without a stimulus. These hallucinations, which are typically strange or unpleasant, are relatively common among individuals who have certain types of focal epilepsy, especially temporal lobe epilepsy. The regions of the brain responsible for gustatory hallucination in this case are the insula and the superior bank of the sylvian fissure.
Olfactory and gustatory hallucinations occur in a significant minority of patients with schizophrenia. For example, Pearlson and colleagues studied 131 patients with schizophrenia and identified gustatory hallucinations in only 12% of patients. In schizophrenia, olfactory, gustatory, and tactile hallucinations usually accompany auditory hallucinations.
Certain drugs, such as marijuana, ecstasy and LSD, blur the lines between consciousness and subconsciousness thereby causing hallucinations. Consuming a high content of alcohol can also lead to the same effect. The occurrence of hallucinations after taking these is common, and one of the withdrawal symptoms of these drugs might also include hallucinations.
Gustatory hallucinations are often experienced as strange tastes in something people are eating or drinking; pizza tasting like blueberries or meat tasting like bleach. For instance, an individual may complain of a persistent taste of metal, onions, etc. This type of hallucination is rare and is more commonly seen in some medical disorders (frontal lobe epilepsy, brain tumors, and migraines) than in mental disorders.
Migraine sufferers can experience illusions or hallucinations of taste as gustatory aura symptoms. The differential diagnosis of these symptoms includes temporal lobe epilepsy, now more commonly called complex partial seizure disorder, so that a neurological examination is warranted in each case presenting with such gustatory symptoms.
Jackson proposed the name "uncinate group of fits" for a group of cases of epilepsy, basing this term on the observations of Ferrier, who had concluded from animal studies that the smell and taste are localized in the uncinate gyrus. Although Jackson created a formal category of seizures whose name, "uncinate fits," has remained to this day, olfactory and gustatory hallucinations had been recognized as manifestations of epileptic discharge at least 30 years earlier.
For about 7 percent of patients with schizophrenia and other psychotic disorders, gustatory hallucinations—phantom tastes that arrive suddenly and fade just as quickly—are a common and disturbing part of life. Moreover, most phantom tastes are far from delicious, says Kathryn Lewandowski, an HMS instructor in psychology at McLean Hospital, who studies psychotic patients to assess the type and range of hallucinations they experience. Rather, the tastes tend to be unsavory and confusing.
Less common than auditory and visual hallucinations are gustatory hallucinations. Patients with gustatory hallucinations experience taste alterations, a sensation of thirst, or excess salivation. Gustatory hallucinations are often caused by temporal lobe disease, parietal operculum lesions, and sinus disease.
Gustatory hallucinations involve a taste lingering in the mouth or the sense that food tastes like something else. The taste may be metallic or bitter or may be represented as a specific taste.
The term gustatory hallucination is indebted to the Latin noun gustus,which means taste. It is used to denote a taste sensation occurring in the absence of an appropriate tastant. Gustatory hallucinations tend to be enduring, unpleasant taste sensations qualified simply in terms of bitter, sour, sweet, 'disgusting', etc, and reports of pleasant taste sensations are rare.
Gustatory hallucinations are most commonly associated with temporal lobe lesions, especially uncinate gyrus seizures. Patients report experiencing bitter, sweet, salty, tobacco-like, metallic, or indescribable strange tastes. They are found in 4% of seizure patients with temporal lobe foci, but may also be a part of seizures originating from the parietal opercular region.