From: Neuropsychiatry, Neuropsychology, Clinical Neuroscience
by R. Joseph, Ph.D
Hallucinations may occur secondary to tumors or seizures involving the occipital, parietal, frontal, and temporal lobe, or arise secondary to drugs, toxic exposure, high fevers, general infections, exhuastion, starvation, extreme thirst, partial or complete hearing loss including otosclerosis, and with partial or complete blindness such as due to glacoma (Bartlet, 1951; Flournoy 1923; Lindal et al. 1994; Pesme, 1939; Rhein, 1913; Ross et al., 1975; Rozanski & Rosen, 1952; Semrad, 1938; Tarachow, 1941). Interestingly, when secondary to peripheral hearing loss, frequently individuals report hearing certain songs and melodies from their childhood --melodies which they had usually long forgotten. In addition, individuals suffering from cortical blindness, i.e. Anton's syndrome (Redlich & Dorsey, 1945) and deafness (Brown, 1972), as well as those recovering from Wernicke's aphasia, frequently experience hallucinations.
In general, hallucinations secondary to loss of visual or auditory input appears to be secondary to the interpretation of neural noise and the spontaneous activation of associated neural circuits. That is, with loss of input various brain regions begin to extract or assign meaningful significance to random neural events, or to whatever input may be received. Thus we find that subjects will hallucinate when placed in sensory reduced environments or even when movement is restricted (Lilly, 1956, 1972; Lindsley, 1961; Shurley, 1962; Zuckerman & Cohen, 1964).
Conversely, hallucinations can occur due to increased levels of neural noise or spontaneous activation of various neural circuits. For example, if an area of the neocortex is abnormally activated that area in turn may act to interpret its own neural activity and may even assign emotional or religious significance to whatever is perceived. However, the degree and type of interpretative activity depends on the type of processing performed in the region involved. For example, tumors or electrical stimulation of the occipital lobe produce simple hallucinations such as colors, stars, spots, balls of fire, flashes of light. Tumors invading the parietal lobe may induce somesthetic hallucinations, including burning, engorgement, stiffness, or electric-shock like pain.
With superior temporal involvement the patient may experience crude noises, such as buzzing, roaring sounds, bells, and an occasional voice or sounds of music (Penfield & Jasper, 1954; Penfield & Perot, 1963), including clicking, ticking, humming, whispering, and ringing, most of which are localized as coming from opposite side of the room. Patients may complain that sounds seem louder and/or softer than normal, closer and/or more distant, strange or even upleasant (Hecaen & Albert, 1978). There is often a repetitive quality which makes the experience even more disagreeable.
However, with anterior, inferior temporal lobe abnormalities, the hallucinations become increasing complex consisting of both auditory and visual features, including faces, people, objects, animals, etc. (Critchley, 1939; Penfield & Perot, 1963; Tarachow, 1941). Presumably, in part this is a consequence of the activation of specific neurons or neural assemblies which normally respond to specific environmental stimuli, such as faces; e.g. feature detector activation in the absence of appropriate external stimuli. As the inferior temporal lobe contains neurons which respond to a variety of complex stimuli, whereas tissues in the occipital lobe are more responsive to simple stimuli, correspondingly, hallucinations become increasingly complex as the disturbance expands from primary to association areas and as involvement moves toward the anterior temporal regions --which is one of the major interpretive regions of the neocortex (Gibbs, 1951; Gloor 1990, 1992; Halgren 1992; Penfield & Perot, 1963).
Presumably, the anterior-inferior temporal lobes and associated limbic nuclei give rise to the most complex forms of imagery because cells in these areas are specialized for the perception and recognition of specific forms, including faces and people. As noted in chapters 3 and 5, it is the inferior temporal lobe, including the amygdala and hippocampus which are also largely involved in the formation of dream images.
