Calcium imaging
What are the cellular properties of auditory neurons, that contribute their specific processing? In order to analyse this question at a subcellular and molecular level, we are using a highly sensitive imaging system to measure the spatio-temporal dynamics of Calcium changes in identified auditory neurons at up-to 90 frames/s. In past experiments we focused on the local Omega neuron, on tibial motoneurons and recently on auditory afferents in bushcrickets.
Due to its "flat" arborisation pattern the local Omega neuron seemed to be particularly suited for these experiments. After loading of the neurons with a calcium sensitive dye (Calcium Green 5N) the optical signal indicates rapid changes in the cytosolic calcium concentration. At least two areas in particular show an increase in the optical signal: the dendrites and the axonal arborisations of the cell. When the calling song with 2 chirps/s is presented a gradual increase and a modulation in the calcium concentration in the rhythm of the chirps can be resolved. Thus the calcium dynamics mirrors the song pattern.
Calcium imaging at the terminals of auditory afferents in the bushcrickets (Mecopoda elongata) demonstrated calcium changes that are linked to the presence of primary afferent depolarisation, indication presynaptic inhibition. Optical signals persist even when spike activity in the afferents has been completely abolished. Primary afferent depolarisations depend of the frequency of the acoustic stimulus and may contribute to frequency processing within the bush-cricket auditory pathway.
Tom Baden is now at: thomas.baden@uni-tuebingen.de
Group Members
Dr Berthold Hedwig (Group Leader)
bh202@cam.ac.uk
Dr Fabienne Dupuy
Research: Auditory motor interface
fyd20@cam.ac.uk
Dr Kostas Kostarakos
Research: Auditory brain neurons
kk437@cam.ac.uk
Dr Stefan Schoeneich
Research:Song pattern generation
ss817@cam.ac.uk
Kelly Seagraves
Research: Directional sensitivity
ks584@cam.ac.uk
Part II Zoology Project Students
Tanya Gunnarsdottir
Gemma Longson