Position PhD Student
Nationality German
Room N7 121
Tel +49 521 106-6569 
e-mail vanessa.kassing[@]uni-bielefeld.de

 

Current Research

 

I. Optical Imaging in the optic tectum of the zebrafish (Danio rerio)

The tectum is well known for its role in coordinating voluntary movements with multimodal sensory input. To achieve this, several sensory modalities are processed and mapped within the tectum. Our first experiments address the question of short-term plasticity of orientation, direction and velocity tuning in the optic tectum of the mature brain. In the developing brain training-induced emergence of direction selectivity and plasticity of orientation tuning appear to be widespread phenomena found in the visual pathway across different classes of vertebrates. Moreover, short-term plasticity of orientation tuning in the adult brain has been demonstrated in several species of mammals. However, it is unclear whether neuronal orientation and direction selectivity in non-mammalian species remains modifiable through short-term plasticity in the fully developed brain. So far, our data indicate that, even within the fully developed optic tectum, short-term plasticity might have an important role in adjusting neuronal tuning functions to current stimulus conditions. Further experiments could deal with multisensory processing in this brain area, especially if and how mechanosensory and visual information are put in register in the tectum. It is also a future aim of our lab to extend the approach of optical imaging to electrolocation as well, but since this is a novel approach not tested in electric fish so far, we’ll initially investigate this in zebrafish.

 

 II. Topographic organisation of the octavolateral line nucleus in zebrafish (Danio rerio)

Topographic and somatotopically organized neuronal maps are frequently found throughout the animal kingdom. A puzzling exception to this ubiquitous representation of the external world in an egocentric manner is the medial nucleus of the mechanosensory lateral line system (MON). The MON is the first-order medullary lateral line sensory nucleus, processing mechanosensory information before it is passed to the ventro-lateral nucleus of the midbrain torus semicircularis (vlTS). Several studies have shown that the peripheral organization of the neuromasts is preserved in the termination of the lateral line nerve in the MON, such that the rostro-caudal fish axis is reflected in the anterio-posterior and ventro-dorsal axis of the terminals in the MON. Further there is physiological evidence that this mapping can also be found in the vlTS of the goldfish. Here neuromast information from anterior body regions is processed more rostrally than that of posterior regions. Thus a topographic representation is well documented at the afferent level and a functional mapping has as well been found in the torus semicircularis. For the MON efferent cells itself however, no topography has been described so far, with the exception of the vocal midshipman (Porychthys notatus). Using the zebrafish Danio rerio we here aim to overcome this gap by focussing on the connectivity between MON and vlTS. To do so, we inject different fluorescent dyes simultaneously into the vlTS along different positions in the rostro-caudal axis. Based on retrogradely labeled neurons in the hindbrain, we reconstruct the connectivity and built a 3D representation to better quantify the mapping between MON and midbrain levels.

 

 III. Anatomical and functional organization of parallel maps in electrolocation

In the last part of the thesis, we will investigate topographic representations of electrosensory information in the weakly electric fish (Gnathonemus petersii). The first stage of processing electrosensory information is the electrosensory lateral line lobe (ELL). Incoming information is here mapped within three different somatotopic maps, the medial zone (MZ), the dorso-lateral zone (DLZ) and the ventro-lateral zone (VLZ). In many verebrates parallel processing in topographically ordered maps is essential for efficient sensory processing. We’ll anatomically explore the degree of convergence of sensory input in the DLZ and MZ, as to better understand the spatial tuning properties of both zones. This will be done by classical tract tracing and labeling studies combined with immunohistochemical analysis of subclasses of neurons enabling us to determine the degree of convergence and to establish if processing in both zones occurs in a columnar fashion. In contrast to the well investigated MZ of the ELL, we presently know little about the organization, connectivity and sensory processing in the DLZ. Contrary to the MZ, the afferents projecting to the DLZ are sensitive to both amplitude and phase information contained in the electric signal, while the MZ receives only amplitude information. Both parameters are essential for the animals to decipher their environment and are thought to at least partially converge in higher brain regions. The second question we address is how this different sensory information is processed in higher brain areas. Therefore, tracing studies where fluorescent dyes are injected into the ELL are performed and the resulting termination sites in the Nucleus lateralis (NL) are observed. With this study we will gain information about the convergence of the sensory information in higher brain areas as well as information about possible available topographic maps in higher brain areas. These data will also be used to investigate which neurons in the ELL convey inter-zonal connectivity and how this may be used to enhance parallel sensory processing.

