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Afrashteh N, Inayat S, Mohsenvand M, Mohajerani MH. Optical-flow analysis toolbox for characterization of spatiotemporal dynamics in mesoscale optical imaging of brain activity. Neuroimage 2017; 153:58-74. [PMID: 28351691 DOI: 10.1016/j.neuroimage.2017.03.034] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 02/10/2017] [Accepted: 03/16/2017] [Indexed: 12/15/2022] Open
Abstract
Wide-field optical imaging techniques constitute powerful tools to investigate mesoscale neuronal activity. The sampled data constitutes a sequence of image frames in which one can investigate the flow of brain activity starting and terminating at source and sink locations respectively. Approaches to the analyses of information flow include qualitative assessment to identify sources and sinks of activity as well as their trajectories, and quantitative measurements based on computing the temporal variation of the intensity of pixels. Furthermore, in a few studies estimates of wave motion have been reported using optical-flow techniques from computer vision. However, a comprehensive toolbox for the quantitative analyses of mesoscale brain activity data is still lacking. We present a graphical-user-interface toolbox based in Matlab® for investigating the spatiotemporal dynamics of mesoscale brain activity using optical-flow analyses. The toolbox includes the implementation of three optical-flow methods namely Horn-Schunck, Combined Local-Global, and Temporospatial algorithms for estimating velocity vector fields of flow of mesoscale brain activity. From the velocity vector fields we determined the locations of sources and sinks as well as the trajectories and temporal velocities of flow of activity. Using simulated data as well as experimentally derived sensory-evoked voltage and calcium imaging data from mice, we compared the efficacy of the three optical-flow methods for determining spatiotemporal dynamics. Our results indicate that the combined local-global method we employed, yields the best results for estimating wave motion. The automated approach permits rapid and effective quantification of mesoscale brain dynamics and may facilitate the study of brain function in response to new experiences or pathology.
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Affiliation(s)
- Navvab Afrashteh
- Canadian Center for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Canada T1K 3M4
| | - Samsoon Inayat
- Canadian Center for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Canada T1K 3M4
| | - Mostafa Mohsenvand
- Canadian Center for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Canada T1K 3M4
| | - Majid H Mohajerani
- Canadian Center for Behavioural Neuroscience, University of Lethbridge, Lethbridge, Canada T1K 3M4.
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Kennerley AJ, Mayhew JE, Boorman L, Zheng Y, Berwick J. Is optical imaging spectroscopy a viable measurement technique for the investigation of the negative BOLD phenomenon? A concurrent optical imaging spectroscopy and fMRI study at high field (7 T). Neuroimage 2012; 61:10-20. [PMID: 22440642 PMCID: PMC3368428 DOI: 10.1016/j.neuroimage.2012.03.015] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2011] [Revised: 02/16/2012] [Accepted: 03/06/2012] [Indexed: 02/05/2023] Open
Abstract
Traditionally functional magnetic resonance imaging (fMRI) has been used to map activity in the human brain by measuring increases in the Blood Oxygenation Level Dependent (BOLD) signal. Often accompanying positive BOLD fMRI signal changes are sustained negative signal changes. Previous studies investigating the neurovascular coupling mechanisms of the negative BOLD phenomenon have used concurrent 2D-optical imaging spectroscopy (2D-OIS) and electrophysiology (Boorman et al., 2010). These experiments suggested that the negative BOLD signal in response to whisker stimulation was a result of an increase in deoxy-haemoglobin and reduced multi-unit activity in the deep cortical layers. However, Boorman et al. (2010) did not measure the BOLD and haemodynamic response concurrently and so could not quantitatively compare either the spatial maps or the 2D-OIS and fMRI time series directly. Furthermore their study utilised a homogeneous tissue model in which is predominantly sensitive to haemodynamic changes in more superficial layers. Here we test whether the 2D-OIS technique is appropriate for studies of negative BOLD. We used concurrent fMRI with 2D-OIS techniques for the investigation of the haemodynamics underlying the negative BOLD at 7 Tesla. We investigated whether optical methods could be used to accurately map and measure the negative BOLD phenomenon by using 2D-OIS haemodynamic data to derive predictions from a biophysical model of BOLD signal changes. We showed that despite the deep cortical origin of the negative BOLD response, if an appropriate heterogeneous tissue model is used in the spectroscopic analysis then 2D-OIS can be used to investigate the negative BOLD phenomenon.