Indeed, it has frequently been reported that as compared to other cortical areas, the most complex and most forms of hallucination occur secondary to temporal lobe involvement (Critchley, 1939; Malh et al., 1964; Horowitz et al., 1968; Penfield & Perot, 1963; Tarachow, 1941) and that the hippocampus and amygdala (in conjunction with the temporal lobe) appear to be the responsible agents (Gloor 1990, 1992; Gloor et al., 1982; Horowitz et al., 1968; Halgren et al., 1978). For example, Bancaud et al. (1994), Halgren et al., (1978), and Horowitz and colleagues (1968) note that hippocampal stimulation was predominatly associated with either fully formed and/or memory-like hallucinations including feelings of familiarity, and secondarily dream-like hallucinations. However, stimulation limited to the neocortex had relatively little effect in this regard (Gloor et al., 1982). It appears, therefore, that limbic activation is necessary in order to bring to a conscious level percepts which are being processed in the temporal lobes.
In general, complex auditory verbal hallucinations seem to occur with right or left temporal destruction or stimulation (Hecaen & Albert, 1978; Penfield & Perot, 1963; Tarachow, 1941) --although left temporal involvement is predominant. Left temporal lobe hallucination may involve single words, sentences, commands, advice, or distant conversations which can't quite be made out. According to Hecaen and Albert (1978), verbal hallucinations may precede the onset of an aphasic disorder, such as due to a developing tumor or other destructive process. Patients may complain of hearing "distorted sentences", "incromprehensible words" etc.
By contrast, Penfield and Perot (1963) report that electrical stimulation of the right superior temporal gyrus, and that patients with tumors and seizure disorders involving the predominantly the right (vs left) temporal region, may experience musical hallucinations. Frequently the same melody is heard over and over. In some instances patients have reported the sound of singing voices and individual instruments may be heard (Hecaen & Albert, 1978). Similarly, complex visual and emotional hallucinations, such as typified by dream imagery or via LSD, is associated with the right temporal lobe (chapter 9).
Complex visual hallucinations are far more likely with right temporal lobe and right hemisphere abnormalities, though visual and auditory hallucinations may occur with injuries involving either side of the brain (chapter 3). With complex auditory hallucinations, and in particular, when patients display disturbed comprehension, abnormalities of speech and thought as well as a schizophrenic psychosis, the left temporal lobe is generally implicated (DeLisi et al. 1991; Dauphinais et al. 1990; Flor-Henry 1983; Perez et al. 1985; Rossi et al. 1990, 1991; Sherwin 1981; Trimble 1991); in paticular, the nuclei of the amygdala and hippocampus.
As noted in chapters 9, 13, presumably it is the left hemisphere and temporal lobe/amygdal/hippocampal complex which provides the verbal monologue which is experienced during dream states and paradoxical sleep. Conversely, the right temporal lobe provides the visual and emotional hallucinatory mosaic which is commonly experienced during REM, and while under LSD, and presumably during related psychotic states. However, as noted above, the most complex hallucinations typically involve the anterior temporal lobes -of either hemisphere; regions which are linked via the anterior commissure and which are therefore subject to abnormal influences that originate in either half of the brain.
Whereas the amygdala and hypothalamus interact in regard to pleasure, rage, and sexuality, the amygdala and hippocampus interact to subserve and mediate wholly different aspects of experience, including memory, dreaming, and hallucinations. The hippocampus in particular appears to be responsible for certain types of "hallucinations" such as the visualizations of astral projection or seeing oneself floating above the body (Joseph 1996, 1999b, 2000a). Some patients report not only floating, but of being embraced by a light and taken to a vast realm of fantastic proportions where they are given access to kowledge of the nature of life and death.
The amygdala, hippocampus, and temporal lobe are richly interconnected and appear to act in concert in regard to mystical experience, including the generation and experience of dream states and complex auditory and visual hallucinations, such as may be induced by LSD (Broughton 1982; Goldstein et al. 1972; Gloor 1986 1992; Hodoba 1986; Horowitz, et al. 1968; Joseph, 1992a; Meyer et al. 1987; Penfield and Perot 1963; Weingarten, et al. 1977; Williams 1956).
If these neurons are hyperactivated, such as occurs during dream states, seizures, physical pain, terror, food deprivation, social and sensory isolation, and under LSD (which disinhibits the amygdala by blocking serotonin) an individual might infuse their perceptions with tremendous religious and emotional feeling. Hence, under these conditions the individual may hallucinate, and ordinary perceptions, objects or people may be perceived as spiritual in nature or endowed with special or religious significance.
