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

Abstract

Animals negotiating complex natural terrain must consider cues around them and alter movement parameters accordingly. 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. In previous studies, CC neurons in various insects responded to visual, chemical, and mechanical stimuli, and genetic or physical lesions affected locomotor behaviors. Additionally, electrical stimulation of the CC led to malformed chirping movements by crickets, and pharmacological stimulation evoked stridulation in grasshoppers, 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.

Electrolytic lesions within central complex neuropils of the cockroach brain affect negotiation of barriers

“…Multi-unit recordings in the FB and EB described numerous multi-sensory units that are responsive to antennal movement as well as to changes in ambient light (Ritzmann et al, 2008). However, these structures are not solely sensory, as the FB and EB receive connections from motor reporter neurons arising from the thoracic ganglia (Homberg, 1994), and stimulation in the CC can produce leg movements or calling song in crickets (Bender et al, 2010;Heinrich et al, 2001;Huber, 1960;Weinrich et al, 2008). Furthermore, the CC and the lateral accessory lobe (LAL), which receives projections from the CC, send axons to the ventral body (a pre-motor region of the brain) (Homberg, 1994;Okada et al, 2003;Strausfeld, 1999).…”

Simultaneous Long-term Recordings at Two Neuronal Processing Stages in Behaving Honeybees

“…Compared to silicon probes commonly used for extracellular recordings in much larger insects like the hawk moth, locust and cockroach 40,[49][50][51] the described micro wire-electrodes are smaller, flexible and can cope easily with potential brain movements and, thus, can be reliably used in small social insects like bees and ants that show a much broader behavioral repertoire. Most silicone probes have sharp shank like structures cutting axons and neural tissue along their insertion channel, while the described micro wires are round, flexible and smaller and are hence less harmful to the surrounding tissue which is a clear advantage if the goal is to study long-term plasticity in an intact and behaving animal.…”

Extracellular Wire Tetrode Recording in Brain of Freely Walking Insects

“…While previous electrophysiological studies on the CC or other regions of the insect brain have provided us with insights into the central control of behavior, most of them were performed in either restrained preparations 9,11 or tethered ones 10,14 . As a result, the animal's sensory experience and physiological state could be very different from those in a natural setting.…”

“…Correlate specific electrical impulses to the activity of single neurons. Follow spike sorting procedures laid out in detail elsewhere 10,14,18 . Use the program KlustaKwik (version 1.5, author K. Harris, Rutgers University) to generate initial, automated clustering.…”

“…In two previous projects, we used bundles of fine wires forming a tetrode to accomplish similar recording properties but in a more robust arrangement. These tetrode bundles allowed us to record from tethered cockroaches and relate CC unit activity to changes in walking speed 14 and turning behavior resulting from antennal contact with a rod 10 .…”