pubmed grinvald
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1: Cereb Cortex. 2007 Dec;17(12):2866-77. Epub 2007 Mar 29.Related Articles, <!–
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Cortical response field dynamics in cat visual cortex.Sharon D, Jancke D, Chavane F, Na’aman S, Grinvald A.
Neurobiology Department, Weizmann Institute of Science, Rehovot 76100, Israel. dahlia@nmr.mgh.harvard.edu
Little is known about the “inverse” of the receptive field–the region of cortical space whose spatiotemporal pattern of electrical activity is influenced by a given sensory stimulus. We refer to this activated area as the cortical response field, the properties of which remain unexplored. Here, the dynamics of cortical response fields evoked in visual cortex by small, local drifting-oriented gratings were explored using voltage-sensitive dyes. We found that the cortical response field was often characterized by a plateau of activity, beyond the rim of which activity diminished quickly. Plateau rim location was largely independent of stimulus orientation. However, approximately 20 ms following plateau onset, 1-3 peaks emerged on it and were amplified for 25 ms. Spiking was limited to the peak zones, whose location strongly depended on stimulus orientation. Thus, alongside selective amplification of a spatially restricted suprathreshold response, wider activation to just below threshold encompasses all orientation domains within a well-defined retinotopic vicinity of the current stimulus, priming the cortex for processing of subsequent stimuli.
Publication Types:
PMID: 17395608 [PubMed - indexed for MEDLINE]
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2: Neuroimage. 2007 Jan 1;34(1):94-108. Epub 2006 Oct 25.Related Articles, <!–
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Independent component analysis of high-resolution imaging data identifies distinct functional domains.Reidl J, Starke J, Omer DB, Grinvald A, Spors H.
Win Group of Olfactory Dynamics, Heidelberger Akademie der Wissenschaften, Germany.
In the vertebrate brain external stimuli are often represented in distinct functional domains distributed across the cortical surface. Fast imaging techniques used to measure patterns of population activity record movies with many pixels and many frames, i.e., data sets with high dimensionality. Here we demonstrate that principal component analysis (PCA) followed by spatial independent component analysis (sICA), can be exploited to reduce the dimensionality of data sets recorded in the olfactory bulb and the somatosensory cortex of mice as well as the visual cortex of monkeys, without loosing the stimulus-specific responses. Different neuronal populations are separated based on their stimulus-specific spatiotemporal activation. Both, spatial and temporal response characteristics can be objectively obtained, simultaneously. In the olfactory bulb, groups of glomeruli with different response latencies can be identified. This is shown for recordings of olfactory receptor neuron input measured with a calcium-sensitive axon tracer and for network dynamics measured with the voltage-sensitive dye RH 1838. In the somatosensory cortex, barrels responding to the stimulation of single whiskers can be automatically detected. In the visual cortex orientation columns can be extracted. In all cases artifacts due to movement, heartbeat or respiration were separated from the functional signal by sICA and could be removed from the data set. sICA following PCA is therefore a powerful technique for data compression, unbiased analysis and dissection of imaging data of population activity, collected with high spatial and temporal resolution.
Publication Types:
PMID: 17070071 [PubMed - indexed for MEDLINE]
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3: Proc Natl Acad Sci U S A. 2005 Oct 4;102(40):14125-6. Epub 2005 Sep 27.Related Articles, <!–
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Comment on:Imaging input and output dynamics of neocortical networks in vivo: exciting times ahead.
Department of Neurobiology, The Weizmann Institute of Science, 76100 Rehovot, Israel. amiram.grinvald@weizmann.ac.il
Publication Types:
PMID: 16189023 [PubMed - indexed for MEDLINE]
PMCID: PMC1242320
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4: J Neurosci. 2005 Mar 2;25(9):2233-44.Related Articles, <!–
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Compartment-resolved imaging of activity-dependent dynamics of cortical blood volume and oximetry.Vanzetta I, Hildesheim R, Grinvald A.
Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel. ivo.vanzetta@incm.cnrs-mrs.fr
Optical imaging, positron emission tomography, and functional magnetic resonance imaging (fMRI) all rely on vascular responses to image neuronal activity. Although these imaging techniques are used successfully for functional brain mapping, the detailed spatiotemporal dynamics of hemodynamic events in the various microvascular compartments have remained unknown. Here we used high-resolution optical imaging in area 18 of anesthetized cats to selectively explore sensory-evoked cerebral blood-volume (CBV) changes in the various cortical microvascular compartments. To avoid the confounding effects of hematocrit and oximetry changes, we developed and used a new fluorescent blood plasma tracer and combined these measurements with optical imaging of intrinsic signals at a near-isosbestic wavelength for hemoglobin (565 nm). The vascular response began at the arteriolar level, rapidly spreading toward capillaries and venules. Larger veins lagged behind. Capillaries exhibited clear blood-volume changes. Arterioles and arteries had the largest response, whereas the venous response was smallest. Information about compartment-specific oxygen tension dynamics was obtained in imaging sessions using 605 nm illumination, a wavelength known to reflect primarily oximetric changes, thus being more directly related to electrical activity than CBV changes. Those images were radically different: the response began at the parenchyma level, followed only later by the other microvascular compartments. These results have implications for the modeling of fMRI responses (e.g., the balloon model). Furthermore, functional maps obtained by imaging the capillary CBV response were similar but not identical to those obtained using the early oximetric signal, suggesting the presence of different regulatory mechanisms underlying these two hemodynamic processes.
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PMID: 15745949 [PubMed - indexed for MEDLINE]
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5: Nat Rev Neurosci. 2004 Nov;5(11):874-85.Related Articles, <!–
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VSDI: a new era in functional imaging of cortical dynamics.Department of Neurobiology, The Weizmann Institute of Science, Rehovot, 76100 Israel. Amiram.Grinvald@weizmann.ac.il
During the last few decades, neuroscientists have benefited from the emergence of many powerful functional imaging techniques that cover broad spatial and temporal scales. We can now image single molecules controlling cell differentiation, growth and death; single cells and their neurites processing electrical inputs and sending outputs; neuronal circuits performing neural computations in vitro; and the intact brain. At present, imaging based on voltage-sensitive dyes (VSDI) offers the highest spatial and temporal resolution for imaging neocortical functions in the living brain, and has paved the way for a new era in the functional imaging of cortical dynamics. It has facilitated the exploration of fundamental mechanisms that underlie neocortical development, function and plasticity at the fundamental level of the cortical column.
Publication Types:
PMID: 15496865 [PubMed - indexed for MEDLINE]
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6: Neuroimage. 2001 Jun;13(6 Pt 1):959-67.Related Articles, <!–
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Comment on:- Neuroimage. 2001 Jun;13(6 Pt 1):1002-15.
- Neuroimage. 2001 Jun;13(6 Pt 1):975-87.
- Neuroimage. 2001 Jun;13(6 Pt 1):988-1001.
Evidence and lack of evidence for the initial dip in the anesthetized rat: implications for human functional brain imaging.
Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel.
Publication Types:
PMID: 11352602 [PubMed - indexed for MEDLINE]
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7: Science. 1999 Nov 19;286(5444):1555-8.Related Articles, <!–
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Increased cortical oxidative metabolism due to sensory stimulation: implications for functional brain imaging.Department of Neurobiology, Center for Research of Higher Brain Functions, Weizmann Institute of Science, Rehovot 76100, Israel.
Modern functional brain mapping relies on interactions of neuronal electrical activity with the cortical microcirculation. The existence of a highly localized, stimulus-evoked initial deoxygenation has remained a controversy. Here, the activity-dependent oxygen tension changes in the microcirculation were measured directly, using oxygen-dependent phosphorescence quenching of an exogenous indicator. The first event after sensory stimulation was an increase in oxygen consumption, followed by an increase in blood flow. Because oxygen consumption and neuronal activity are colocalized but the delayed blood flow is not, functional magnetic resonance imaging focused on this initial phase will yield much higher spatial resolution, ultimately enabling the noninvasive visualization of fundamental processing modules in the human brain.
Publication Types:
PMID: 10567261 [PubMed - indexed for MEDLINE]
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8: Science. 1996 Apr 26;272(5261):551-4.Related Articles, <!–
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Interactions between electrical activity and cortical microcirculation revealed by imaging spectroscopy: implications for functional brain mapping.Department of Neurobiology, Weizmann Institute of Science, Rehovot, Israel.
Modern neuroimaging techniques use signals originating from microcirculation to map brain function. In this study, activity-dependent changes in oxyhemoglobin, deoxyhemoglobin, and light scattering were characterized by an imaging spectroscopy approach that offers high spatial, temporal, and spectral resolution. Sensory stimulation of cortical columns initiates tissue hypoxia and vascular responses that occur within the first 3 seconds and are highly localized to individual cortical columns. However, the later phase of the vascular response is less localized, spreading over distances of 3 to 5 millimeters.
