- Email: [email protected]
DORSAL STREAM DISSOCIATION IN DWI: CASE STUDIES IN SEMANTIC DEMENTIA AND POSTERIOR CORTICAL ATROPHY
Poster Presentations: Saturday, July 23, 2016 Orangeburg, NY, USA; 5New York University-Langone Medical Center, New York, NY, USA; 6Institute for Stroke and Dementia Research, Klinikum der Universitaet Muenchen, Ludwig-Maximilians-University Munich, Munich, Germany; 7Institute for Stroke and Dementia Research, M€unchen, Germany; 8Institute for Stroke and Dementia Research, Munich, Germany; 9 University Medicine Rostock, Rostock, Germany. Contact e-mail: [email protected] Background: Impaired consolidation of information into episodic
long-term memory is a hallmark of amnestic mild cognitive impairment (aMCI). Consolidation relies upon the hippocampus, which is affected in aMCI. The “primacy effect”, i.e., the phenomenon that the first items of a series are remembered better than the following items, is an indicator for consolidation. A recent study showed that hippocampal volume correlated with the number of primacy words recalled by healthy adults [1]. In aMCI, however, we did not find such a correlation. One could speculate that regions functionally connected with the hippocampus might play an increased role in consolidation when the hippocampus is already dysfunctional. Therefore, in this study, we investigated the association of the primacy effect and functional connectivity (FC) of the hippocampus with other brain regions. Methods: We derived FC from fMRI data of 87 aMCI patients and assessed delayed primacy as recall of the first four words from a list of ten words. FC maps were calculated using the anterior hippocampus as seed region. We used multiple regression analysis of FC of the anterior left hippocampus and delayed primacy performance, controlled for age, gender, education, and total recall. Additionally, we performed partial least squares (PLS) analysis of pair-wise FC between regions of the dorsal DMN and primacy performance, removing cases with floor effects. Results: Delayed primacy performance correlated positively with FC of the left anterior hippocampus with bilateral temporal regions (p<.001, uncorr.). PLS analysis showed the strongest positive associations of primacy performance with FC between both hippocampi; FC between left hippocampus and middle cingulate cortex, posterior cingulate cortex/precuneus, and thalamus; and FC between right hippocampus and middle cingulate gyrus, (p<.040). Conclusions: In aMCI subjects, hippocampus FC with the regions middle and posterior cingulate cortex/precuneus, and thalamus was associated with primacy performance. These regions might be part of a compensatory network for consolidation function. References: [1] Bruno, D., Grothe, M. J., Nierenberg, J., Zetterberg, H., Blennow, K., Teipel, S. J., & Pomara, N. (2015). A study on the specificity of the association between hippocampal volume and delayed primacy performance in cognitively intact elderly individuals. Neuropsychologia, 69, 1-8. IC-P-036
VENTRAL/DORSAL STREAM DISSOCIATION IN DWI: CASE STUDIES IN SEMANTIC DEMENTIA AND POSTERIOR CORTICAL ATROPHY 1,2
3,4
1
P33
functions are sustained by the ventral (what) and dorsal (where) stream respectively. The ventral stream is constituted by the inferior longitudinal fascicles (ILF) and the inferior fronto-occipital fasciculus (IFOF), whereas the dorsal stream includes the superior longitudinal fascicles (SLF 1, 2, 3). Nonetheless, no study has directly compared the cerebral connections in these dementia using state of the art tractography analyses. Methods: 1 patient suffering from mild SD (right-side form) and 1 patient suffering from mild PCA were compared to 12 matched controls. The patients underwent an extensive neuropsychological assessment. High resolution anatomical imaging and 64-direction diffusion magnetic resonance imaging (dMRI) were also acquired for all participants in a 3-Tesla Siemens MRI. Diffusion data were corrected, denoised, registered and then modeled using high angular resolution diffusion-weighted imaging (HARDI) models. Then, four tracts of interest were reconstructed in each hemisphere: ILF, IFOF, and SLF-2 and 3. Results: Neuropsychological results confirm the semantic impairment in the patient with DS and the visuospatial deficits in the patient with PCA. The DS patient suffers from right anterior temporal lobe atrophy, whereas the PCA patient exhibits a more pronounced alteration of the right fronto-parietal regions. Tractography analyses show significant alterations of the right SLF in the patient with PCA, but remarkably preserved IFL and IFOF in both hemispheres. Reversely, the patient with DS exhibits preserved ILF in both hemispheres, but a major deterioration of the right IFOF and noticeable alterations of the right IFL mostly restricted to the anterior part of the tract. Conclusions: DS and PCA are characterized by specific and distinct cognitive profiles associated with a marked dissociation between the impairment of the ventral and posterior tracts. Patients also exhibit a clear hemispheric dissociation with almost completely preserved left side tracts compared to the right hemisphere. This is highlighting the importance to analyze tracts in their different portions. IC-P-037
SIMULTANEOUS EEG-FMRI IN PATIENTS WITH ALZHEIMER’S DISEASE: ARE BOLD SIGNAL FLUCTUATIONS IN THE DEFAULT MODE NETWORK CORRELATED WITH ALPHA BAND POWER?
