Event Abstract

Structural networks, language deficits, and aphasia recovery

  • 1 Medical Center, Georgetown University, Center for Brain Plasticity and Recovery, United States
  • 2 MedStar National Rehabilitation Hospital, Research Division, United States
  • 3 Drexel University, Department of Psychology, United States
  • 4 Perelman School of Medicine, University of Pennsylvania, Department of Neurology, United States

Brain lesions in chronic stroke survivors are typically defined based on the location of the gliotic and necrotic tissue, but there is growing evidence that dysfunction resulting from stroke extends far beyond the main site of injury. Severing of axonal pathways that run through the lesion and loss of white matter projections from the site of stroke lead to remote deafferentation and disconnection. It follows that the disconnected cortex lacks input to exert its activity, and the result of this network disruption is behavioral impairment greater or different than might otherwise be expected from the focal lesion. This mechanism of dysfunction has been discussed since the early days of aphasia research in the 19th century, in the form of classical disconnection syndromes. After in vivo brain imaging became widely available, a more general importance of this phenomenon was suggested when researchers noted that deep white matter lesions portend poor outcomes from aphasia. Until recently, however, it was not possible to directly measure axonal pathway integrity after a stroke, so the full contributions of network disconnections to behavioral deficits were not quantifiable. With diffusion-based MRI, it is now possible to chart axonal projections across the entire brain and quantify the residual integrity of medium to large scale white matter projections. This method provides a powerful probe of how structural networks are disrupted by stroke, and how these disruptions shape deficits in people with aphasia. This enables researchers to extend classical and modern lesion methods to understand the brain networks that support language. Importantly, since diffusion imaging can also measure pathways not directly affected by lesions, it allows assessment of the contributions of spared parts of the network to recovery. Incorporating graph theory analyses allows description of the effects of stroke and ensuing recovery on complex network organization. This presentation will first outline the methods used to map structural integrity after stroke, comparing diffusion imaging-based lesion analysis to conventional lesion-symptom mapping. Then, we will discuss diffusion imaging-based lesion studies that have advanced our understanding of language network organization in the brain, the contributions of network disconnection to deficits in aphasia, and pathways and networks important for recovery. Finally, we will discuss integration of diffusion imaging-based lesion mapping with other methods to provide a fuller assessment of the brain basis of aphasia.

Keywords: Aphasia, connectome-lesion mapping, disconnection syndromes, Diffusion Magnetic Resonance Imaging, aphasia recovery, stroke recovery

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

Presentation Type: symposium

Topic: not eligible for a student prize

Citation: Turkeltaub PE, Kelkar A and Medaglia JD (2019). Structural networks, language deficits, and aphasia recovery. Conference Abstract: Academy of Aphasia 56th Annual Meeting. doi: 10.3389/conf.fnhum.2018.228.00002

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Received: 30 Apr 2018; Published Online: 22 Jan 2019.

* Correspondence: Dr. Peter E Turkeltaub, Medical Center, Georgetown University, Center for Brain Plasticity and Recovery, Washington D.C., United States, turkeltp@georgetown.edu