In this post I will draw heavily on Dr. Oliver Sacks book: Hallucinations. To whom all or most credit should be attributed to, unless otherwise specified.
“…there’s no consensual validation, you realize with a shock…” that only you, see the image, which is actually “in your head”.
Misperceptions or illusions are not hallucinations per se. They usually involve improper identification of someone or something present.
“…hallucinations are conjured out of thin air.”
Pseudo-hallucinations “are not projected into external space but are seen, so to speak, on the inside of one’s eyelids…typically occurs in near-sleep states”
misperceptions: polyopia is identifying something one visualizes not as single figure but multiplied.
Palinopsia, a misperception in which an object or person crosses the field of view repetitively.
“dreams are both neurological & psychological” “dreamers are active participants” even though not aware most of the time.
Charles Bonnet Syndrome are visualizations onto external space of which the viewer is conscious that despite their uniqueness are not really there.
hallucinations of faces & color are activated in the ventral visual pathway in the visual cortex.
Faces are also activated in fusiform gyrus. Deformations of these, show more activity in the superior temporal sulcus.
Text hallucinations show up as abnormal activity in the left hemisphere.
CBS images are not interactive with the viewer & are “without sound, smell, or tactile sensation.”
Viewer realizes that they aren’t real, however may initially think they are going crazy.
hallucinations of voice can appear, wherein a person can hear conversations, arguments, etc between people, who are not in the room & may be felt to be distant in space.
the difference between schizophrenic voices & voices that are solely hallucinatory in nature, is that the former tend to be “accusing, threatening, jeering, or persecuting.”
in ancient cultures “hearing voices had been accorded great importance” as messages from disembodied spirits, gods & the like. This is seen in Greek myth.
On fMRI, activations are noted in the occipital cortex & in the inferotemporal cortex, when hallucinations occur. Bottom up activation.
In contrast with visual recall or visualizations the prefrontal cortex is involved.
Further study of auditory hallucinations needs to occur. Currently the understanding is that it “may be associated with abnormal activation of the primary auditory cortex.” Or “failure to recognize internally generated speech”, thus “heard” as an external voice, or “abnormal attention to subvocal streams which accompanies verbal thinking”.
Other hallucinations include tinnitus, “hummings, mutterings, twitterings, rappings, rustlings, ringings, muffled voices”. At times these “may be aggravated by [any of multiple] factors.”
Sarah Lipman, sent a message to Dr. Sacks in which she notices that the ringing of phones is often a common auditory hallucination, as well as the cry of her baby. She states this may be likely due to a “hyper-alert state” in which these sounds can be heard.
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