Mechanisms and streams for processing of "what" and "where" in auditory cortex - PubMed (original) (raw)
Comparative Study
Mechanisms and streams for processing of "what" and "where" in auditory cortex
J P Rauschecker et al. Proc Natl Acad Sci U S A. 2000.
Abstract
The functional specialization and hierarchical organization of multiple areas in rhesus monkey auditory cortex were examined with various types of complex sounds. Neurons in the lateral belt areas of the superior temporal gyrus were tuned to the best center frequency and bandwidth of band-passed noise bursts. They were also selective for the rate and direction of linear frequency modulated sweeps. Many neurons showed a preference for a limited number of species-specific vocalizations ("monkey calls"). These response selectivities can be explained by nonlinear spectral and temporal integration mechanisms. In a separate series of experiments, monkey calls were presented at different spatial locations, and the tuning of lateral belt neurons to monkey calls and spatial location was determined. Of the three belt areas the anterolateral area shows the highest degree of specificity for monkey calls, whereas neurons in the caudolateral area display the greatest spatial selectivity. We conclude that the cortical auditory system of primates is divided into at least two processing streams, a spatial stream that originates in the caudal part of the superior temporal gyrus and projects to the parietal cortex, and a pattern or object stream originating in the more anterior portions of the lateral belt. A similar division of labor can be seen in human auditory cortex by using functional neuroimaging.
Figures
Figure 1
Mapping of lateral belt areas in the rhesus monkey. (A) Band-passed noise (BPN) bursts of various bandwidths and constant center frequency are displayed as spectrograms. (B) Scattergram comparing responses to BPN and pure-tone (PT) stimuli in the same neurons. (C) Reconstruction of best center frequency maps showing cochleotopic organization of anterolateral (AL), middle lateral (ML), and caudolateral (CL) areas on the STG of one monkey (32). BFc, best center frequency; cs, central sulcus; ls, lateral sulcus; sts, superior temporal sulcus; ncr, no clear response.
Figure 2
Spectral and temporal integration in single neurons of the lateral belt in primates. Digitized monkey vocalizations were presented as stimuli, either as complete calls or as components manipulated in the spectral or temporal domain. (A) Nonlinear spectral summation. The “coo” call consists of a number of harmonic components and elicits a good response. If the call is low-pass-filtered with a cutoff frequency of 2 kHz, a much smaller response is obtained. The same is true for the high-pass-filtered version. Stimulation with the whole signal is repeated to demonstrate the reliability of the result (Bottom) (32). (B) Nonlinear temporal summation. The “harmonic arch” call consists of two “syllables.” Each of them alone elicits a much smaller response than the complete call.
Figure 3
Monkey-call preference index (MCPI) and spatial half width in the same neurons of rhesus monkey lateral belt. Results from the AL and CL areas are plotted in A and B, respectively.
Figure 4
Functional MRI study of the STG in a human subject while listening to speech sounds. A phonemic map may be recognized anterior of Heschl's gyrus resulting from superposition of activation by three different consonant/vowel combinations [ba, da, ga (64); courtesy of Brandon Zielinski, Georgetown University].
Figure 5
PET activation of the human brain during localization of virtual auditory space stimuli. (A) Statistical parametric mapping (SPM) projections of significant areas of activation from sagittal, coronal, and axial directions. PET areas are superimposed onto representative MRI sections. (B) Area of_de_-activation in the right anterior STG caused by auditory localization. [Based on data from Weeks et al. (58).]
Figure 6
Schematic flow diagram of “what” and “where” streams in the auditory cortical system of primates. The ventral “what”-stream is shown in green, the dorsal “where”-stream, in red. [Modified and extended from Rauschecker (35); prefrontal connections (PFC) based on Romanski et al. (46).] PP, posterior parietal cortex; PB, parabelt cortex; MGd and MGv, dorsal and ventral parts of the MGN.
References
- Zeki S M. Nature (London) 1978;274:423–428. - PubMed
- DeYoe E A, Van Essen D C. Trends Neurosci. 1988;11:219–226. - PubMed
- Ungerleider L G, Mishkin M. In: Analysis of Visual Behaviour. Ingle D J, Goodale M A, Mansfield R J W, editors. Cambridge, MA: MIT Press; 1982. pp. 549–586.
- Mishkin M, Ungerleider L G, Macko K A. Trends Neurosci. 1983;6:414–417.
- Livingstone M S, Hubel D H. Science. 1988;240:740–749. - PubMed
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