Position Master student
Nationality German
Room N7 121
Tel +49 521 106-6569
e-mail johanna.kabbert[@]uni-bielefeld.de

 

Current Projects

Transversal section of the zebrafish left optic tectum. Somata, axons and dendrites are stained with DAPI.

Currently, our focus of interest comprises the investigation of underlying mechanisms involved in neuronal short-term plasticity to motion adaptation in neurons in the optic tectum of adult zebrafish. Over the past years studies in various species of fish have shown that the optic tectum is critically linked with visual tasks, such as prey detection or optic flow evaluation. Neurons in the optic tectum in fish, as well as in the primary visual cortex in cats and area MT in macaques appear to be involved in the discrimination of texture orientation as well as speed of motion and direction (Hietanen et al., 2007; Krekelberg et al., 2006; Niell and Smith, 2005). Neurons in the optic tectum in fish respond to certain velocity ranges of pattern motion (Grama and Engert, 2012). However, activity dependent shifts of the velocity range, which have been described for mammalian visual cortex, have not yet been demonstrated in fish. Within the last years the usage of transgenic zebrafish lines and the application of calcium sensitive dyes have become a common approach to investigate neuronal processing. However, studies concerning visual motion processing are mostly performed on zebrafish larvae due to their simple maintenance and easy methodological handling. In particular with regard to neuronal plasticity, it is questionable whether obtained data in still developing brain areas are transferable to adult zebrafish. As opposed to the mentioned studies, we are investigating the underlying neuronal mechanisms of short-term plasticity regarding the velocity tuning functions of single neurons in the optic tectum of adult zebrafish.                    

So far, from preliminary results, we conclude that neurons in the optic tectum of adult zebrafish indeed indicate the ability to show short-term plasticity in response to velocity adaptation protocols. Moreover, we could show that velocity tuning functions of tectal neurons do not appear to follow fixed cell properties, but rather exhibit plastic characteristics that can be disclosed by velocity adaptation protocols. In general, the majority of cells display orientation selectivity for 0°/180° and motion responses peak in a range from 4 Hz to 12 Hz. Motion adaptations below or above peak velocity lead to repulsive shifts of the tuning functions, inferring increased relative sensitivity for the non-adapted velocities. In contrast, adaptation at peak velocity generates a bimodal velocity tuning. Additionally, adaptation tends to cause response attenuation over the entire velocity range. In turn, this is consistent with a proposed two-channel model of speed adaptation by Hietanen et al., 2007. Thus, implications for physiological relevance of velocity adaptation might include “novelty detection”, as cells become more sensitive to novel stimuli during sustained uniform stimulation. In addition, the observed overall attenuation of response magnitude might be a feature to optimize energy expenditure. Our future prospects also comprise the investigation of dendritic tuning functions for the investigation of computational mechanisms underlying short-term plasticity and to unravel potential interactions between different cell types and structures. Accordingly, with the use of histological techniques, such as zebrafish brain bleaching in urea solution and production of histological sections, processed with DAPI, we aim to distinctly identify individual cells as well as their potential affiliation to certain brain layers. Ultimately, it is also of great interest to conduct behavioural studies, deducing and inferring implications of adaptation-induced changes of neuronal tuning for associated locomotor control.

Publications & News

Conference Proceedings | Posters

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 tecttum of adult zebrafish (Danio rerio). 107th annual meeting of the DZG 2014, Goettingen, Germany.

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

Bachelor Thesis

Impact of Citrobacter rodentium infection on Innate Lymphoid Cells (ILCs) and Cytokine expression in B57 BL/6N mice and germ free mice (GF)