Brain Connectivity Supporting Language Recovery in Aphasia
Condition: Aphasia; Stroke; Speech Disorders; Communications Disorders
MeSH terms: Aphasia; Speech Disorders; Communication Disorders
Study type: Observational

Summary: 
      The integrity of structural connectivity supporting cortical regions in the left brain
      hemisphere is hypothesized to enable treatment-induced naming recovery in persons with
      language difficulties after a stroke (aphasia). The investigators will map whole brain
      connectivity (i.e., the brain connectome) to investigate the role of cortical connectivity in
      impairment (Aim 1) and recovery (Aim 2) in patients with aphasia undergoing treatment. This
      information will be used to construct personalized markers of anomia treatment outcome (Aim
      3), which may serve as a guide for speech-language pathologists and neurologists when facing
      patient management decisions.
    

Detailed description: 
      Aphasia, an impairment of language processing, is one of the most common consequences of
      strokes affecting the dominant brain hemisphere4. Patients with aphasia are usually incapable
      of working, and their interactions with family and friends are often severely affected. The
      hallmark deficit of aphasia is the inability to name objects or people (anomia)12. The
      severity of anomia is closely related to a poor quality of life.

      While many patients with aphasia exhibit some language recovery in the first days to weeks
      after the stroke, 30-40% persist with long lasting naming impairments4. Fortunately, speech
      therapy can be very effective to improve naming for some patients with chronic aphasia5-8.
      However, it is well recognized among clinicians that speech therapy can be ineffective for
      other patients, making it difficult to predict how and why some patients benefit from naming
      treatment, while others show little or no improvement.

      Here, the investigators propose to evaluate whether naming impairment and naming recovery are
      related to the extent of structural damage to the cortical language network. Importantly, the
      investigators will evaluate damage as the combined effect of cortical necrosis and cortical
      disconnection. The investigators hypothesize that assessing anomia as being either due to
      gray matter necrosis or due to cortical disconnection constitutes a false dichotomy since
      most chronic patients exhibit gray and white matter damage. Furthermore, the investigators
      propose that disconnection of seemingly spared cortical areas has up till now been
      underappreciated in patients with stroke due to limitations in brain connectivity assessment
      tools. By examining only areas of cortical necrosis without considering disconnected areas,
      one may underestimate the magnitude of language network damage. A better understanding of the
      effects from both cortical damage and disconnection on anomia and its recovery could lead to
      an improved clinical management of aphasia.

      The investigators will employ the innovative concept of the brain connectome, i.e., the
      individualized map of neural connections in the brain, to evaluate whether naming recovery is
      supported by preserved gray matter and preserved connectivity involving key language areas in
      the left hemisphere. The investigators propose that left frontal and left temporal
      connectivity mapped based on the individual's connectome is an important explanatory variable
      towards naming impairment and recovery.

      The investigators believe that this research is significant for the three main reasons.
      First, it can have a direct clinical impact by providing a better understanding of which
      patients can benefit from therapy. Second, it can unveil the neurobiological mechanisms
      supporting language recovery, improving our understanding of brain plasticity related to
      language rehabilitation. Finally, if disconnection contributes to language impairment, our
      methods can be developed to test specific theories of language organization in the brain. The
      significance of these aspects is explained in detail below.
    

Observational model: Other
Time perspective: Prospective
Sampling method: Probability Sample
Study population: 
        No new patients will be recruited for the current project. We will rely solely on data
        collection in the tDCS-Trial (U01 DC011739, period 7/1/2012-6/31/2017). All information
        used in our experiments will be available as a result of the standardized set of tests that
        patients undergo in the trial.
      
Keywords: Aphasia; Brain; Stimulation; Communication; Stroke; Speech Disorders; Communications Disorders; Neurobehavioral Manifestations; Neurologic Manifestations; Nervous System Diseases; Signs and Symptoms