Raul Hernandez Peon, Mexican neurophysiologist (Merida, Yucatan 16 July 1924 – Ciudad
de Mexico 16 April 1968) Authored about 150 papers Regarded as one of the leading world
researchers in the field of neurophysiological mechanisms of sleep ACHIEVEMENTS
Established that sensorial impulses are sorted
at low levels of nervous system Determined the existence of a cholinergic
system of sleep proposing its mechanism and anatomical structure Concluded that activation of reticular
formation of brain stem exerts a descendent influence on sensorial pathways by
means of inhibiting centrifugal fibers Postulated that supra-mesencephalic structures
are not essential to habituation development Theorized that reticular formation receives and
controls the external information With French & Livingston showed clearly
that the same system of neurons which mediated the ascending arousing or
activating response was itself under the influence of impulses descending in
corticofugal pathways (1952-3) and confirmed the existence of reticulofugal
inhibitory mechanisms acting upon the first sensory synapse (1954-5) Theorized that wakefulness-sleep systems and
the positive-negative motivational systems are subserved by common anatomic
subcortical limbic-midbrain structures and are reciprocally connected in
dynamic equilibrium so that the level of activity in each system is modified by
impulses coming from sensory receptors or from the neocortex First to demonstrate that the cortical
potential evoked by a sensory stimulus and previously diminished by
habituation, increases in voltage during reinforcement Concluded that electrical activity of the
olfactory bulb was indicative of the state of activation of the brainstem
arousal system Predicted that many psychiatric disorders were
associated with the failure to inhibit responses to stimuli which have little
informational value Put forward the concept that habituation is not
only the primary learning process, but seems to be a common denomination for
the establishment of all other more complex types of learning (1959) Showed that rostral side of reticular formation
of brain stem was essential to awakening and wake maintenance Enunciated the concept that rostral brainstem
influences that inhibit the mesencephalic reticular system primarily in the
limbic system (1960) Demonstrated that the medial forebrain bundle
forms a key part in the rostral sleep system into which there is confluence of
heterogeneous hypnogenic pathways and also showed these elements to act by
inhibiting the meso-diencephalic arousing neurons Introduced a model indicating reciprocal
connections between the cerebral cortical system which rather accurately
predicted the organization of the hypnogenic circuits in the brain as shown in
his subsequent works (1961) Showed that when micro-crystals of cholinergic
agents were applied to specific neural circuits the sleep was produced in all
its various phases and stages Proved the descending path of the hypnogenic
influences Concluded that descending and ascending paths
of cholinergic hypnogen system act to induce sleep by inhibiting the
meso-diencephalic activating system BIBLIOGRAPHY Physiology & Behavior 5(4):379-88, 1970 (includes complete bibliography of Hernandez Peón) |
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