scholarly journals The left inferior frontal gyrus is causally involved in selective semantic retrieval: Evidence from tDCS in primary progressive aphasia

2020 ◽  
Author(s):  
Zeyi Wang ◽  
Bronte N Ficek ◽  
Kimberly T Webster ◽  
Chiadi U Onyike ◽  
John E Desmond ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Inferior Frontal Gyrus ◽  
Primary Progressive Aphasia ◽  
Superior Temporal Gyrus ◽  
Semantic Fluency ◽  
Semantic Retrieval ◽  
Left Inferior Frontal Gyrus ◽  
Progressive Aphasia ◽  
Temporal Lobes ◽  
Primary Progressive

Lesion and imaging studies have shown that the left inferior frontal gyrus (IFG) is involved in selective semantic retrieval of information from the temporal lobes. However, causal, i.e., interventional, evidence is sparse. In the present study we addressed this question by testing whether transcranial direct current stimulation (tDCS) over the left IFG in a group of individuals with primary progressive aphasia may improve semantic fluency, a task that relies to selective semantic retrieval. Semantic fluency improved significantly more in the tDCS vs. sham condition immediately post-treatment and improvement lasted up to 2 months. We further addressed the question of who will benefit most from such an intervention by testing possible demographic, clinical and functional connectivity variables that may predict the behavioral tDCS effect. We found that patients with stronger baseline functional connectivity between the subareas of the left IFG opercularis and triangularis, and between the middle temporal pole and superior temporal gyrus. were the most likely to benefit from tDCS over the left IFG. We thus provided causal evidence that the left IFG is the neural substrate of selective semantic retrieval and tDCS over the left IFG may improve semantic fluency in individuals with stronger baseline functional connectivity.

Sleep as a predictor of tDCS and language therapy outcomes

SLEEP ◽  
2021 ◽  
Author(s):  
Olivia Herrmann ◽  
Bronte Ficek ◽  
Kimberly T Webster ◽  
Constantine Frangakis ◽  
Adam P Spira ◽  
...  
Keyword(s):  
Inferior Frontal Gyrus ◽  
Primary Progressive Aphasia ◽  
Sleep Time ◽  
Sleep Efficiency ◽  
Language Therapy ◽  
Double Blind ◽  
Progressive Aphasia ◽  
Primary Progressive ◽  
Time In Bed ◽  
Sham Condition

Abstract Study Objectives To determine whether sleep at baseline (before therapy) predicted improvements in language following either language therapy alone or coupled with transcranial direct current stimulation (tDCS) in individuals with primary progressive aphasia (PPA). Methods Twenty-three participants with PPA (mean age 68.13 ± 6.21) received written naming/spelling therapy coupled with either anodal tDCS over the left inferior frontal gyrus (IFG) or sham condition in a crossover, sham-controlled, double-blind design (ClinicalTrials.gov identifier: NCT02606422). The outcome measure was percent of letters spelled correctly for trained and untrained words retrieved in a naming/spelling task. Given its particular importance as a sleep parameter in older adults, we calculated sleep efficiency (total sleep time/time in bed x100) based on subjective responses on the Pittsburgh Sleep Quality Index (PSQI). We grouped individuals based on a median split: high versus low sleep efficiency. Results Participants with high sleep efficiency benefited more from written naming/spelling therapy than participants with low sleep efficiency in learning therapy materials (trained words). There was no effect of sleep efficiency in generalization of therapy materials to untrained words. Among participants with high sleep efficiency, those who received tDCS benefitted more from therapy than those who received sham condition. There was no additional benefit from tDCS in participants with low sleep efficiency. Conclusion Sleep efficiency modified the effects of language therapy and tDCS on language in participants with PPA. These results suggest sleep is a determinant of neuromodulation effects. Clinical Trial: tDCS Intervention in Primary Progressive Aphasia https://clinicaltrials.gov/ct2/show/NCT02606422

scholarly journals Functional Connectivity is Reduced in Early-stage Primary Progressive Aphasia When Atrophy is not Prominent

