PubMed · 5777952
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R L Cahoon. 1969. Physiological arousal and time estimation.. https://doi.org/10.2466/pms.1969.28.1.259
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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.
A randomized, double-blind, placebo-controlled trial was conducted to assess the acute effects of placebo and three doses of methylphenidate (MPH) (0.3, 0.6, 0.9 mg/kg) on cognitive flexibility and overt behavior in 28 children with a confirmed diagnosis of attention deficit-hyperactivity disorder. Two underlying cognitive processes (response inhibition and response reengagement) were assessed by measuring the probability and speed with which subjects could inhibit responses to a primary task (forced-choice letter discrimination) and immediately execute a response to a secondary task (simple reaction time) when given a signal to do so. Results indicated that MPH enhanced cognitive flexibility, although the high dose was less effective than lower doses in enhancing response inhibition. Dissociations of dose effects on cognitive function and behavior were demonstrated: Dose-response functions for changes in behavior were linear, whereas the function for response inhibition was U-shaped. Findings argue against the typical clinical practice of determining the response to stimulant treatment from a single measure such as parent report of child behavior.
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.