TY - JOUR
T1 - Variability in blood oxygen level dependent (BOLD) signal in patients with stroke-induced and primary progressive aphasia
AU - Bonakdarpour, B.
AU - Beeson, P. M.
AU - Demarco, A. T.
AU - Rapcsak, S. Z.
N1 - Funding Information:
This study was supported by: the University of Arizona Department of Neurology Rayphole Neuroscience Fund (Borna Bonakdarpour, MD) and NIDCD grant DC008286 (Stephen Wilson, PhD). The authors would like to thank Bruce Coull, MD (Professor, University of Arizona Department of Neurology), David Labiner, MD (Professor and Chair, University of Arizona Department of Neurology), and Stephen Wilson, PhD (Assistant Professor, University of Arizona Department of Speech, Language, and Hearing Sciences) for their support of this project. We also thank Drs. Todd Parrish and Jennie Chen (Department of Radiology, Northwestern University), for their help with the interpretation of the results, and Dr. Elena Barbieri (Department of Communication Sciences and Disorder, Northwestern University), for her input regarding statistical analysis.
Publisher Copyright:
© 2015 The Authors.
PY - 2015
Y1 - 2015
N2 - Abstract Although fMRI is increasingly used to assess language-related brain activation in patients with aphasia, few studies have examined the hemodynamic response function (HRF) in perilesional, and contralesional areas of the brain. In addition, the relationship between HRF abnormalities and other variables such as lesion size and severity of aphasia has not been explored. The objective of this study was to investigate changes in HRF signal during language-related neural activation in patients with stroke-induced aphasia (SA). We also examined the status of the HRF in patients with aphasia due to nonvascular etiology, namely, primary progressive aphasia (PPA). Five right handed SA patients, three PPA patients, and five healthy individuals participated in the study. Structural damage was quantified with T1-weighted MR images. Functional MR imaging was performed with long trial event-related design and an overt naming task to measure BOLD signal time to peak (TTP) and percent signal change (ΔS). In SA patients, the average HRF TTP was significantly delayed in the left hemisphere regions involved in naming compared to healthy participants and PPA patients. However, ΔS was not different in SA patients compared to the other two groups. Delay in HRF TTP in the left hemisphere naming network of SA patients was correlated with lesion size and showed a negative correlation with global language function. There were no significant differences in the HRF TTP and ΔS in the right hemisphere homologues of the naming network or in the left and the right occipital control regions across the three groups. In PPA patients, HRF had a normal pattern. Our results indicate that abnormal task-related HRF is primarily found in the left hemisphere language network of SA patients and raise the possibility that abnormal physiology superimposed on structural damage may contribute to the clinical deficit. Follow-up investigations in a larger sample of age-matched healthy individuals, SA, and PPA patients will be needed to further confirm and extend our findings.
AB - Abstract Although fMRI is increasingly used to assess language-related brain activation in patients with aphasia, few studies have examined the hemodynamic response function (HRF) in perilesional, and contralesional areas of the brain. In addition, the relationship between HRF abnormalities and other variables such as lesion size and severity of aphasia has not been explored. The objective of this study was to investigate changes in HRF signal during language-related neural activation in patients with stroke-induced aphasia (SA). We also examined the status of the HRF in patients with aphasia due to nonvascular etiology, namely, primary progressive aphasia (PPA). Five right handed SA patients, three PPA patients, and five healthy individuals participated in the study. Structural damage was quantified with T1-weighted MR images. Functional MR imaging was performed with long trial event-related design and an overt naming task to measure BOLD signal time to peak (TTP) and percent signal change (ΔS). In SA patients, the average HRF TTP was significantly delayed in the left hemisphere regions involved in naming compared to healthy participants and PPA patients. However, ΔS was not different in SA patients compared to the other two groups. Delay in HRF TTP in the left hemisphere naming network of SA patients was correlated with lesion size and showed a negative correlation with global language function. There were no significant differences in the HRF TTP and ΔS in the right hemisphere homologues of the naming network or in the left and the right occipital control regions across the three groups. In PPA patients, HRF had a normal pattern. Our results indicate that abnormal task-related HRF is primarily found in the left hemisphere language network of SA patients and raise the possibility that abnormal physiology superimposed on structural damage may contribute to the clinical deficit. Follow-up investigations in a larger sample of age-matched healthy individuals, SA, and PPA patients will be needed to further confirm and extend our findings.
KW - Aphasia
KW - Blood oxygen level dependent (BOLD) signal
KW - Hemodynamic response function (HRF)
KW - Primary progressive aphasia (PPA)
KW - Stroke
KW - Time to peak (TTP)
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U2 - 10.1016/j.nicl.2015.03.014
DO - 10.1016/j.nicl.2015.03.014
M3 - Article
C2 - 26106531
AN - SCOPUS:84926466580
SN - 2213-1582
VL - 8
SP - 87
EP - 94
JO - NeuroImage: Clinical
JF - NeuroImage: Clinical
M1 - 471
ER -