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. Author manuscript; available in PMC: 2012 Nov 1.
Published in final edited form as: Neuropsychologia. 2011 Sep 12;49(13):3563–3572. doi: 10.1016/j.neuropsychologia.2011.09.008

Figure 3.

Figure 3

Positive correlation with phonotactic frequency in the pars triangularis

Words that consisted of more frequent phoneme pairs elicited the highest activity in the PTr. A) Voxels shown in red passed a threshold of t(34) = 3.35, p = 0.001 uncorrected, with cluster-size corrected p < 0.001, displayed on the rendered grey matter template in study-specific space. B) Joint phonotactic frequency effects in the current results and Vaden et al. (2011). In order to compare the significant positive correlations in both studies within a common stereotactic space, we segmented the template used in Vaden et al. (2011) then normalized the gray matter template and results from the current study into that space using ANTS (http://www.picsl.upenn.edu/ANTS). We assessed the joint statistic maps at a threshold of p = 0.001 (uncorrected), based on the conjunction of each study’s positive phonotactic frequency statistic maps, thresholded at p =0.01. Different thresholds were needed for each study since they differed in degrees of freedom: t(33) = 3.36 for the current study and t(16)=3.69 for Vaden et al (2011). Significant voxels (red) formed two clusters in the left IFG extending from the lateral pars triangularis into medial pars opercularis, and lateral inferior frontal sulcus to medial anterior insula. This illustrates voxels in both studies in a common stereotactic space that increased activity in response to high phonotactic frequency words, with the caveat that different preprocessing steps were used in each study, including normalization methods and smoothing kernel. We elaborate on differences that related to the significance of this replication in the discussion section. C) The reaction time control analysis demonstrated a significant positive correlation between reaction time and activity in neighboring frontal sub-regions including pars orbitalis, lateral anterior insula, and motor cortex (green), with only one voxel overlap with the phonotactic frequency effect (red). Voxels were thresholded at t(33) = 3.36, p = 0.001 uncorrected, cluster size p = 0.05 corrected (30 voxels minimum).