GATING OF SENSORY RESPONSES OF DESCENDING BRAIN NEURONS DURING WALKING IN CRICKETS

Single descending brain neurones were recorded and stained intracellul arly in the neck connectives of crickets while they walked upon a styr ofoam ball under open-loop conditions, The animal's translational and rotational velocities were measured simultaneously, and various stimul i were used to investigate the neuronal response characteristics. Stim ulation with a moving grating or an artificial calling song of 5 kHz i nduced optomotor behaviour and positive phonotaxis. An acoustic stimul us of 20 kHz elicited negative phonotaxis. We report the first clear e vidence for behaviourally dependent gating of sensory responses of ide ntified descending brain neurones. Most descending cells only responde d to visual stimuli or to an artificial calling song of 5 kHz while th e animal was walking, indicating that the responses to these stimuli w ere gated by the walking activity of the animal, In contrast to this, responses to stimuli that elicit negative phonotaxis, such as acoustic stimuli of 20 kHz, were not gated. This indicates that the gating of sensory responses in these cells depends on the behavioural context of the stimulus. From these findings, we conclude that significant infor mation about the properties of sensory processing in higher-order neur ones can only be gained from tests in behaviourally relevant paradigms . Important characteristics might otherwise be missed, thus leading to misinterpretations regarding their function.