PubMed · 6078379
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F M Levine. 1967. Reply to "Note".. https://doi.org/10.2466/pr0.1967.21.1.275
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Subjective consciousness suggests a unity of the sensing and perceiving self that is difficult to reconcile with the multiplicity of sensory analyzers and the absence of a convergence zone in the brain. This has led--on the one hand--to the dead-end assumption of a unifying sentient homunculus and--on the other--to a denial of conscious unity. The sketchpad model presented here avoids this dilemma by viewing conscious thought as a selfreferent loop of neural activity, rather than as the information content of a fictitious set of output neurons. Use is made of the numerous neural pathways that originate at various cortical and subcortical areas and terminate in the thalamus. The model assumes that primary sensory inputs are modified by such feedback in the thalamic relay nuclei through hill-climbing processes that tend to optimize global responses.
Vasovagal reactions during blood donation were assessed in 185 individuals with and 298 individuals without a parental history of hypertension. It was predicted that individuals at genetic risk for hypertension would be less likely to faint or suffer pronounced vasovagal reactions, presumably by virtue of altered baroreflex sensitivity. A relationship between a parental history of hypertension and vasovagal responses was observed, albeit modified by blood donation experience and sex. Nurses obtaining blood from inexperienced donors without a parental history of hypertension were significantly more likely to recline the subject's chair than those obtaining blood from inexperienced donors with a parental history of hypertension or experienced donors. Questionnaire data were consistent with these findings. These results may be an interesting reflection of group differences in baroreflex sensitivity and have implications for screening potential donors.
The literature on state-dependent fluctuations in thalamocortical activities indicates that in electrophysiological terms, waking and paradoxical sleep are fundamentally identical states, with the provision that the handling of sensory information is altered in REM sleep. The central paradox of REM sleep, namely the apparent lack of cognitive responsiveness to sensory stimulation in spite of increased thalamocortical responsiveness to sensory stimuli, will lead us to hypothesize that the processing of sensory inputs in REM sleep is similar to that underlying preconscious processing of sensory inputs in the waking state. This will lead to a general discussion of the role of fast (approximately equal to 40 Hz) thalamocortical oscillations and temporal binding in sensory processing and conscious experience.