Electrophysiological abnormalities as indicators of early-stage pathology in Primary Progressive Aphasia (PPA): A case study in semantic variant PPA

ABSTRACT

Language induced and spontaneous oscillatory activity was measured using MEG in a patient with the semantic variant of Primary Progressive Aphasia (svPPA) and 15 healthy controls.The patient showed oscillatory slowing in the left anterior temporal lobe (ATL) that extended into non-atrophied brain tissue in left and right frontal areas. The white matter connections were reduced to the left and right ATL and left frontal regions, exhibiting electrophysiological abnormalities. Altered diffusion metrics in all four language tracts, indicted compromised white matter integrity. Task-related and spontaneous oscillatory abnormalities can indicate early neurodegeneration in svPPA, providing promising targets for intervention.

KEYWORDS:

• Semantic PPA
• MEG
• sentence comprehension
• resting state oscillations
• slowing

Acknowledgments

We thank the participating volunteers and their families.

Abbreviations

MOCA: Montreal Cognitive Assessment (Nasreddine et al., 2005). Measured out of 30 points; Values from 30 to 26 points indicate normal performance.

BNT = Boston Naming Test (Kaplan et al., 2001); PPVT = Peabody Picture Vocabulary Test (Dunn and Dunn, 2007); Camel and Cactus (Adlam et al., 2010); Letter and Category fluency from D-KEFS: (Delis et al., 2001); CNRT = Children’s Test of Nonword Repetition (Gathercole et al., 1991); NAVS SCT = Northwestern Assessment of Verbs and Sentences-Sentence Comprehension Test (Cho-Reyes & Thompson, 2012; Thompson, 2011), can = canonical sentences percent correct, noncan = noncanonical sentences percent correct; PALPA = Psycholinguistic Assessments of Language Processing in Aphasia (Kay et al., 1992).

WAB = Western Aphasia Battery (scores out of 10): Bedside version, Flu = Spontaneous Speech Fluency, Rep = Repetition, Comp = Auditory Verbal Comprehension, Com = Sequential Commands, Naming = Object naming, BAS: Bedside Aphasia Score; BLS: Bedside Language Score; NT: Test scores not available; Control participants did not complete WAB.

Bedside Language Score (WAB_BLS) was determined by summing the Speech Content, Fluency, Auditory Verbal Comprehension, Sequential Commands, Repetition, Object Naming, Reading, and Writing scores, dividing the sum by 8 and multiplying the result by 10.

Bedside Aphasia Score (WAB_ BAS) was determined by summing the Speech Content, Fluency, Auditory Verbal Comprehension, Sequential Commands, Repetition, and Object Naming scores, dividing the sum by 6 and then multiplying result by 10.

BDAE = Boston Diagnostic Aphasia Examination (Goodglass et al., 2001), Controls did not complete this test.

ABCD = Arizona Battery for Communication Disorders (Bayles & Tomoeda, 1991), Controls did not complete this test.

N/A indicates that the test was not performed. We did not administer WAB, BDAE, and ABCD to controls because these are clinical test batteries developed to assess language deficits in aphasia.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

The data that support the findings of this study are available from the corresponding author, AK, upon reasonable request.

Supplementary material

Supplemental data for this article can be accessed here

Additional information

Funding

This work was supported by a Basic Science Grant from the OntarioBrain Institute Ontario Neurodegenerative Disease Research Initiative(ONDRI), Canada to JAM, and Alzheimer's Association NewInvestigator Research Grant (NIRG-12-236224), Canada to JAM, and apostdoctoral research award from the Ontario Research Coalition,Canada to AK.