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Imagery or meaning? Evidence for a semantic origin of category-specific brain activity in metabolic imaging.

Hauk O, Davis MH, Kherif F, Pulvermüller F - Eur. J. Neurosci. (2008)

Bottom Line: First, we corroborated previous results showing that action-relatedness modulates neural responses in action-related areas, while word imageability modulates activation in object processing areas.Second, we provide novel results showing that activation negatively correlated with word frequency in the left fusiform gyrus was specific for visually related words, while in the left middle temporal gyrus word frequency effects emerged only for action-related words.Following the dominant view in the literature that effects of word frequency mainly reflect access to lexico-semantic information, we suggest that category-specific brain activation reflects distributed neuronal ensembles, which ground language and concepts in perception-action systems of the human brain.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council, Cognition and Brain Sciences Unit, Cambridge, UK. olaf.hauk@mrc-cbu.cam.ac.uk

ABSTRACT
Category-specific brain activation distinguishing between semantic word types has imposed challenges on theories of semantic representations and processes. However, existing metabolic imaging data are still ambiguous about whether these category-specific activations reflect processes involved in accessing the semantic representation of the stimuli, or secondary processes such as deliberate mental imagery. Further information about the response characteristics of category-specific activation is still required. Our study for the first time investigated the differential impact of word frequency on functional magnetic resonance imaging (fMRI) responses to action-related words and visually related words, respectively. First, we corroborated previous results showing that action-relatedness modulates neural responses in action-related areas, while word imageability modulates activation in object processing areas. Second, we provide novel results showing that activation negatively correlated with word frequency in the left fusiform gyrus was specific for visually related words, while in the left middle temporal gyrus word frequency effects emerged only for action-related words. Following the dominant view in the literature that effects of word frequency mainly reflect access to lexico-semantic information, we suggest that category-specific brain activation reflects distributed neuronal ensembles, which ground language and concepts in perception-action systems of the human brain. Our approach can be applied to any event-related data using single-stimulus presentation, and allows a detailed characterization of the functional role of category-specific activation patterns.

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Category-specific effects of word frequency. (A) Brain areas significantly negatively correlated with Frequency for action-related words (red) and visually related words (blue) separately, projected on the surface (top) and on cortical slices (bottom) of a standard brain. Activation is displayed at a statistical threshold P < 0.001 uncorrected. The rendered image at the upper right represents the overlap of activations from this analysis with that presented in Fig. 1A at threshold P < 0.01. Colour coding reflects t-values. Coordinates and statistics are provided in Table 2. (B) The left diagram presents parameter estimates for the variable Frequency for action-related words and visually related words separately, for peak voxels in the left middle temporal gyrus (LMT) and left fusiform gyrus (LFF). The right diagram shows parameter estimates for the same voxels but for the variables Action-relatedness (Act.-rel.) and Imageability (Imag.) across all words independent of word category. The error bars represent within-subject standard errors.
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fig02: Category-specific effects of word frequency. (A) Brain areas significantly negatively correlated with Frequency for action-related words (red) and visually related words (blue) separately, projected on the surface (top) and on cortical slices (bottom) of a standard brain. Activation is displayed at a statistical threshold P < 0.001 uncorrected. The rendered image at the upper right represents the overlap of activations from this analysis with that presented in Fig. 1A at threshold P < 0.01. Colour coding reflects t-values. Coordinates and statistics are provided in Table 2. (B) The left diagram presents parameter estimates for the variable Frequency for action-related words and visually related words separately, for peak voxels in the left middle temporal gyrus (LMT) and left fusiform gyrus (LFF). The right diagram shows parameter estimates for the same voxels but for the variables Action-relatedness (Act.-rel.) and Imageability (Imag.) across all words independent of word category. The error bars represent within-subject standard errors.

Mentions: The crucial prediction of our study was tested in a separate analysis that looked at the two critical word categories separately. Words were grouped into action- and visually related words, which were specified as different columns of the design matrix. Each of these two word groups was assigned the same five simultaneous regressors as in the first analysis, including the crucial variable, Frequency. This model yielded the results presented in Fig. 2 and Table 2.


