Olfactory behaviour

Odd neutrons & higher olfactory centres

How do the Odd neurons link higher Olfactory centers to motor circuits controlling chemotaxis?
To answer this question the goal is to construct a detailed circuit map
1. In collaboration with Albert Cardona (Janelia/Cambridge) I will map, at the ultrastructural level, the neural circuitry linking the Odd neurons to locomotor circuitry at larval stages. This information will help us to identify the number of neural components and complexity of neurons within the chemotaxis pathway. This work will also reveal the anatomy of individual neurons within the pathway.
2. With this information in hand we can use the large collection of enhancer fly lines from Janelia to screen for driver lines that are expressed in neural components postsynaptic to the Odd neurons and match the anatomy identified above. This will allow me to generate a genetic toolkit through which I can target the cells to which the Odd neurons are directly or indirectly connected. This will allow us to modulate neural function specifically in neurons that are postsynaptic to the Odd neurons. For example, we can silence the neurons by expressing Kir2.1 or make neurons more excitable using NaChbac and address how manipulating neural activity affect chemotaxis behaviour

Sensory information transmittal

How is sensory information transmitted from one region of the brain to another?
We will now use the genetic tools identified in 1 to characterize each neural component of the pathway downstream of the Odd neurons. First we will measure activity patterns in postsynaptic targets in response to different types of odours and changing odour concentrations using functional imaging and targeted expression of genetically encoded calcium indicators in the postsynaptic targets. Once we have characterized the response properties of the downstream targets we can address how upstream input modulates the activity of downstream neurons to develop an understanding of how odour information is transferred through the pathway. We will achieve this aim through a combination of functional imaging and genetically encoded neural modulators. Finally we will investigate the functional role of each component of the chemotaxis pathway using behavioral assays in combination with neural manipulation. We have shown that Odd neurons are an important link from higher olfactory centers towards motor output neurons. To fully understanding information transfer within the chemotaxis pathway we need to characterize how the Odd neurons themselves are modulated by upstream input. We will achieve this by manipulating neural function in neurons upstream of the Odd neurons while measuring neural activity in the Odd neurons using genetically encoded calcium sensors and functional imaging. Our preliminary data show that Odd neurons form synapses with MB neurons (Kenyon cells). This is interesting since the MB is associated with olfactory memory formation and short term memory is thought to be required during chemotaxis. The connectivity between the Odd neurons and the MB neurons could suggest that Odd neural activity may also be modulated by memory traces laid down in the Kenyon cells. We will investigate the functional interaction between Odd neurons and their upstream input (PNs and Kenyon cells) using a combination of neural modulation and functional imaging. In addition we will address the role of Odd neurons in memory and learning using appetitive conditioning behavioral assays. Preliminary data from my lab has already shown that silencing the Odd neurons impair reward learning.