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Parallel processing channels for binaural cues in the Lateral Superior Olive.

Jimena Ballestero

  • CABA,
  • Argentina
  • Jimena Ballestero ¹
  • , Andrew Brughera ²𝄒³
  • , Jason Mikiel-Hunter ³
  • , David McAlpine ³
  • 1 Instituto de Fisiología y Biofísica (IFIBIO) Bernardo Houssay, Grupo de Neurociencia de Sistemas, Universidad de Buenos Aires, CONICET, Buenos Aires, Argentina.
  • 2 Boston University Dept. of Biomedical Engineering, U.S.A.
  • 3 Macquarie University Hearing and Dept. of Linguistics, Australia

The lateral superior olive (LSO) and medial superior olive (MSO) are the first nuclei in the ascending auditory pathway that encode binaural information. MSO principal neurons extract information concerning the temporal fine structure of sounds underpinning sensitivity to interaural time differences (ITDs). LSO neurons extract interaural level differences (ILDs) and ITDs conveyed in the envelope of high frequency sounds (envelope-ITDs). LSO neurons are heterogeneous both in their intrinsic properties as well as in their synaptic inputs. How this heterogeneity impacts the coding properties of LSO neurons has been source of debate. In a previous work we have proposed to characterize the responses of LSO and MSO neurons in terms of their filtering properties in response to fast variation of electrical inputs (ZAP stimulus). Here, by using the ZAP stimulus, we assessed the filtering properties of a large population of LSO neurons. We have identified two neural populations: low-pass neurons characterized by a low frequency cut-off frequency (< 100Hz) and resonant neurons characterized by a high cut-off frequency (> 100 Hz) sometimes accompanied by a peak in the impedance profile. The filtering profile could be modulated both by blocking Kv1.1/2 channels and by changing the cell membrane potential. Both types of neurons were present along the tonotopic axis of the LSO. We suggest these two populations constitute parallel channels of processing for high frequency sound in the LSO.