Analysis of auditory information in the brains of cetaceans

Abstract

A characteristic feature of the brains of toothed cetaceans is the exclusive development of the auditory neural centers. The location of the projection sensory zones, including the auditory zones, in the cetacean cortex is significantly different from that in other mammals. The characteristics of evoked potentials demonstrate the existence of several functional subdivisions in the auditory cortex. Physiological studies of the auditory neural centers of cetaceans have been performed predominantly using the evoked potentials method. Of the several types of evoked potentials available for non-invasive recording, the most detailed studies have been performed using short-latency auditory evoked potentials (SLAEP). SLAEP in cetaceans are characterized by exclusively high time resolution, with integration times of about 0.3 msec, which on the frequency scale corresponds to a cut-off frequency of 1700 Hz. This is more than an order of magnitude greater than the time resolution of hearing in terrestrial mammals. The frequency selectivity of hearing in cetaceans has been measured using several versions of the masking method. The acuity of frequency selectivity in cetaceans is several times greater than that in most terrestrial mammals (except bats). The acute frequency selectivity allows the discrimination of very fine spectral patterns of sound signals.

Topographical and structural characterization of the V1–V2 transition zone in the visual cortex of the long‐finned pilot whale Globicephala melas (Traill, 1809)

“…Pioneering electrophysiological studies identified motor areas in the cortex of the common dolphin (Kesarev, 1971; Kesarev & Malofeeva, 1969; Lende & Akdikmen, 1968) and the unique pattern of sleep of the pilot whale and bottlenose dolphin (Mukhametov, Supin, & Polyakova, 1977; Serafetinides, Shurley, & Brooks, 1971; Shurley, Serafetinides, Brooks, Elsner, & Kenney, 1969). Evoked‐potential sensory areas were formally identified (Ladygina, Mass, & Supin, 1978; Popov, Ladygina, & Supin, 1986; Popov & Supin, 2007; Sokolov et al, 1972), including the visual area, in the harbor porpoise Phocoena phocoena and bottlenose dolphin. Two zones were identified based on quicker (V1) or slower (V2) neuron firing, and mapped along the medial edge of the hemispheres (Figure 1) and not in the occipital position known in most mammals (Morgane, Jacobs, & Galaburda, 1986; Supin et al, 2001; for general reference see Cozzi et al, 2017; Huggenberger, Oelschläger, & Cozzi, 2019).…”

Infrasonic and Ultrasonic Hearing Evolved after the Emergence of Modern Whales

“…Mysticeti (baleen whales) and Odontoceti (toothed whales) today greatly differ in their hearing abilities: Mysticeti are presumed to be sensitive to infrasonic noises [1][2][3], whereas Odontoceti are sensitive to ultrasonic sounds [4][5][6]. Two competing hypotheses exist regarding the attainment of hearing abilities in modern whales: ancestral low-frequency sensitivity [7][8][9][10][11][12][13] or ancestral high-frequency sensitivity [14,15].…”

The auditory time resolution in bottlenose dolphins: Behavioral experiments versus auditory evoked potential methods

“…Auditory temporal resolution in bottlenose dolphins is believed to be around 300 µs, which is close the physiological limit imposed by the duration of a single nerve spike of hundreds microseconds. The bottlenose dolphin auditory 300-µs time resolution measured using AEP methods is claimed to be in full agreement with behavioral measurements [1,2]. Results on auditory temporal summation, double clicks discrimination and temporal masking are taken to support the claim.…”

“…In cetacean, fundamental physiological mechanisms common to all mammals appear to support much more extensive hearing capacity than that known for most terrestrial mammals [1,2]. Auditory temporal resolution in bottlenose dolphins is believed to be around 300 µs, which is close the physiological limit imposed by the duration of a single nerve spike of hundreds microseconds.…”