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Rucci et al. present an algorithm which performs auditory localization and combines auditory and visual localization in a common SC map. The mapping between the representations is learned using value-dependent learning.

Rucci et al.'s neural network learns how to align ICx and SC (OT) maps by means of value-dependent learning: The value signal depends on whether the target was in the fovea after a saccade.

Rucci et al.'s model of learning to combine ICx and SC maps does not take into account the point-to-point projections from SC to ICx reported later by Knudsen et al.

The external nucleus of the inferior colliculus (ICx) used to be called the space-mapped region of the nucleus mesencephalicus lateralis pars dorsalis (MLD),

Like many other auditory brain regions, the IC is tonotopically organized, except for ICx.

Rucci et al.'s system comprises artificial neural populations modeling MSO (aka. the nucleus laminaris), the central nucleus of the inferior colliculus (ICc), the external nucleus of the inferior colliculus (ICx), the retina, and the superior colliculus (SC, aka. the optic tectum). The population modeling the SC is split into a sensory and a motor subpopulation.

In Rucci et al.'s system, the MSO is modeled by computing Fourier transforms for each of the auditory signals. The activity of the MSO neurons is then determined by their individual preferred frequency and ITD and computed directly from the Fourier-transformed data.

In Rucci et al.'s model, neural weights are updated between neural populations modeling

  • ICC and ICx
  • sensory and motor SC.

ICx projects to intermediate and deep layers of SC.

The shift in the auditory map in ICx comes with changed projections from ICc to ICx.

SC receives auditory localization-related inputs from the IC.

The external nucleus of the inferior colliculus (ICx) of the barn owl represents a map of auditory space.

The map of auditory space in the nucleus of the inferior colliculus (ICx) is calibrated by visual experience.

The optic tectum (OT) receives information on sound source localization from ICx.

Hyde and Knudsen found that there is a point-to-point projection from OT to IC.

A faithful model of the SC should probably adapt the mapping of auditory space in the SC and in another model representing ICx.

Mammals seem to have SC-IC connectivity analogous to that of the barn owl.

Audio-visual map registration has its limits: strong distortions of natural perception can only partially be compensated through adaptation.

Visual localization has much greater precision and reliability than auditory localization. This seems to be one reason for vision guiding hearing (in this particular context) and not the other way around.