280 likes | 293 Views
Auditory Computation. Overview: I. Physiological Foundations II. Elements of Auditory Computation. I. Physiological Foundations. Auditory perception – subjective experience :
E N D
Auditory Computation Overview: I. Physiological Foundations II. Elements of Auditory Computation
I. Physiological Foundations Auditory perception – subjective experience: “What you hear is not what is out there in the outside world, but instead what has been created all inside of your head.” What is the sound of falling tree in no-man’s land?
What is sound? • Sound is the psychological sensation that is internally generated in the brain as a response to an external physical stimulus called the ‘sound’ wave. • Two necessary ingredients of sound: • (1) Source • (2) Listener
A sound wave is the pressure cycle (compression & rarefaction) of air molecules.
Steps of Auditory Computation • 1: Outer ear (eardrum) (sound detection) • 2: Middle ear (sound amplification) • 3: Inner ear (neural pulse generation) • 4: Superior olive (relay station - interaural mixing) • 5: Auditory cortex (conscious perception)
Inner Ear -- Cochlea (coiled tube) • - neural pulse generation
Steps of Auditory Computation • 1: Outer ear (eardrum) (sound detection) • 2: Middle ear (sound amplification) • 3: Inner ear (neural pulse generation) • 4: Superior olive (relay station - interaural mixing) • Q: What computational advantages?? • 5: Auditory cortex (conscious perception)
II. Elements of Auditory Computation 1. Frequency-to-location coding 2. Frequency sensitive cells 3. Frequency coding in cortex 4. Sound localization
1. Frequency-to-location Coding • - Each group of cells has its own fundamental frequency, to which it maximally responds. Note the nonlinearity of the map. Why nonlinear??
Topographic mapping of auditory information: • Similar frequencies are mapped to nearby points in the cortex • Q: What computational advantages of such topo map??
4. Sound Localization • by interaural time difference(ITD)
Neural Circuit for Computing ITD • via Time-to-Position Coding: • Coincidence detector • for each frequency channel -- physiologically confirmed
Ambiguity Resolution by Across-frequency Comparison • -- physiologically confirmed