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Affiliation(s)
- Aneurin J Kennerley
- Centre for Signal Processing in Neuroimaging and Systems Neuroscience (SPiNSN), Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TN, UK.
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Song Y, Mellott JG, Winer JA. Microvascular organization of the cat inferior colliculus. Hear Res 2011; 274:5-12. [PMID: 20206676 PMCID: PMC2896976 DOI: 10.1016/j.heares.2010.02.014] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 02/21/2010] [Accepted: 02/26/2010] [Indexed: 11/27/2022]
Abstract
Brain neural activity depends critically on the blood supply to a given structure. The blood supply can differ within and between divisions, which may have functional significance. We analyzed the microvascular organization of the cat inferior colliculus (IC) to determine if the capillary distribution is homogenous throughout. The IC consists of the central nucleus (CN), the dorsal cortex (DC), and the lateral cortex (LC), each with different roles in auditory behavior and perception. Plastic-embedded tissue was studied from adult cats in 1-μm thick semi-thin sections stained with toluidine blue; tissue was sampled from the IC in a caudal-rostral series of sections. The architectonic subdivisions were drawn independently based on Golgi impregnations. We used the nearest neighbor distance (NND) method to quantify capillary density between subdivisions. Overall, the distribution of capillary density was non-homogenous across the IC. We found significant capillary NND differences between the CN and LC (Mann-Whitney test; p ≤ 0.05), CN and DC (Mann-Whitney test; p ≤ 0.05), and LC and DC (Mann-Whitney test; p ≤ 0.05). The CN had the lowest NND values among all three divisions, indicating the highest capillary density. NND values changed gradually as analysis moved from the center of the IC towards the periphery. The significantly higher microvascular density in the CN may imply that the lemniscal auditory pathway has higher levels of blood flow and metabolic activity than non-lemniscal areas of the IC. The non-homogenous microvascular organization of the IC supports parcellation schemes that delineate three major subdivisions and confirms that the borders between the three regions are not sharp.
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Affiliation(s)
- Yohan Song
- Division of Neurobiology, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
| | - Jeffrey G. Mellott
- Division of Neurobiology, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
| | - Jeffery A. Winer
- Division of Neurobiology, Department of Molecular and Cell Biology, University of California at Berkeley, Berkeley, CA, USA
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Kennerley AJ, Berwick J, Martindale J, Johnston D, Zheng Y, Mayhew JE. Refinement of optical imaging spectroscopy algorithms using concurrent BOLD and CBV fMRI. Neuroimage 2009; 47:1608-19. [PMID: 19505581 PMCID: PMC2782682 DOI: 10.1016/j.neuroimage.2009.05.092] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2009] [Revised: 04/23/2009] [Accepted: 05/27/2009] [Indexed: 11/22/2022] Open
Abstract
We describe the use of the three dimensional characteristics of the functional magnetic resonance imaging (fMRI) blood oxygenation level dependent (BOLD) and cerebral blood volume (CBV) MRI signal changes to refine a two dimensional optical imaging spectroscopy (OIS) algorithm. The cortical depth profiles of the BOLD and CBV changes following neural activation were used to parameterise a 5-layer heterogeneous tissue model used in the Monte Carlo simulations (MCS) of light transport through tissue in the OIS analysis algorithm. To transform the fMRI BOLD and CBV measurements into deoxy-haemoglobin (Hbr) profiles we inverted an MCS of extra-vascular MR signal attenuation under the assumption that the extra-/intravascular ratio is 2:1 at a magnetic field strength of 3 T. The significant improvement in the quantitative accuracy of haemodynamic measurements using the new heterogeneous tissue model over the original homogeneous tissue model OIS algorithm was demonstrated on new concurrent OIS and fMRI data covering a range of stimulus durations.
