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

Abstract

SUMMARYAnimals must negotiate obstacles in their path in order to successfully function within natural environments. These actions require transitions from walking to other behaviors, many of which are more involved than simple reflexes. For these behaviors to be successful, insects must evaluate objects in their path and then use that information to change posture or re-direct leg movements. Some of this control may occur within a region of the brain known as the central complex (CC). We used discrete electrolytic lesions to examine the role of certain sub-regions of the CC in various obstacle negotiation behaviors. We found that cockroaches with lesions to the protocerebral bridge (PB) and ellipsoid body (EB) exhibit abnormalities in turning and dealing with shelf-like objects; whereas, individuals with lesions to the fan-shaped body (FB) and lateral accessory lobe (LAL), exhibit abnormalities of those behaviors as well as climbing over blocks and up walls to a horizontal plane. Abnormalities in block climbing include decreased success rate, changes in climbing strategy, and delayed response to the block. Increases in these abnormal behaviors were significant in individuals with lesions to the FB and LAL. Although turning abnormalities are present in individuals with lesions to the LAL, EB and the lateral region of the FB, there are some differences in how these deficits present. For instance, the turning deficits seen in individuals with lateral FB lesions only occurred when turning in the direction opposite to the side of the brain on which the lesion occurred. By contrast, individuals with lesions to the EB and LAL exhibited turning abnormalities in both directions. Lesions in the medial region of the FB did not result in directional turning deficits, but in abnormalities in block climbing. Supplementary material available online at

What can parasitoid wasps teach us about decision-making in insects?

“…In several behavioural paradigms, flies from mutant strains with altered structure of the CBC walk more slowly than wild-type flies, react less quickly to changing stimuli during flight and show altered orientation behaviour toward landmarks (Strauss, 2002). Harley and Ritzmann (Harley and Ritzmann, 2010) reported recently that cockroaches with lesions to the CBC exhibit abnormalities in turning and climbing, and Bender et al (Bender et al, 2010) used chronic multi-neuron extracellular recording, a technique that provides suitable temporal resolution, to show that neural activity in the CBC is strongly correlated with and sometimes predictive of stepping frequency. Last but not least, electrical stimulation of the CBC evokes or modifies walking.…”

Neural activity in the central complex of the cockroach brain is linked to turning behaviors

“…This suggests that an intact brain is both necessary and sufficient to control or correct asymmetrical movements. In cockroaches, discrete electrolytic lesions on the midline of the EB and FB altered climbing but had little or no effect on turning behaviors (Harley and Ritzmann, 2010). However, lesions in the lateral FB led to turning deficits.…”

“…As our data were opposite to the previously reported results, we were particularly careful to avoid such reversals. However, a re-examination of the sections used by Harley and Ritzmann (Harley and Ritzmann, 2010) could not eliminate the possibility that a reversal occurred in those data (C. M. Harley, personal communication). As the ganglia that were studied were all completely sectioned, it is impossible to resolve this issue with the original data at this time.…”

“…Flies with a defective CC failed to correct their walking path, resulting in severe circling behavior even in the presence of attractive cues (Strauss and Heisenberg, 1993;Strauss, 2002). Discrete electrolytic lesions in cockroaches revealed site-specific deficits in a range of turning and climbing behaviors (Harley and Ritzmann, 2010).…”

Encoding wide-field motion and direction in the central complex of the cockroach, Blaberous discoidalis

“…In the cockroach, Blaberus discoidalis, further lesion studies have implicated the CX in forward walking, turning, climbing and tunnelling (Ridgel et al, 2007;Harley and Ritzmann, 2010). Moreover, extracellular neural activity recorded in the CX has been correlated with walking speed, turning direction and climbing (Bender et al, 2010;Guo and Ritzmann, 2013;Guo et al, 2014).…”