Brain lesion can lead to hallucinations

Visual hallucinations are no longer necessarily evidence of mental illness because they appear in a variety of different disorders. It is even possible to get the mentally healthy average person to experience massive hallucinations within a short period of time. In the meantime, there is a wide range of knowledge about the organic basis of these self-made perceptions.

"Bright-colored and tangled mushrooms, worms, snakes and all sorts of animals, animals of modernity and decay, grew out of the base of the tongue, but in full strength and colorful rising from the darkness of the base of the tongue."

When hearing the word "hallucination", even experts spontaneously think of a very specific illness, namely schizophrenia. In fact, hallucinations are one of the most important symptoms of psychosis. Schizophrenics are usually not aware that their misperceptions do not correspond to reality. Usually perceived as real and tormenting by those affected, they often have a personified character and trigger fears. Various examples can be found in textbooks on clinical psychology, for example Comer lists, among other things, the case of a psychotic who repeatedly had the feeling of transforming himself into a wolf and then not only felt this change on his skin, but also saw it in the mirror. The hallucinations that Hanna Green in the psychiatry classic are more complex "I never promised you a rose garden" describes. At the side of the unreal god Anterrabae she falls into her private hell called "Yr", a world in ruins. A schizophrenic young woman suffers horrific hallucinations in the film "Disgust" by Roman Polanski: Again and again she sees gaping cracks in the brickwork or hands stretch out of the walls towards her. In the book "Schizophrenia and Family", Laing describes the example of a schizophrenic who had the feeling that people lay on her at night and had sexual intercourse with her; after being admitted to the hospital, she gave birth to a rat; she thought she saw herself on television. When asked who she was, she vacillated between the Virgin Mary and Elvis Presley's wife. In the book "Irre", Reinold Goetz particularly impressively describes a mentally ill person who suddenly falls into the mouth of the other during a conversation "gruesome picture" sees:

"Don't think about a crocodile at all!" - A simple trick, but there is probably no person who does not see the image of a crocodile in the mind's eye for at least a fraction of a second after this ban. This simple request shows one of the most fascinating abilities of the human brain: we can imagine things, animals or people that are not even there. And, as the example shows, it can be difficult to suppress these ideas. It is often only a tiny step which lies between the imagination of the average man and the hallucinations of the insane.

excessive dopamine production, but then also found a higher number of dopamine-2 receptors in the brain of schizophrenics. Recently, however, some studies have also found excessive activity of the neurotransmitter serotonin. Through this excessive activation, memories are evidently constantly being recalled without being asked, which are so believable that the schizophrenic cannot distinguish them from actual reality.

However, it has also been found that the schizophrenic's ventricles are larger than those of the average person. It could also be based on a lesion, a brain damage which, through the failure of an inhibiting brain center, enables the unrestrained flow of information from the memory stores to the consciousness in the first place. The frontal lobe of schizophrenics also often shows less activity than normal, which in turn indicates an organic brain deficit. The reduction in frontal brain activity may mean that there is no inhibition of memory content that can now flow freely and unfiltered into the consciousness.

Excessive visual impressions are not only found in schizophrenia. Even after taking psychotropic substances, visual illusions and hallucinations appear almost regularly. The Swiss chemist A. Hofmann, who discovered LSD, already experienced "... fantastic images of extraordinary plasticity, combined with an intense, kaleidoscopic play of colors". In another description it said: "Crystal landscapes can appear, covered with jewels." Mountains of gold, geometric figures, flowers, birds, butterflies and colored fountains. This often turns into lively scenes with animals, things, people and voices from early childhood - and one often relives events from the past ".

An essential element of hallucinations in drug intoxication is the perception of a radiant, bright light, which can be found in many descriptions. In "Chemistry of the Psyche" reports Solomon Snyder after taking LSD to have observed a purple-colored border around the objects in his vicinity. Aldous Huxley describes in "The Doors of Perception"that he saw a slow dance of golden lights after taking mescaline; a little later he sees bright knots of energy that vibrate from a constantly changing, pattern-forming life. Typical examples can also be found in Carlos Castaneda's cult book of the sixties "The Teachings of Don Juan" remove. After enjoying peyote buttons, Castaneda's perception changed significantly: “I could only see the dog begin to glow; a strong light radiated from his body. I saw the water flow through him again, it lit him up like a bonfire. I got to the water, lowered my face into the pot, and drank with him.

