Fig. 7.

Hindbrain electrosensory neurons respond to envelopes. (A) Left: morphology of different electrosensory lateral line lobe (ELL) pyramidal cell classes. Note the large differences in dendritic tree length. Superficial pyramidal cells have the largest dendritic trees and are found superficially while deep pyramidal cells have the smallest dendritic trees and are found deep in the pyramidal cell layer. Intermediate pyramidal cells are in between. Right: firing rate and dendritic tree length are strongly negatively correlated. (B) Responses of example superficial (left) and deep (right) ELL pyramidal cells. (C) Phase histograms from these same cells to the AM stimulus. Note that only the superficial pyramidal cell (left) displays strong phase locking because the count is zero for phases between −π/2 and π/2. (D) Envelope response as a function of AM response for ELL pyramidal cells. Note that all cells respond to both. (E) Proposed neural circuit by which ELL pyramidal cells can respond to envelopes. An inhibitory interneuron, the ovoid cell, responds to the envelope via the non-linear action potential generation mechanism and sends this information primarily to superficial ELL pyramidal cells.