1
|
Roland PE, Bonde LH, Forsberg LE, Harvey MA. Breaking the Excitation-Inhibition Balance Makes the Cortical Network's Space-Time Dynamics Distinguish Simple Visual Scenes. Front Syst Neurosci 2017; 11:14. [PMID: 28377701 PMCID: PMC5360108 DOI: 10.3389/fnsys.2017.00014] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2016] [Accepted: 03/03/2017] [Indexed: 11/21/2022] Open
Abstract
Brain dynamics are often taken to be temporal dynamics of spiking and membrane potentials in a balanced network. Almost all evidence for a balanced network comes from recordings of cell bodies of few single neurons, neglecting more than 99% of the cortical network. We examined the space-time dynamics of excitation and inhibition simultaneously in dendrites and axons over four visual areas of ferrets exposed to visual scenes with stationary and moving objects. The visual stimuli broke the tight balance between excitation and inhibition such that the network exhibited longer episodes of net excitation subsequently balanced by net inhibition, in contrast to a balanced network. Locally in all four areas the amount of net inhibition matched the amount of net excitation with a delay of 125 ms. The space-time dynamics of excitation-inhibition evolved to reduce the complexity of neuron interactions over the whole network to a flow on a low-(3)-dimensional manifold within 80 ms. In contrast to the pure temporal dynamics, the low dimensional flow evolved to distinguish the simple visual scenes.
Collapse
Affiliation(s)
- Per E Roland
- Faculty of Health Sciences, Center for Neuroscience, University of Copenhagen Copenhagen, Denmark
| | - Lars H Bonde
- Faculty of Health Sciences, Center for Neuroscience, University of Copenhagen Copenhagen, Denmark
| | - Lars E Forsberg
- Faculty of Health Sciences, Center for Neuroscience, University of Copenhagen Copenhagen, Denmark
| | - Michael A Harvey
- Department of Physiology, University of Fribourg Fribourg, Switzerland
| |
Collapse
|
2
|
de Jong LW, Vidal JS, Forsberg LE, Zijdenbos AP, Haight T, Sigurdsson S, Gudnason V, van Buchem MA, Launer LJ. Allometric scaling of brain regions to intra-cranial volume: An epidemiological MRI study. Hum Brain Mapp 2016; 38:151-164. [PMID: 27557999 DOI: 10.1002/hbm.23351] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 07/31/2016] [Accepted: 08/09/2016] [Indexed: 11/09/2022] Open
Abstract
There is growing evidence that sub-structures of the brain scale allometrically to total brain size, that is, in a non-proportional and non-linear way. Here, scaling of different volumes of interest (VOI) to intra-cranial volume (ICV) was examined. It was assessed whether scaling was allometric or isometric and whether scaling coefficients significantly differed from each other. We also tested to what extent allometric scaling of VOI was introduced by the automated segmentation technique. Furthermore, reproducibility of allometric scaling was studied different age groups and study populations. Study samples included samples of cognitively healthy adults from the community-based Age Gene/Environment Susceptibility-Reykjavik Study (AGES-Reykjavik Study) (N = 3,883), the Coronary Artery Risk Development in Young Adults Study (CARDIA) (N =709), and the Alzheimer's Disease Neuroimaging Initiative (ADNI) (N = 180). Data encompassed participants with different age, ethnicity, risk factor profile, and ICV and VOI obtained with different automated MRI segmentation techniques. Our analysis showed that (1) allometric scaling is a trait of all parts of the brain, (2) scaling of neo-cortical white matter, neo-cortical gray matter, and deep gray matter structures including the cerebellum are significantly different from each other, and (3) allometric scaling of brain structures cannot solely be explained by age-associated atrophy, sex, ethnicity, or a systematic bias from study-specific segmentation algorithm, but appears to be a true feature of brain geometry. Hum Brain Mapp 38:151-164, 2017. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Laura W de Jong
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Jean-Sébastien Vidal
- Geriatrics Department, AP-HP, Broca Hospital, Paris, 75013, France.,Université Paris Descartes, Sorbonne Paris V, Paris, EA, 4468, 75006, France