My hands were on the floor in front of him, and as I drank I saw the liquid trickle through my veins, shades of red, yellow, and green. I drank more and more. I drank until I went up in flames; I was a single glow. " Elsewhere, Castaneda wrote: “I went through the peyote field and called the name Mescalito had taught me. Something emerged from a strange, star-shaped light from a peyote plant. It was a long, shiny object - a glowing stick of light the size of a man. For a moment it illuminated the whole field with a strong yellowish or amber light, then it illuminated the whole sky above into a vast, magnificent sight. I thought I would go blind if I kept looking at it. "

However, it is known that these three systems are also responsible for mental and psychiatric illnesses. The norepinephrine and serotonin systems play a decisive role in depression, the overactive dopamine system has something to do with schizophrenia. It is believed that one of the tasks of the dopamine system is to separate important from unimportant associations. With excessive excitement, this task no longer succeeds; senseless associations break into consciousness. It is also interesting that all three systems have extensions into the frontal cortex, which confirms the above-mentioned assumption that damage to the frontal lobe could have something to do with hallucinations.

The effect of these hallucinogens is known to be based on their similarity to transmitter substances in the brain. Mescaline is similar to norepinephrine and dopamine, and psilocybin and LSD are similar to serotonin. The serotonin projections in the human brain have a main center in the raphe nuclei in the brain stem and then move to the limbic system and the frontal lobe. One of the most important centers that uses the neurotransmitter norepinephrine is located in the locus coeroleus in the brain stem; it is also closely connected to the limbic system and the frontal cortex. Dopaminergic pathways have a center in the substantia nigra. The different hallucinogens seem to affect these two groups of transmitters differently. For example, LSD was found to inhibit the serotonin system, while the neurons in the locus coeruleus fired faster. It is believed that a center is hidden here that essentially integrates sensory inputs from different channels such as hearing, seeing, feeling, smelling and tasting. In the case of excessive stimulation, the boundaries are apparently blurred, changes in sensory perception, hallucinations and synesthesia occur. However, the results are not yet uniform, as other substances apparently activate the serotonin system. Also too little is known about the exact interaction with the dopamine system.

The neurosurgeon Wilder Penfield provided an early indication that hallucinations primarily represent a disordered retrieval of information stored in memory in the 1930s. Penfield electrically stimulated the cortical surface of patients during brain operations and had the perceived changes described. In response to such stimulation, depending on the location of the stimulation, lively acoustic or visual hallucinations ensued, which the patients experienced as overwhelmingly real despite the sober atmosphere of the operating room and sometimes described them down to the smallest detail. This attention to detail led Penfield to believe that the brain retains virtually a complete memory of all events in life. The real achievement of the mind is probably to encapsulate the huge amount of memories that one takes in in the course of life and only to let them become conscious on demand.

The brain occasionally performs this type of electrical stimulation itself. Many epileptics experience a short-term aura in the run-up to a seizure. Here, too, there are sometimes brief visual hallucinations.

However, it does not always have to be too much neuronal stimulation that creates visual illusions, but sometimes too little. Everyone knows the experience of going black in front of your eyes or seeing asterisks if you kneeled too long while gardening and then suddenly get up. The cause is a short-term undersupply of the occipital brain with sufficient oxygen-rich blood. Apparently, the deficiency does not only lead to negative symptoms, but to a kind of emergency reaction with excessive neuronal activity.

In migraines caused by sudden contraction of the cerebral arteries, there are also visual phenomena. Flickering scotomas are typical of migraines, often moving from one side of the field of vision to the other and changing the shape in the process. In his neurological bestseller "The man who mistook his wife for a hat", Oliver Sacks describes the case of Hildegard von Bingen, a nun who lived around 1100 and was haunted by visions that she described as follows: "But suddenly goes ... . from the mystery of the one sitting on the throne a great star in light shine and radiant beauty. Numerous sparkling sparks followed it ... With all its satellites, the star moves towards the south ... Immediately they went out and became black as coal. .. They fell into the abyss, and you did not see any of them again. " Sacks' interpretation was simply that as a result of a migraine attack, phosphene followed by a negative scotoma crossed her field of vision.

But even the normal, completely healthy person occasionally has hallucinations. Our body needs around eight hours of sleep a night; Although sleep is a state that is arbitrarily induced by the brain, the brain is evidently far too boring even this break: It then starts telling itself stories in the middle of the night at comparatively regular intervals, and at the same time vivid, but mostly completely nonsensical Paint pictures. According to the definition, one does not speak of hallucinations here, but rather describes these processes as "dreams".