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Affiliation(s)
- Aneurin J Kennerley
- Centre for Signal Processing in Neuroimaging and Systems Neuroscience (SPiNSN), Department of Psychology, University of Sheffield, Western Bank, Sheffield, UK.
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Vanzetta I, Grinvald A. Coupling between neuronal activity and microcirculation: implications for functional brain imaging. HFSP JOURNAL 2008; 2:79-98. [PMID: 19404475 PMCID: PMC2645573 DOI: 10.2976/1.2889618] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Accepted: 02/11/2008] [Indexed: 01/12/2023]
Abstract
In the neocortex, neurons with similar response properties are often clustered together in column-like structures, giving rise to what has become known as functional architecture-the mapping of various stimulus feature dimensions onto the cortical sheet. At least partially, we owe this finding to the availability of several functional brain imaging techniques, both post-mortem and in-vivo, which have become available over the last two generations, revolutionizing neuroscience by yielding information about the spatial organization of active neurons in the brain. Here, we focus on how our understanding of such functional architecture is linked to the development of those functional imaging methodologies, especially to those that image neuronal activity indirectly, through metabolic or haemodynamic signals, rather than directly through measurement of electrical activity. Some of those approaches allow exploring functional architecture at higher spatial resolution than others. In particular, optical imaging of intrinsic signals reaches the striking detail of approximately 50 mum, and, together with other methodologies, it has allowed characterizing the metabolic and haemodynamic responses induced by sensory-evoked neuronal activity. Here, we review those findings about the spatio-temporal characteristics of neurovascular coupling and discuss their implications for functional brain imaging, including position emission tomography, and non-invasive neuroimaging techniques, such as funtional magnetic resonance imaging, applicable also to the human brain.
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Affiliation(s)
- Ivo Vanzetta
- Department of Neurobiology, The Weizmann Institute of Science, 76100 Rehovot, Israel
- Institut de Neurosciences Cognitives de la Méditerranée, CNRS UMR 6193, Aix-Marseille Université, 13402 Marseille Cedex 20, France
| | - Amiram Grinvald
- Department of Neurobiology, The Weizmann Institute of Science, 76100 Rehovot, Israel
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Vanzetta I. Hemodynamic responses in cortex investigated with optical imaging methods. Implications for functional brain mapping. ACTA ACUST UNITED AC 2007; 100:201-11. [PMID: 17329084 DOI: 10.1016/j.jphysparis.2007.01.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
During the last 20 years, optical imaging methods - either alone or in combination with other recording techniques - has proven a fruitful approach to explore both the physiological and the functional aspects of activity-evoked hemodynamic responses in cortex. One of the main advantages of optical imaging consists in its high spatio-temporal resolution (in the order of few microns and milliseconds), allowing not only to unambiguously distinguish between activity patterns relating to the underlying functional architecture and those originating from the activation of medium/large blood vessels, but also to investigate the various activity-evoked hemodynamic processes at very fine detail. Here, we briefly review the principal findings obtained by optical imaging about the spatio-temporal properties of the various hemodynamic responses in cortex, i.e., changes in blood-oxygenation, blood-volume, and, to some extent, blood-flow. We also discuss the implications of those findings for non-invasive high-resolution functional brain imaging, in particular for fMRI. Finally, we underscore the importance of novel approaches for high-resolution blood-flow imaging, in the context of the need to gather information at fine spatial detail about the blood-flow response, necessary to constrain the multiple free parameters of hemodynamic response models.
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Affiliation(s)
- Ivo Vanzetta
- Institut de Neurosciences Cognitives de la Méditerranée, Centre National de la Recherche Scientifique Unité Mixte de Recherche 6193, Aix-Marseille Université, Marseille, France.
