Prey location in Owls - Hardware and Mechanisms

Auditory processing for Owl Prey Location

The exact location of a sound source is determined with regard to azimuth (i.e., angle in horizontal plane) and elevation. The system conducts a binaural comparison with respect to:

• Sound intensity (elevation)
• Time of arrival (azimuth)
• Phase difference (azimuth)

Brain systems:

Cochlear nucleus: The cochlear nucleus on each side processes a temporal train of sound information from that ear only. This information is then channelled into two parallel paths, which respectively analyze:

• Disparity in binaural intensity: Angular nucleus, Posterior lateral lemniscal nucleus, to the inferior colliculus of the midbrain
• Disparity in binaural arrival time/phase difference: Magnocellular nucleus, Laminar nucleus, Anterior lateral lemniscal nucleus, to the inferior colliculus of the midbrain

Neurons of the Angular nucleus are sensitive to different sound intensities and not to frequency information

Magnocellular nucleus neurons produce phase-locked responses to monaural input but are not very sensitivity to differences in intensity. The laminar nucleus integrates phase information from the two ears using coincidence detection. The main feature of this design utilizes delay lines that slow the signal from one ear relative to that from the other. Binaural fusion <integration of sound information received by the two ears> is achieved by feeding the input from one ear into one side of a symmetrical, laminar structure and the second ear information from the other side. The area of the array in which the two inputs coincide will lie in the center if the sound arrives at the same time at both ears, or it will lie towards one or the other side of the structure if there is a disparity in arrival time between the ears.

Neurons in the inferior colliculus are arranged in somatotopic fashion where both azimuth and elevation are mapped for an estimate of the precise 3 dimensional location.