Katharina Brueggen1, Carmen Fiala1, Claudio Babiloni2, Christoph Berger3, Stefan J. Teipel1,4, 1German Center for Neurodegenerative Diseases (DZNE), Rostock, Germany; 2Department of Physiology and Pharmacology, University of Rome, Rome, Italy; 3 University Medical Center of Rostock, University of Rostock, Rostock, Germany; 4University Medicine Rostock, Rostock, Germany. Contact e-mail: [email protected] Background: Neural oscillations within the alpha band, which is the
2,5
Guillaume T. Vallet , Isabelle Rouleau , Arnaud Bore , Nathalie Bier , Julien Doyon1, Nadia Gosselin2, Sven Joubert1,2, Simona M. Brambati1,2, 1 Centre de Recherche de l’Institut Universitaire de Geriatrie de Montreal (CRIUGM), Montreal, QC, Canada; 2University of Montreal, Montreal, QC, Canada; 3Universite du Quebec a Montreal, Montreal, QC, Canada; 4 Centre de Recherche du Centre Hospitalier Universitaire de Montreal, Montreal, QC, Canada; 5Centre de Recherche de l’Institut Universitaire de Geriatrie de Montreal (CRIUGM), Montreal, QC, Canada. Contact e-mail: [email protected] Background: Semantic Dementia (SD) and Posterior Cortical Atrophy (PCA) are two rare dementia associate with very distinct but complementary cognitive profiles. DS is defined by major semantic-related deficits, whereas PCA is characterized by marked visuospatial deficits. According to neuroanatomical models, these
dominant frequency during resting state in healthy adults, show a reduced power in Alzheimer’s disease (AD). In addition, AD is characterized by altered functional connectivity within the default mode network (DMN). In healthy adults, simultaneous EEG-fMRI studies showed that fluctuations in blood-oxygen-level-dependent (BOLD) signal within the DMN co-varied with occipital alpha band power. In the present study, we aimed to investigate the correlation of BOLD signal changes in the DMN and occipital alpha power fluctuations in AD patients compared to a healthy control (HC) group. Methods: We measured simultaneous EEG-fMRI using a 32-channel MR-compatible EEG system in 14 patients with mild AD and 14 HC subjects. Groups were matched for gender, age, and education. BOLD signal changes over time from each voxel in the brain were regressed onto alpha band (8-12 Hz) power fluctuations over time, pooled across occipital electrodes. Using t-tests, correlation
long-term memory is a hallmark of amnestic mild cognitive impairment (aMCI). Consolidation relies upon the hippocampus, which is affected in aMCI. The “primacy effect”, i.e., the phenomenon that the first items of a series are remembered better than the following items, is an indicator for consolidation. A recent study showed that hippocampal volume correlated with the number of primacy words recalled by healthy adults [1]. In aMCI, however, we did not find such a correlation. One could speculate that regions functionally connected with the hippocampus might play an increased role in consolidation when the hippocampus is already dysfunctional. Therefore, in this study, we investigated the association of the primacy effect and functional connectivity (FC) of the hippocampus with other brain regions. Methods: We derived FC from fMRI data of 87 aMCI patients and assessed delayed primacy as recall of the first four words from a list of ten words. FC maps were calculated using the anterior hippocampus as seed region. We used multiple regression analysis of FC of the anterior left hippocampus and delayed primacy performance, controlled for age, gender, education, and total recall. Additionally, we performed partial least squares (PLS) analysis of pair-wise FC between regions of the dorsal DMN and primacy performance, removing cases with floor effects. Results: Delayed primacy performance correlated positively with FC of the left anterior hippocampus with bilateral temporal regions (p<.001, uncorr.). PLS analysis showed the strongest positive associations of primacy performance with FC between both hippocampi; FC between left hippocampus and middle cingulate cortex, posterior cingulate cortex/precuneus, and thalamus; and FC between right hippocampus and middle cingulate gyrus, (p<.040). Conclusions: In aMCI subjects, hippocampus FC with the regions middle and posterior cingulate cortex/precuneus, and thalamus was associated with primacy performance. These regions might be part of a compensatory network for consolidation function. References: [1] Bruno, D., Grothe, M. J., Nierenberg, J., Zetterberg, H., Blennow, K., Teipel, S. J., & Pomara, N. (2015). A study on the specificity of the association between hippocampal volume and delayed primacy performance in cognitively intact elderly individuals. Neuropsychologia, 69, 1-8. IC-P-036
