Sensory integration

How do visual auditory and olfactory systems integrate with each other?

Behavioural decisions are often based on the simultaneous input from different sensory modalities. For example, recognition of objects, estimation of their speed and position, depends on information coming from visual, olfactory and auditory systems. It is yet unclear how different sensory modalities interact and influence each other to achieve more reliable outcome. We try to understand how this happens by studying brain areas that simultaneously process different sensory modalities. For example, optic tectum not only processes visual information but also receives inputs from lateral line, auditory system and olfactory terminal nerve. We image the neuronal activity in the tectum and investigate how the information from different sensory modalities is integrated by tectal neurons. In collaboration with Federico Ceriani and Suresh Jesuthasan.

What is the organisation of the neural circuits processing visual information?

Using a combination of behavioural and imaging techniques we study how the zebrafish visual system processes visual information. Our main goal is to understand how information about object identity is encoded in the activity of visual neurons. In particular, we try to define what features are extracted by the early visual system in order to make object recognition efficient; how these features converge to form receptive fields of object recognising neurons and the role of synaptic plasticity and adaptation in this process.

To answer these questions, we image neuronal activity in zebrafish larvae. We use zebrafish lines expressing calcium activity indicators in all or subset of visual neurons. These indicators change their brightness when neuron is active. The advantage of this method is that it is non-invasive and allows for the simultaneous study of a large population of neurons – something that is currently unfeasible using other techniques. Because processing of sensory information becomes more sophisticated with age we have developed and characterised a novel pan-neuronal line, driving expression of calcium reporters in later stages of development. Using this line and specific imaging conditions we were able to image neuronal activity in fish up to 21 days postfertilisation (Bergmann et al., 2018)

To understand how memory is encoded in changes in synaptic strength.

We develop GFP based reporters of long-term potentiation and long-term depression. These reporters will be used in vivo to understand how simple forms of associative and non-associative memory are implemented in changes in synaptic strength. To answer these questions we are developing behavioural paradigms that will allow us to combine evaluation of memory formation with in vivo imaging of synaptic strength.

Can we build a sensory system from scratch?

One way to understand neural circuit is to build it. In collaboration with Paul Gokhale in our department we try to build very simple neural circuits with given properties (e.g. logical AND, logical NOT etc.) out of cancer stem cells (NT-2 and Neuroblastoma cell lines) differentiated into neurons. We would like to optimise the conditions of differentiation into different types of neurons, make cells grow axons in a particular direction and form synapses with particular neurons in a controlled way. This is a new project and all results, meta data, Python scripts and data for 3D printing for this project will appear online.