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The Journal of Neuroscience, May 14, 2008, 28(20):5344-5349; doi:10.1523/JNEUROSCI.5039-07.2008

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Brief Communications
Temporal Characteristics of Audiovisual Information Processing

Galit Fuhrmann Alpert,^1 * Grit Hein,^1 * Nancy Tsai,¹ Marcus J. Naumer,³ and Robert T. Knight^1,2

¹Helen Wills Neuroscience Institute and ²Psychology Department, University of California, Berkeley, Berkeley, California 94720, and ³Institute of Medical Psychology, J. W. Goethe University, 60528 Frankfurt am Main, Germany

Correspondence should be addressed to Galit Fuhrmann Alpert, Helen Wills Neuroscience Institute, University of California, Berkeley, 132 Barker Hall, Berkeley, CA 94720. Email: galit{at}berkeley.edu

In complex natural environments, auditory and visual information often have to be processed simultaneously. Previous functional magnetic resonance imaging (fMRI) studies focused on the spatial localization of brain areas involved in audiovisual (AV) information processing, but the temporal characteristics of AV information flow in these regions remained unclear. In this study, we used fMRI and a novel information–theoretic approach to study the flow of AV sensory information. Subjects passively perceived sounds and images of objects presented either alone or simultaneously. Applying the measure of mutual information, we computed for each voxel the latency in which the blood oxygenation level-dependent signal had the highest information content about the preceding stimulus. The results indicate that, after AV stimulation, the earliest informative activity occurs in right Heschl's gyrus, left primary visual cortex, and the posterior portion of the superior temporal gyrus, which is known as a region involved in object-related AV integration. Informative activity in the anterior portion of superior temporal gyrus, middle temporal gyrus, right occipital cortex, and inferior frontal cortex was found at a later latency. Moreover, AV presentation resulted in shorter latencies in multiple cortical areas compared with isolated auditory or visual presentation. The results provide evidence for bottom-up processing from primary sensory areas into higher association areas during AV integration in humans and suggest that AV presentation shortens processing time in early sensory cortices.

Key words: auditory; fMRI; information theory; multisensory; prefrontal cortex; visual

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Received Nov. 13, 2007; revised Feb. 29, 2008; accepted March 23, 2008.

Correspondence should be addressed to Galit Fuhrmann Alpert, Helen Wills Neuroscience Institute, University of California, Berkeley, 132 Barker Hall, Berkeley, CA 94720. Email: galit{at}berkeley.edu

Related articles in J. Neurosci.:

Propagation of Brain Activity during Audiovisual Integration

Meng Liang, Tessa M. van Leeuwen, and Michael J. Proulx
J. Neurosci. 2008 28: 8861-8862. [Full Text]  

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				M. Liang, T. M. van Leeuwen, and M. J. Proulx Propagation of Brain Activity during Audiovisual Integration J. Neurosci., September 3, 2008; 28(36): 8861 - 8862. [Full Text] [PDF]

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