A shared speed encoding model for running and backing away behaviours in segregated neural circuits.

Area of Science:

• Neuroscience
• Motor Control
• Computational Neuroscience

Background:

• The neural basis for encoding behavioral intensity, such as running speed, remains poorly understood.
• The dorsal periaqueductal grey (dPAG) circuit, receiving input from the temporal association cortex (TeA) and superior colliculus (SC), is known to initiate running behavior.

Purpose of the Study:

• To investigate how neuronal firing patterns within the dPAG circuit encode behavioral intensity.
• To elucidate the specific neural mechanisms underlying different motor behaviors and their transitions.

Main Methods:

• In vivo loose-patch recordings were performed in mice.
• Circuit manipulations were employed to activate specific neuronal populations.
• Neuronal firing rates were correlated with running speed.
• A computational model was developed to describe the firing-speed relationship.

Main Results:

• Activation of the dPAG circuit induced two distinct behavioral patterns: backing away and rebound running.
• CaMKIIα neurons in the dPAG act as distinct "behavioral units," controlling running and backing away.
• Unidirectional inhibition from the backing away unit to the running unit, mediated by somatostatin (SOM) neurons, enables transitions between four behavioral states (running, backing away, stopping, rebound running).
• Both running and backing away behaviors adhere to a unified motor encoding model described by a single-phase association equation.

Conclusions:

• The dPAG circuit employs distinct neuronal units and inhibitory interactions to control and transition between different motor behaviors.
• A unified motor encoding model explains the relationship between neuronal activity and behavioral intensity for both running and backing away.