Dreams show that not only a neural hyperactivity of the brain must be the cause of hallucinations, but apparently also an undersupply of current information. Much of our human intelligence has been bought by the fact that we now have a brain that demands constant stimulation. If this does not take place for a long time, the brain gets some information from the memory stores, mostly without any external stimulators and without being dependent on the sensory organs. In some cases, day-to-day experiences are emulated or even anticipated. On the other hand, ancient information from adolescence or childhood often emerges, which we believed to have long been forgotten and which effectively underlines Penfield's view that the brain stores almost all memories.

Scientifically, the function of the dream has been valued very differently in the last hundred years. Sigmund Freud hoped in a dream to have found the ideal route to the unconscious, the analysis of which would bring the deepest layers of the personality to light. Hobson and McCarley of Harvard University in Cambridge, on the other hand, said that dreams have no special meaning at all, but that they are merely random spontaneous activities of nerve cells. Finally, the Nobel Prize winner Francis Crick even claimed that dreams serve to forget unimportant content and associations. Jonathan Winson, New York's Rockefeller University, on the other hand, believed that animals in dreams practice actions such as flight, defense, attack and sexuality in order to be better prepared for them when they are awake. As evidence, he argues that a certain neuronal excitation pattern, the PGO activation, occurs in animals both during high levels of alertness and during REM sleep.

From the author's point of view, it is most likely just a matter of spontaneous discharges of memory content. In this case, however, the dream would be associated with an exercise effect that should not be underestimated, since the activation of the corresponding control circuits briefly strengthens the neural connection and could thus protect it from being finally forgotten. In this respect, the ideas occurring in the dream would fulfill an important function. In the dream, however, nonsensical or completely new associations are no longer so strongly inhibited as in waking consciousness. At least it can also happen that the solution to a problem was found through this, which one could not find on the day with strict convergent thinking. Interestingly, many inventors and even some Nobel Prize winners reported that they came up with the solution to a problem while they were asleep.

A particularly intense nocturnal hallucination which is extremely frightening and which is felt to be absolutely real even more than the normal dream is the so-called "night terror". Here, the sleeper is still in a state of sleep paralysis, so he cannot move his body at all; but is psychologically completely awake and has the feeling that something infinitely evil has entered his room and to which he is defenseless. Despite massive efforts, the person concerned is unable to move, which intensifies the feeling of absolute helplessness. About the causes little is known about this poorly researched evil.

The theory of neuronal overactivity as the only explanation of the cause of hallucinations begins to falter when you realize that even a healthy normal person can be made to develop massive hallucinations even in broad daylight within a short period of time. There are two very simple ways to do this: sleep deprivation and isolation. Even after a few days without REM sleep, significant hallucinations occur, even during the day: alcohol and barbiturates, which suppress REM sleep, can therefore lead to hallucinations in the long term. Davison and Neale impressively describe the example of the withdrawal reaction of a barbiturate-dependent woman who, among other things, drinks from an imaginary glass, picks up non-existent objects and thinks she recognizes people on the tree in front of the window.

Complete withdrawal of stimuli, on the other hand, can lead to hallucinations even after a few hours. People who spend a long time alone in darkened and soundproof rooms always develop hallucinations. The isolation experiments of the Munich psychology professor Jürgen Aschoff have become known. The Italian cave explorer Maurizio, who spent a total of 210 days underground alone, described in his diary that on the 16th day he saw a non-existent bird fly through the cave for the first time. Later he thinks he hears distant cries for help. Then he saw brightly colored surfaces appear on the gray ceiling of the cave. From the 60th day on, he wrote that characters appeared who initially only whispered, but later spoke out loud to him. He knows this is all just a fantasy. In the further course his fantasy figures become more and more clear. Finally, he even greets the nonexistent people, some of whom have no heads at all.

Ronald Siegel, American psychology professor and hallucination expert, put himself in a self-experiment for several hours in a completely dark salt water tank, which practically no longer allowed any sensory sensations. The first hallucinations appeared after just a few hours, initially small objects and strange shapes with glowing edges. Later, skyscrapers made of light fill his field of vision with futuristic architecture, pulsating blue light emanated from a tunnel, and finally he sees a laughing Buddha in front of him.

Incidentally, it can also be done faster. The human eye has to constantly perform small microsaccades so that the nerve cells of the retina are constantly re-stimulated. If you suppress these tiny eye movements by stubbornly looking at a point for a few minutes and also avoiding blinking, strange optical phenomena quickly arise. First, the view from the edge becomes increasingly blurred, the field of vision narrows in a tunnel-shaped manner and finally cloud-like dark or light spots form. An interesting little experiment with which you can get to know visual changes due to deprivation in a very short time.

