The Role of The Left and Right Inferior Frontal Gyrus in Language Recovery in Aphasia

The role of the left and right inferior frontal gyrus in language recovery in aphasia INTRODUCTION RESULTS 1. Research Question 1: Correlations between % spared tissue and ipsilesional % signal change Only one region, the IFG triangularis, showed a correlation that approached significance (rho = -1, p = .08). – • Some studies have underlined the role of LIFG in recovery mechanisms (Sebastian & Kiran, 2011; Saur et al., 2006; Fridriksson, 2010). • Other studies have implicated the RIFG in compensatory functions (Abo et al., 2004; Fridriksson & Morrow, 2005). 2 % Signal Change in Ipsilesional IFGtri Main Hypothesis: LIFG is very important in language recovery to the extent that LIFG tissue is spared post stroke. Research Question: What is the relationship between % spared tissue and % signal change 1) in the IFG and ipsilesional tissue? 2) in the IFG and corresponding contralesional tissue? 3) in the IFG and all other regions? Correlation Between % Signal Change and % Spared Tissue in IFGtri Lesion Region Left MCA Lesion Size (volume of cortex) P3 55 Male 76 P4 54 Male 108 P5 59 Male 144 P6 59 Male 23 P7 49 Male 168 Left ICA Left MCA Right MCA Left MCA Left MCA Left MCA 85cc 112cc 133cc 180cc 180cc 228cc 314 cc 60 80 Correlation Between Ipsilesional % of Spared Tissue and Contralesional % Signal Change in IFGtri 1 0.8 0.6 0.4 rho = -0.95, p =0.003 0.2 0 -0.2 -0.4 0 10 20 30 40 50 Percentage of Spared Tissue in Ipsilesional IFGop 1.2 1 0.8 0.6 0.4 0 -0.2 -0.4 20 40 60 80 100 Percentage of Spared Tissue in Ipsilesional IFGtri Correlation between % of Spared Tissue in Ipsilesional IFGop and % Signal Change in Contralesional MFG 0.4 0.3 0.2 rho = -0.82, p = 0.03 0.1 0 -0.1 0 10 20 30 40 50 -0.2 -0.3 -0.4 -0.5 Percentage of Spared Tissue in Ipsilesonal IFGop 1.2 1 0.8 0.6 0.4 rho = -0.78, p = 0.04 0.2 0 -0.2 0 -0.4 10 20 30 40 50 Percentage of Spared Tissue in Ipsilesional IFGop Percent Signal Change in Ipsilesional MFG Correlation Between % of Spared Tissue in Ipsilesional IFGtri and % Signal Change in Ipsilesional MFG 0.4 rho = -0.85, p = 0.01 0.2 0 0 20 40 60 80 100 -0.2 -0.4 -0.6 Percentage of Spared Tissue in Ipsilesional IFGtri 4. How does the extent of damage determine engagement? Patient 3 0.25 Percent Signal Change 0.2 0.15 0.1 0.05 0 -0.05 -0.1 -0.15 -0.2 LIFGop (24% spared) RIFGop LIFGtri (70% spared) RIFGtri LMFG (73% spared) RMFG LMTG (14% spared) RMTG RMFG LMTG (82% spared) RMTG RMFG LMTG (5% spared) RMTG Patient 6 1.4 1.2 1 Percent Signal Change IFG opercularis IFG orbitalis IFG triangularis Middle Frontal Gyrus Superior Frontal Gyrus Angular + Suprmarginal Gyri Middle Temporal Gyrus Anterior Cingulate 0 Three regions showed a significant negative correlation between ipsilesional spared tissue in the IFG and signal changes within the MFG, two approached significance. i. IFG opercularis to ipsilesional MFG (rho = -0.82, p = 0.03) ii. IFG triangularis to ipsilesional MFG (rho = -0.85, p = 0.01) iii. IFG orbitalis to ipsilesional MFG (rho = -0.75, p = 0.07) iv. IFG opercularis to contralesional MFG (rho = -0.78, p = 0.04) v. IFG triangularis to contralesional MFG (rho = -0.70, p = 0.08) Statistical Modeling in SPM8 Bilateral ROIs rho = -0.85, p = 0.01 0.2 3. Research Question 3: Correlations between % spared tissue in IFG and % signal change in other brain regions Preprocessing in SPM8 Fixed Effects Analysis using GLM Canonical HRF and its Temporal Derivative High Pass Filter of 128 s 100 % of Spared Tissue 1.2 Percent Signal Change in Ipsilesional MFG Participants were scanned once while performing a semantic language task in English. Data Acquisition Parameters: • T1: 140 sagittal slices, 1mm3 voxels, 240 x 240 matrix, FOV = 240 mm, flip angle = 8, fold-over direction = AP, TR = 8.2ms, TE = 3.8ms • BOLD:31 axial slices (3mm thick, 0.3 interslice gap), 3mm3 voxels, 80 x 78 matrix, FOV = 240, flip angle = 90, fold-over direction = AP, TR = 2000ms, TE = 35ms • • • • • • • • 40 Correlation Between % of Spared Tissue in Ipsilesional IFGop and % Signal Change in Ipsilesional MFG METHODS • • • 20 Correlation Between Ipsilesional % of Spared Tissue and Contralesional % Signal Change in IFGop Lesion overlap in left hemisphere (n=6) and right hemisphere (n=1) Lesion Masking (MRIcron) Slice Timing Realignment Coregistration Segmentation (lesion masked as Brett et al., 2001) • Normalization • ART Repair (Mazaika et al., 2009) 0 Two regions showed a significant negative correlation between ipsilesional spared tissue and contraslesional signal changes. i. IFG opercularis (rho = -0.93, p = 0.003) ii. IFG triangularis (rho = -0.85, p = 0.01) – – • • • • • 0 Percent Signal Change in Contralesional MFG Age Gender Months Post Stroke P2 66 Female 15 rho = -1, p = 0.08 0.5 2. Research Question 2: Correlations between % spared tissue and contralesional % signal change Percent Signal Change in Contralesional IFGop P1 56 Female 38 1 -0.5 PARTICIPANTS Table 1. Participant Profiles 1.5 Percent Signal Change in Contralesional IFGtri The mechanisms of the involvement of the left and right inferior frontal gyrus (IFG) in the process of post-stroke language recovery are not well understood. 0.8 0.6 0.4 0.2 0 -0.2 -0.4 LIFGop (0% spared) RIFGop LIFGtri (0% spared) RIFGtri LMFG (21% spared) ROI and Correlation Analysis • • Subtracted normalized lesion maps from ROI maps (AAL atlas) Calculated ROI volumes using MRIcron Calculated % of spared tissue as (Anatomical ROI Volume –Lesion Volume)/(Anatomical ROI Volume) Calculated % signal change in ROIs using Marsbar (Brett et al., 2002) Non-parametric Spearman correlation determined for the % spared tissue in each ipsilesional ROI and % signal change within each ROI Patient 5 2 1.5 Percent Signal Change • • • 1 0.5 0 -0.5 LIFGop (19% spared) RIFGop LIFGtri (24% spared) RIFGtri LMFG (74% spared) CONCLUSIONS • Despite extensive damage, spared LIFG tissue shows consistent activation in a semantic task. • In the IFGop and IFGtri, increased damage is also associated with significantly increased signal change in the contralesional IFG and MFG and the ipsilesional MFG. • When the IFG is not spared, contralesional IFG is engaged. When some IFG is spared, ipsilesional structures (IFG, MFG) are engaged. • These data therefore highlight the importance of the preservation and consequent activation of left IFG in language recovery in aphasia.