VENTRAL/DORSAL STREAM DISSOCIATION IN DWI: CASE STUDIES IN SEMANTIC DEMENTIA AND POSTERIOR CORTICAL ATROPHY 1,2
3,4
1
P33
functions are sustained by the ventral (what) and dorsal (where) stream respectively. The ventral stream is constituted by the inferior longitudinal fascicles (ILF) and the inferior fronto-occipital fasciculus (IFOF), whereas the dorsal stream includes the superior longitudinal fascicles (SLF 1, 2, 3). Nonetheless, no study has directly compared the cerebral connections in these dementia using state of the art tractography analyses. Methods: 1 patient suffering from mild SD (right-side form) and 1 patient suffering from mild PCA were compared to 12 matched controls. The patients underwent an extensive neuropsychological assessment. High resolution anatomical imaging and 64-direction diffusion magnetic resonance imaging (dMRI) were also acquired for all participants in a 3-Tesla Siemens MRI. Diffusion data were corrected, denoised, registered and then modeled using high angular resolution diffusion-weighted imaging (HARDI) models. Then, four tracts of interest were reconstructed in each hemisphere: ILF, IFOF, and SLF-2 and 3. Results: Neuropsychological results confirm the semantic impairment in the patient with DS and the visuospatial deficits in the patient with PCA. The DS patient suffers from right anterior temporal lobe atrophy, whereas the PCA patient exhibits a more pronounced alteration of the right fronto-parietal regions. Tractography analyses show significant alterations of the right SLF in the patient with PCA, but remarkably preserved IFL and IFOF in both hemispheres. Reversely, the patient with DS exhibits preserved ILF in both hemispheres, but a major deterioration of the right IFOF and noticeable alterations of the right IFL mostly restricted to the anterior part of the tract. Conclusions: DS and PCA are characterized by specific and distinct cognitive profiles associated with a marked dissociation between the impairment of the ventral and posterior tracts. Patients also exhibit a clear hemispheric dissociation with almost completely preserved left side tracts compared to the right hemisphere. This is highlighting the importance to analyze tracts in their different portions. IC-P-037
SIMULTANEOUS EEG-FMRI IN PATIENTS WITH ALZHEIMER’S DISEASE: ARE BOLD SIGNAL FLUCTUATIONS IN THE DEFAULT MODE NETWORK CORRELATED WITH ALPHA BAND POWER?
Katharina Brueggen1, Carmen Fiala1, Claudio Babiloni2, Christoph Berger3, Stefan J. Teipel1,4, 1German Center for Neurodegenerative Diseases (DZNE), Rostock, Germany; 2Department of Physiology and Pharmacology, University of Rome, Rome, Italy; 3 University Medical Center of Rostock, University of Rostock, Rostock, Germany; 4University Medicine Rostock, Rostock, Germany. Contact e-mail: [email protected] Background: Neural oscillations within the alpha band, which is the
2,5
Guillaume T. Vallet , Isabelle Rouleau , Arnaud Bore , Nathalie Bier , Julien Doyon1, Nadia Gosselin2, Sven Joubert1,2, Simona M. Brambati1,2, 1 Centre de Recherche de l’Institut Universitaire de Geriatrie de Montreal (CRIUGM), Montreal, QC, Canada; 2University of Montreal, Montreal, QC, Canada; 3Universite du Quebec a Montreal, Montreal, QC, Canada; 4 Centre de Recherche du Centre Hospitalier Universitaire de Montreal, Montreal, QC, Canada; 5Centre de Recherche de l’Institut Universitaire de Geriatrie de Montreal (CRIUGM), Montreal, QC, Canada. Contact e-mail: [email protected] Background: Semantic Dementia (SD) and Posterior Cortical Atrophy (PCA) are two rare dementia associate with very distinct but complementary cognitive profiles. DS is defined by major semantic-related deficits, whereas PCA is characterized by marked visuospatial deficits. According to neuroanatomical models, these
dominant frequency during resting state in healthy adults, show a reduced power in Alzheimer’s disease (AD). In addition, AD is characterized by altered functional connectivity within the default mode network (DMN). In healthy adults, simultaneous EEG-fMRI studies showed that fluctuations in blood-oxygen-level-dependent (BOLD) signal within the DMN co-varied with occipital alpha band power. In the present study, we aimed to investigate the correlation of BOLD signal changes in the DMN and occipital alpha power fluctuations in AD patients compared to a healthy control (HC) group. Methods: We measured simultaneous EEG-fMRI using a 32-channel MR-compatible EEG system in 14 patients with mild AD and 14 HC subjects. Groups were matched for gender, age, and education. BOLD signal changes over time from each voxel in the brain were regressed onto alpha band (8-12 Hz) power fluctuations over time, pooled across occipital electrodes. Using t-tests, correlation