Imagery or meaning? Evidence for a semantic origin of category-specific brain activity in metabolic imaging.

Hauk O, Davis MH, Kherif F, Pulvermüller F - Eur. J. Neurosci. (2008)

Category-specific effects of word frequency. (A) Brain areas significantly negatively correlated with Frequency for action-related words (red) and visually related words (blue) separately, projected on the surface (top) and on cortical slices (bottom) of a standard brain. Activation is displayed at a statistical threshold P < 0.001 uncorrected. The rendered image at the upper right represents the overlap of activations from this analysis with that presented in Fig. 1A at threshold P < 0.01. Colour coding reflects t-values. Coordinates and statistics are provided in Table 2. (B) The left diagram presents parameter estimates for the variable Frequency for action-related words and visually related words separately, for peak voxels in the left middle temporal gyrus (LMT) and left fusiform gyrus (LFF). The right diagram shows parameter estimates for the same voxels but for the variables Action-relatedness (Act.-rel.) and Imageability (Imag.) across all words independent of word category. The error bars represent within-subject standard errors.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2327213&req=5

fig02: Category-specific effects of word frequency. (A) Brain areas significantly negatively correlated with Frequency for action-related words (red) and visually related words (blue) separately, projected on the surface (top) and on cortical slices (bottom) of a standard brain. Activation is displayed at a statistical threshold P < 0.001 uncorrected. The rendered image at the upper right represents the overlap of activations from this analysis with that presented in Fig. 1A at threshold P < 0.01. Colour coding reflects t-values. Coordinates and statistics are provided in Table 2. (B) The left diagram presents parameter estimates for the variable Frequency for action-related words and visually related words separately, for peak voxels in the left middle temporal gyrus (LMT) and left fusiform gyrus (LFF). The right diagram shows parameter estimates for the same voxels but for the variables Action-relatedness (Act.-rel.) and Imageability (Imag.) across all words independent of word category. The error bars represent within-subject standard errors.
Mentions: The crucial prediction of our study was tested in a separate analysis that looked at the two critical word categories separately. Words were grouped into action- and visually related words, which were specified as different columns of the design matrix. Each of these two word groups was assigned the same five simultaneous regressors as in the first analysis, including the crucial variable, Frequency. This model yielded the results presented in Fig. 2 and Table 2.

Bottom Line: First, we corroborated previous results showing that action-relatedness modulates neural responses in action-related areas, while word imageability modulates activation in object processing areas.Second, we provide novel results showing that activation negatively correlated with word frequency in the left fusiform gyrus was specific for visually related words, while in the left middle temporal gyrus word frequency effects emerged only for action-related words.Following the dominant view in the literature that effects of word frequency mainly reflect access to lexico-semantic information, we suggest that category-specific brain activation reflects distributed neuronal ensembles, which ground language and concepts in perception-action systems of the human brain.

View Article: PubMed Central - PubMed

Affiliation: Medical Research Council, Cognition and Brain Sciences Unit, Cambridge, UK. olaf.hauk@mrc-cbu.cam.ac.uk

ABSTRACT
Category-specific brain activation distinguishing between semantic word types has imposed challenges on theories of semantic representations and processes. However, existing metabolic imaging data are still ambiguous about whether these category-specific activations reflect processes involved in accessing the semantic representation of the stimuli, or secondary processes such as deliberate mental imagery. Further information about the response characteristics of category-specific activation is still required. Our study for the first time investigated the differential impact of word frequency on functional magnetic resonance imaging (fMRI) responses to action-related words and visually related words, respectively. First, we corroborated previous results showing that action-relatedness modulates neural responses in action-related areas, while word imageability modulates activation in object processing areas. Second, we provide novel results showing that activation negatively correlated with word frequency in the left fusiform gyrus was specific for visually related words, while in the left middle temporal gyrus word frequency effects emerged only for action-related words. Following the dominant view in the literature that effects of word frequency mainly reflect access to lexico-semantic information, we suggest that category-specific brain activation reflects distributed neuronal ensembles, which ground language and concepts in perception-action systems of the human brain. Our approach can be applied to any event-related data using single-stimulus presentation, and allows a detailed characterization of the functional role of category-specific activation patterns.

Show MeSH