Dr Mikko Juusola: Research Themes

Visual information is of key significance for many organisms, yet routing and processing of visual information in the nervous system is poorly understood. We have recently shown - contrary to the previous believes of many - that information in the visual systems of insects flows in two ways: from the eyes to the brain and from the brain to the eyes. The dynamic properties of the neural network in the eyes set the limits for the visual information that can reach the central nervous system and be perceived, but the processing and routing of that information is modulated by the brain's wishes to look at interesting objects (Zheng et al., 2006; Tang & Juusola, 2010). There are many open questions both in retinal and central signalling that still remain unanswered.

Our current research is aimed at understanding this neural complexity, concentrating on the filtering (amplification and adaptation) and integration of signals from visual periphery to central networks, and on the attentional top-down regulation of sensory information. This project relies on four approaches:

The Use of Simple Photoreceptors and

Interneuron Networks
(in the eyes and the visual brain centres of fruitfly, Drosophila melanogaster), whose functional architecture is known in great detail. The recordings are done in intact animals currently using single-electrode current- and voltage-clamp techniques, extracellular multiunits and optical imaging.

The Use of Eye Mutants

The voltage responses of photoreceptors, visual interneurones and central neurones are the end products of long and complicated reaction cascades. By using Drosophila eye-mutants, we can analyse the role of specific elements (enzymes, receptors, ion channels) of the cascade. Hence a mutation-induced change in the cascade can be seen as an altered electrical response, and classified by comparing it to the responses of normal cells.

The Use of Modern Dynamic Non-Linear and Statistical Models

Complex, dynamic behaviour is characteristic of many sensory systems, and requires the use of integrated non-linear models to characterise the natural components of the neural responses.

The Use of Behavioural Experiments and Analysis

While electrophysiological and imaging experiments may tell a lot about how individual or groups of neurons process visual signals, ultimately it is only behavioural experiments, combined with analysis of activity that have the power to either support or falsify different hypotheses about visual information processing. The behavioural set-ups, such as Drosophila flight simulator or y-tube systems, combined with genetic and imaging and electrophysiological approaches, provides ideal test beds for evaluating how the fly brains are organised or optimised for processing information about the properties and patterns of visual environments.