Background and activities

Research topics

1: Microcircuits and synaptic connectivity in 3-Dimensions

2: Is Alzheimer’s disease a synaptic disease? 

A confocal and ultrastructural investigation in three dimensions of circuits involved in navigation and orientation during memory consolidation, learning and exploiting learned skills.

We want to investigate whether there are rules that explain how neurons connect in complex networks, especially inhibitory local neuronal connections. Neuronal communication must be considered as a dynamic process derived from integration of movements at subcellular scales. Mapping synaptic connectivity, ranging from synaptic fields of individual neurons, synapse stability in wiring diagrams and synaptic vesicle distribution can now be achieved in 3D confocal and volume scanning electron microscopy. The combination allows visualization of synaptic membranes in their native context. This context is important since synaptic input on soma, spine or dendrite can have rather different functional effects, as well as the size and shape of synaptic complexes. The combined light, confocal and volume SEM is a new technology that overcomes restrictions in electron tomography and ion beam EM and will provide structural details at the level of membrane domains

The central nervous system is a complex and precise mechanism that controls the most highest functions of the body. All of them depend on the cellular and molecular interactions. The ability of neuronal circuits and associated connections to adapt their activity in response to environmental stimuli is a vital process for most organisms. Communication between neurons, which is the basis of brain activity, requires the synthesis of many molecules involved in the formation and stabilization of synaptic connections. The central nervous system is a flexible structure, however its regeneration after damage is limited. Advanced in our knowledge of structures and mechanisms underlying synaptic plasticity and brain repair and identifying the localization and distribution of molecules that promote these processes can open new ways in the development of therapeutic tools to understand learning and  memory related processes.

The aim of my work is to provide a structural basis at the highest resolution of the molecular and cellular components.

Figure of Parvalbumin labelled neurons, vibratome section, 45 um thick entorhinal cortex from rat. Layer 1 is almost free of any labelled cell. Layer 2, the darker strip, shows more intense labelling of cell bodies and dendrites  (Figure provided by Nina Berggaard).

Methodological and technical aspects

Focus will be on the application of correlative microscopy technology to identify and localize molecules within cells and their matrix. The advantage of traditional light microscopy, fluorescent labeling and confocal microscopy is its dynamics and relatively fast processing. The resolution of the electron microscope will enable identification of the true substrate that can be imaged with the fluorescent dye. Often there are applications with fluorogold secondary antibodies to combine this approach. Otherwise conversion of the chromogen DAB to an electron dense gold precipitate is a familiar and sensitive technique.

Traditional electron microscopic techniques, immunolabeling with pre- and post-embedding use of epon and lowicryl resins, need to be extended with large scale ultrastructural microscopy. Modern application of computerized scanning transmission electron microscopy allows to acquire datasets in an automated way that permits analysis of large numbers of spines and synapses. This is of great advantage in electron microscopy since high resolution images can be compared over large surface areas and allow to study details that up till now were easily overlooked.

Fig 2, examples of ultrathin sections in transmission EM of rat postnatal day 30 entorhinal cortex, layer 2 terminal boutons, labelled for PV according a modified DAB-gold intensification. Often the terminals are filled with a large mitochondrion, clear electron lucent vesicles, in some cases asymmetric synapses are seen (unpublished data from Nina Berggaard). .

Scientific, academic and artistic work

A selection of recent journal publications, artistic productions, books, including book and report excerpts. See all publications in the database

Journal publications