Abstract
Sound localization is an important function of the human brain, but the underlying cortical mechanisms remain unclear. In this study, we recorded auditory stimuli in three-dimensional space and then replayed the stimuli through earphones during functional magnetic resonance imaging (fMRI). By employing a machine learning algorithm, we successfully decoded sound location from the blood oxygenation level-dependent signals in the temporal lobe. Analysis of the data revealed that different cortical patterns were evoked by sounds from different locations. Specifically, discrimination of sound location along the abscissa axis evoked robust responses in the left posterior superior temporal gyrus (STG) and right mid-STG, discrimination along the elevation (EL) axis evoked robust responses in the left posterior middle temporal lobe (MTL) and right STG, and discrimination along the ordinate axis evoked robust responses in the left mid-MTL and right mid-STG. These results support a distributed representation of acoustic space in human cortex.
Highlights
Sound localization plays an important role in everyday life
Univariate functional magnetic resonance imaging (fMRI) Data Analysis During Experiment 3, functional images were collected for each subject while they were listening to the individually recorded stimuli
Consistent with previous studies (Wessinger et al, 2001; Pavani et al, 2002; Zimmer et al, 2006; Deouell et al, 2007; Lewald et al, 2008), univariate analysis revealed that the stimuli, when combined, evoked significant fMRI responses across the auditory cortex bilaterally (Figure 3)
Summary
We can automatically identify the location of an acoustic target even in a noisy environment This perception is mainly derived from interaural time differences (ITD), interaural level differences (ILD) and spectral cues (Blauert, 1997; Cohen and Knudsen, 1999; Grothe et al, 2010). It is reasonable to expect a topographic representation of sound location in the auditory cortex (Jeffress, 1948) because topographic representations, such as the tonotopic map found in primary auditory cortex (Merzenich et al, 1975) and the orientation map found in primary visual cortex (Hubel and Wiesel, 1959), seem to be a hallmark of cortical organization. Such a representation has not been found even after
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