Direct Electrical Measurement of Mental Processes

Individual experiments have established that each of the events specified in Table 1 occurs during cognitive experiences (although the grand experiment of simultaneously recording all those measures has not been attempted). The various mental events are similar, then, in that they all involve covert activities throughout the body, including the brain.

The unique mentalistic terms for mental events exist because the experiences occur under different environmental and organismic conditions. Night dreams, daydreams, and directed rational thought all differ, for instance, because of the degree to which they are influenced by environmental input. During "sleep thoughts" or images of night dreams, most environmental stimulation is physiologically shut off, apparently at the reticular activating system. Consequently, the mental activity of dreaming is chaotic, since it is not directed by external reality, or, as one psychiatrist put it, a night dream allows us all to go safely insane for a brief period of time. Similar mental processes occur in the daydream, but they are partially influenced by the external environment. During directed problem solving, rational thought processes are largely controlled by repeated reference to the environment.

Hallucinations—false perceptions that the patient confuses with real ones—are akin to night dreams in that they are controlled by internal stimuli, although they are mistakenly ascribed to external forces. Neuromuscular circuits that generate visual hallucinations presumably include the occipital lobe at the back of the brain and the eyes. Auditory hallucinations are similarly thought to be generated when auditory and linguistic regions of the brain interact with muscles of the ears and speech. Auditory hallucinations, for instance, seem to be produced when the patient subvocal-

Figure 1. A sample tracing of the report of a hallucination. The 2-sec intervals before and after the report are marked on the event line at the top. Next in order are the pneumogram, arm electromyogram, chin elec-tromyogram, tongue electromyogram, and the sound record. The increase in chin electromyographic activity and in subvocalization (bottom trace) coincide with the hallucinatory experience.

Figure 1. A sample tracing of the report of a hallucination. The 2-sec intervals before and after the report are marked on the event line at the top. Next in order are the pneumogram, arm electromyogram, chin elec-tromyogram, tongue electromyogram, and the sound record. The increase in chin electromyographic activity and in subvocalization (bottom trace) coincide with the hallucinatory experience.

izes, as indicated by auditory and electromyographical recording of covert speech (Figure 1).

Auditory components of night dreams are apparently generated by neuromuscular circuits like those for auditory hallucinations. Figure 2 illustrates small-scale, rapid covert muscle activity in the lips and chin when one experiences conversations in dreams. These covert speech responses are not present during visual dreams or non-dreaming periods.

Deaf individuals who are not proficient in oral speech use dactylic ("sign" or "manual") language for communication. The muscles for the fingers therefore are the locus of

Figure 2. Illustration of signals during a conversational dream. From the top down, the signals are lip electromyogram, chin electromyogram, horizontal eye placement, and frontal electroencephalogram. Amplitude for the top three traces is 50 mV/division, and 100 mV/division for the electroencephalogram. Time is 1 sec/division.

Figure 2. Illustration of signals during a conversational dream. From the top down, the signals are lip electromyogram, chin electromyogram, horizontal eye placement, and frontal electroencephalogram. Amplitude for the top three traces is 50 mV/division, and 100 mV/division for the electroencephalogram. Time is 1 sec/division.

their linguistic response mechanisms. For them, consequently, the speech musculature is not engaged during thought. Instead, they make covert finger responses when thinking. In addition, individuals who are proficient in both oral and manual language processes engage both the speech musculature and the fingers covertly during thought.

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