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Hasanzadeh N, Rezaei M, Faraz S, Popovic MR, Lankarany M. Necessary Conditions for Reliable Propagation of Slowly Time-Varying Firing Rate. Front Comput Neurosci 2020; 14:64. [PMID: 32848685 PMCID: PMC7405925 DOI: 10.3389/fncom.2020.00064] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2020] [Accepted: 05/28/2020] [Indexed: 11/13/2022] Open
Abstract
Reliable propagation of slow-modulations of the firing rate across multiple layers of a feedforward network (FFN) has proven difficult to capture in spiking neural models. In this paper, we explore necessary conditions for reliable and stable propagation of time-varying asynchronous spikes whose instantaneous rate of changes-in fairly short time windows [20-100] msec-represents information of slow fluctuations of the stimulus. Specifically, we study the effect of network size, level of background synaptic noise, and the variability of synaptic delays in an FFN with all-to-all connectivity. We show that network size and the level of background synaptic noise, together with the strength of synapses, are substantial factors enabling the propagation of asynchronous spikes in deep layers of an FFN. In contrast, the variability of synaptic delays has a minor effect on signal propagation.
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Affiliation(s)
- Navid Hasanzadeh
- Clinical and Computational Neuroscience, Krembil Research Institute, University Health Network, Toronto, ON, Canada.,School of Electrical and Computer Engineering, College of Engineering, University of Tehran, Tehran, Iran
| | - Mohammadreza Rezaei
- Clinical and Computational Neuroscience, Krembil Research Institute, University Health Network, Toronto, ON, Canada.,KITE Research Institute, Toronto Rehabilitation Institute, University Health Network, Toronto, ON, Canada
| | - Sayan Faraz
- Clinical and Computational Neuroscience, Krembil Research Institute, University Health Network, Toronto, ON, Canada
| | - Milos R Popovic
- KITE Research Institute, Toronto Rehabilitation Institute, University Health Network, Toronto, ON, Canada.,Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
| | - Milad Lankarany
- Clinical and Computational Neuroscience, Krembil Research Institute, University Health Network, Toronto, ON, Canada.,KITE Research Institute, Toronto Rehabilitation Institute, University Health Network, Toronto, ON, Canada.,Institute of Biomedical Engineering, University of Toronto, Toronto, ON, Canada
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Soldan A, Moghekar A, Walker KA, Pettigrew C, Hou X, Lu H, Miller MI, Alfini A, Albert M, Xu D, Xiao MF, Worley P. Resting-State Functional Connectivity Is Associated With Cerebrospinal Fluid Levels of the Synaptic Protein NPTX2 in Non-demented Older Adults. Front Aging Neurosci 2019; 11:132. [PMID: 31231205 PMCID: PMC6568192 DOI: 10.3389/fnagi.2019.00132] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2019] [Accepted: 05/20/2019] [Indexed: 12/16/2022] Open
Abstract
Intrinsic functional connectivity of large-scale brain networks has been shown to change with aging and Alzheimer’s disease (AD). These alterations are thought to reflect changes in synaptic function, but the underlying biological mechanisms are poorly understood. This study examined whether Neuronal Pentraxin 2 (NPTX2), a synaptic protein that mediates homeostatic strengthening of inhibitory circuits to control cortical excitability, is associated with functional connectivity as measured by resting-state functional magnetic resonance imaging (rsfMRI) in five large-scale cognitive brain networks. In this cross-sectional study, rsfMRI scans were obtained from 130 older individuals (mean age = 69 years) with normal cognition (N = 113) and Mild Cognitive Impairment (N = 17); NPTX2 was measured in the same individuals in cerebrospinal fluid (CSF). Higher levels of NPTX2 in CSF were associated with greater functional connectivity in the salience/ventral attention network, based on linear regression analysis. Moreover, this association was stronger among individuals with lower levels of cognitive reserve, as measured by a composite score (comprised of years of education, reading, and vocabulary measures). Additionally, higher connectivity in the salience/ventral attention network was related to better performance on a composite measure of executive function. Levels of NPTX2 were not associated with connectivity in other networks (executive control, limbic, dorsal attention, and default-mode). Findings also confirmed prior reports that individuals with MCI have lower levels of NPTX2 compared to those with normal cognition. Taken together, the results suggest that NPTX2 mechanisms may play a central role among older individuals in connectivity within the salience/ventral attention network and for cognitive tasks that require modulation of attention and response selection.
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Affiliation(s)
- Anja Soldan
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Abhay Moghekar
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Keenan A Walker
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Corinne Pettigrew
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Xirui Hou
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States
| | - Hanzhang Lu
- Department of Radiology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States
| | - Michael I Miller
- Department of Biomedical Engineering, Johns Hopkins University, Baltimore, MD, United States
| | - Alfonso Alfini
- Department of Mental Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
| | - Marilyn Albert
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Desheng Xu
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Mei-Fang Xiao
- Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Paul Worley
- Department of Neurology, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, MD, United States
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