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Marine Mammal Bioacoustics: The Central Auditory System
Peter M. Scheifele MDr, PhD, LCDR USN (Ret.)University of Cincinnati
Communication Sciences and Disorders, Neuroaudiology Dept.University Medical Center
Central Nervous System1. Consists of: spinal cord & brain
spinal cord • conducts sensory information• conducts motor information The brain • receives sensory input from the spinal cord and cranial nerves• devotes most of its volume (and computational power) to processing its
various sensory inputs and initiating appropriate — and coordinated — motor outputs.
From: asymptotia.com/wp-images/2007/08/ 3CSD 512 L1
The Brain- by System
• Reptilian brain• Limbic system• Neocortex
From: spinwarp.ucsd.edu/NeuroWeb/Text/br-800epi.htm and http://www.ascd.org/portal/site/ascd/template.chapter/menuitem.b71d101a2f7c208cdeb3ffdb62108a0c/?chapterMgmtId=effbcba5ddcaff00VgnVCM1000003d01a8c0RCRD
From: http://www.crystalinks.com/reptilianbrain.html 4CSD 512 L1
Cerebral Cortex
• SULCI – shallow groove or depression
• FISSURE – a surface groove dividing and organ
• GYRI – Convolution of the brain surface separated by sulci
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cerebellum
Temporal
Frontal
ParietalOccipital
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The Cerebrum: Ascending auditory system from thalamic to cortex- or…Gray
matter over white matter…What’s the matter?
Deep-lying structures: Basal ganglia; amygdala; hippocampus
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More Gross Anatomy (Exterior)Supramarginal
Gyrus
Auditory
Visual
Somesthetic
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Synaptic Vesicle
Receptors
Autoreceptors
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BRAINS OF VARIOUS ANIMALS
ANIMAL
BRAIN WEIGHT (G)BRAINWEIGHT
BODY WEIGHT % BODY WT
SPERM WHALE 7800 g15 tons=30,000 pounds= 13500 kg
0.06 %
ELEPHANT 6000
BOTTLE-NOSED DOLPHIN 1500 g 500 kg 0.3 %
HUMAN ADULT 1300-1400 150 pounds= 68 kg=68000 g 2 %
HORSE 532
CHIMPANZEE 420
HUMAN BABY 350 - 400
DOG (BEAGLE) 72 9 to 18 kg 0.5 %
CAT 30
SQUIRREL 22
ALLIGATOR 8.4 250 kg 0.003 %
OWL 2.2
RAT 2 400 gm 0.5 %
TURTLE 0.3
VIPER 0.1
GREEN LIZARD 0.08
540 kg
10,000
Cranial Nerves
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Cranial Nerves
Images from: /www.med.umich.edu/lrc/coursepages/M1/anatomy/html/atlas/images/
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Classification of NervesDivided into Sensory and Motor divisions
Sensory (afferent) nerves
Motor (efferent) nerves
Mixed nerves
Image from: www.merck.com/mmhe/sec06/ch077/ch077c.html16CSD 512 L1
The Central Auditory Nervous System (CANS)
• Sound localization and lateralization• Auditory discrimination
– Frequency discrimination– Intensity discrimination– Quality (timbre)
• Pattern recognition• Temporal discrimination
– temporal resolution,– temporal masking, – temporal integration, – temporal ordering
• Auditory performance in presence of competing signals• Auditory performance in the presence of degraded signals
Acoustical Roles of the Brain
• Processing of sound– Localization– Temporal discrimination– Intensity discrimination– Frequency discrimination
• Vocalization development– Motor functions for vocalization– Sound ordering and development
• Communication and maybe language
Ear and Brain are BOTH Required for Hearing
• Brain is also tonotopically organized• Brain performs acoustic processing functions– Discrimination– Localization– Patternization
• Brain makes use of the processed sound– Links to memory and understanding
• Fight or flight• Language• Vocalization links
Brain Comparison
Central Auditory Pathways
Medulla
Pons
Thalamus
MGB
Inferior Colliculus
Region of Cochlear Nucleus
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The cochlear nuclei
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TRAPEZOID BODY
The trapezoid body calculates interaural intensity differences
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LATERAL LEMNISCUS
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The inferior colliculus: processes sounds for auditory perception and reflex adjustments
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The brachium of the inferior colliculus and the medial geniculate nucleus
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2 – inferior colliculus
18 – brachium of the inferior colliculus
21- medial geniculate body
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Transverse temporal gyri
SOME GROSS OBSERVATIONS
• Large, unusually shaped
• Well-fissured• Olfactory bulbs absent• Radical hypertrophy of
acoustic areas
BRAIN STRUCTURES: Possible Neurological Meaning
• Is relative size of specific areas a definite expression of the importance of its principal function?
• Past slide preparations of non-perfused brains have given only limited data regarding architectural arrangements of the cortex.
• Recent advances in anesthesia have allowed brains to be perfused in situ for histoarchitectural studies.
Auditory Cortex
Cetacean Auditory Anatomy
Image from: http://instruct1.cit.cornell.edu/courses/bionb424/students2004/kls36/neuroanatomy.htm
Comparative Auditory Anatomy
• Auditory brainstem nuclei and corresponding fiber diameters much larger than human equivalents
• Auditory structures are also much larger in odontocetes than mysticetes
Fini