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Berwick J, Johnston D, Jones M, Martindale J, Redgrave P, McLoughlin N, Schiessl I, Mayhew JEW. Neurovascular coupling investigated with two-dimensional optical imaging spectroscopy in rat whisker barrel cortex. Eur J Neurosci 2006; 22:1655-66. [PMID: 16197506 DOI: 10.1111/j.1460-9568.2005.04347.x] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Optical imaging slit spectroscopy is a powerful method for estimating quantitative changes in cerebral haemodynamics, such as deoxyhaemoglobin, oxyhaemoglobin and blood volume (Hbr, HbO2 and Hbt, respectively). Its disadvantage is that there is a large loss of spatial data as one image dimension is used to encode spectral wavelength information. Single wavelength optical imaging, on the other hand, produces high-resolution spatiotemporal maps of brain activity, but yields only indirect measures of Hbr, HbO2 and Hbt. In this study we perform two-dimensional optical imaging spectroscopy (2D-OIS) in rat barrel cortex during contralateral whisker stimulation to obtain two-dimensional maps over time of Hbr, HbO2 and Hbt. The 2D-OIS was performed by illuminating the cortex with four wavelengths of light (575, 559, 495 and 587 nm), which were presented sequentially at a high frame rate (32 Hz). The contralateral whisker pad was stimulated using two different durations: 1 and 16 s (5 Hz, 1.2 mA). Control experiments used a hypercapnic (5% CO2) challenge to manipulate baseline blood flow and volume in the absence of corresponding neural activation. The 2D-OIS method allowed separation of artery, vein and parenchyma regions. The magnitude of the haemodynamic response elicited varied considerably between different vascular compartments; the largest responses in Hbt were in the arteries and the smallest in the veins. Phase lags in the HbO2 response between arteries and veins suggest that a process of upstream signalling maybe responsible for dilating the arteries. There was also a consistent increase in Hbr from arterial regions after whisker stimulation.
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Affiliation(s)
- J Berwick
- Department of Psychology, University of Sheffield, Western Bank, Sheffield S10 2TP, UK.
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Kennerley AJ, Berwick J, Martindale J, Johnston D, Papadakis N, Mayhew JE. Concurrent fMRI and optical measures for the investigation of the hemodynamic response function. Magn Reson Med 2005; 54:354-65. [PMID: 16032695 DOI: 10.1002/mrm.20511] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Functional magnetic resonance imaging (fMRI) signal variations are based on a combination of changes in cerebral blood flow (CBF) and volume (CBV), and blood oxygenation. We investigated the relationship between these hemodynamic parameters in the rodent barrel cortex by performing fMRI concurrently with laser Doppler flowmetry (LDF) or optical imaging spectroscopy (OIS), following whisker stimulation and hypercapnic challenge. A difference between the positions of the maximum blood oxygenation level-dependent (BOLD) and CBV changes was observed in coronal fMRI maps, with the BOLD region being more superficial. A 6.5% baseline blood volume fraction in this superficial region dropped to 4% in deeper cortical layers (corresponding to total hemoglobin baseline volumes Hbt0 = 110 microM and 67 microM, respectively), as inferred from maps of deltaR2*. Baseline volume profiles were used to parameterize the Monte Carlo simulations (MCS) to interpret the 2D OIS. From this it was found that the optical blood volume measurements (i.e., changes in total hemoglobin) equated with CBV-MRI measurements when the MRI data were taken from superficial cortical layers. Optical measures of activation showed a good spatial overlap with fMRI measurements taken in the same plane (covering the right hemisphere surface). Changes in CBV and CBF followed the scaling relationship CBV = CBF(alpha), with mean alpha = 0.38 +/- 0.06.
