Sensorimotor integration in the primate superior colliculus. II. Coordinates of auditory signals.
Level 5 - mechanism / opinion, no new human data
Animal single-unit neurophysiology study (Level 5 under Oxford CEBM criteria).
PubMed 3559680 · doi:10.1152/jn.1987.57.1.35
What was done
Extracellular single-unit recordings were performed in monkey superior colliculus (SC) and inferior colliculus while animals performed delayed saccades to auditory or visual targets with a stationary head in a darkened room. Auditory receptive fields were mapped during fixation at one of three horizontal targets spaced 24 degrees apart to determine whether auditory signals are encoded in head-centered or motor-error coordinates. Potential confounding effects of ear movements were tested by mechanically restraining the pinnae.
What was found
For 99 of 121 SC cells, the spatial location of the auditory receptive field was significantly altered by eye position in the orbit. In contrast, 5 sound-sensitive neurons in the inferior colliculus showed no receptive field shifts with eye position. Mechanical restraint of the pinnae did not abolish the eye-position effect in SC neurons. The average shift of the collicular auditory receptive field was 12.9 degrees in response to a 24-degree change in eye position.
Why it matters
These findings show that auditory spatial representations in the primate superior colliculus are not purely head-centered, but instead undergo coordinate transformations linked to gaze position, likely reflecting an intermediate stage in converting sensory input into motor commands for saccades.
Limits
The total number of monkeys tested is not stated in the abstract. The sample of inferior colliculus control neurons was very small (n = 5). The 12.9-degree receptive field shift only partially matched the 24-degree eye displacement, leaving the precise computational transformation incomplete and subject to alternative interpretations.
Cited by
- supports The superior colliculus is responsive to both visual and auditory stimuli, and its auditory receptive fields shift depending on eye position.
- supports Auditory signals in the superior colliculus are modulated by eye position at the time a sound is presented.