2. Behavioral Biology TALKS - Deutsche Zoologische Gesellschaft

fully understand how fish reach the stunning behavioral discrimination performance
[3].
We here present our analysis of object detection and object discrimination
performance of single neurons recorded in ELL. As a stimulus we used a metal cube (1
cm3). It was presented at fixed distances from the receptive field centre of individual
neurons (1 - 23 mm distance). We quantified the neuronal performance in cube
detection and distance discrimination with a ROC analysis.
With increasing distance, detection probability showed exponential decrease, with
spike latency being the more sensitive measure. Regarding discrimination, our data
show that with increasing object distances, the minimal distance to a second object
needed to be increased for a successful discrimination. However, in a number of
single cells distance discrimination thresholds (17 to 1 mm) are comparable to
behavioral data.
In a next step we will compare the physical basis of the differences in electric images
to both the single neuronal and the animal performance, using methods currently
established in our labs.
�92 Vanessa Kassing A 701 / 15:15
Monitoring single cell responses via calcium imaging in the optic tectum of the
adult zebrafish (Danio rerio)
Authors: Vanessa Kassing 1 , Jacob Engelmann 1 , Rafael Kurtz 1
Affiliation: 1 Univerisity of Bielefeld, Faculty of Biology, AG Active Sensing
During the last years the zebrafish (Danio rerio) became a popular model organism in
neurophysiology and developmental neurobiology. The optic tectum is the main
center for processing visual information in fish and it is well known for its role in
coordinating voluntary movements with multimodal sensory input. To achieve this,
several sensory modalities are mapped within the tectum.
We have established a method of in-vivo calcium imaging of tectal neurons in adult
zebrafish. This approach is extensively used in larval zebrafish but only up to the age
of 9 days post-fertilization. Skin pigmentation and the development of a bony cranial
roof after day 9 limited the technique to early larvae thus far. Moreover, we use
conventional widefield fluorescence microscopy, in contrast to previous studies, in
which two-photon imaging was necessary to resolve somatic signals from individual
neurons. To this end, we use dextran-coupled dyes, which can be loaded into small
groups of cells by a mechanical procedure or via local electroporation. Compared to
the previously used procedure of pressure injection of a membrane-permeable dye,
which stains numerous of neurons, our methods reduce crosstalk between individual
neurons. The experiments show that our new approach for this technique leads to
convincing results in the optic tectum of adult zebrafish. We were able to
characterize direction and orientation selective cells with different stimuli, e.g.
moving bars and dots, full field and counter phase flicker.
Our further experiments deal with short-term plasticity of visual computation in the
adult zebrafish, and may in the future open a way to ask how maps of different
modalities are integrated at the level of the optic tectum.
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