Hebbian learning is basis of neuronal plasticity and its effect can best be seen in the induced ocular dominance columns in three eyed frogs where retina ganglion cell axons segregate from each other driven by induced and spontaneous activity. We have developed a new model, the three eared frog model, which allows us to induce vestibular dominance column depending on the orientation and thus stimulation of the grafted ear and have further developed our three- eared model to uncouple linear and angular acceleration and observe the effects on the vestibular-ocular reflex (VOR). In addition, we can use the single pair of Mauthner cells to visualize the segregation of afferents from two ears at the level of a single cell.
Aim1 will combine ear transplantations with various colored fluorescent proteins to image segregation of different semicircular canals in the vestibular nucleus and on Mauthner cell dendrites. In addition, we can observe the effects of motor output by monitoring the VOR in animals with tandem aligned and misaligned semicircular canals.
In Aim 2 this novel model will be utilized to dissect the significance of all activity in this process. Specifically, uing the newly developed CRISPER technique we will delete a gene that has been identified as producing an essential protein for the docking of synaptic vesicles. Without such docking neither spontaneous nor induced activity will be propagated through the nervous system. We will test in specific combinations of the frogs whether the lack of activity in the transplanted ear or in the host or both is particularly important to drive the afferent segregation process. Combined, these two aims will establish that activity is an essential factor for inner ear afferent segregation and will establish the three-eared frog model as a new model to understand those plasticity processes at a cellular level, using the only neuron that can be identified in the vertebrate central nervous system, the Mauthner cell, as an example.
In analogy to three-eyed frogs, we have generated three-eared frogs that demonstrate afferent fiber segregation into vestibular dominance columns. Using this model we will expand mechanisms for plasticity developed in the visual field into the vestibular research. Vestibular plasticity is essential to adjust to differences between ears and changes in vestibular sensation over time, including compensations after vestibular defects.
