Most of us have experienced mind-bending hallucinations that can be frightening once we realize that what we're feeling, smelling, hearing, or seeing while awake isn't real at all. Although they can be convincingly real, and are known as the hallmark of mental illness, hallucinations are not uncommon or dangerous, since almost half of the population experiences them.

Understanding The Mind’s Eye

Hallucinations are considered to be a delicate and very complex regulation that scientists are just beginning to understand. They derive from false sensory perceptions of things that are not there, unlike illusions or delusions. Illusions are usually misperceptions of sensory things that are, in fact, there. Meanwhile, delusions are deeply fixed beliefs that are “solidified” by the individual despite the contrary information or evidence.

Dr. Gabriella Farkas, a psychiatrist-in-training at Long Island Jewish Medical Center in New York believes episodes of hallucinations can reveal details about the individual. "In most of the cases it is the interplay of genetic vulnerability, and different stressors (trauma, substance use, stressful life events etc.) that can cause psychotic symptoms. Psychodynamic concepts exist about delusions being specific to an individual or a culture although we see a lot of common themes across different patient populations," Farkas told Medical Daily in an email.

Hallucinations can be seen in patients with the following mental disorders: psychotic disorders, bipolar disorder, psychotic depression, PTSD, delirium, or dementia. They are commonly reported by up to 75 percent of schizophrenic patients who perceive these hallucinations to be something as very real even though it isn’t real at all.

However, this is not to say hallucinations are limited to people who are mentally or physically ill. Drug-induced hallucinations such as amphetamines, cocaine, hallucinogens (LSD and PCP), steroids, and types of marijuana can lead to spontaneous visual hallucinations. Even those who withdraw from alcohol, sedatives, hypnotics, or anxiolytics can also experience hallucinations.

The general population is susceptible to hallucinations during sensory, sleep, food, and water deprivation. They may be normal, especially during the bereavement process. For example, hearing the voice of, or seeing a loved one who has passed away can be part of the process.

Mind Games

The Schizophrenic Hallucination

Scientists have studied hallucinations for years in schizophrenic patients, since they are prone to daily episodes. Although hallucinations can involve any one of the senses including sight, sound, taste, smell or touch, the most common among schizophrenic patients are auditory in nature.

Distinguished Professor of Electrical and Computer Engineering at the University of New Mexico (UNM), Vince Calhoun, looked for ways to identify and characterize mental illness, specifically schizophrenia using magnetic resonance imaging (MRI) and magnetoencephalography (MEG) scanners to detect activity in various regions of the brain. It is known auditory and visual hallucinations are one of the ways to search for signs of the illness. In the UNM video, “Tracking Hallucinations Inside the Brain,” Calhoun and his research team scanned the brains of individuals as they hallucinated.

In the video, the team looks for brain patterns that are evolving as they hallucinate. Interesting brain networks connect, for example, when they see an increase in activity in the auditory regions and other regions that are more frontal oriented. This leads them to further investigate the relationship between frontal regions and the auditory regions in the temporal lobe of the brain.

Researchers are still unraveling the changes in brain structure and function that leads to hallucinations in patients with mental illnesses like schizophrenia. In mental illness, hallucinations are more likely to tell us more about the connectivity between different brain regions rather than specifically how an isolated region in the brain is working.

“Emerging research (particularly in 'resting state fMRI') seems to point to abnormal connectivity between different brain regions as being present among people having schizophrenia. This evidence seems to point to differences in resting state fMRI and resting state EEG that may reflect differences in the way the brain is organized that predispose a person to schizophrenia,” Dr. Brendan Kelley, a neurologist at The Ohio State University Wexner Medical Center, told Medical Daily in an email.

Typically, if we see things or hear things, we feel as if we’re going mad. However, when it comes to psychotic hallucinations, whether they are visual or vocal, they address you. Oliver Sacks, a physician, best-selling author, and professor of neurology at the NYU School of Medicine describes in the TED Talk “Oliver Sacks: What Hallucination Reveals About Our Minds,” psychotic hallucinations are jeers. “They accuse you. They seduce you. They humiliate you. You interact with them.” Basically, they intimidate the patient to have an inner conflict with themselves.

Auditory Versus Visual Hallucinations

Primary sensory hallucinations that individuals experience are auditory — when you hear voices when no one has spoken. But it also includes the visual — seeing something that isn’t there.

Auditory hallucinations involve voices talking to or about the person. Most of the time these voices either provide running commentary for schizophrenics on what they’re doing or tell the person what he/she should do. For example, in the movie A Beautiful Mind, the object of hallucination for John Nash, a Nobel Laureate in Economics, is a human, so it looks like visual hallucination, but it’s auditory. This is due to the film’s limitation in its inability to describe auditory hallucination. Schizophrenic patients rarely have episodes of visual ones.

Visual hallucinations are likely to reflect neurological conditions. According to Kelley, about 15 percent of migraine sufferers experience visual aura, which can range from vision loss, to simple hallucinations (typically these are linear or geometric). Some people may experience vision distortions in association with migraine as well.

The hallucination in these cases is suggested to be related to changes in blood flow that occur as part of the migraine. Visual hallucinations may occur in people having epilepsy, either as a premonitory aura before a seizure, or as the epileptic seizure itself. Epileptic seizures from the occipital lobe of the brain (where the primary visual cortex is located) may result in circular or spherical patterns, sometimes brightly colored. For epilepsy patients, these hallucinations are believed to be a result from abnormal electrical activity related to the epileptic seizure.

What It’s Like To Hallucinate

Visual hallucinations, specifically “simple hallucinations” are more prevalent among the general population. These hallucinations include lights, colors, lines, or simple geometric shape. They can “reflect abnormal activity anywhere along the visual pathways in the eye or the brain,” Kelley said.

When people have these simple geometrical hallucinations, the primary visual cortex is activate. This is the part of the brain that perceives edges and patterns. Images cannot be formed with the primary visual cortex. They generate when a higher part of the visual cortex, according to Sacks, is involved in the temporal lobe, specifically the fusiform gyrus.

To experience a drug-free hallucination, click on the video below to see the “world melting” before your eyes with objects and people distorted in real-time, the DailyMail reported. This is known as motion aftereffects, which makes you see movement in objects that are stationary. You can recreate the effect on-the-go with the Strobe Illusion iPhone app for 99 cents.

The mind is a terrible thing to waste, so use it wisely.