We are interested in the mechanisms of olfactory habituation - a phenomenon by which exposure to an odorant results in a reversible blunting of subsequent behavioral response. Using an odorant choice assay (Y-maze), we have characterized two different forms of olfactory habituation in Drosophila. Brief odorant stimulation results in short-term habituation (STH), which lasts for 45min. On the other hand, prolonged odorant exposure results in long-term habituation (LTH), which recovers in days. Our recent study suggests that glomerular selective potentiation drives olfactory habituation in flies (Das, Sadanandappa et. al 2011, Sudhakaran et. al 2012).

In collaboration with: Prof. Mani Ramaswami

   Sudeshna Das

 sdas [at] ncbs.res.in

Role of retrograde signaling in olfactory habituation

Our lab has previously demonstrated that Drosophila show olfactory Short Term and Long Term Habituation (STH & LTH) after continuous exposure to an odorant. Habituation arises due to potentiation of specific LN- PN (Local Interneuron-Projection Neuron) synapses which occurs in an NMDAR dependent manner also requiring cAMP signalling in LN1 neurons (Das, Sadanandappa et.al 2011). It has been also found that miRNA mediated local translational regulation in PNs is necessary (McCann, Holohan, Das, 2011) and feedback from PNs act as a constant source of LN stimulation is capable of driving habituation. However what signals from PNs are capable of inducing rutabaga dependent potentiation of LNs is not clearly understood. In this regard we are studying whether feedback from PN- LN is mediated by retrograde signals. Retrograde signals are secreted from the post- synapse on activity induction and act onto the pre- synapse to mediate presynaptic facilitation. Specifically we will be looking at some candidate retrograde signaling molecule such as nitric oxide, neurexin- neuroligin, delta- notch, etc in specific types of habituation, translational dependent LTH and translational independent STH.
 

Indulekha P.S

induaps [at] ncbs.res.in

Initial part of my work focused on understanding the role of Projection Neurons in habituation and recently we had reported that plasticity of recurrent inhibition in the antennal lobe is mediated by feedback from the PNs (Sudhakaran et. al. 2012). Along with colleagues in Mani Ramaswami’s lab, I am now looking into the translational regulatory mechanisms underlying habituation, focusing mainly on the dFmr1 protein. We have identified various mRNP (messengerRiboNucleoParticles) components required for habituation and the interactions among many of these proteins that are vital to habituation. Using translational reporters we have looked into how mRNP components regulate target transcripts in neurons. Our data points to an interesting mechanism on how components of RNA regulatory pathways act differentially to regulate common targets. Ongoing work deals with understanding this in greater details.

Madhumala K.S

In a collaboration with other lab members (Das, Sadanandappa et.al 2011), I have shown that cAMP–signaling dependent pre-synaptic facilitation of GABAergic local interneurons in the antennal lobe onto projection neurons underlies olfactory habituation. The differential regulation of cAMP signaling in establishing the different forms of habituation remains elusive. Thus my present work aims to understand the molecular mechanism for the neurotransmitter release from the local interneurons during habituation.

Collaborator: Prof. Erich Buchner, University of Wuerzburg, Germany.

Ankita Chodankar

How is the critical period established in habituation?

During critical period an organism has heightened sensitivity to external stimuli, which is essential for the acquisition of a particular skill. If the skill is not acquired during the critical period, it is much more difficult, or sometimes even impossible for the animal to acquire the skill. Previous studies have demonstrated that, flies show long-term olfactory habituation if they are less than 12 hours old, however 2 day old flies don't habituate. We aim to find the molecular and cellular mechanisms involved in establishment of the critical period during LTH.

Swati Trisal

    swatit [at] ncbs.res.in

Role of neuromodulation in Habituation

It is known that prolonged exposure to stimulus brings a drop in the response of flies to that stimulus. This phenomenon is known as habituation. However, getting habituated to a stimulus relevant to the fly in terms of a reward or punishment might be detrimental to the fly. So additional regulatory mechanisms mediated by neuromodulators could be employed to regulate what stimulus induces habituation. Neuromodulation can work at three stages- neuromodulation can gate habituation so that fly does not get habituated to relevant stimulus. Neuromododulation can also mediate habituation since these act as ligands for GPCRs, downstream molecules of which have already been shown to be indispensible for habtuation. Neuromodulators can also regulate response based on motivation or attention of the fly as in case of dishabituation. My work focuses on studying neuromodulators having role in gating habituation. I am working on understanding the synaptic targets of these neuromodulatory neurons and the downstream pathway by which neuromodulatory neurons communicate with their targets to regulate habituation.

Pushkar Pranjape

  pushkarp [at] ncbs.res.in

We don't understand the factors that determine behavioral response versus inaction to various stimuli. A tap on the back in a public hall may make one turn to reply but in an empty reading room it will startle. Either exchange above two responses with each other or eliminate the ability to switch between them and the result is a disordered individual. In general, the ability to get accustomed to insignificant stimuli is termed habituation in the literature. In order to get detailed circuit and molecular understanding of this behavior I work on Drosophila gustatory and visual pathways using behavioral and electro-physiological techniques.