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Affiliation(s)
- Aneurin J Kennerley
- Centre for Signal Processing in Neuroimaging and Systems Neuroscience, Department of Psychology, University of Sheffield, Sheffield, UK
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Fukuda M, Rajagopalan UM, Homma R, Matsumoto M, Nishizaki M, Tanifuji M. Localization of activity-dependent changes in blood volume to submillimeter-scale functional domains in cat visual cortex. ACTA ACUST UNITED AC 2004; 15:823-33. [PMID: 15459078 DOI: 10.1093/cercor/bhh183] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
We have examined whether blood volume changes induced by neural activation are controlled precisely enough for us to visualize the submillimeter-scale functional structure in anesthetized and awake cat visual cortex. To activate the submillimeter-scale functional structures such as iso-orientation domains in the cortex, visual stimuli (gratings) were presented to the cats. Two methods were used to examine the spatial precision of blood volume changes including changes in total hemoglobin content and changes in plasma volume: (i) intrinsic signal imaging at the wavelength of hemoglobin's isosbestic point (569 nm) and (ii) imaging of absorption changes of an intravenously injected dye. Both measurements showed that the visual stimuli elicited stimulus-nonspecific and stimulus-specific blood volume changes in the cortex. The former was not spatially localized, while the latter was confined to iso-orientation domains. From the measurement of spatial separation of the iso-orientation domains, we estimated the spatial resolution of stimulus-specific blood volume changes to be as high as 0.6 mm. The changes in stimulus-nonspecific and -specific blood volume were not linearly correlated. These results suggest the existence of fine blood volume control mechanisms in the capillary bed in addition to global control mechanisms in arteries.
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Affiliation(s)
- Mitsuhiro Fukuda
- Laboratory for Integrative Neural Systems, RIKEN Brain Science Institute, 2-1 Hirosawa, Wako-shi, Saitama, 351-0198, Japan
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Penschuck S, Chen-Bee CH, Prakash N, Frostig RD. In vivo modulation of a cortical functional sensory representation shortly after topical cholinergic agent application. J Comp Neurol 2002; 452:38-50. [PMID: 12205708 DOI: 10.1002/cne.10361] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The aim of the present study was to determine whether cholinergic increase in the size of a functional representation (collective evoked response from a large population of neurons) can be observed shortly (within an hour) after treatment onset and whether nicotinic receptors can participate in this type of modulation. Cholinergic agonist application has been found previously to increase the response of a single cortical neuron to a stimulus. Also, pairing cholinergic basal forebrain stimulation with delivery of a tone has been reported to increase the size of that tone's functional representation. Whereas the increase in a single cortical neuron response can occur within seconds after cholinergic agonist application, to date the increase in the size of a functional representation has only been investigated within one to several weeks after the onset of pairing basal forebrain stimulation with tone delivery. Furthermore, primarily muscarinic receptors have been implicated in these types of changes in cortical activity. By using optical imaging of intrinsic signals in vivo, we found that the size of a whisker's functional representation in the primary somatosensory cortex of the rat increases substantially within 69 or 46 minutes after topical application of either a muscarinic or nicotinic agonist to the exposed cortex, respectively, and decreases within 23 minutes after topical application of a muscarinic antagonist. For each cholinergic agent, we verified that delivery of a cholinergic agent by means of topical application can lead to the agent's successful penetration through the cortical layers in the time allotted to complete an imaging experiment. Furthermore, the time course of penetration for each agent was characterized. Based on the combined imaging/penetration results, we speculate on potential sites of cholinergic action in the cortex. Irrespective of the exact mechanism of action, we demonstrate here that an increase in the size of a functional sensory representation can occur shortly by means of activation of either nicotinic or muscarinic receptors.
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Affiliation(s)
- Silke Penschuck
- Department of Neurobiology and Behavior and the Center for the Neurobiology of Learning and Memory, University of California at Irvine, Irvine, California 92697-4550, USA
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Berwick J, Martin C, Martindale J, Jones M, Johnston D, Zheng Y, Redgrave P, Mayhew J. Hemodynamic response in the unanesthetized rat: intrinsic optical imaging and spectroscopy of the barrel cortex. J Cereb Blood Flow Metab 2002; 22:670-9. [PMID: 12045665 DOI: 10.1097/00004647-200206000-00005] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Optical imaging spectroscopy was used to measure the hemodynamic response of somatosensory cortex to stimulation of the whiskers. Responses to brief puffs of air were compared in anesthetized and unanesthetized rats. The hemodynamic response was approximately four times larger in the unanesthetized animal than the corresponding anesthetized animal. In unanesthetized animals, a short-latency (approximately 400 milliseconds) short-duration (approximately 300 milliseconds) hemodynamic startle response was observed. General linear model analysis was used to extract this component from the time series, and revealed an underlying short-latency increase in deoxygenated hemoglobin in response to somatosensory stimulation. It is proposed that anesthesia can have a marked affect on the relation between changes in blood volume and blood flow. This work represents a step in the development of an experimental model that can be used to investigate fundamental neurologic processes in the awake-behaving rodent.
