NTT Research and Development 2009 Review of Activities

Overview

Humans have the ability to quickly identify the location of object that emits sound and light at the same time. This is because the brain is hardwired with a scheme for integrating location information from multiple sensory modalities — hearing, seeing, feeling, etc. This integration is processed in a brain region, the superior colliculus^*1, by way of a common neurological representation called a space map^*2. Acoustic information regarding the location of sounds captured by our two ears is converted to form the space map in the superior colliculus. Yet, until now everything we knew about this conversion process was derived from studies on birds. Based on neurophysiological studies on gerbils, we found this process in mammals works differently from the textbook thinking of the past derived from birds. This is a major new insight in our understanding of the space perception mechanism of mammals, including of humans.

Features

• Investigated the map forming process by examining multiple stages/multiple regions of the brain from the ears to the superior colliculus
• Discovered the auditory map is gradually formed over neural pathways in the brain, and completed in the superior colliculus
• Findings revealed the map is incomplete until a relatively late stage for neural processing, so past thinking must be revised
• Applied latest acoustic space techniques (virtual reality) to animal experiments
• New insight into brain mechanisms for space perception governing reflexive behavior of humans

Application scenarios

• Design of audio, video spatial devices that take reflexive actions into account
• Development of binaural hearing aids providing effective sense of direction

• *1 superior colliculus: A region of the brain; known as the nucleus where multiple sensory modalities are processed.
• *2 space map: Mapping representation of neuro-anatomical locations reflecting physical spatial locations.