In addition to staying in isolation rooms, there is a much simpler way of sensory deprivation. Hallucinations also occur in the deepest state of contemplation, with closed eyes and reduction of thinking to a single word (so-called mantra). Consciousness-expanding experiences and confrontation with old memories, which are often experienced in transcendental meditation, for example, can then be explained by the fact that the brain begins to hallucinate in the absence of current information. Meditators, too, often report of radiantly bright, luminous phenomena that they saw in the state of contemplation. In the past millennia these have often been interpreted as divine visions.

There are patients who have such experiences involuntarily, because some diseases force such sensory deprivation. People who become blind often report complex visual hallucinations if the visual cortex is intact and there is only one lesion in both eyes or optic nerves; after the discoverer, this is known as the Charles Bonnet Syndrome. The hallucinations are vivid and often even pleasant in nature. Similar acoustic hallucinations can also occur in patients with acquired hearing impairment. A large number of recent studies show that the Charles Bonnet syndrome occurs more frequently in older people, since a certain cerebral dysfunction occurs with increasing age, which apparently favors the development of the syndrome.

Brain damage is of course not linked to old age, but can arise from a variety of causes. In fact, some patients also have hallucinations after a traumatic brain injury or stroke. Professor Kölmel has been researching this group for more than twenty years, and according to his research data, up to 50% of patients with partial blindness suffer from deceptions, illusions or visual hallucinations in the blind half of the visual field as a result of brain damage. These are summarized under the collective term Positive Spontaneous Visual Phenomena (PSVP). Kölmel distinguishes between different typical shapes: in addition to simple points of light or flashes of light (so-called photopsias or phosphenes), there are also basic geometric shapes such as triangles, squares, hexagons, circles or ellipses. There are neural assemblies in the brain that are precisely responsible for recognizing these patterns. Apparently, these cell networks occasionally fire spontaneously when there is no longer any external flow of information. However, more complicated shapes, objects, people, animals or even entire scenes are often created.

Brain-damaged patients usually perceive the PSVPs in the blind half-field, they often only last a few seconds, a maximum of a few minutes. Kölmel reports various case studies, e.g. that of a 34-year-old nurse who woke up one morning with a sharp left-sided headache. Three hours later, she noticed that her right field of view was cut off. After the patient noticed the loss of the visual field, several hours passed, then suddenly bright, silver stars flashed again and again in this darkened field, mainly above. Less often, about ten times a day, but often for hours, a group of glistening bright, colorful spots in the form of spheres, ellipses, squares and hexagons appeared in the darkness at the top left, fell through the field of vision and suddenly went out, as if they were behind disappeared on a black wall. It wasn't until two days later that she decided to see an ophthalmologist. This determined a partial blindness.
In addition to such simple illusions, Kölmel also describes complex hallucinations in which objects or people are seen, sometimes even entire scenic processes. The causative brain injuries in patients with visual hallucinations and illusions were usually more extensive than in the group who only saw photopsia. In addition to the occipital lesion, there was usually temporal or parietal brain damage. Kölmel's patients consistently reported that the complex hallucinations always disappeared when they tried to look at them more closely or when they moved their eyes or head. Some patients used this technique for self-therapy against the annoying symptoms: In a 68-year-old patient, a left parieto-occipital brain tumor had been surgically removed, resulting in blindness in one half of the visual field. From the second to about the 30th postoperative day, the patient then initially perceived various photopsias in the blind area. They hardly worried him. On the other hand, he believed he had lost his mind when strange perceptions arose, which he initially only confided to his bed neighbor. On the right side, where he couldn't see anything since the operation, several small men suddenly appeared. They stood quietly in line, up to 20 at a time. They looked like the other, were well dressed, wore top hats, and were as distinguished as English lords. If he wanted to take a closer look at individual people, they all disappeared like a ghost.

Photopsias are generally interpreted as a disruption of the primary visual center (area 17) in the occipital lobe, but it is difficult to assign a location for visual hallucinations. As early as 1940, Weinberger and Grant found that the same damage could result in very different visual hallucinations and that the hallucinations could therefore not be assigned any localizing value. However, as early as 1918 Löwenstein and Borchardt had stimulated the visual center of a brain-injured patient with direct current and found that after a longer period of stimulation, the simple hallucination turned into a complex one. Foerster found in his electrical stimulus experiments in 1929 that stimulation of Area 17 caused simple photopsies such as dots, lines and circles; the irritation of Area 19 but complex hallucinations. Here, too, the photopsias turned into complex hallucinations when stimulated for a long time.

