Anatomical correlates of reading in the elderly brain: an FDG-PET analysis of the reading performance in Alzheimer's Disease
Valeria
Isella1, 2*,
Ilaria
Falci3,
Daniele
Licciardo1, 2,
Paolo
Urso3,
Valentina
Impagnatiello1,
Cinzia
Crivellaro1, 2,
Sabrina
Morzenti1, 2 and
Claudio
G.
Luzzatti2, 3
-
1
Università degli studi di Milano Bicocca, Department of Medicine and Surgery, Italy
-
2
Milan Center for Neuroscience (NeuroMi), Italy
-
3
Università degli studi di Milano Bicocca, Department of Psychology, Italy
Introduction. Patients with dementia of the Alzheimer type (AD) become progressively unable to read (Ripamonti et al., 2017), but the loci of neurodegeneration underpinning reading deficits are still unclear. The Dual Route Cascaded model (Taylor et al., 2013) proposes that reading is accomplished by a dorsal, sublexical pathway and a ventral, lexical pathway: they both stem from the extrastriate occipital and occipito-temporal cortex where early visual processing of written stimuli takes place, and project to the dorsal frontal lobe, running through the inferior parietal cortex, in the dorsal route, and the posterior temporal cortex plus angular gyrus, in the ventral route. The ventral route processes familiar regular or irregular words by activating lexical orthograpic representations, while the dorsal route allows to read aloud nonwords and regular words, utilizing grapheme-to-phoneme conversion rules.
We investigated the neural foundation of reading through the study of metabolic abnormalities associated with dyslexia along the two reading pathways in a mixed population of amnesic, aphasic (logopenic) and posterior variants of AD.
Materials and methods. We assessed the ability to read different types of words, nonwords and trisyllable words with unpredictable stress position (WUSP - the major irregularity in reading Italian) in 45 AD patients (25 amnesic, 11 posterior, and nine logopenic PPA cases), and correlated the reading performance with distribution of hypometabolism on brain FDG-PET using SPM8 (p <.001 uncorrected, k: 100 voxels). Twenty-five matched healthy controls were also enrolled for the behavioural study.
Results. Phonological dyslexia emerged in six patients (13.3%), and undifferentiated dyslexia in four (8.9%). At the group level, repeated measures ANOVA (between-subject variable: group, within-subject variable: stimulus type) showed significantly poorer reading of nonwords for AD patients (p <.02); lexicality, frequency and grammatical class effects emerged in patients and control participants to a similar extent, while no concreteness effect was found.
Significant clusters of hypometabolism are shown in the Figure. Inaccuracy in reading high frequency concrete nouns was associated with decreased FDG uptake in the left occipito-temporal cortex and posterior middle temporal and angular gyri. Poor reading of low-frequency concrete and high-frequency abstract nouns correlated with hypometabolism in the left extrastriate and occipito-temporal cortex, and in the left inferior parietal lobule; additional clusters involved the left temporal pole for low-frequency nouns, and the mid portion of the left superior and middle temporal gyri for abstract nouns. Errors with WUSP correlated with hypometabolism in the left temporal pole. The main areas of decreased metabolism associated with poor scores for nonwords were in the left occipital and occipito-temporal cortex and left inferior parietal lobule
Discussion. Our main findings suggest that dyslexia in AD derives from dysfunction of the visual analysis areas, the posterior temporal plus angular regions belonging to the ventral route, and the inferior parietal cortex belonging to the dorsal route. Critically, the inability to read low-frequency and low-imageability nouns is apparently due to damage along the dorsal sublexical pathway, while deficits in predicting stress position depends on damage along the ventral lexical route.
References
Ripamonti, E., Lucchelli, F., Lazzati, G., Martini, E., & Luzzatti, C. (2017). Reading impairment in neurodegenerative diseases: A multiple single-case study. Aphasiology, 31, 519–541. doi: 10.1080/02687038.2016.1208802
Taylor, J.S.H., Rastle, K., & Davis, M.H. (2013). Can cognitive models explain brain activation during word and pseudoword reading? A meta-analysis of 36 neuroimaging studies. Psychological Bulletin, 139, 766–791. doi: 10.1037/a0030266
Keywords:
Alzheimer's disease (AD),
Neuroimaging,
Dyslexia, Acquired,
Dual-route models of reading,
Lexical Processing,
Sublexical processing
Conference:
Academy of Aphasia 56th Annual Meeting, Montreal, Canada, 21 Oct - 23 Oct, 2018.
Presentation Type:
poster presentation
Topic:
not eligible for a student prize
Citation:
Isella
V,
Falci
I,
Licciardo
D,
Urso
P,
Impagnatiello
V,
Crivellaro
C,
Morzenti
S and
Luzzatti
CG
(2019). Anatomical correlates of reading in the elderly brain: an FDG-PET analysis of the reading performance in Alzheimer's Disease.
Conference Abstract:
Academy of Aphasia 56th Annual Meeting.
doi: 10.3389/conf.fnhum.2018.228.00053
Copyright:
The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers.
They are made available through the Frontiers publishing platform as a service to conference organizers and presenters.
The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated.
Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed.
For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions.
Received:
27 Apr 2018;
Published Online:
22 Jan 2019.
*
Correspondence:
Dr. Valeria Isella, Università degli studi di Milano Bicocca, Department of Medicine and Surgery, Milan, Italy, valeria.isella@unimib.it