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Neural Correlates of Sentence Comprehension Recovery – A Longitudinal Study

Shannon M. Sheppard1*, Kevin Kim1, Lynsey M. Keator1, Bonnie L. Breining1, Donna C. Tippett1, 2, 3 and Argye E. Hillis1, 2, 4
  • 1 Johns Hopkins Medicine, Department of Neurology, United States
  • 2 Johns Hopkins Medicine, Department of Physical Medicine & Rehabilitation, United States
  • 3 Johns Hopkins University, Department of Otolaryngology—Head and Neck Surgery, United States
  • 4 Johns Hopkins University, Department of Cognitive Science, United States

Introduction Left-hemisphere (LH) damage following stroke often results in sentence comprehension impairments. Several LH areas have been implicated including Broca’s area (pars opercularis (IFGop) and pars triangularis (IFGtr) in Inferior Frontal Gyrus (IFG), Middle Frontal Gyrus (MFG), Superior Temporal Gyrus (STG), Middle Temporal Gyrus (MTG), and Angular Gyrus(AG)) [1–3]. Most studies examining sentence comprehension have focused on individuals with chronic aphasia; the likelihood of recovery from acute to chronic stages is largely unknown. The current study aimed to investigate longitudinal sentence comprehension recovery from acute to chronic stages; taking into account percent damage to critical LH regions and initial performance. Percent damage to six ROIs were examined: IFGop, IFGtr, MFG, STG, MTG, and AG. Four sentence types were assessed: actives, subject relatives (SR), passives, and object relatives (OR) using the SOAP [4]. Methods Thirteen participants (mean age = 56±15.77 years; 5 women) were followed from acute (within 48 hours of stroke) to chronic (6 months post stroke) recovery stages following LH ischemic stroke. Participants with previous symptomatic strokes were excluded. Acutely, participants received an MRI, including diffusion-weighted imaging (DWI). Areas of acute ischemia were identified and traced on DWI images using MRIcron software [5]. The SOAP was administered at acute and chronic time points. DWI Trace images and lesions traced on these images were normalized using SPM12 in Matlab. Using the NiiStat toolbox (http://www.mccauslandcenter.sc.edu/CRNL/tools/niistat), the proportion of damaged tissue in each of the parcels in the JHU atlas [6] were calculated each patient. Multivariable linear regressions were carried out to predict chronic SOAP scores for each sentence type, based on acute SOAP scores, the percentage of voxels damaged in each ROI, age, and total lesion volume. Results Together, percent damage to several ROIs could account for a large percentage of degree of recovery of three sentence types: active (F (4, 9) =112.5, p < .001; R2 = .987); SR (F (4, 9) = 337.2, p < .001; R2 =.996); passive (F (4, 9) = 21.96, p = .003); and OR (F (4, 9) = 33.89, p = .001) sentences. Significant predictors (p) for actives included: acute scores (.041), lesion volume (.028), percent damage to IFGop (.21), MFG (.004), and STG (.037). For SRs, acute scores (.004), lesion volume (.005), and percent damage to IFGtri (.036), MFG (.018), MTG (.018), STG (.009) and AG (.050), were significant predictors. Finally, significant predictors for ORs were age (.028) and percent damage to MFG (.048). Overall, sentence comprehension improved in 61.5%, maintained in 7.69%, and declined in 30.7% of participants. Discussion The results demonstrate sentence comprehension can recover from acute to chronic stages, although about 1/3 of participants showed decline. Recovery of each sentence type was predicted by a different pattern of lesion location. MFG, but not Broca’s area was imperative for the recovery of complex OR sentence comprehension. Interestingly, acute scores on non-canonical sentences (ORs/passives) were not significant predictors of recovery. These results offer an critical insight into post-stroke functional reorganization and important factors to consider when predicting recovery and planning treatment.

Acknowledgements

This work was supported by the National Institute of Deafness and Other Communication Disorders (NIDCD) [grant number R01 DC005375].

References

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Keywords: Aphasia, acute stroke, sentence comprehension, Recovery, syntax

Conference: Academy of Aphasia 56th Annual Meeting, Montreal, Canada, 21 Oct - 23 Oct, 2018.

Presentation Type: poster presentation

Topic: not eligible for a student prize

Citation: Sheppard SM, Kim K, Keator LM, Breining BL, Tippett DC and Hillis AE (2019). Neural Correlates of Sentence Comprehension Recovery – A Longitudinal Study. Conference Abstract: Academy of Aphasia 56th Annual Meeting. doi: 10.3389/conf.fnhum.2018.228.00099

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Received: 01 May 2018; Published Online: 22 Jan 2019.

* Correspondence: Dr. Shannon M Sheppard, Johns Hopkins Medicine, Department of Neurology, Baltimore, MD, 21287, United States, sheppard@jhmi.edu