Page 103 - MEGIN Book Of Abstracts - 2023

Keywords: Alzheimer’s disease detection, Convolutional Behaviourally, patients with svPPA manifest marked
neural network, Deep learning, Ensemble model, Magne- lexico-semantic impairments including difficulties in
toencephalography reading words with exceptional orthographic to pho-
nological correspondence (irregular words). Moreover,
Artificial intelligence in medicine (2020), Vol. 107 they present with focal neurodegeneration in the
(32828459) (15 citations) anterior temporal lobe, affecting primarily the ventral,
occipito-temporal, lexical route. Therefore, this clinical
population allows for testing of specific hypotheses on
Taking the sublexical route: brain dynamics the neural implementation of the dual-route model for
of reading in the semantic variant of primary reading, such as whether damage to one route can be
progressive aphasia (2020) compensated by over-reliance on the other. To this end,
we reconstructed and analysed time-resolved whole-
Borghesani, Valentina; Hinkley, Leighton B N; brain activity in 12 svPPA patients and 12 healthy age-
Ranasinghe, Kamalini G; Thompson, Megan M C; Shwe, matched control subjects while reading irregular words
Wendy; Mizuiri, Danielle; Lauricella, Michael; Europa, (e.g. yacht) and pseudowords (e.g. pook). Consistent
Eduardo; Honma, Susanna; Miller, Zachary; Miller, with previous findings that the dorsal route is involved
Bruce; Vossel, Keith; Henry, Maya M L; Houde, John F; in sublexical, phonological processes, in control par-
Gorno-Tempini, Maria L; Nagarajan, Srikantan S ticipants we observed enhanced neural activity over
dorsal occipito-parietal cortices for pseudowords, when
Memory and Aging Center, Department of Neurology, compared to irregular words. This activation was mani-
University of California San Francisco, USA; Department of fested in the beta-band (12-30 Hz), ramping up slowly
Radiology and Biomedical Imaging, University of California over 500 ms after stimulus onset and peaking at ∼800
San Francisco, USA; UC Berkeley-UC San Francisco Gradu- ms, around response selection and production. Consis-
ate Program in Bioengineering, University of California, San tent with our prediction, svPPA patients did not exhibit
Francisco, USA; Department of Neurology, University of Min- this temporal pattern of neural activity observed in
nesota, Minneapolis, USA; Department of Communication controls this contrast. Furthermore, a direct comparison
Sciences and Disorders, University of Texas at Austin, USA; of neural activity between patients and controls re-
Department of Otolaryngology, University of California San vealed a dorsal spatiotemporal cluster during irregular
Francisco, USA; Department of Neurology, Dyslexia Center, word reading. These findings suggest that the sublexi-
University of California, San Francisco, CA, USA cal/phonological route is involved in processing both
irregular and pseudowords in svPPA. Together these re-
ABSTRACT Reading aloud requires mapping an or- sults provide further evidence supporting a dual-route
thographic form to a phonological one. The mapping model for reading aloud mediated by the interplay
process relies on sublexical statistical regularities (e.g. between lexico-semantic and sublexical/phonological
'oo' to |u∼|) or on learned lexical associations between neurocognitive systems. When the ventral route is dam-
a specific visual form and a series of sounds (e.g. yacht aged, as in the case of neurodegeneration affecting the
to/j∼t/). Computational, neuroimaging, and neuropsy- anterior temporal lobe, partial compensation appears
chological evidence suggest that sublexical, phono- to be possible by over-recruitment of the slower, serial
logical and lexico-semantic processes rely on partially attention-dependent, dorsal one.
distinct neural substrates: a dorsal (occipito-parietal)
and a ventral (occipito-temporal) route, respectively. Keywords: MEG, dual-model of reading, semantic variant
Here, we investigated the spatiotemporal features of primary progressive aphasia, surface dyslexia
orthography-to-phonology mapping, capitalizing on
the time resolution of magnetoencephalography and Brain: a journal of neurology (2020), Vol. 143, No. 8
the unique clinical model offered by patients with se- (32789455) (11 citations)
mantic variant of primary progressive aphasia (svPPA).

 ontents  Index 82
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