Corticofugal Modulation of Initial Sound Processing in the Brain

Dolphin brain size with respect to body size ranks between that of apes and humans. The hypertrophic auditory structures, the large cerebrum with extended gyrification and the highly cognitive capabilities of toothed whales seem to be in paradoxical contrast to their thin neocortex with a plesiomorphic or paedomorphic cytoarchitecture. The total number of neurons in the delphinid neocortex is comparable to that of the chimpanzee (Primates), but, in relation to body weight, in the magnitude of the hedgehog (Insectivora) neocortex since cetaceans may be able to obtain larger body sizes than terrestrial mammals due to reduced gravitational effects in water. During evolution, dolphins may have increased the computational performance of their cytoarchitectonically ‘simple’ neocortex by a multiplication of relevant structures (resulting in a hypertrophic surface area) instead of increasing its complexity. Based on this hypothesis, I suggest that the evolution of the large dolphin brain was possible due to a combination of different prerequisites based on adaptations to the aquatic environment including the sonar system. The latter facilitated a successful feeding strategy to support an increased metabolic turnover of the brain and led to a hypertrophic auditory system. Moreover, the rudimentary pelvic girdle did not limit brain size at birth. These adaptations favoured the evolutionary size increase of the cerebral cortex in dolphins facilitating highly cognitive capabilities as well as precise and rapid sound processing using a ‘simple’ kind of neocortical cytoarchitecture.

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Good vibrations: Music and the single hair cell

The Biochemist ◽

10.1042/bio02406012 ◽

2002 ◽

Vol 24 (6) ◽

pp. 12-14

Author(s):

Corné Kros

Keyword(s):

Hair Cell ◽

Inner Ear ◽

Hair Cells ◽

Auditory Nerve ◽

Sound Stimulus ◽

Mechanical Stimuli ◽

Sensory Receptors ◽

Nerve Fibres ◽

Sound Processing ◽

The Brain

Hair cells are the sensory receptors in the inner ear, and the hair bundles that protrude from their upper surfaces transduce mechanical stimuli into electrical responses. This article examines the key molecules involved in the different stages of sound processing within these extraordinarily sensitive and intricate cells, from the reception of the sound stimulus to the release of neurotransmitters on to the auditory nerve fibres that signal to the brain that a sound has been received.

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Rhythm, reading, and sound processing in the brain in preschool children

npj Science of Learning ◽

10.1038/s41539-021-00097-5 ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Silvia Bonacina ◽

Stephanie Huang ◽

Travis White-Schwoch ◽

Jennifer Krizman ◽

Trent Nicol ◽

...

Keyword(s):

Auditory Processing ◽

Reading Skills ◽

Classroom Setting ◽

Sound Processing ◽

Rhythm Reading ◽

Sensorimotor Systems ◽

Preliteracy Skills ◽

Listening In Noise ◽

The Relationship ◽

The Brain

AbstractA child’s success in school relies on their ability to quickly grasp language and reading skills, the foundations of which are acquired even before entering a formal classroom setting. Previous studies in preschoolers have begun to establish relationships linking beat synchronization, preliteracy skills, and auditory processing. Beat synchronization involves the integration of sensorimotor systems with auditory and cognitive circuits and, therefore calls on many of the same neural networks as language. Using a drumming task, we analyzed the relationship between children’s ability to maintain an isochronous beat with preliteracy skills and frequency following responses (FFRs) in over 150 preschoolers. We show that preschoolers who performed well on the beat synchronization task outscored their peers on all preliteracy measures and had more robust FFRs. Furthermore, the good synchronizers experienced less degradation of certain FFR measures when listening in noise. Together, our results are consistent with the view that rhythm, preliteracy, and auditory processing are interconnected during early childhood.

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