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Affiliation(s)
- Jason Berwick
- Department of Psychology and Artificial Intelligence Vision Research Unit, University of Sheffield, Western Bank, Sheffield, UK
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12
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Mayhew J, Johnston D, Berwick J, Jones M, Coffey P, Zheng Y. Spectroscopic analysis of neural activity in brain: increased oxygen consumption following activation of barrel cortex. Neuroimage 2000; 12:664-75. [PMID: 11112398 DOI: 10.1006/nimg.2000.0656] [Citation(s) in RCA: 112] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
This research investigates the hemodynamic response to stimulation of the barrel cortex in anaesthetized rats using optical imaging and spectroscopy (Bonhoeffer and Grinvald, 1996; Malonek and Grinvald, 1996; Mayhew et al., 1999). A slit spectrograph was used to collect spectral image data sequences. These were analyzed using an algorithm that corrects for the wavelength dependency in the optical path lengths produced by the light scattering properties of tissue. The analysis produced the changes in the oxy- and deoxygenation of hemoglobin following stimulation. Two methods of stimulation were used. One method mechanically vibrated a single whisker, the other electrically stimulated the whisker pad. The electrical stimulation intensity varied from 0.4 to 1.6 mA. The hemodynamic responses to stimulation increased as a function of intensity. At 0.4 mA they were commensurate with those from the mechanical stimulation; however, the responses at the higher levels were greater by a factor of approximately 10. For both methods of data collection, the results of the spectroscopic analysis showed an early increase in deoxygenated hemoglobin (Hbr) with no evidence for a corresponding decrease in oxygenated hemoglobin (HbO(2)). Evidence for increased oxygen consumption (CMRO(2)) was obtained by converting the fractional changes in blood volume (Hbt) into estimates of changes in blood flow (Grubb et al., 1974) and using the resulting time course to scale the fractional changes in Hbr. The results show an early increase CMRO(2) peaking approximately 2 s after stimulation onset. Using these methods, we find evidence for increased oxygen consumption following increased neural activity even at low levels of stimulation intensity.
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Affiliation(s)
- J Mayhew
- Artificial Intelligence Vision Research Unit and Department of Psychology, University of Sheffield, Sheffield S10 2TP, United Kingdom
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Malformation of the functional organization of somatosensory cortex in adult ephrin-A5 knock-out mice revealed by in vivo functional imaging. J Neurosci 2000. [PMID: 10908626 DOI: 10.1523/jneurosci.20-15-05841.2000] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The molecular mechanisms that coordinate the functional organization of the mammalian neocortex are largely unknown. We tested the involvement of a putative guidance label, ephrin-A5, in the functional organization of the somatosensory cortex by quantifying the functional representations of individual whiskers in vivo in adult ephrin-A5 knock-out mice, using intrinsic signal optical imaging. In wild-type mice ephrin-A5 is expressed in a gradient in the somatosensory cortex during development. In adult ephrin-A5 knock-out mice, we found a spatial gradient of change in the amount of cortical territory shared by individual whisker functional representations across the somatosensory cortex, as well as a gradient of change in the distance between the functional representations. Both gradients of change were in correspondence with the developmental expression gradient of ephrin-A5 in wild-type mice. These changes involved malformations of the cortical spacing of the thalamocortical components, without concurrent malformations of the intracortical components of individual whisker functional representations. Overall, these results suggest that a developmental guidance label, such as ephrin-A5, is involved in establishing certain spatial relationships of the functional organization of the adult neocortex, and they underscore the advantage of investigating gene manipulation using in vivo functional imaging.
