Neural coding in the chick cochlear nucleus

Mark E. Warchol*, Peter Dallos

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

151 Scopus citations

Abstract

Physiological recordings were made from single units in the two divisions of the chick cochlear nucleus - nucleus angularis (NA) and nucleus magnocellularis (NM). Sound evoked responses were obtained in an effort to quantify functional differences between the two nuclei. In particular, it was of interest to determine if nucleus angularis and magnocellularis code for separate features of sound stimuli, such as temporal and intensity information. The principal findings are: 1. Spontaneous activity patterns in the two nuclei are very different. Neurons in nucleus angularis tend to have low spontaneous discharge rates while magnocellular units have high levels of spontaneous firing. 2. Frequency tuning curves recorded in both nuclei are similar in form, although the best thresholds of NA units are about 10 dB more sensitive than their NM counterparts across the entire frequency range. A wide spread of neural thresholds is evident in both NA and NM. 3. Large driven increases in discharge rate are seen in both NA and NM. Rate intensity functions from NM units are all monotonic, while a substantial percentage (22%) of NA units respond to increased sound level in a nonmonotonic fashion. 4. Most NA units with characteristic frequencies (CF) above 1000 Hz respond to sound stimuli at CF as 'choppers', while units with CF's below 1000 Hz are 'primary-like'. Several 'onset' units are also seen in NA. In contrast, all NM units show 'primary-like' response. 5. Units in both nuclei with CF's below 1000 Hz show strong neural phase-locking to stimuli at their CF. Above 1000 Hz, few NA units are phase-locked, while phase-locking in NM extends to 2000 Hz. 6. These results are discussed with reference to the hypothesis that NM initiates a neural pathway which codes temporal information while NA is involved primarily with intensity coding, similar in principle to the segregation of function seen in the cochlear nucleus of the barn owl (Sullivan and Konishi 1984).

Original languageEnglish (US)
Pages (from-to)721-734
Number of pages14
JournalJournal of Comparative Physiology A
Volume166
Issue number5
DOIs
StatePublished - Mar 1990

Keywords

  • Auditory system
  • Chicken
  • Cochlear nucleus
  • Hearing

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physiology
  • Animal Science and Zoology
  • Behavioral Neuroscience

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