No abstract

The auditory cortex of the mustache bat, Pteronotus parnellii rubiginosus, is composed of functional divisions which are differently organized to be suited for processing the elements of its biosonar signal according to their biological significance. Unlike the Doppler-shifted-CF (constant frequency) processing area, the area processing the frequency-modulated components does not show clear tonotopic and amplitopic representations, but consists of several clusters of neurons, each of which is sensitive to a particular combination (or combinations) of information-bearing elements of the biosonar signal and echoes. The response properties of neurons in the major clusters indicate that processing of information carried by the frequency-modulated components of echoes is facilitated by the first harmonic of the emitted biosonar signal. The properties of some of these neurons suggest that they are tuned to a target which has a particular cross-sectional area and which is located at a particular distance.

No abstract

Human speech and animal sounds contain phonemes with prominent and meaningful harmonics. The biosonar signals of the mustache bat also contain up to four harmonics, and each consists of a long constant-frequency component followed by a short frequency-modulated component. Neurons have been found in a large cluster within auditory cortex of this bat whose responses are facilitated by combinations of two or more harmonically related tones. Moreover, the best frequencies for excitation of these neurons are closely associated with the constant-frequency components of the biosonar signals. The properties of these neurons make them well suited for identifying the signals produced by other echolocating mustache bats. They also show how meaningful components of sound are assembled by neural circuits in the central nervous system and suggest a method by which sounds with important harmonics (or formants) may be detected and recognized by the brain in other species, including humans.

Low TIMP-2/MMP-2 and TIMP-2/MMP-9 ratios might play an important role in the onset of aortic dissection, when the tunica media becomes fragile with chronic breakage and degradation of the extracellular matrix.