Reduced phonemic fluency in progressive supranuclear palsy is due to dysfunction of dominant BA6

Abstract

BackgroundReduced phonemic fluency is extremely frequent in progressive supranuclear palsy (PSP), but its neural correlate is yet to be defined.ObjectiveWe explored the hypothesis that poor fluency in PSP might be due to neurodegeneration within a dominant frontal circuit known to be involved in speech fluency, including the opercular area, the superior frontal cortex (BA6), and the frontal aslant tract connecting these two regions.MethodsWe correlated performance on a letter fluency task (F, A, and S, 60 s for each letter) with brain metabolism as measured with Fluoro-deoxy-glucose Positron Emission Tomography, using Statistical Parametric Mapping, in 31 patients with PSP.ResultsReduced letter fluency was associated with significant hypometabolism at the level of left BA6.ConclusionOur finding is the first evidence that in PSP, as in other neurogical disorders, poor self-initiated, effortful verbal retrieval appears to be linked to dysfunction of the dominant opercular-aslant-BA6 circuit.

A modified neural circuit framework for semantic memory retrieval with implications for circuit modulation to treat verbal retrieval deficits

“…Correlational studies based on fMRI BOLD signal also demonstrate more activation in the pre‐SMA in voluntary speech (generating a word compared to reading a word in Tremblay & Gracco, 2006 ; volitional word production compared to forced word production in Tremblay & Gracco, 2010 ) and speech‐specific production (word production requiring selection compared to word production without selection in Alario et al., 2006 ). Impaired verbal fluency has been linked to lesions or dysfunction of the pre‐SMA in patients with stuttering, stroke, or neurodegenerative diseases such as progressive supranuclear palsy (Busan, 2020 ; Isella et al., 2022 ; Obayashi, 2020 ). Surgical removal or ischemic damage of the SMA/pre‐SMA with neighboring tissues may lead to SMA syndrome, characterized by reduced fluency to the point of speech arrest (Pinson et al., 2022 ; Potgieser et al., 2014 ).…”

A modified neural network framework for semantic memory retrieval with implications for circuit modulation to treat verbal retrieval deficits

“…Correlational studies based on fMRI BOLD signal also demonstrate more activation in the pre-SMA in voluntary speech (generating a word compared reading a word in Tremblay and Gracco, 2006; volitional word production comopared to forced word production in Tremblay and Gracco, 2010) and speechspecific production (word production requiring selection compared to word production without selection in Alario et al, 2006). Impaired verbal fluency has been linked to lesions or dysfunction of the pre-SMA in patients with stuttering, stroke, or neurodegenerative diseases such as progressive supranuclear palsy (Isella et al, 2022;Obayashi, 2020;Busan, 2020;Masdeu et al, 1978). Surgical removal or ischemic damage of the SMA/pre-SMA with neighboring tissues may lead to SMA syndrome, characterized by reduced fluency to the point of speech arrest (Pinson et al, 2021;Potgieser et al, 2014;Masdeu et al, 1978).…”