Transcript Evolution of brain and behaviour

The auditory system
Chapter 9
The physics of sound
Measuring sound intensity
• We are sensitive to an enormous range of
intensities, so a logarithmic scale works
well
• intensity in dB=20 x log (P1/P2)
– where P2 is 0.0002 dynes2/cm2
• remember log(1)=0, log(10)=1, log(100)=2
– (and also, log(.1)=-1)
Remember this….
Fourier analysis
Any complex
waveform can be
represented as the
sum of a series
of sine waves of
different
frequencies and
amplitudes
The human ear
The middle ear
The inner ear
The mechanics of the basilar
membrane
Auditory hair cells and the
auditory nerve
Transduction at hair cells
Central auditory pathways
Tonotopic organization
Tonotopic organization in cortex
Auditory localization - sources of
information
Auditory localization - a possible
mechanism
Complex auditory processing
• Bregman’s analogy and auditory scene
analysis
-reconstructing a three-dimensional world from
soundscapes
Complex auditory processing
Language processing and Wernicke’s area
Complex auditory processing
-music perception
Evidence for a biological basis of
music
Amusia both in ‘normals’ and after brain injury
-inability to perceive dissonance and/or rhythm
Musical savants (often autistics)
Imaging evidence suggests that a complex network of areas is
involved in music perception with a partial but not complete overlap
with language probably some unique processing in right temporal
lobe
If music is hard-wired then it must be adaptive
- remember Geoffrey Miller’s sexual selection idea
-also some arguments that music serves to bond communities
or to help individuals recognize familiar groups
Echolocation in bats