Chemotopic Organization in the Bulbar Gustatory Relay of the Rat

Abstract

IN the relay nuclei of the mammalian auditory system, one representation of sound frequency is the location of maximum neural activity within a nucleus. This spatial representation of stimulus quality is called tonotopic organization¹. In the gustatory system, change in the response magnitudes to chemicals as a function of change in tongue region stimulated has already been demonstrated in the nucleus of the fasciculus solitarius (NFS)². The preliminary data to be presented here indicate that discrete sub-areas which are highly responsive to some chemicals are located in the anterior tongue zone of the bulbar gustatory relay of the rat. The recording and stimulating techniques have been described previously^2,3. The active electrode was a nickel-chrome wire, 25.4µ in diameter, insulated except at the tip. The multi-unit neural activity was led through an electronic summator⁴ into a recording milliammeter. The stimuli were liquids which flowed over the anterior tongue through a tongue chamber.