Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia

The middle longitudinal fascicle (MdLF) is a recently delineated association cortico-cortical fiber pathway in humans, connecting superior temporal gyrus and temporal pole principally with the angular gyrus, and is likely to be involved in language processing. However, the MdLF has not been studied...

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Main Authors:	Chunyan Luo, Sara Makaretz, Michael Stepanovic, George Papadimitriou, Megan Quimby, Senthil Palanivelu, Bradford C. Dickerson, Nikos Makris
Format:	Article
Language:	English
Published:	Elsevier 2020-01-01
Series:	NeuroImage: Clinical
Online Access:	http://www.sciencedirect.com/science/article/pii/S2213158219304620

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record_format	Article
collection	DOAJ
language	English
format	Article
sources	DOAJ
author	Chunyan Luo Sara Makaretz Michael Stepanovic George Papadimitriou Megan Quimby Senthil Palanivelu Bradford C. Dickerson Nikos Makris
spellingShingle	Chunyan Luo Sara Makaretz Michael Stepanovic George Papadimitriou Megan Quimby Senthil Palanivelu Bradford C. Dickerson Nikos Makris Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia NeuroImage: Clinical
author_facet	Chunyan Luo Sara Makaretz Michael Stepanovic George Papadimitriou Megan Quimby Senthil Palanivelu Bradford C. Dickerson Nikos Makris
author_sort	Chunyan Luo
title	Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia
title_short	Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia
title_full	Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia
title_fullStr	Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia
title_full_unstemmed	Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia
title_sort	middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia
publisher	Elsevier
series	NeuroImage: Clinical
issn	2213-1582
publishDate	2020-01-01
description	The middle longitudinal fascicle (MdLF) is a recently delineated association cortico-cortical fiber pathway in humans, connecting superior temporal gyrus and temporal pole principally with the angular gyrus, and is likely to be involved in language processing. However, the MdLF has not been studied in language disorders as primary progressive aphasia (PPA). We hypothesized that the MdLF will exhibit evidence of neurodegeneration in PPA patients. In this study, 20 PPA patients and 25 healthy controls were recruited in the Primary Progressive Aphasia program in the Massachusetts General Hospital Frontotemporal Disorders Unit. We used diffusion tensor imaging (DTI) tractography to reconstruct the MdLF and extract tract-specific DTI metrics (fractional anisotropy (FA), radial diffusivity (RD), mean diffusivity (MD) and axial diffusivity (AD)) to assess white matter changes in PPA and their relationship with language impairments. We found severe WM damage in the MdLF in PPA patients, which was principally pronounced in the left hemisphere. Moreover, the WM alterations in the MdLF in the dominant hemisphere were significantly correlated with impairments in word comprehension and naming, but not with articulation and fluency. In addition, asymmetry analysis revealed that the DTI metrics of controls were similar for each hemisphere, whereas PPA patients had clear laterality differences in MD, AD and RD. These findings add new insight into the localization and severity of white matter fiber bundle neurodegeneration in PPA, and provide evidence that degeneration of the MdLF contribute to impairment in semantic processing and lexical retrieval in PPA. Keywords: Diffusion tensor imaging, Middle longitudinal fascicle, Middle longitudinal fasciculus, Primary progressive aphasia, Semantic processing
url	http://www.sciencedirect.com/science/article/pii/S2213158219304620
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spelling	doaj-a8ed8dc6ca6346c6a1dc557b73ae53ab2020-11-25T03:48:15ZengElsevierNeuroImage: Clinical2213-15822020-01-0125Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasiaChunyan Luo0Sara Makaretz1Michael Stepanovic2George Papadimitriou3Megan Quimby4Senthil Palanivelu5Bradford C. Dickerson6Nikos Makris7Frontotemporal Disorders Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Department of Neurology, West China Hospital, Sichuan University, Chengdu, Sichuan, ChinaFrontotemporal Disorders Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USAFrontotemporal Disorders Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USACenter for Morphometric Analysis, Massachusetts General Hospital, 149 13th Street, Office 10.006, Charlestown, MA 02129, USA; Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USAFrontotemporal Disorders Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USACenter for Morphometric Analysis, Massachusetts General Hospital, 149 13th Street, Office 10.006, Charlestown, MA 02129, USA; Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USAFrontotemporal Disorders Unit, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Alzheimer's Disease Research Center, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital and Harvard Medical School, Charlestown, MA, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USACenter for Morphometric Analysis, Massachusetts General Hospital, 149 13th Street, Office 10.006, Charlestown, MA 02129, USA; Department of Neurology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Department of Psychiatry, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA; Correspondence author at: Center for Morphometric Analysis, Massachusetts General Hospital, 149 13th Street, Office 10.006, Charlestown, MA 02129, USA.The middle longitudinal fascicle (MdLF) is a recently delineated association cortico-cortical fiber pathway in humans, connecting superior temporal gyrus and temporal pole principally with the angular gyrus, and is likely to be involved in language processing. However, the MdLF has not been studied in language disorders as primary progressive aphasia (PPA). We hypothesized that the MdLF will exhibit evidence of neurodegeneration in PPA patients. In this study, 20 PPA patients and 25 healthy controls were recruited in the Primary Progressive Aphasia program in the Massachusetts General Hospital Frontotemporal Disorders Unit. We used diffusion tensor imaging (DTI) tractography to reconstruct the MdLF and extract tract-specific DTI metrics (fractional anisotropy (FA), radial diffusivity (RD), mean diffusivity (MD) and axial diffusivity (AD)) to assess white matter changes in PPA and their relationship with language impairments. We found severe WM damage in the MdLF in PPA patients, which was principally pronounced in the left hemisphere. Moreover, the WM alterations in the MdLF in the dominant hemisphere were significantly correlated with impairments in word comprehension and naming, but not with articulation and fluency. In addition, asymmetry analysis revealed that the DTI metrics of controls were similar for each hemisphere, whereas PPA patients had clear laterality differences in MD, AD and RD. These findings add new insight into the localization and severity of white matter fiber bundle neurodegeneration in PPA, and provide evidence that degeneration of the MdLF contribute to impairment in semantic processing and lexical retrieval in PPA. Keywords: Diffusion tensor imaging, Middle longitudinal fascicle, Middle longitudinal fasciculus, Primary progressive aphasia, Semantic processinghttp://www.sciencedirect.com/science/article/pii/S2213158219304620

Middle longitudinal fascicle is associated with semantic processing deficits in primary progressive aphasia

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