Neural Activity in the Central Complex of the Insect Brain Is Linked to Locomotor Changes

Animals negotiating complex natural terrain must consider cues around them and alter movement parameters accordingly [1, 2]. In the arthropod brain, the central complex (CC) receives bilateral sensory relays and sits immediately upstream of premotor areas, suggesting that it may be involved in the context-dependent control of behavior [3]. In previous studies, CC neurons in various insects responded to visual, chemical, and mechanical stimuli [4-7], and genetic or physical lesions affected locomotor behaviors [8-11]. Additionally, electrical stimulation of the CC led to malformed chirping movements by crickets [12], and pharmacological stimulation evoked stridulation in grasshoppers [13], but no more precise relationship has been documented between neural activity in the CC and movements in a behaving animal. We performed tetrode recordings from the CC of cockroaches walking in place on a slippery surface. Neural activity in the CC was strongly correlated with, and in some cases predictive of, stepping frequency. Electrical stimulation of these areas also evoked or modified walking. Many of the same neural units responded to tactile antennal stimulation while the animal was standing still but became unresponsive during walking. Therefore, these CC units are unlikely to be reporting only sensory signals, but their activity may be directing changes in locomotion based on sensory inputs.