2017 ◽  
Vol 31 (2) ◽  
pp. 101-106 ◽  
Author(s):  
Borna Bonakdarpour ◽  
Emily J. Rogalski ◽  
Allan Wang ◽  
Jaiashre Sridhar ◽  
M.M. Mesulam ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Early Stage ◽  
Primary Progressive Aphasia ◽  
Progressive Aphasia ◽  
Primary Progressive

scholarly journals Effects of tDCS on Sound Duration in Patients with Apraxia of Speech in Primary Progressive Aphasia

2021 ◽  
Author(s):  
Charalambos Themistocleous ◽  
Kimberly Webster ◽  
Kyrana Tsapkini
Keyword(s):  
Speech Therapy ◽  
Inferior Frontal Gyrus ◽  
Primary Progressive Aphasia ◽  
Preliminary Evidence ◽  
Apraxia Of Speech ◽  
Post Intervention ◽  
Left Inferior Frontal Gyrus ◽  
Primary Progressive ◽  
Speech Fluency ◽  
Sound Duration

Transcranial direct current stimulation (tDCS) over the left Inferior Frontal Gyrus (IFG) was found to improve apraxia of speech (AOS) in post-stroke aphasia, speech fluency in adults who stutter, naming and spelling in primary progressive (PPA). This paper aims to determine whether tDCS over the left IFG coupled with AOS therapy improves speech fluency in patients with PPA more than sham. Eight patients with non-fluent PPA with AOS symptoms received either active or sham tDCS, along with speech therapy for 15 weekday sessions. Speech therapy consisted of repetition of increasing syllable-length words. Evaluations took place before, immediately after, and two months post-intervention. Words were segmented into vowels and consonants and the duration of each vowel and consonant was measured. Segmental duration was significantly shorter after tDCS than sham for both consonants and vowels. tDCS gains generalized to untrained words. The effects of tDCS sustained over two months post-treatment in trained words. Taken together, these results demonstrate that the tDCS over the left IFG facilitates speech production by reducing segmental duration. The results provide preliminary evidence that tDCS can maximize efficacy of speech therapy in non-fluent PPA with AOS.

scholarly journals The effect of tDCS on functional connectivity in primary progressive aphasia

2018 ◽  
Vol 19 ◽  
pp. 703-715 ◽  
Author(s):  
Bronte N. Ficek ◽  
Zeyi Wang ◽  
Yi Zhao ◽  
Kimberly T. Webster ◽  
John E. Desmond ◽  
...  
Keyword(s):  
Functional Connectivity ◽  
Primary Progressive Aphasia ◽  
Progressive Aphasia ◽  
Primary Progressive

scholarly journals Effects of tDCS on Sound Duration in Patients with Apraxia of Speech in Primary Progressive Aphasia

2021 ◽  
Vol 11 (3) ◽  
pp. 335
Author(s):  
Charalambos Themistocleous ◽  
Kimberly Webster ◽  
Kyrana Tsapkini
Keyword(s):  
Speech Therapy ◽  
Inferior Frontal Gyrus ◽  
Primary Progressive Aphasia ◽  
Motor Disorder ◽  
Apraxia Of Speech ◽  
Post Intervention ◽  
Progressive Aphasia ◽  
Primary Progressive ◽  
Post Stroke ◽  
Sound Duration

Transcranial direct current stimulation (tDCS) over the left inferior frontal gyrus (IFG) was found to improve oral and written naming in post-stroke and primary progressive aphasia (PPA), speech fluency in stuttering, a developmental speech-motor disorder, and apraxia of speech (AOS) symptoms in post-stroke aphasia. This paper addressed the question of whether tDCS over the left IFG coupled with speech therapy may improve sound duration in patients with apraxia of speech (AOS) symptoms in non-fluent PPA (nfvPPA/AOS) more than sham. Eight patients with non-fluent PPA/AOS received either active or sham tDCS, along with speech therapy for 15 sessions. Speech therapy involved repeating words of increasing syllable-length. Evaluations took place before, immediately after, and two months post-intervention. Words were segmented into vowels and consonants and the duration of each vowel and consonant was measured. Segmental duration was significantly shorter after tDCS compared to sham and tDCS gains generalized to untrained words. The effects of tDCS sustained over two months post-treatment in trained and untrained sounds. Taken together, these results demonstrate that tDCS over the left IFG may facilitate speech production by reducing segmental duration. The results provide preliminary evidence that tDCS may maximize efficacy of speech therapy in patients with nfvPPA/AOS.

