Figure 1: Big question: How does the retina take part in the brain-wide complex feedback circuits?

Figure 1: Big question: How does the retina take part in the brain-wide complex feedback circuits?

The Asari group combines experimental and computational approaches to study the principles and the function of neuronal circuits, specifically in the early visual system in mice.

Previous and current research

How do neurons interact with each other to perform specific neurological functions? To address this question, my postdoctoral research focused on the circuit functions of the retina because it is an experimentally most accessible part of the central nervous system that performs considerable computations with well-defined input stimuli and output responses. Specifically, I explored how signals flow in the inner retinal circuits, and showed that a given principal neuron (bipolar cell) can send dramatically different signals to its various postsynaptic partners (ganglion cells) by forming distinct local microcircuits with inhibitory interneurons (amacrine cells). This indicates that each of these microcircuits serves as a computational unit for visual processing in the retina.

Future projects and goals

As we have learned more about local circuit functions of individual brain areas, it becomes increasingly important to understand (a) how these areas interact with each other to modulate their local circuit functions; and (b) how such interactions help process sensory and motor signals to organize an animal’s behaviour. An excellent model system to address these questions is the mouse retina. First, the retina is one of the best understood circuits in the brain, and the physiological functions are known in detail from the molecular to the cellular circuit level. Second, various tools are available in mice to label, monitor, and manipulate specific cell types and circuits. Third, although the retina is often thought to make only feed-forward connections to the brain, there is an anatomical substrate of efferent inputs from multiple brain areas to the retina across species.

We will thus focus on the bidirectional interactions between the retina and the brain under different behavioural and internal states of an animal, and analyse the functional role of the retinal efferents and their impact on the retinal afferents from the viewpoint of visual computation (Figure 1). The results will clarify how visual processing in the retina is dynamically modulated by efferent inputs under different behavioural conditions, and how a diverse set of retinal outputs serves as a basis for visual computation along the afferent visual pathways. This will help explain what each stage of visual processing is for, and also help refine an input-output model to better describe visual responses at each stage of the visual system. Ultimately, the outcome of our research will support a future development of visual prosthetic devices by faithfully emulating the function of the early visual system, in particular, the retina.