The responses of individual neurons to 4 typical guinea pig vocalization calls (purr, chutter, chirp, and whistle) were recorded in the inferior colliculus (IC) of anesthetized guinea pigs. All calls elicited a response in about 80% of units. Unit selectivity for individual calls was low, given that a majority of neurons (55% of 124 units) responded to all vocalizations and only a small portion of neurons (3%) responded to only one call or did not respond to any of the calls (3%). In 15% of units, the response to one call was > or =25% stronger than the response to any other sound (tone, noise, and other calls); these neurons were selective for chirp or whistle, and no unit preferred chutter or purr. Neuronal activity provided information about the spectrotemporal patterns of the calls. Peristimulus time histograms (PSTHs) reflected the energy of the near-characteristic frequency band, and the population PSTH reliably matched the sound envelope for calls characterized by one or more short impulses (chirp, purr, and chutter) but did not exactly fit the envelope for whistle--a slow-modulated and relatively long call. Calculations based on firing rates indicated the approximate positions of the main spectral peaks but did not always reflect their relative magnitude. The time-reversed version of whistle elicited on average a weaker response than did the natural whistle (by 24%), but there were neurons with a significantly stronger response to the natural ("forward-selective," 30%) as well as to the time-reversed whistle ("reverse-selective," 15%). This study does not prove the existence of units selectively responding to animal calls, but it provides evidence for the encoding of the spectrotemporal acoustic patterns of vocalizations by IC units.
The inferior colliculus (IC) represents a mid-brain structure which integrates information from many ascending auditory pathways, descending corticotectal projections and intercollicular pathways. The processing of information is different in each of the three main subdivisions of the IC--the central nucleus (CNIC), the dorsal cortex (DCIC) and the external cortex (ECIC)--which may be distinguished morphologically as well as by different inputs and outputs. To assess the differences in information processing we compared the response properties of single neurons in individual subnuclei of the IC in anesthetized guinea pigs. In comparison with DCIC and ECIC neurons, the CNIC neurons as a group were characterized by a sharper frequency tuning (as expressed by Q10 values), a lower average threshold, a shorter average first-spike latency of response to tones at the characteristic frequency (CF), a higher occurrence of non-monotonic rate/level functions and a higher rate of spontaneous activity. CNIC neurons and DCIC neurons reacted to tones at the CF more frequently by a sustained type of response than did ECIC neurons. The difference between the parameters of DCIC neuronal activity and ECIC neuronal activity was found to be smaller. The frequency tuning (expressed in Q10 values), spontaneous activity and dominance of monotonic rate/level functions were very similar in both structures; ECIC neurons expressed a higher average threshold and a shorter average first-spike latency than did DCIC neurons. Responsiveness expressed as the average maximal firing rate to tones at the CF was significantly higher in the CNIC than in the ECIC. The results give additional support to the idea that the CNIC is a part of a fast, frequency-tuned, low threshold and intensity-sensitive ascending pathway, whereas the other two subdivisions are involved in additional processing of information that involves feedback loops and polysensory pathways.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.