A monaural space map in the guinea-pig superior colliculus.

Area of Science:

• Neuroscience
• Auditory Neuroscience
• Sensory Systems

Background:

• The superior colliculus (SC) in guinea pigs contains a topographical map of auditory space.
• Previous research established this map relies on binaural cues for azimuthal representation.

Purpose of the Study:

• To investigate the roles of monaural and binaural cues in generating the auditory space map in the guinea pig SC.
• To determine the contribution of individual ear inputs and external ear structures to auditory spatial processing.

Main Methods:

• Experiments were conducted under anechoic conditions using a horizontal loudspeaker array.
• Auditory spatial representations were studied in the deep layers of the SC.
• Monaural occlusion and unilateral cochlear destruction were performed.
• Cochlear microphonic (CM) potentials were measured.
• The effects of removing the pinna and concha were assessed.

Main Results:

• Binaural cues are essential for suprathreshold auditory spatial representation (>20 dB above threshold).
• A threshold-based, monaural auditory space map exists, independent of binaural input.
• Removal of the contralateral pinna and concha abolished the monaural map, indicating their importance.
• Pinna and concha influence spectral patterns at the tympanic membrane, potentially aiding sound localization.

Conclusions:

• Auditory spatial maps in the guinea pig SC are constructed from both binaural and monaural cues.
• Monaural cues, particularly those processed by the pinna and concha, are critical for low-threshold sound localization.
• The SC integrates complex auditory spatial information for effective navigation and environmental awareness.