Fig. 6.

A mechanistic view of the neural codes for the efficient navigation strategy. a A trajectory of a navigating animal in a Gaussian spatial gradient of an attractant. Dashed lines mark turning events. b The temporal gradient sensed by the navigating worm in search for the attractant source. c AWA and AWC dynamics in response to the sensed gradient. AWA stochastic pulsatile activity controls the worm forward movement. AWA adapts to the first derivative of the gradient, so when the gradient begins to flatten (and although the first derivative is still positive), AWA activity decays, thereby promoting a turn. In case the turn steers the worm away from the target, the negative gradient is immediately sensed by the AWC neuron, which responds robustly and deterministically to promote a second turn. Thus, the orchestrated activity of AWA and AWC underlies the efficient navigation strategy in chemical gradients