Intense activation of the temporal lobe, hippocampus, and amygdala has been reported to give rise to a host of sexual, religious and spiritual experiences; and chronic hyperstimulation can induce an individual to become hyper-religious or to visualize and experience ghosts, demons, angels, and even "God," as well as claim demonic and angelic possession or the sensation of having left their body.
In some instances the individual may come to believe he or she is hearing, seeing, and interacting with gods, angels and demons when in fact they are hallucinating. These false beliefs are accentuated further because they are excessively emotionally and religiously aroused and are experiencing an "enkephalin" high and feelings of rapture or "nirvana."
In many cases, however, the individual is not hallucinating. Rather, their eyes have been opened, and they suddenly see as gods... knowing good and evil.
The amygdala is capable of processing visual, tactile, auditory, gustatory, olfactory, and emotional stimuli simultaneously. Amygdaloid neurons are multimodally responsive. Normally much of this data is suppressed and filtered so as to prevent the tasting of colors, the visualization of sound, and so on.
Under conditions of hyperactivity, limbic sensory acuity is increased and in many respects what is perceived is not necessarily a hallucination but instead represents the perception of overlapping sensory qualities that are normally filtered out. Colors may be felt and tasted, music may be observed as well as heard, the molecular composition of ceilings, floor and walls may be parted so that one can see through the spaces between where molecules join together. And the pulse of life may be experienced as it ebbs and flows in a leaf one holds between their finger tips.
Consider, for example, a description of someones first LSD "trip."
"It was 1966... Jimi Hendrix was singing about purple haze, and that is exactly what we scored up in Haight Ashbury--mixed by the master himself, Stanley Osley..."
"About half an hour after I'd taken it, I was walking toward the park to meet and trip with my fellow tripsters when I began to notice the incredible clarity and vividness of my surroundings. Colors were brighter, plants seem to sparkle...and I stopped and touched a leaf...I could feel its energy, its life... I could taste it through my fingers...And when I got to the park I was so overwhelmed with the colors, the tastes, the smells, the incredible vividity and clarity that I felt almost overwhelmed and sat down to take it all in..."
"And then I heard a jet somewhere in the distance, and I
looked into the sky but couldn't see it but my ears led my eyes
to one of the mountains surrounding the valley, and oh my god,
I could see right through the mountain. It was like the molecular
composition of the mountain was parting into separate molecules.
I could see the spaces between the molecules which were all in
a frenzy of activity.... it was as if I had achieved X-ray vision,
and there were these crystal blue holes--like bubbles--and I could
see right through the mountain and I could see the sky on the other
side, including the jet. I could see the jet on the other side
of the mountain by looking right through the mountain, by looking
right through those gaps in the spaces between the molecules which
were zipping along in their own unique pattern. And then the jet
flew over the top of the mountain and instead of one jet I could
see ten, then a hundred, and a kaleidoscope of jets in the sky."
"I raised my hand to point to this incredible sight, and instead of one hand, there were these trails of hands. And I did that again, waved my hand and there were these hand-arm trails of hands-hands-hands catching up and then merging... and it was then that I realized I could see through my hand. So I gazed at it for closer inspection. It was as if my eyes became a tunneling microscope--and this was 10 years before they invented tunneling microscopes."
"At first I could see the incredible cellular structure of the skin, and then the molecular structure...the pulsating molecules themselves... and then I could see between the spaces where the molecules joined together... my sight penetrated the skin and I could see the blood vessels, and then my eyes penetrated the blood vessels and I could see inside the blood vessel, I could see the blood platelets and the white corpuscles as they swirled through the vessel--and I kept thinking: How come I never noticed this before? I had forgotten that I had taken LSD."
Hallucinogens, of course, are an age-old means of obtaining access
to alternate realities, including the realities of "god." Hallucinogens
are said to enable an individual to peer between the space that
separate this reality from all other realities, such that what
was concealed is suddenly revealed.