The storage of new information in the vertebrate brain requires the rearrangement of synaptic connections and consequently will result in different patterns of neuronal activity in response to sensory inputs. We hypothesize that these changes in neuronal activity in response to specifically learned stimuli can be localized and quantified with calcium imaging methods in the intact zebrafish brain.
Aim 1. generate a robust assay for visual learning in the larval zebrafish
Aim 2. improve and adapt functional two-photon laser scanning microscopy in the living zebrafish to analyse learning induced changes in neuronal activity
Learning assay: We are developing a robust learning assay that allows us to teach fish from early developmental (pf7 – seven days post fertilization) to juvenile stages to swim away from specific visual cues. In order to induce this aversion, freely swimming fish receive mild electroshocks in synchrony with the delivery of previously neutral visual stimuli.
Imaging: calcium indicators like Oregon-Green-Bapta are delivered either to individual neurons by single cell electroporation of its dextran form or, alternatively, neurons are bulk labeled by injection of the AM-esther into the brain region of choice. Calcium signals are then used to report neuronal activity in different areas of the fish brain. A particularly interesting example is the identified reticulospinal neurons, MeLc and MeLr, which are found in the nucleus of the medial longitudinal fasciculus of the tegmentum. These neurons extend dendrites into the ipsilateral tectum and project axons into the spinal cord and are thus placed in a key position to integrate relevant sensory information and send it on to the spinal cord.