Auditory motion direction detection requires much larger angular sweeps than static sound localization does.

Evidence

The angular range covered by the noise sweeps in our experiments exerted the strongest effect on the owl’s sensitivity. To solve the task, the angular range had to be at least 24°. The angular range necessary for motion direction discrimination was much larger than the mean error for locating points in azimuth as indicated by the head orienting response towards the sound source elicited by broadband noise bursts (Knudsen et al. 1979 ) or by the owl’s minimum audible angle (Bala et al. 2007 ). Using a pupillary dilation response, Bala et al. ( 2007 ) measured a minimum audible angle of 3° in azimuth. In the horizontal plain, Knudsen et al. ( 1979 ) observed a localization error being as low as 2° for broadband sounds in the frontal direction (open-loop conditions). The azimuth localization error increased to 6° if the target location was 50° lateral. The small localization error in comparison to the minimum angular range needed for motion direction discrimination suggests that at least partially different neuronal circuits are involved in the location of stationary and of moving sound sources. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3181

The angular range covered by the noise sweeps in our experiments exerted the strongest effect on the owl’s sensitivity. To solve the task, the angular range had to be at least 24°. The angular range necessary for motion direction discrimination was much larger than the mean error for locating points in azimuth as indicated by the head orienting response towards the sound source elicited by broadband noise bursts (Knudsen et al. 1979 ) or by the owl’s minimum audible angle (Bala et al. 2007 ). Using a pupillary dilation response, Bala et al. ( 2007 ) measured a minimum audible angle of 3° in azimuth. In the horizontal plain, Knudsen et al. ( 1979 ) observed a localization error being as low as 2° for broadband sounds in the frontal direction (open-loop conditions). The azimuth localization error increased to 6° if the target location was 50° lateral. The small localization error in comparison to the minimum angular range needed for motion direction discrimination suggests that at least partially different neuronal circuits are involved in the location of stationary and of moving sound sources. … Furthermore, the large difference between the localization accuracy and the minimum angular range needed for motion direction discrimination renders it unlikely that the owls solve the motion direction discrimination task by a “snapshot” mechanism. The snapshot hypothesis suggests that the processing of motion simply relies on comparing starting and endpoint of the moving stimulus (e.g., Perrot and Marlborough 1989 ). The snapshot hypothesis was also dismissed in human psychophysical studies determining the minimum audible movement angle (reviewed by Middlebrooks and Green 1991 ). The difference between the barn owl’s sensitivity for comparing angular locations of static sounds (Bala et al. 2007 ) and the large angular range needed for direction discrimination (present study) suggests that the snapshot hypothesis does not apply to barn owls. — Dijk, Pim van, Physiology, Psychoacoustics and…, 3216

Categorization

• XREF: Connects to the reader’s interest in what neural circuits distinguish — static (stationary) sound location vs. motion direction processing appear to be dissociable systems in the same brain.
• QUESTION: Worth chasing: does this static-vs-motion circuit dissociation generalize to humans, where ‘binaural sluggishness’ (slow time constant for ITD changes) is a known phenomenon?
• corroborated: 2 independent passages support this claim — Dijk, Pim van, Physiology, Psychoacoustics and…, 3181; Dijk, Pim van, Physiology, Psychoacoustics and…, 3216