Neuronale Intergration paralleler sensorischer Kanäle im elektrosensorischen System

01/08/2019 to 31/07/2022

Multisensory integration joins information provided by different
senses into a unified percept. In situations of conflicting
information it may lead to perceptional shifts such as the ventriloquist
illusion. Combining congruent information from multiple senses,
however, often improves behavioral performances by reduced reaction
times or improved stimulus detection. Often, this integration is
Bayes-optimal, that is, information channels are weighted according to
their respective reliability. On the neuronal level, increased
responsiveness, reduced response latencies, and improved phase locking
have been described as effects of multisensory integration. How
information from multiple channels is integrated has been investigated
in a multitude of studies. Mathematical as well as phenomenological
models have been developed to understand the guiding
principles. However, our understanding of the physiolgical processes
underlying these computational principles is still weak. In
particular, electrophysiological data allowing to investigate the
subthreshold mechanisms are missing.

We will address this gap between theory and physiology in the context
of the encoding of electrocommunication signals in the weakly electric
fish Eigenmannia virescens. In Eigenmannia, communication signals,
called chirps, are modulations of the fish's own electric organ
discharge which stimulates three parallel electrosensory
pathways. Initially, information is processed separately, but is
eventually joined in the torus semicircularis (TS) of the midbrain,
the teleost homolog to the mammalian inferior colliculus. Our previous
analyses on the level of the electroreceptors suggest that chirp
detection should be improved by combining information from the
parallel pathways. By means of in vivo intracellular recordings of
neurons in the parallel channels in the hindbrain and of integrating and non-integrating
neurons in the TS we will gather the required data of pre- and
postsynaptic activity to analyze the mechanism of integration in the
subthreshold regime.

With the proposed study we aim at open questions regarding the
encoding of electrocommunication signals in integrating and non-integrating
neurons in the hind- and midbrain. Based on the acquired data we will
analyze the subthreshold mechansims involved in the integration
processes in multichannel neurons in the TS. These will be interpreted
in the context of the known theories of multisensory integration.