Marine Mammal Bioacoustics: The Central Auditory System

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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
• scheifpr_at_uc.edu

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Central Nervous System

• 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/
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The Brain- by System

• Reptilian brain
• Limbic system
• Neocortex

From spinwarp.ucsd.edu/NeuroWeb/Text/br-800epi.ht
m and http//www.ascd.org/portal/site/ascd/templ
ate.chapter/menuitem.b71d101a2f7c208cdeb3ffdb62108
a0c/?chapterMgmtIdeffbcba5ddcaff00VgnVCM1000003d0
1a8c0RCRD
From http//www.crystalinks.com/reptilianbrain.ht
ml
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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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Parietal
Occipital
Frontal
Temporal
cerebellum
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The Cerebrum Ascending auditory system from
thalamic to cortex- orGray matter over white
matterWhats 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
Autoreceptors
Receptors
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BRAINS OF VARIOUS ANIMALS
10,000
540 kg
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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 Nerves
Divided into Sensory and Motor divisions Sensory
(afferent) nerves Motor (efferent) nerves Mixed
nerves
Image from www.merck.com/mmhe/sec06/ch077/ch077c.
html
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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

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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

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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

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Brain Comparison
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Thalamus
MGB
Central Auditory Pathways
Pons
Inferior Colliculus
Region of Cochlear Nucleus
Medulla
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The cochlear nuclei
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The trapezoid body calculates interaural
intensity differences

TRAPEZOID BODY
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LATERAL LEMNISCUS
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0
The inferior colliculus processes sounds for
auditory perception and reflex adjustments
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0
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
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SOME GROSS OBSERVATIONS

• Large, unusually shaped
• Well-fissured
• Olfactory bulbs absent
• Radical hypertrophy of acoustic areas

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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.

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Auditory Cortex
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Cetacean Auditory Anatomy
Image from http//instruct1.cit.cornell.edu/cours
es/bionb424/students2004/kls36/neuroanatomy.htm
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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

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Fini