Multisensory integration is at the core of many cognitive phenomena. It provides a survival advantage because it allows the brain to combine the independent estimates available from different sensory modalities into a single estimate that is more accurate than any single modality in isolation. A key obstacle to progress is our lack of knowledge about how the brain combines different modalities. If sensory modality #1 claims that the environment is "X" while sensory modality #2 claims that the environment is "Y", how can the estimates best be combined to guide behavior? An important finding in behavioral studies is that multisensory integration is Bayes-optimal-that is, the reliability of different sensory modalities are taken into account when integrating them. Sensory inputs that are reliable (more informative) receive greater weights, while sensory inputs that are less informative receive less weight. The goal of this proposal is to uncover the neural mechanisms for optimal visual-tactile integration. Our central hypothesis takes the form of a simple model in which the strengths of connections from unisensory to multisensory brain areas are modulated by the reliability of the stimulus in each modality. An unreliable stimulus results in a weak connection, decreasing the effectiveness of that modality in the integration area, while a reliable stimulus results in a strong connection and increased ability to drive behavior. To test our model, we propose four specific aims that will examine two distinct paradigms: a touch delivered to the hand that is both seen and felt;and speech that is both seen and heard. In the first aim, we will determine the brain areas involved in these two types of stimuli using blood oxygen-level dependent functional magnetic resonance imaging (BOLD fMRI). We will test the hypothesis that the intraparietal sulcus (IPS) will respond to visual and tactile touch and that the superior temporal sulcus (STS) will respond to auditory and visual speech. In the second aim, we will show that neural connection strengths are proportional to stimulus reliability. We will test the hypothesis that the effective connectivity between unisensory and multisensory areas will be proportional to the reliability of the stimulus presented in that modality. In the third aim, we will demonstrate a correlation between multisensory brain activity and behavior using multi-voxel pattern analysis (MVPA). In the fourth aim, we will reveal a causal link between brain activity and behavioral multisensory integration. Using fMRI-guided transcranial magnetic stimulation (TMS), we will test the hypothesis that TMS of multisensory areas will eliminate the behavioral advantage of multisensory stimuli and the hypothesis that TMS of unisensory areas will impair behavioral performance proportional to the reliability of the stimulus in that modality.

Public Health Relevance

Multisensory integration is at the core of many cognitive phenomena. We will use functional magnetic resonance imaging (fMRI) and transcranial magnetic stimulation (TMS) in normal human subjects to study the organization and operation of the brain during multisensory integration.

Agency
National Institute of Health (NIH)
Institute
National Institute of Neurological Disorders and Stroke (NINDS)
Type
Research Project (R01)
Project #
5R01NS065395-05
Application #
8604429
Study Section
Cognitive Neuroscience Study Section (COG)
Program Officer
Gnadt, James W
Project Start
2010-02-01
Project End
2015-01-31
Budget Start
2014-02-01
Budget End
2015-01-31
Support Year
5
Fiscal Year
2014
Total Cost
$259,337
Indirect Cost
$85,693
Name
University of Texas Health Science Center Houston
Department
Neurosciences
Type
Schools of Medicine
DUNS #
800771594
City
Houston
State
TX
Country
United States
Zip Code
77225
Magnotti, John F; Beauchamp, Michael S (2015) The noisy encoding of disparity model of the McGurk effect. Psychon Bull Rev 22:701-9
Baum, Sarah H; Beauchamp, Michael S (2014) Greater BOLD variability in older compared with younger adults during audiovisual speech perception. PLoS One 9:e111121
Ro, Tony; Ellmore, Timothy M; Beauchamp, Michael S (2013) A neural link between feeling and hearing. Cereb Cortex 23:1724-30
Nath, Audrey R; Beauchamp, Michael S (2012) A neural basis for interindividual differences in the McGurk effect, a multisensory speech illusion. Neuroimage 59:781-7
Chen, Gang; Saad, Ziad S; Nath, Audrey R et al. (2012) FMRI group analysis combining effect estimates and their variances. Neuroimage 60:747-65
Nath, Audrey R; Fava, Eswen E; Beauchamp, Michael S (2011) Neural correlates of interindividual differences in children's audiovisual speech perception. J Neurosci 31:13963-71
Beauchamp, Michael S; Beurlot, Michelle R; Fava, Eswen et al. (2011) The developmental trajectory of brain-scalp distance from birth through childhood: implications for functional neuroimaging. PLoS One 6:e24981
Nath, Audrey R; Beauchamp, Michael S (2011) Dynamic changes in superior temporal sulcus connectivity during perception of noisy audiovisual speech. J Neurosci 31:1704-14
Beauchamp, Michael S; Pasalar, Siavash; Ro, Tony (2010) Neural substrates of reliability-weighted visual-tactile multisensory integration. Front Syst Neurosci 4:25
Beauchamp, Michael S; Nath, Audrey R; Pasalar, Siavash (2010) fMRI-Guided transcranial magnetic stimulation reveals that the superior temporal sulcus is a cortical locus of the McGurk effect. J Neurosci 30:2414-7

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