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Chen-Bee CH, Polley DB, Brett-Green B, Prakash N, Kwon MC, Frostig RD. Visualizing and quantifying evoked cortical activity assessed with intrinsic signal imaging. J Neurosci Methods 2000; 97:157-73. [PMID: 10788670 DOI: 10.1016/s0165-0270(00)00180-1] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Intrinsic signal imaging (ISI) measures changes in light reflectance from the illuminated cortex (intrinsic signals or IS) attributed to various vascular and metabolic sources that, when using illumination in the 600 nm range, appear to co-localize with neuronal activity. Given the multiple sources contributing to the collected IS, the common practice of averaging across an extended post-stimulus time epoch before dividing by baseline data typically visualizes evoked IS overlying both the cortical tissue and the large surface blood vessels. In rat PMBSF, the contribution from these vessels are problematic as they do not co-localize with known PMBSF function. Determining a means for quantifying the evoked IS area poses an additional challenge. Here, we describe how exploiting IS collected shortly after stimulus onset (within 1.5 s), which coincides with fast oxygen consumption of active neurons, visualizes evoked IS overlying the cortical tissue without the large surface vessels. We also describe how the use of absolute thresholds combined with a baseline determined from data collected immediately prior to stimulus onset (within 1 s) targets most precisely a specific evoked IS amplitude, a method that should be especially useful when evoked areas are expected to occupy a substantial portion of the total imaged area and/or when peak activity is expected to differ between subjects.
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Affiliation(s)
- C H Chen-Bee
- Department of Neurobiology and Behavior and Center for the Neurobiology of Learning and Memory, University of California, Irvine 92697-4550, USA
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Nomura Y, Fujii F, Sato C, Nemoto M, Tamura M. Exchange transfusion with fluorocarbon for studying synaptically evoked optical signal in rat cortex. BRAIN RESEARCH. BRAIN RESEARCH PROTOCOLS 2000; 5:10-5. [PMID: 10719260 DOI: 10.1016/s1385-299x(99)00051-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Optical imaging of intrinsic signal is a powerful technique for studying the functional organization of the brain [T. Bonhoeffer, D. S. Kim, D. Malonek, D. Shoham, A. Grinvald, Optical imaging of the layout of functional domains in area 17 and across the area 17/18 border in cat visual cortex, Eur. J. Neurosci. 7 (1995) 1973-1988; M. Hubener, D. Shoham, A. Grinvald, T. Bonhoeffer, Spatial relationships among three columnar systems in cat area 17, J. Neurosci. 17 (1997) 9270-9284; D. Malonek, A. Grinvald, Interactions between electrical activity and cortical microcirculation revealed by imaging spectroscopy: implications for functional brain mapping, Science 272 (1996) 551-554; A. Shmuel, A. Grinvald, Functional organization for direction of motion and its relationship to orientation maps in cat area 18, J. Neurosci. 16 (1996) 6945-6964] [1] [10] [14] [22]. Three components of intrinsic optical signal can be distinguished. Two of these components can be attributed either to changes in blood volume or to changes in oxygen consumption [R.D. Frostig, E.E. Lieke, D.Y. Ts'o, A. Grinvald, Cortical functional architecture and local coupling between neuronal activity and the microcirculation revealed by in vivo high resolution optical imaging of intrinsic signals, Proc. Natl. Acad. Sci. U. S. A. 87 (1990) 6082-6086] [7]. The origin of the third component is not yet clear but the component seems to be based on scattered light [H.U. Dodt, G. D'Arcangelo, E. Pestel, W. Zieglgansberger, The spread of excitation in neocortical columns visualized with infrared-dark field videomicroscopy, NeuroReport 7 (1996) 1553-1558; K. Holthoff, O.W. Witte, Intrinsic optical signals in rat neocortical slices measured with near-infrared dark-field microscopy reveal changes in extracellular space, J. Neurosci. 