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NJIT Mathematical Biology Seminar

Tuesday, November 2, 2010, 2:30pm
Cullimore Hall 611
New Jersey Institute of Technology

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Selectivity to slowly rising stimuli in frog auditory neurons

Alla Borisyuk

Department of Mathematics, University of Utah

Many acoustic communication signals, including phonemes of human speech, are differentiated in the time from onset to peak amplitude (rise time). Currently, little is known about how auditory systems differentiate between signals that differ in rise time. Gray treefrogs, Hyla versicolor have advertisement calls that consist of a series of sound pulses that are longer in duration and rise slowly in amplitude, whereas the sound pulses of their cousin species are shorter in duration and have short rise times.

Behavioral studies have shown that H. versicolor strongly prefers pulses that have long (conspecific) rise times. Correspondingly, there are neurons in the midbrain of H. versicolor that respond selectively to slowly rising pulses. We investigate possible mechanisms that underlie this rise-time selectivity. In particular, we want to find out whether the rise-time selectivity arises in midbrain or is inherited from lower level structures.

I will present three computational models of possible slow rise-time selectivity mechanisms: local inactivation of inhibition, fast-rise-time sensitive inhibition and interval counting with adaptation. I will also discuss the evidence from in vivo recordings (coupled with conductance reconstruction procedures) in support of the models. Finally, I will show model predictions, which will allow to distinguish between the proposed mechanisms as more data becomes available.