Figure 5. Corollary discharge used for sensory analysis and stability.

Aa | The illustration on the left is of the mormyrid species Gnathonemus petersii. The mormyrid generates electrical signals to probe the aquatic environment. Multiple types of corollary discharge (CD) of electrolocation commands allow the fish to gate, amplify or predict the return signal. The schematic of the mormyrid brain on the right illustrates pathways of the electrosensory system. Electric organ CD (EOCD; shown in blue) from the electric-organ motor command centre (which generates the motor command, shown in purple) reaches cellular networks of the electrosensory lateral line lobe (ELL), following which a host of interactions with electrosensory input (shown in orange) occur. Ab | The CD circuit that connects the command centre and the ELL is represented as a link between lower motor and lower sensory levels. Ba | The illustration on the left is of the bat species Rhinolophus rouxi. During high-speed flight, this bat uses sound to hunt. It compares a CD of the sonic probe to the measured echo to interpret the acoustic input. The schematic on the right shows how CD is used in this system. CD (shown in blue) represents the efferent motor command and innervates the inferior colliculus, where it is compared with the echo input. Differences between the CD and the input (shown as dashed lines) are analysed by higher-order centres to estimate the size, location and speed of the object that caused the echo. Bb | The CD signals could arise from any number of subcortical and cortical structures, corresponding to multiple pathways emerging from both higher and lower motor levels.