![]() ![]() At the final level, a ‘tonal-scream detector’ is created by again combining output from neurons T1 and T2 nonlinearly. The output of these FM detectors is combined nonlinearly at the next level: the target neurons T1 and T2 possess a high threshold and fire only if all inputs are activated. At the lowest level, there are neurons serving as FM detectors tuned to the rate and direction of FM sweeps these detectors extract each FM component (shown in cartoon spectrograms) in the upward and downward sweeps of the scream. The neural circuitry for processing such calls is thought to consist of small hierarchical networks. Harmonic calls, such as the vocal scream from the rhesus monkey repertoire depicted here by its spectrogram and time signal amplitude (A, measured as output voltage of a sound meter), consist of fundamental frequencies and higher harmonics. A new model connects structures in the temporal, frontal and parietal lobes linking speech perception and production.Ĭommunication calls consist of elementary features, such as bandpass noise bursts or frequency-modulated (FM) sweeps. We will identify roles for different cortical areas in the perceptual processing of speech and review functional imaging work in humans that bears on our understanding of how the brain decodes and monitors speech. ![]() Chief among these are physiological and anatomical studies showing that primate auditory cortex, across species, shows patterns of hierarchical structure, topographic mapping and streams of functional processing. In this paper, we will demonstrate how our understanding of speech perception, one important facet of language, has profited from findings and theory in nonhuman primate studies. Yet, in evolution, spoken language must have emerged from neural mechanisms at least partially available in animals. Speech and language are considered uniquely human abilities: animals have communication systems, but they do not match human linguistic skills in terms of recursive structure and combinatorial power. ![]()
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