| | - Lars E Forsberg
- Department of Clinical Neuroscience Karolinska Institute, Stockholm, Sweden
| | | | - Thaddeus Haight
- Intramural Research Program of the National Institute on Aging, Bethesda, Maryland
| | | | | | | | - Mark A van Buchem
- Department of Radiology, Leiden University Medical Center, Leiden, The Netherlands
| | - Lenore J Launer
- Intramural Research Program of the National Institute on Aging, Bethesda, Maryland
| |
Collapse
|
3
|
Forsberg LE, Bonde LH, Harvey MA, Roland PE. The Second Spiking Threshold: Dynamics of Laminar Network Spiking in the Visual Cortex. Front Syst Neurosci 2016; 10:65. [PMID: 27582693 PMCID: PMC4987378 DOI: 10.3389/fnsys.2016.00065] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 07/12/2016] [Indexed: 11/30/2022] Open
Abstract
Most neurons have a threshold separating the silent non-spiking state and the state of producing temporal sequences of spikes. But neurons in vivo also have a second threshold, found recently in granular layer neurons of the primary visual cortex, separating spontaneous ongoing spiking from visually evoked spiking driven by sharp transients. Here we examine whether this second threshold exists outside the granular layer and examine details of transitions between spiking states in ferrets exposed to moving objects. We found the second threshold, separating spiking states evoked by stationary and moving visual stimuli from the spontaneous ongoing spiking state, in all layers and zones of areas 17 and 18 indicating that the second threshold is a property of the network. Spontaneous and evoked spiking, thus can easily be distinguished. In addition, the trajectories of spontaneous ongoing states were slow, frequently changing direction. In single trials, sharp as well as smooth and slow transients transform the trajectories to be outward directed, fast and crossing the threshold to become evoked. Although the speeds of the evolution of the evoked states differ, the same domain of the state space is explored indicating uniformity of the evoked states. All evoked states return to the spontaneous evoked spiking state as in a typical mono-stable dynamical system. In single trials, neither the original spiking rates, nor the temporal evolution in state space could distinguish simple visual scenes.
Collapse
Affiliation(s)
- Lars E Forsberg
- Brain Research, Department of Neuroscience, Karolinska Institute Solna, Sweden
| | - Lars H Bonde
- Signalling Lab, Department of Neuroscience, Faculty of Health Sciences, University of Copenhagen Denmark
| | - Michael A Harvey
- Brain Research, Department of Neuroscience, Karolinska Institute Solna, Sweden
| | - Per E Roland
- Signalling Lab, Department of Neuroscience, Faculty of Health Sciences, University of Copenhagen Denmark
| |
Collapse
|
4
|
de Jong LW, Forsberg LE, Vidal JS, Sigurdsson S, Zijdenbos AP, Garcia M, Eiriksdottir G, Gudnason V, van Buchem MA, Launer LJ. Different susceptibility of medial temporal lobe and basal ganglia atrophy rates to vascular risk factors. Neurobiol Aging 2013; 35:72-8. [PMID: 23992618 DOI: 10.1016/j.neurobiolaging.2013.07.009] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Revised: 07/01/2013] [Accepted: 07/15/2013] [Indexed: 10/26/2022]
Abstract
Atrophy of the medial temporal lobe (MTL) and basal ganglia (BG) are characteristic of various neurodegenerative diseases in older people. In search of potentially modifiable factors that lead to atrophy in these structures, we studied the association of vascular risk factors with atrophy of the MTL and BG in 368 nondemented men and women (born, 1907-1935) who participated in the Age, Gene/Environment, Susceptibility-Reykjavik Study. A fully automated segmentation pipeline estimated volumes of the MTL and BG from whole-brain magnetic resonance imaging performed at baseline and 2.4 years later. Linear regression models showed higher systolic and diastolic blood pressures and the presence of Apo E ε4 were independently associated with increased atrophy of the MTL but no association of vascular risk factors with atrophy of the BG. The different susceptibility of MTL and BG atrophy to the vascular risk factors suggests perfusion of the BG is relatively preserved when vascular risk factors are present.
