Abstract
The evolutionary transition from mammal like reptiles to mammals is accompanied by two major phylogenetic changes that affected the development of acoustic communication: First, changes in the jaw joint freed the later middle ear ossicles from participating in the feeding apparatus and thereby creating a functional middle ear. This functional middle ear is a basic requirement for perceiving air borne sound and was of fundamental importance for small nocturnal mammals to survive in a world dominated by dinosaurs. Second, a major increase of the neocortex occurred. This increase of the neocortex induced significant changes in the basic anatomy of the central sensory, but affected them in different ways. A topographic somatosensory representation of the body surface in terms of a highly ordered map only exists in the neocortex and has no precursor in other brain structures, and thus has most likely been established in the context the development of the neocortex. The dominating sensory system of the mammal-like reptiles, the visual system, has been fundamentally chang-ed: The primary visual center, the tectum opticum in the midbrain, has been replaced by a new neocortical center, the visual cortex. In contrast, in the auditory system the original basic subcortical integration center, the inferior colliculus has been preserved. The inferior colliculus has multiple connections to premotor and motor centers as well as to centers of major importance for motivation and mental status. Higher centers of auditory processing of speech and semantic information have been established behind the inferior colliculus but did not replace it. This conservation of the direct connection of a subcortical integration center with centers of motivational control that in turn can affect the neocortex might be the reason for the successful use of music and familiar voices as treatment in persistent-vegetative-state-rehabilitation.
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More From: Physikalische Medizin, Rehabilitationsmedizin, Kurortmedizin
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