femme Neuroscience Notes

Some Topics

Out of Body

A big question in the study of consciousness is where are events actually occurring? There is an inescapable logic that places all events in the brain with or without corresponding events elsewhere. A normal person has confidence in external events only because his or her brain makes a distinction between inside and outside events.

One way we distinguish between a normal and abnormal person is to study “reality testing” which requires this distinction to be present, complete, and convincing. Abnormal people become confused and fail to make this distinction. Weber invented the law of projection to describe the way in which human brains construct reality by identifying some brain activity with a source out there.

An example of erroneous projection occurs when a leg is amputated but the legless person continues to report an itch in the absent big toe. The easiest explanation is that signals continue to arrive at the neurons that used to be connected to the toe and these neurons dutifully report the toe’s status to consciousness. The itch is convincing even though the afflicted person knows that there is no leg and no toe.

De Ridder et al reported electrical stimulation of the brain elicited out-of-body experiences during which the “self” was perceived as being outside of the body. A 63-year-old Danish man had electrodes placed over the right temporoparietal area (auditory cortex) in an attempt to suppress tinnitus. The researchers became interested in his out of body experiences and used electrical stimulation and positron emission tomography (PET) to locate brain activation  during out of body events to the angular–supramarginal gyrus junction and the superior temporal gyrus–sulcus on the right side. Activation was also seen in the right precuneus and posterior thalamus with stimulation, extending into the superior vermis.

We have already defined images of events from inside the brainbodymind as noumena or subjective experiences. Samples of the brain’s inner workings sometimes appear in consciousness – ghost images, selftalk, dreams are all normal noumena. Phantom limbs and out of body experiences are abnormal noumena as are illusions, delusions and hallucinations.

Noumena may be projected out there as external events or may be recognized as coming from within. Confusion about the origin of noumena is a major problem for humans. We have declared that images of events that originate from the outside tend to be detailed and explicit in consciousness as phenomena. Representations of phenomena are said to be objective. The inescapable logic is that all phenomena, no matter how convinced you are of their external origin, must become noumenal and conscious before their existence is known.