Collapse
Affiliation(s)
- Laura W de Jong
- Department of Radiology, Leiden University Medical Center, Leiden, the Netherlands
| | | | | | | | | | | | | | | | | | | |
Collapse
|
5
|
Ma Z, Lavebratt C, Almgren M, Portwood N, Forsberg LE, Bränström R, Berglund E, Falkmer S, Sundler F, Wierup N, Björklund A. Evidence for presence and functional effects of Kv1.1 channels in β-cells: general survey and results from mceph/mceph mice. PLoS One 2011; 6:e18213. [PMID: 21483673 PMCID: PMC3071710 DOI: 10.1371/journal.pone.0018213] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2010] [Accepted: 03/01/2011] [Indexed: 01/26/2023] Open
Abstract
Background Voltage-dependent K+ channels (Kv) mediate repolarisation of β-cell action potentials, and thereby abrogate insulin secretion. The role of the Kv1.1 K+ channel in this process is however unclear. We tested for presence of Kv1.1 in different species and tested for a functional role of Kv1.1 by assessing pancreatic islet function in BALB/cByJ (wild-type) and megencephaly (mceph/mceph) mice, the latter having a deletion in the Kv1.1 gene. Methodology/Principal Findings Kv1.1 expression was detected in islets from wild-type mice, SD rats and humans, and expression of truncated Kv1.1 was detected in mceph/mceph islets. Full-length Kv1.1 protein was present in islets from wild-type mice, but, as expected, not in those from mceph/mceph mice. Kv1.1 expression was localized to the β-cell population and also to α- and δ-cells, with evidence of over-expression of truncated Kv1.1 in mceph/mceph islets. Blood glucose, insulin content, and islet morphology were normal in mceph/mceph mice, but glucose-induced insulin release from batch-incubated islets was (moderately) higher than that from wild-type islets. Reciprocal blocking of Kv1.1 by dendrotoxin-K increased insulin secretion from wild-type but not mceph/mceph islets. Glucose-induced action potential duration, as well as firing frequency, was increased in mceph/mceph mouse β-cells. This duration effect on action potential in β-cells from mceph/mceph mice was mimicked by dendrotoxin-K in β-cells from wild-type mice. Observations concerning the effects of both the mceph mutation, and of dendrotoxin-K, on glucose-induced insulin release were confirmed in pancreatic islets from Kv1.1 null mice. Conclusion/Significance Kv1.1 channels are expressed in the β-cells of several species, and these channels can influence glucose-stimulated insulin release.
Collapse
Affiliation(s)
- Zuheng Ma
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Catharina Lavebratt
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Malin Almgren
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Neil Portwood
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Lars E. Forsberg
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Robert Bränström
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Erik Berglund
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
| | - Sture Falkmer
- Laboratory of Pathology and Clinical Cytology, Ryhov Hospital, Jönköping, Sweden
| | - Frank Sundler
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Nils Wierup
- Department of Experimental Medical Science, Lund University, Lund, Sweden
| | - Anneli Björklund
- Department of Molecular Medicine and Surgery, Karolinska Institutet, Karolinska University Hospital, Stockholm, Sweden
- * E-mail:
| |
Collapse
|
6
|
Abstract
Cytoarchitectonic delineation of areas in post-mortem human brains provides the precise location of these areas. It has been possible to study the size and location of areas between post-mortem brains with multi-subject cytoarchitectonic data. If the structure-function relationship is assumed to be a one-to-one mapping for the purposes of inter-subject variability, then functional areas in the cortex will also adhere to the structure, and therefore, the location and size of cytoarchitectonic areas in the brain. Thus, it is possible to use the cytoarchitectonic data as being representative of the size and location of functional activations. Under this assumption, we simulated activations in cytoarchitectonic areas from ten post-mortem brains in this study. We then treated these data as we would a normal PET experiment. The purpose of this study is to demonstrate a standard PET image analysis on a simulated ten-subject PET study using cytoarchitecture to localize the activations. By doing so, we simulate activations with real inter-subject variability with the size and location of each area. Significant activations were obtained for activations simulated in areas 3a and 3b. A voxel-wise conjunction between simulated data and experimental data was made to better determine the underlying areas activated by the experimental tasks. This study presents a novel technique for demonstrating the effect of standard image analysis on the location and size of simulated activations as determined by cytoarchitectonic data from multiple subjects. Furthermore, this technique has been applied to better determine the underlying areas activated in an experiment.
Collapse
Affiliation(s)
- Jeremy P Young
- Division of Human Brain Research, Department of Neuroscience, Karolinska Institute, Retzius v, 8, A3:3, Stockholm, Sweden.
| | | |
Collapse
|