16 (1996) 2740-2749; B.A. MacVicar, D. Hochman, Imaging of synaptically evoked intrinsic optical signals in hippocampal slices, J. Neurosci. 11 (1991) 1458-1469; L. Trachsel, H.U. Dodt, W. Zieglgansberger, The intrinsic optical signal evoked by chiasm stimulation in the rat suprachiasmatic nuclei exhibits GABAergic day-night variation, Eur. J. Neurosci. 8 (1996) 319-328] [3] [9] [13] [24]. A spectral fitting method with three components is used for the analysis of intrinsic optical signal [M. Nemoto, Y. Nomura, C. Sato, M. Tamura, K. Houkin, I. Koyanagi, H. Abe, Analysis of optical signals evoked by peripheral nerve stimulation in rat somatosensory cortex: dynamic changes in hemoglobin concentration and oxygenation, J. Cereb. Blood Flow Metab. 19 (1999) 246-259] [17]. In order to validate the analysis, we need the knowledge on contribution of signal resulted from hemoglobin to total intrinsic optical signal. The exchange transfusion with fluorocarbon has the advantage that can change the spectral contribution of hemoglobin [M. Ferrari, M.A. Williams, D.A. Wilson, N.V. Thakor, R.J. Traystman, D.F. Hanley, Cat brain cytochrome-c oxidase redox changes induced by hypoxia after blood-fluorocarbon exchange transfusion, Am. J. Physiol. 269 (1995) H417-H424; A.L. Sylvia, C.A. Piantadosi, O(2) dependence of in vivo brain cytochrome redox responses and energy metabolism in bloodless rats, J. Cereb. Blood Flow Metab. 8 (1988) 163-172] [6] [23]. Here we describe a new method of the reduction of hemoglobin signal from somatosensory evoked optical intrinsic signal in rat cortex by the combination of exchange transfusion with fluorocarbon and imaging system of thinned skull cranial window. The method allows for the study of the synaptically evoked changes in light scattering as well as fluorescence of calcium indicator or voltage-sensitive dye without absorption of hemoglobin.
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Affiliation(s)
- Y Nomura
- Biophysics Division, Research Institute for Electronic Science, Hokkaido University, Sapporo, Japan.
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Nemoto M, Nomura Y, Sato C, Tamura M, Houkin K, Koyanagi I, Abe H. Analysis of optical signals evoked by peripheral nerve stimulation in rat somatosensory cortex: dynamic changes in hemoglobin concentration and oxygenation. J Cereb Blood Flow Metab 1999; 19:246-59. [PMID: 10078876 DOI: 10.1097/00004647-199903000-00002] [Citation(s) in RCA: 61] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The origins of reflected light changes associated with neuronal activity (optical signals) were investigated in rat somatosensory cortex with optical imaging, microspectrophotometry, and laser-Doppler flowmetry, and dynamic changes in local hemoglobin concentration and oxygenation were focused on. Functional activation was carried out by 2-second, 5-Hz electrical stimulation of the hind limb under chloralose anesthesia. These measurements were performed at the contralateral parietal cortex through a thinned skull. Regional cortical blood flow (rCBF) started to rise 1.5 seconds after the stimulus onset, peaked at 3.5 seconds (26.7% +/- 9.7% increase over baseline), and returned to near baseline by 10 seconds. Optical signal responses at 577, 586, and 805 nm showed a monophasic increase in absorbance coincident with the increase in rCBF; however, the signal responses at 605 and 760 nm were biphasic (an early increase and late decrease in absorbance) and microanatomically heterogeneous. The spectral changes of absorbance indicated that the concentrations of both total hemoglobin and oxyhemoglobin increased together with rCBF; deoxyhemoglobin, increased slightly but distinctly (P = 0.016 at 1.0 seconds, P = 0.00038 at 1.5 seconds) just before rCBF increases, then decreased. The authors conclude that activity-related optical signals are greatly associated with a moment-to-moment adjustment of rCBF and metabolism to neuronal activity.
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Affiliation(s)
- M Nemoto
- Department of Neurosurgery, Hokkaido University School of Medicine, Sapporo, Japan
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