In the natural world, most animals interact and orient to objects in three dimensional space. Previous work has implicated the midbrain superior colliculus (SC) in orienting an animal towards salient stimuli in two dimensions (azimuth and elevation). The majority of prior work on the SC has employed 2 dimensional, artificial stimuli which has limited the relevance of these studies to real-world, three dimensional conditions. Using the flying echolocating bat as a model, we provide evidence for the role of the superior colliculus as a sensorimotor integration center for orienting an animal in 3D space.
To understand the role of the SC in 3D orienting behaviors we utilized the following experimental setup.
1) Bats are trained to fly across the room and land on a platform where they are rewarded.
2) High speed video cameras (Miro, Vision Research) and motion capture systems (Vicon) are used to reconstruct the flight trajectory of the bat and also capture the 3D head aim vector while the bat is flying.
3) Ultrasonic microphones (Pettersson Elektronik) are used to capture the bats sonar vocalizations and beam pattern.
4) Once bats are trained to perform the behavior, a 16 channel NeuroNexus probe is chronically implanted into the right superior colliculus.
5) A TBSI telemetry system linked with Plexon A/D are used to record neural data.
The problem of understanding echo sensory space in a flying bat
Once the bat's echo acoustic scene is recreated we computed spatial tuning profiles of different neurons.
The figure below shows spatial tuning profiles of 2 simultaneously recorded neurons during one experimental session.