Reading words and other people: A comparison of exception word, familiar face and affect processing in the left and right temporal variants of primary progressive aphasia

Abstract

Semantic variant primary progressive aphasia (svPPA) typically presents with left-hemisphere predominant rostral temporal lobe atrophy and the most significant complaints within the language domain. Less frequently, patients present with right-hemisphere predominant temporal atrophy coupled with marked impairments in processing of famous faces and emotions. Few studies have objectively compared these patient groups in both domains and therefore it is unclear to what extent the syndromes overlap. Clinically diagnosed svPPA patients were characterized as left- (n= 21) or right-predominant (n = 12) using imaging and compared along with 14 healthy controls. Regarding language, our primary focus was upon two hallmark features of svPPA; confrontation naming and surface dyslexia. Both groups exhibited naming deficits and surface dyslexia although the impairments were more severe in the left-predominant group. Familiarity judgments on famous faces and affect processing were more profoundly impaired in the right-predominant group. Our findings suggest that the two syndromes overlap significantly but that early cases at the tail ends of the continuum constitute a challenge for current clinical criteria. Correlational neuroimaging analyses implicated a mid portion of the left lateral temporal lobe in exception word reading impairments in line with proposals that this region is an interface between phonology and semantic knowledge.

Regional and hemispheric susceptibility of the temporal lobe to FTLD-TDP type C pathology

“…In right-predominant cases, we observed significant atrophy not only in the right temporal pole, right fusiform and right lingual gyri, but also in the left temporal pole and left inferior frontal gyrus. These results are in line with previous studies comparing left and right temporal variant of FTD (Binney et al, 2016;Brambati et al, 2009;Kumfor et al, 2016;Rogalski et al, 2014).…”

“…Significant differences from healthy controls indicate semantic deficits and impaired comprehension with no sign of apraxia of speech or dysarthria. In line with previous evidence, the same overall pattern is observed when left-predominant and right-predominant cases are considered separately, yet interesting distinctions can also be appreciated (Binney et al, 2016;Lambon Ralph et al, 2001;M. Mendez, Kremen, Tsai, & Shapira, 2010;Mion et al, 2010).…”

“…inferior (BA 20) temporal gyri. In both hemisphere amygdala, hippocampus and parahippocampal regions were severely affected, with an anterior-to-posterior gradient (Binney et al, 2016;Chan et al, 2001). We then investigated subject-specific atrophy asymmetry in a data-driven fashion.…”

“…These patients almost invariably meet current consensus criteria for svPPA (Gorno-tempini et al, 2011). On the other hand, the clinical phenotype of right ATL atrophy is less well defined and has been associated with various degrees of socio-emotional, semantic (person-specific knowledge) and face recognition impairments (Binney et al, 2016;Chan et al, 2009;Edwards-Lee et al, 1997;Julie Snowden et al, 2017;Woollams & Patterson, 2017). These patients do not clearly meet criteria for svPPA (McCarthy & Warrington, 2016), as their nonverbal semantic loss can only be captured with specialized neuropsychological tests (e.g., identification of famous faces).…”

“…To date, our understanding of the right temporal variants has relied on data stemming from single cases (e.g., (Barbarotto R, Capitani E, Spinnler H, 1995;Gainotti, Barbier, & Marra, 2003;ML Gorno-Tempini et al, 2004;Henry, 2014;Joubert et al, 2004;M. F. Mendez & Ghajarnia, 2001)), or small samples without pathological diagnosis (e.g., (Binney et al, 2016;Brambati et al, 2009;Chen et al, 2018;Hodges et al, 2010;Kumfor et al, 2016;Mion et al, 2010;J. S. Snowden, Thompson, & Neary, 2012;Julie Snowden et al, 2017;Thompson et al, 2003;Woollams & Patterson, 2017)).…”