Responses of neurons in the visual cortex of an echolocating bat

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Rousettus aegyptiacus (suborder Megachiroptera) has well developed nocturnal vision but is capable of facultative echolocation when insufficient light is available for visual guidance. About 150 single units were studied under scotopic conditions using tungsten microelectrodes. Most recordings were from awake animals paralyzed with Flaxedil; others were from bats lightly anesthetized with sodium pentobarbital. The retinotopic projection to the cortex is rotated 90° from that reported for most other animals, making the anterior portion of the visual cortex binocular. Visual receptive fields (RF) varied in size from those subtending less than 1 degree of visual angle to a few encompassing most of the visual field. Simple units whose RF could be mapped into anatagonistic regions by flashed stationary stimuli were rare. All units responded best to moving visual stimuli. About 20% of these showed no clear directional selectivity. Of the directionally selective units, about one third had a null direction 90° from the preferred direction: in the remainder the null direction was 180° from the preferred direction. Velocity of stimulus movement varied in importance. Many directional units also appeared to be orientation selective. Most of these had a complex RF, although a number of hypercomplex units were also found. Only a few cells responded to auditory as well as visual stimuli.

Original languageEnglish (US)
Pages (from-to)No. 1244
JournalFederation Proceedings
Issue number3
StatePublished - Jan 1 1977

ASJC Scopus subject areas

  • Medicine(all)

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