scholarly journals Selective Functional Network Changes following tDCS-augmented 2 Language Treatment in Primary Progressive Aphasia

2021 ◽  
Author(s):  
Yuan Tao
Keyword(s):  
Lexical Processing ◽  
Inferior Frontal Gyrus ◽  
Primary Progressive Aphasia ◽  
Functional Network ◽  
Processing Efficiency ◽  
Progressive Aphasia ◽  
Primary Progressive ◽  
Language System ◽  
Before And After ◽  
Global Connectivity

Objective Transcranial direct current stimulation (tDCS) has shown promising results when used as an adjunct to behavioral training in neurodegenerative diseases. However, the underlying neural mechanisms are not understood and neuroimaging evidence from pre/post treatment has been sparse. In this study, we examined tDCS-induced neural changes in a language intervention study for primary progressive aphasia (PPA), a neurodegenerative syndrome with language impairment as the primary clinical presentation. Anodal tDCS was applied to the left inferior frontal gyrus (LIFG). To evaluate the hypothesis that tDCS promotes system segregation, analysis focused on understanding tDCS-induced changes in the brain-wide functional network connectivity of the targeted LIFG MethodsResting-state fMRI data were obtained from 32 participants with PPA before and after receiving a written naming therapy, accompanied either by tDCS or sham stimulation. We focused on evaluating changes in the global connectivity of the stimulated LIFG-triangularis (LIFG-tri) region given its important role in lexical processing. Global connectivity was indexed by the graph-theoretic measure participation coefficient (PC) which quantifies a region’s level of system segregation. The values before and after treatment were compared for each condition (tDCS or Sham) as well as with age-matched healthy controls (n=19).Results Higher global connectivity of the LIFG-tri before treatment was associated with greater dementia severity. After treatment, the tDCS group showed a significant decrease in global connectivity whereas the Sham group’s did not change, suggesting specific neural effects induced by tDCS. Further examination revealed that the decrease was driven by reduced connectivity between the LIFG-tri and regions outside the perisylvian language area, consistent with the hypothesis that tDCS enhances the segregation of the language system and improves processing efficiency. Additionally, we found that these effects were specific to the LIFG-tri and not observed in other control regions.ConclusionsTDCS-augmented language therapy in PPA increased the functional segregation of the language system, a normalization of the hyper-connectivity observed before treatment. These findings add to our understanding of the nature of tDCS-induced neural changes in disease treatment and have applications for validating treatment efficacy and designing future tDCS and other non-invasive brain stimulation (NIBS) treatments.

scholarly journals Altered functional connectivity of cortical networks in semantic variant Primary Progressive Aphasia

2020 ◽  
Author(s):  
Haroon Popal ◽  
Megan Quimby ◽  
Daisy Hochberg ◽  
Bradford C. Dickerson ◽  
Jessica A. Collins
Keyword(s):  
Functional Connectivity ◽  
Default Mode Network ◽  
Large Scale ◽  
Network Connectivity ◽  
Primary Progressive Aphasia ◽  
Cognitive Networks ◽  
Default Mode ◽  
Progressive Aphasia ◽  
Primary Progressive ◽  
Semantic Variant

AbstractAs their illness progresses, patients with the semantic variant of Primary Progressive Aphasia (svPPA) frequently exhibit peculiar behaviors indicative of altered visual attention or an increased interest in artistic endeavors. In the present study, we examined changes within and between large-scale functional brain networks that may explain this altered visual behavior. We first examined the connectivity of the visual association network, the dorsal attention network, and the default mode network in healthy young adults (n=89) to understand the typical architecture of these networks in the healthy brain. We then compared the large-scale functional connectivity of these networks in a group of svPPA patients (n=12) to a group of age-matched cognitively normal controls (n=30). Our results showed that the between-network connectivity of the dorsal attention and visual association networks was elevated in svPPA patients relative to controls. We further showed that this heightened between-network connectivity was associated with a decrease in the within-network connectivity of the default mode network, possibly due to progressive degeneration of the anterior temporal lobes in svPPA. These results suggest that focal neurodegeneration can lead to the reorganization of large-scale cognitive networks beyond the primarily affected network(s), possibly contributing to cognitive or behavioral changes that are commonly present as part of the clinical phenotype of svPPA.

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