Adaptation in the avian IC on the cellular level
Response adaptation occurs in the avian inferior colliculus (IC) and is thought to play a role in complex auditory functions like echo-suppression or direction selectivity. However, magnitude and time-constant of adaptation varies considerably between recording sites and reports. In-vivo recordings also did not yet address cellular mechanisms of adaptation nor rigorously distinguished between different physiological sources. Notably, one study in the barn owl IC reported a double-exponential recovery from adaptation suggesting two mechanisms with distinct temporal profiles (Singheiser et al., 2012). We hypothesize here that rapid adaptation may be mediated by intrinsic ion channel properties of the IC neurons and longer-lasting adaptation may be attributed to synaptic short-term plasticity.
We test this by performing whole-cell patch clamp recordings from neurons in the central IC in acute chicken embryonic (E20) brain slices.
We first perform a detailed biophysical characterization of chicken IC neurons. Then, intrinsic adaptation is elicited by injection of current stimuli with varying inter-stimulus intervals. Action potentials are counted and analyzed in detail.
Properties of synaptic inputs are examined by recording postsynaptic potentials and currents in the chicken IC neurons after electrical stimulation of ascending auditory axons.
Neurons are filled with biocytin during recordings and their dendritic fields are visualized with confocal microscopy.
Dr. Thomas Künzel
Sebastian Malinowski, BSc. -- Intrinsic adaptation in the ICCc, pharmacology of chicken IC synapses
Jana Wolf -- Synaptic physiology of chicken ICCc neurons
Sven Kuspiel -- Intrinsic adaptation in the ICX
Kuenzel T, Malinowski S, Kurth S, Wagner H. In-vitro analysis of intrinsic and synaptic contributions to adaptation in the avian central nucleus of the inferior colliculus. PD202, 39th Annual Midwinter Meeting of the Association for Research in Otolaryngology