The superior colliculus (SC) plays a critical role in integrating visual and auditory inputs to assess
saliency and promote action. However, the underlying cell types and circuitry used to encode multimodal
information and the mechanisms used during development to form the circuitry remain largely unknown.
The recent explosion of new technology in mouse genetics allows neurons and circuits to be manipulated
and specific genes to be removed, but surprisingly, the mouse has not yet been shown to be a model to
study sensory integration. The overall objective of this proposal is to determine the functional properties of
visual/auditory multisensory neurons in the mouse SC, to determine how these properties change in a
mouse line genetically engineered to test hypotheses about how these properties develop. The central
hypothesis to be tested is that visual and auditory information converge in the mouse SC to create
multimodal neurons that form a multimodal map of space, and that map alignment forms using a visual map
The goal of Specific Aim 1 is to identify, and determine the response properties of, mouse SC
visual/auditory multimodal neurons. To accomplish this, awake, head-fixed mice, allowed to freely run on a
treadmill, will be stimulated with spatially/temporally/spectrally restricted visual and auditory stimuli while the
SC neuronal response properties are being recorded using high-density silicon probes. The SC neural
activity of ~170 neurons will be simultaneously recorded from in each mouse, using high-density silicon
probes. Data analysis will determine the spatiotemporal receptive fields of the visual, auditory and
visual/auditory multimodal neurons, their sensory integration properties, and the spatial/temporal/spectral
components of the stimulus needed to elicit integration. Innovations include the use of virtual auditory space
stimuli to present localized sound, and the recording and data analysis methods used.
Experiments proposed in Specific Aim 2 will test the longstanding hypothesis that the alignment and
integration of the visual and auditory inputs in the SC form using the visual map as a template. The
approach will be to record and analyze the auditory and visual response properties as in Aim 1 but from
transgenic mice engineered to have a duplicated visual map in the SC, and determine if the auditory map
rearranges to align and integrate with the duplicated visual map.
The proposed research is significant because it will provide the first comprehensive analysis of the receptive
field properties of visual/auditory integrative neurons in the mouse SC, and will determine the general
principles of how these properties develop. The results of this work can be exploited immediately and in the
future, to determine the underlying circuitry used to integrate sensory information, the specific cell types
involved, and how the state of the animal modulates these properties.