@article {48192, title = {Electrophoresis of polar fluorescent tracers through the nerve sheath labels neuronal populations for anatomical and functional imaging.}, journal = {Scientific Reports}, volume = {7}, year = {2017}, month = {2017 Jan 13}, pages = {40433}, abstract = {

The delivery of tracers into populations of neurons is essential to visualize their anatomy and analyze their function. In some model systems genetically-targeted expression of fluorescent proteins is the method of choice; however, these genetic tools are not available for most organisms and alternative labeling methods are very limited. Here we describe a new method for neuronal labelling by electrophoretic dye delivery from a suction electrode directly through the neuronal sheath of nerves and ganglia in insects. Polar tracer molecules were delivered into the locust auditory nerve without destroying its function, simultaneously staining peripheral sensory structures and central axonal projections. Local neuron populations could be labelled directly through the surface of the brain, and in-vivo optical imaging of sound-evoked activity was achieved through the electrophoretic delivery of calcium indicators. The method provides a new tool for studying how stimuli are processed in peripheral and central sensory pathways and is a significant advance for the study of nervous systems in non-model organisms.

}, issn = {2045-2322}, doi = {10.1038/srep40433}, author = {Isaacson, Matthew D and Hedwig, Berthold} } @article {47850, title = {Behavioural integration of auditory and antennal stimulation during phonotaxis in the field cricket Gryllus bimaculatus (DeGeer).}, journal = {The Journal of Experimental Biology}, volume = {219}, year = {2016}, month = {2016 Sep 8}, pages = {3575-86}, abstract = {

Animals need to flexibly respond to stimuli from their environment without compromising behavioural consistency. For example, female crickets orienting toward a conspecific male{\textquoteright}s calling song in search of a mating partner need to stay responsive to other signals that provide information about obstacles and predators. Here, we investigate how spontaneously walking crickets and crickets engaging in acoustically guided goal-directed navigation, i.e. phonotaxis, respond to mechanosensory stimuli detected by their long antennae. We monitored walking behaviour of female crickets on a trackball during lateral antennal stimulation, which was achieved by moving a wire mesh transiently into reach of one antenna. During antennal stimulation alone, females reduced their walking speed, oriented toward the object and actively explored it with antennal movements. Additionally, some crickets initially turned away from the approaching object. Females responded in a similar way when the antennal stimulus was presented during ongoing phonotaxis: forward velocity was reduced and phonotactic steering was suppressed while the females turned toward and explored the object. Further, rapid steering bouts to individual chirps, typical for female phonotaxis, no longer occurred.Our data reveals that in this experimental situation antennal stimulation overrides phonotaxis for extended time periods. Phonotaxis in natural environments, which require the integration of multiple sensory cues, may therefore be more variable than phonotaxis measured under ideal laboratory conditions. Combining this new behavioural paradigm with neurophysiological methods will show where the sensory-motor integration of antennal and acoustic stimulation occurs and how this is achieved on a mechanistic level.

}, issn = {1477-9145}, doi = {10.1242/jeb.141606}, author = {Haberkern, Hannah and Hedwig, Berthold} } @article {47161, title = {Imaging fictive locomotor patterns in larval Drosophila.}, journal = {Journal of Neurophysiology}, volume = {114}, year = {2015}, month = {2015 Nov 06}, pages = {2564-77}, abstract = {

We have established a preparation in larval Drosophila to monitor fictive locomotion simultaneously across abdominal and thoracic segments of the isolated CNS with genetically encoded Ca(2+) indicators. The Ca(2+) signals closely followed spiking activity measured electrophysiologically in nerve roots. Three motor patterns are analyzed. Two comprise waves of Ca(2+) signals that progress along the longitudinal body axis in a posterior-to-anterior or anterior-to-posterior direction. These waves had statistically indistinguishable intersegmental phase delays compared with segmental contractions during forward and backward crawling behavior, despite being \~{}10 times slower. During these waves, motor neurons of the dorsal longitudinal and transverse muscles were active in the same order as the muscle groups are recruited during crawling behavior. A third fictive motor pattern exhibits a left-right asymmetry across segments and bears similarities with turning behavior in intact larvae, occurring equally frequently and involving asymmetry in the same segments. Ablation of the segments in which forward and backward waves of Ca(2+) signals were normally initiated did not eliminate production of Ca(2+) waves. When the brain and subesophageal ganglion (SOG) were removed, the remaining ganglia retained the ability to produce both forward and backward waves of motor activity, although the speed and frequency of waves changed. Bilateral asymmetry of activity was reduced when the brain was removed and abolished when the SOG was removed. This work paves the way to studying the neural and genetic underpinnings of segmentally coordinated motor pattern generation in Drosophila with imaging techniques.

}, issn = {1522-1598}, doi = {10.1152/jn.00731.2015}, author = {Pulver, Stefan R and Bayley, Timothy G and Taylor, Adam L and Berni, Jimena and Bate, Michael and Hedwig, Berthold} } @article {45053, title = {Phase shifts in binaural stimuli provide directional cues for sound localisation in the field cricket Gryllus bimaculatus.}, journal = {Journal of Experimental Biology}, volume = {217}, year = {2014}, month = {2014 Jul 1}, pages = {2390-8}, abstract = {

The cricket{\textquoteright}s auditory system is a highly directional pressure difference receiver whose function is hypothesised to depend on phase relationships between the sound waves propagating through the auditory trachea that connects the left and right hearing organs. We tested this hypothesis by measuring the effect of experimentally constructed phase shifts in acoustic stimuli on phonotactic behavior of Gryllus bimaculatus, the oscillatory response patterns of the tympanic membrane, and the activity of the auditory afferents. The same artificial calling song was played simultaneously at the left and right sides of the cricket, but one sound pattern was shifted in phase by 90 deg (carrier frequencies between 3.6 and 5.4 kHz). All three levels of auditory processing are sensitive to experimentally induced acoustic phase shifts, and the response characteristics are dependent on the carrier frequency of the sound stimulus. At lower frequencies, crickets steered away from the sound leading in phase, while tympanic membrane vibrations and auditory afferent responses were smaller when the ipsilateral sound was leading. In contrast, opposite responses were observed at higher frequencies in all three levels of auditory processing. Minimal responses occurred near the carrier frequency of the cricket{\textquoteright}s calling song, suggesting a stability at this frequency. Our results indicate that crickets may use directional cues arising from phase shifts in acoustic signals for sound localisation, and that the response properties of pressure difference receivers may be analysed with phase-shifted sound stimuli to further our understanding of how insect auditory systems are adapted for directional processing.

}, issn = {1477-9145}, doi = {10.1242/jeb.101402}, author = {Seagraves, Kelly M and Hedwig, Berthold} }