Complex visual hallucinations usually set in quickly after the damage, but rarely last longer than one to two weeks. Since the phenomena described mainly occur when the visual field defects are still in the process of regression in patients after brain lesions, according to Kölmel PSVPs could be interpreted as signs of a "self-healing attempt" of the brain after the damage. This sensitization seems to be an essential prerequisite for the spontaneous remission of lesions of the CNS. A stronger excitability after damage could possibly even stimulate the plasticity of neuronal systems, so that existing functional failures can be compensated.

The author himself had the opportunity a few years ago to examine a patient who had hallucinations for years. The patient suffered not only from a lesion in the visual center in the area striata as a result of a stroke of the arteria cerebri posterior but also from a frontal lesion of unknown origin. Since multiple references have already been cited which suggest that a frontal underfunction may promote hallucinations, this may be the reason why the hallucinations did not go away in this patient.

Another area that one does not immediately think of when talking about hallucinations are "near-death studies", reports from reanimated people who describe so-called "death experiences". Here, with astonishing correspondence, an intense white light is portrayed in the course of the dying process, then scenes from one's own life that were believed to be forgotten are seen, and finally some people report the filigree patterns and landscapes they see. Raymond A. Moody, discoverer of this typical and since then controversial process, quoted a multitude of reports in his first book "Life after Death", for example: "It was all pitch black, only very far in the distance could I see this light, this incredibly bright light "; in another place: “... and further up into this pure, crystal clear light - a brilliant white light.

It was beautiful and so bright, so radiant, but it didn't hurt your eyes. Such a light cannot be described here on earth at all. "Or:" A wonderful, radiant light shone around. And the surroundings were beautiful too. There were colors there, shining brightly, not like here on earth, but indescribably intense ... Water flashed, fountains sprayed, a city of light, that's the best way to describe it. It was wonderful."

This description does not seem unknown. It is very similar to what Albert Hoffmann wrote about the effects of LSD. Without wanting to deprive these reports of their mysticism, one could interpret the white light as a global photopsia and the later visual impressions as complex visual hallucinations or illusions that arise from a collapse of the inhibitions in the brain as a result of the dying process. Schroeter-Kunhardt pointed out in 1995 that many of these experiences can be explained by the release of endogenous hallucinogens with the involvement of the temporo-limbic system. Probably the control by the frontal lobe decreases rapidly in the priority of dying, whereby all otherwise inhibited memory contents can spring forth unchecked. The fact that those concerned suddenly remember episodes from their life story that were believed to have long been forgotten could also be explained by the breakdown of neuronal inhibitions, which in the case of a brain lesion may break down earlier than excitatory systems. It can be assumed that in the process of dying, as a catastrophic reaction, transmitters are suddenly released in large quantities.

In summary, hallucinations have lost a lot of their eerie flair; they are considered a natural reaction of our brain that can arise due to various influences. The main cause seems to be (a) on the one hand the withdrawal of stimuli (e.g. isolation, sleep, meditation, blindness), here the brain stimulates itself when no more external stimuli come in; (b) on the other hand, hyperfunction (e.g. drugs, pathological changes in the release of transmitter substances such as dopamine, serotonin and noradrenaline, electrical convulsive discharge in epilepsy). The question is, of course, why both under and over function, i.e. two opposites, can lead to the same result? Here you have to see that the under-function in one place of the brain can lead to an over-function in another place due to a lack of inhibition. Every active brain function inhibits other brain functions (e.g. pain is no longer perceived as strongly when one consciously concentrates on something else).

Hallucinations are also based essentially on memory content that has been stored at some point. Excessive excitation of the memory structures as well as a lack of inhibition of information stored in the memory both lead to the uncontrolled intrusion of such memories into consciousness. Since every perception ultimately takes place in the brain, such hallucinations can be experienced as completely real.

Schematically, there is an interaction between three parts of the brain that can be involved in the development of visual hallucinations: the visual system, the association cortex in the frontal lobe, and memory. Disruption of any part can cause visual hallucinations. Damage to the visual system, e.g. blindness, leads to images being projected into the blind area. Frontal brain damage can obviously have the consequence that contents stored in the memory can no longer be sufficiently inhibited so that they flow unchecked into the consciousness. One could visually imagine that the frontal lobe has the function of a watchdog who sits on a constantly overflowing, brimming barrel of memories. As soon as the attention of the frontal lobe wanes, memory contents well up and form ideas, dreams and even hallucinations. This also makes it understandable why it is so difficult to find a definable location in people with brain damage that is responsible for all visual hallucinations. As always, everything in the brain is interconnected with everything and the actual symptom only arises from deficits in the interaction.

Halucination book


Erich Kasten: The unreal world in our head - hallucinations, visions, dreams. Munich: Reinhardt-Verlag.