Publications

 

Hollmann V, Hofmann V, Engelmann J (2016) A somatotopic map of the active electrosensory sense in the midbrain of the mormyrid Gnathonemus petersii | Journal of Comparative Neurology (accepted)

Hollmann V, Lucks V, Kurtz R, Engelmann J (2015) Adaptation-induced modification of motion selectivity tuning in visual tectal neurons of adult zebrafish | Journal of Neurophysiology 114: 2893–2902, DOI: 10.1152/jn.00568.2015 | LINK

Kassing V, Engelmann J, Kurtz R (2013) Monitoring of single-cell responses in the optic tectum of adult zebrafish with dextran-coupled calcium dyes deliverd via local electroporation PLoS ONE 8(5): e62846, doi:10.1371/journal.pone.0062846, | LINK

Pusch R, Kassing V, Riemer U, Wagner HJ, von der Emde G, Engelmann J (2013) A grouped retina provides high temporal resolution in the weakly electric fish Gnathonemus petersii J Phys-Paris 107: 84-94, | LINK

Conference Proceedings | Talks

Hollmann V, Hofmann V, Engelmann J (2015) Anatomical and functional connectivity of sensory maps in electrolocation. Satellite Symposium "Neuroethology" of the 108th annual meeting of the DZG, Graz, Austria.

Kassing V, Engelmann J, Kurtz R (2012) Monitoring of single-cell responses in the optic tectum of adult zebrafish via optical imaging. 105th annual meeting of the DZG, Konstanz, Germany.

Conference Proceedings | Posters

Hollmann V, Hofmann V, Engelmann J (2015) Anatomical and functional connectivity of sensory maps in electrolocation. 108th annual meeting of the German Zoological Society, Graz, Austria.

Hollmann V & Engelmann J (2015) Topographic organisation of the octavolateral line nucleus in zebrafish, Danio rerio. 108th annual meeting of the German Zoological Society, Graz, Austria.

Lucks V, Hollmann V, Kurtz R, Engelmann J (2015) Adaptation-induced modification of motion selectivity tuning in visual tectal neurons of adult zebrafish. 108th annual meeting of the German Zoological Society, Graz, Austria.

Kassing V, Engelmann J (2014) A quest for excitation: Immunohistochemical analysis of a circuit for sensory gating in the ELL of Gnathonemus petersii. 107th annual meeting of the German Zoological Society, Göttingen, Germany.

Lucks V, Kassing V, Kabbert J, Kurtz R, Engelmann J (2014) Short-term plasticity of orientation tuning in the optic tectum of adult zebrafish (Danio rerio). 107th annual meeting of the German Zoological Society, Göttingen, Germany.

Kabbert J, Lucks V, Kassing V, Engelmann J, Kurtz R (2014) The Need for Speed: Alteration of Velocity Tuning Functions via Adaptation in the Optic Tectum of Adult Zebrafish (Danio rerio). 107th annual meeting of the German Zoological Society, Göttingen, Germany.

Kassing V, Engelmann J (2013) Connectivity of the MON of the Zebrafish, Danio rerio. 106th annual meeting of the German Zoological Society, Munich, Germany.

Kassing V, Hofmann V, Engelmann J (2013) Functional connectivity between ELL and the torus semicircularis of the weakly electric fish Gnathonemus petersii. Sattelite Symposium "Neuroethology" of the 106th annual meeting of the German Zoological Society, Munich, Germany.

Kassing V, Engelmann J, Kurtz R (2012) Calcium Imaging in the optic tectum of adult zebrafish (Danio rerio), 10th International Congress of Neuroethology, College Park, MD, USA.

Kassing V, Engelmann J (2012) Anatomical and functional organization of parallel maps in electrolocation, Satellite Symposium of the ICN 2012, Weakly electric fishes: Neural systems, behavior and evolution, College Park, MD, USA.

Kassing V, Wilkens L, Hofmann M (2010) Physiology and Morphology of different units in the tectum opticum of the paddlefish (Polyodon spathula), 9th Congress of the International Society for Neuroethology. Salamanca, Spain

Kassing V, Wilkens LA, Hofmann MH (2010) Multimodal units in the tectum opticum of the paddlefish (Polyodon spathula), 103. Jahresversammlung der Deutschen Zoologischen Gesellschaft, Hamburg, Germany

Kassing V, Wilkens LA, Hofmann MH (2010) Multimodal units in the tectum opticum of the paddlefish (Polyodon spathula), International graduate course “Sensory Ecology”, University of Lund, Sweden.

Diploma Thesis

Funktionsmorphologie und Neurobiologie der basalen Pectenmuskeln bei Skorpionen der Gattung Pandinus (Functional morphology and neurobiology of the basal pectine muscles of scorpions of the genus Pandinus). Rheinische Friedrich-Wilhelms-Universität Bonn