Changes in Functional Connectivity Associated with Direct Training and Generalization Effects of a Theory-Based Generative Naming Treatment
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1
Boston University, Speech, Language, and Hearing Sciences, United States
Introduction
Persons with aphasia (PWA) who are trained to generate abstract words (e.g., justice) in a specific context-category (e.g., courthouse) have been shown to improve not only on the trained items, but also on concrete words (e.g., lawyer) in the same context-category (Kiran, Sandberg, & Abbott, 2009; Sandberg & Kiran, in press). However, the underlying neural mechanism of this generalization effect is unknown. Using graph theory, the current study examines changes in task-based functional connectivity in PWA before and after training abstract word retrieval to help uncover the neural mechanisms associated with direct training and generalization.
Methods
Ten right-handed, English-speaking PWA in the chronic phase of recovery secondary to left hemisphere stroke (3 female, 7 male; mean age: 59) participated in the experiment. All PWA were scanned using fMRI before and after a theory-based generative naming treatment in which training abstract words promotes generalization to concrete words in the same context-category (Kiran et al., 2009; Sandberg & Kiran, in press). Additionally, three PWA served as their own controls, participating in two fMRI scans, 10 weeks apart, before treatment began.
The fMRI task consisted of a word judgment paradigm in which participants explicitly labeled words as either abstract or concrete. Task-based functional connectivity analyses were performed using the CONN toolbox for SPM8. Regions of interest (ROI) were created by constructing a 5 mm sphere around peak activations for abstract and concrete words both pre- and post-treatment. Semipartial ROI-ROI correlations were conducted individually for each patient to define an “abstract network” and a “concrete network” for each time point (i.e., pre- and post-treatment). The pre- and post-treatment correlation matrices for each network were subtracted from each other to directly evaluate changes in functional connectivity. To identify specific regions heavily involved in pre- to post-treatment changes in functional connectivity, we calculated node degree for regions involved in significant changes in correlation strength.
Results
Nine PWA improved on the trained abstract words; seven PWA also showed generalization to concrete words in the same context-category. The region with the highest node degree in the trained abstract network across PWA was left inferior frontal gyrus pars triangularis (L IFGtri); while the highest node degree in the generalized concrete network was left precentral gyrus. Regions that showed increased connectivity for both training and generalization included L IFGtri, right middle frontal gyrus (MFG), and bilateral angular gyrus. Regions that showed increased connectivity regardless of whether or not treatment was given and whether or not treatment was successful included left MFG and bilateral superior frontal gyrus. Additionally, PWA who generalized showed more left than right hemisphere changes in both abstract and concrete networks; while PWA who improved on the trained abstract words, but did not generalize to concrete words showed more left than right hemisphere changes for the abstract network, but more right than left hemisphere changes for the concrete network. These results suggest that (a) direct training and generalization are tapping into similar neural mechanisms, and (b) changes in the left hemisphere coincide with better treatment outcomes.
Acknowledgements
This research was supported by the National Institute On Deafness And Other Communication Disorders of the National Institutes of Health under Award Number F31DC011220.
References
Kiran, S., Sandberg, C., & Abbott, K. (2009). Treatment for lexical retrieval using abstract and concrete words in persons with aphasia: Effect of complexity. Aphasiology, 23, 835-853.
Sandberg, C. W., & Kiran, S. (in press). How Justice Can Affect Jury: Training Abstract Words Promotes Generalization to Concrete Words in Patients with Aphasia. Neuropsychological Rehabilitation.
Keywords:
Aphasia treatment,
functional connectivity,
fMRI,
graph theoretical analysis,
neuroplasticity
Conference:
Academy of Aphasia -- 52nd Annual Meeting, Miami, FL, United States, 5 Oct - 7 Oct, 2014.
Presentation Type:
Poster presentation ONLY
Topic:
Student award eligible
Citation:
Sandberg
CW,
Kiran
S and
Bohland
JW
(2014). Changes in Functional Connectivity Associated with Direct Training and Generalization Effects of a Theory-Based Generative Naming Treatment.
Front. Psychol.
Conference Abstract:
Academy of Aphasia -- 52nd Annual Meeting.
doi: 10.3389/conf.fpsyg.2014.64.00052
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Received:
25 Apr 2014;
Published Online:
04 Aug 2014.
*
Correspondence:
Dr. Chaleece W Sandberg, Boston University, Speech, Language, and Hearing Sciences, Boston, MA, 02215, United States, cws18@psu.edu