Functional connectivity in post-stroke aphasia: innovative tools at the service of evidence-based practice
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1
Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Canada
Introduction:
Stroke remains a major health problem with over 800,000 people living with post-stroke aphasia in Canada. In post-stroke aphasia, the resulting language deficits are the source of long-term handicap. From a neurofunctional perspective, aphasia affects the integrity of neural networks contributing to language processing. Specifically, the canonical language network (CLN), including Broca and Wernicke is altered after a stroke. More recently, our team documented poor integration within the default mode network (DMN), in patients with chronic aphasia, and improved connectivity after noun anomia therapy with SFA/N (Semantic Feature Analysis). The purpose of the present study was to examine DMN network dynamics within the context of verb anomia therapy with a modified version of SFA, adapted to verb anomia therapy (SFA/V) More specifically, the aim is to examine DMN integration before and after therapy with SFA, and to gather functional connectivity pre-therapy markers that characterize a good response to SFA/V.
Methodology:
Nine participants with chronic aphasia and moderate to severe anomia, secondary to a left-hemisphere stroke (between 4 and 25 years post-stroke) received from SFA/V to improve verb production. Functional connectivity markers of good response to SFA/V were gathered within the DMN. Measures were collected in healthy controls, and in persons with aphasia during two fMRI sessions, prior- and post SFA/V therapy. Functional connectivity was quantified via integration measures reflecting synchronously different brain areas are engaged during a given task.
Results:
Prior to SFA/V, functional integration with the DMN was decreased in participants with aphasia, as compared with controls. After SFA/V, a functional connectivity within the DMN improved, concurrently with behavioral improvement in verb naming. Moreover, functional connectivity within the DMN showed a distinct pattern following SFA/V, as compared to SFA/N, from our previous work (Marcotte et al 2013). Specifically, with SFA/V a normalization of integration values was observed particularly in the anterior DMN sub-network, whereas with SFA/N, the main contribution to normalization within the DMN connectivity came from the posterior sub-network. Moreover, there was a positive correlation between DMN connectivity prior to therapy, and verb naming recovery following SFA/V (r=0.710, p= 0.032), mostly explained by the posterior subnetwork contribution (r = 0.817; p= 0.007)
Discussion:
This study presents an innovative approach to clinical management in post-stroke aphasia. Specifically, the evidence shows that specific anomia therapy for verbs normalizes DMN integration, thus reflecting the large scope impact of speech therapy. Also, the correlation between DMN integration values and reactivity to SFA/V shows that DMN status before therapy can be predictive of response to specific therapy. Altogether, these results show that functional integration measures of the DMN can highlight prognosis and therapy efficiency in aphasia rehabilitation.
References
Binder, J. R., Desai, R. H., Graves, W. W., & Conant, L. L. (2009). Where is the semantic system? A critical review and meta-analysis of 120 functional neuroimaging studies. Cereb Cortex, 19(12), 2767-2796.
Buckner, R. L., Andrews-Hanna, J. R., & Schacter, D. L. (2008). The brain's default network: anatomy, function, and relevance to disease. Ann N Y Acad Sci, 1124, 1-38. doi: 10.1196/annals.1440.011
Marrelec, et al., (2008), Regions, systems, and the brain: Hierarchical measures of functional integration in fMRI, Medical Image Analysis, 12, 484–496.
Keywords:
Aphasia,
DMN,
neuroplasticity markers,
connectivity,
Recovery of Function
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:
Durand
E
(2014). Functional connectivity in post-stroke aphasia: innovative tools at the service of evidence-based practice.
Front. Psychol.
Conference Abstract:
Academy of Aphasia -- 52nd Annual Meeting.
doi: 10.3389/conf.fpsyg.2014.64.00083
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Received:
30 Apr 2014;
Published Online:
04 Aug 2014.
*
Correspondence:
Miss. Edith Durand, Centre de Recherche de l'Institut Universitaire de Gériatrie de Montréal, Montreal, Canada, edith.durand@umontreal.ca