Modulation of the FFA and PPA while listening to sentences about faces and places

1. Modulation of the FFA and PPA while listening to sentences about faces and places Lisa Aziz-Zadeh, Christian Fiebach, Srini Naranayan, Jerome Feldman, Ellen Dodge, Richard Ivry University of California, Berkeley & International Computer Science Institute BACKGROUND • The thesis of embodied semantics holds that conceptual representations accessed during linguistic processing include sensory/motor representations of the concept in question. • Here we consider semantic representations for faces and places. • Will the FFA and PPA show modulation for sentences relating to faces/places? Figure 3:Signal change in the FFA and PPA for observation of faces (grey) and places (white), in peak voxels for the FFA and PPA defined individually for each subject. Note that as expected, each set of peak voxels responds most strongly to the observation of the entity on the basis of which it was identified. METHODS • 13 Participants listened to sentences describing faces, places, or objects. • In the first run, all sentences pertained to generic faces/places. In the second run, the sentences referred to famous faces/places. • A visual localizer task was used to identify the left and right FFA & PPA in each subject. • The percent signal change when listening to sentences related to faces/places was compared to rest was found for each ROI. Figure 4:(c) Signal change in the left FFA and left PPA for reading of phrases related to famous faces and famous places (ie. “Marilyn Monroe has blond hair and smooth pale skin.”), in the same voxels identified in Figure 3. Note that each set of peak voxels is most inhibited by listening to phrases relating to its preferred stimulus of observation. The interaction of voxel by stimulus type was significant. (d) As for (c), but in the right hemisphere. There was no significant interaction. RESULTS: Figure 1: All language trials compared to rest. In red, generic sentence trials (Run 1); and in blue, famous sentence trials (Run 2). Temporal auditory areas are significantly activated as are the posterior language areas. Broca’s area is significantly active only in Run 1. Figure 5:(e&f) The same as (c&d), but for listening to generic faces and places sentences (i.e. “The farmer has bush eyebrows above his large brown eyes”). There was no significant interaction, but the same pattern is observed bilaterally for the FFA, and in the right hemisphere for the PPA. DISCUSSION: • Contrary to our expectations, FFA was less active when listening to sentences describing faces, whereas PPA was less active when listening to sentences describing places. The latter effect was limited to the famous places condition. • This modulation was only significant in the left hemisphere. • Processing sentences may require inhibition of visual processing areas in a content-specific manner. Perhaps this inhibition prevents current perceptual input from interfering with retrieval of semantic referents. Figure 2: ROIs in three sample subjects: Observation of faces compared to places activates the fusiform face area (FFA, red) and observation of places compared to faces activates the parahippocampal place area (PPA, blue). In 8/13 participants, activations were bilateral. For the other 5 participants, a left hemisphere FFA was not observed. For each subject, the ROIs in each area consisted of the peak voxel with a surrounding 16 mm Gaussian.