Greg Detre
3/12/99
perhaps use timing code for low frequences and place code after
central auditory system is very complex
3-6 synaptic stations between cochlear and A1
superior olivary complex � first place where input from the two ears comes together
ventral/dorsal cochlear nuclei
VLN anterior/posterior
largest synapses in the CNS
preserve timing � spherical bushy cells
CN � first inhibition��������� type IV + V help with speech sounds
Shannon � just 4 frequency bands temporally modulated
speech still comprehensible
telephone < 4kHz
AVLN � SOC������ (where pathway)
DLN + PVCN � midbrain����������������� functional segration?
where � sound source
inter-aural time difference
inter-aural intensity difference - higher amplitude in one ear
outer ear � front vs back position
large spherical bushy cells � bipolar in the medial superior olivary nucleus
dual excitatory
AP � limited conduction velocity������� delay lines
offset ITD coding
barn owls � Konishi soundproof IR-lit lab
heightened sense of sound localisation
biologically plausible situation: free field rather than closed sound delivery system
top-down approach � started by recordings in the midbrain (inferior colliculus)
very small receptive field neurons
unusual � computational maps of auditory space
owls � opening to left ear is higher
ITD + IID � sound azimuths + elevation (different planes)
why two eyes of equal spatial acuity???
why not 1�???