Use of Intrinsic Optical Signals to Monitor Physiological Changes in Brain Tissue Slices

Aitken, Peter G.; Fayuk, Dmitriy; Somjen, George G.; Turner, Dennis A.

doi:10.1006/meth.1999.0762

Cited by 133 publications

(104 citation statements)

References 34 publications

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“…In these preparations, therefore, the origin of IOSs is related to scatter changes unless a change in absorption is expected by the cytochromes' redox state. Some preparations allow for a differentiation between scatter and absorption changes by comparing reflectance and transmission ʈ (Aitken et al, 1999). Several studies have reported that an increase in cell volume leads to a decrease in reflectance.…”

Section: Brain Slice Preparationsmentioning

confidence: 99%

“…In the adult rat brain slice they have shown that, for spontaneous neuronal hyperactivity, transmission changes have an opposite response direction, depending on whether the discharges represent synaptic or nonsynaptic mechanisms (Fayuk et al, 2002). Aitken et al (1999) have differentiated between 4 subtypes of IOS responses, that is, responses to (1) synaptic activation, (2) hypoxia, (3) classical normoxic spreading depression, and (4) those stemming from osmolarity changes in the bath. The underlying mechanisms are cell swelling (inversely correlated to the extracellular space) and swelling of cell organelles, in particular, mitochondria (not influencing the extracellular space).…”

Section: Brain Slice Preparationsmentioning

confidence: 99%

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Beyond the Visible—Imaging the Human Brain with Light

Obrig

Villringer

2003

J Cereb Blood Flow Metab

547

215

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Summary:Optical approaches to investigate cerebral function and metabolism have long been applied in invasive studies. From the neuron cultured in vitro to the exposed cortex in the human during neurosurgical procedures, high spatial resolution can be reached and several processes such as membrane potential, cell swelling, metabolism of mitochondrial chromophores, and vascular response can be monitored, depending on the respective preparation. The authors focus on an extension of optical methods to the noninvasive application in the human. Starting with the pioneering work of Jöbsis 25 years ago, nearinfrared spectroscopy (NIRS) has been used to investigate functional activation of the human cerebral cortex. Recently, several groups have started to use imaging systems that allow the generation of images of a larger area of the subject's head and, thereby, the production of maps of cortical oxygenation changes. Such images have a much lower spatial resolution compared with the invasively obtained optical images. The noninvasive NIRS images, however, can be obtained in undemanding set-ups that can be easily combined with other functional methods, in particular EEG. Moreover, NIRS is applicable to bedside use. The authors briefly review some of the abundant literature on intrinsic optical signals and the NIRS imaging studies of the past few years. The weaknesses and strengths of the approach are critically discussed. The authors conclude that NIRS imaging has two major advantages: it can address issues concerning neurovascular coupling in the human adult and can extend functional imaging approaches to the investigation of the diseased brain. Key Words: Near-infrared spectroscopy-Cerebral oxygenation-Vascular imagingNoninvasive.The first investigations into the functional anatomy of the human cerebral cortex were based on lesion studies. The role of specific cortical areas involved in a specific task was inferred by comparing a patient's dysfunction to the lesion seen at autopsy (Fig. 1A). Whereas initially only electrophysiologic techniques allowed noninvasive functional studies of the human brain, the advent of modern imaging techniques such as functional magnetic resonance imaging (fMRI) and positron emission tomography (PET) have increasingly dominated the field during the past decade. The great advantage is the spatial resolution, which for fMRI is steadily improving and may even allow the differentiation of different cortical layers.There is an increasing need, however, for a better understanding of the signal physiology, in particular of blood oxygenation level-dependent (BOLD) contrast, since the basic principles of the coupling between the neuronal and the vascular response to functional stimulation are still not fully understood (Villringer and Dirnagl, 1995).In the present article we focus on noninvasive imaging approaches in the human using light. Near-infrared spectroscopy (NIRS),* the technique on which such imaging approaches are based, has been covered in previous articles that reviewed its potential...

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Section: Brain Slice Preparationsmentioning

confidence: 99%

Section: Brain Slice Preparationsmentioning

confidence: 99%

Beyond the Visible—Imaging the Human Brain with Light

Obrig

Villringer

2003

J Cereb Blood Flow Metab

547

215

View full text Add to dashboard Cite

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“…These signals give in principle the same results though with different polarity (Aitken et al 1999): with transmitted light, the signal intensity increases when the preparation is superfused with a hypotonic solution causing cell swelling, while it decreases with absorbed light. While the transmitted light integrates the properties of the whole trans-illuminated slice, the changes in light reflectance will mainly reflect changes in the surface layers of the slice preparation.…”

Section: Technical Considerationsmentioning

confidence: 65%

“…A change of light transmission by cell swelling was first demonstrated in erythrocytes (see Aitken et al 1999). This cell swelling does not depend on the presence of haemoglobin and can also be recorded from leukocytes and tumour cells.…”

Section: Introductionmentioning

confidence: 97%

Cell swelling and ion redistribution assessed with intrinsic optical signals

Witte

Niermann

Holthoff

2001

An. Acad. Bras. Ciênc.

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Cell volume changes are associated with alterations of intrinsic optical signals (IOS). In submerged brain slices in vitro, afferent stimulation induces an increase in light transmission. As assessed by measurement of the largely membrane impermeant ion tetramethylammonium (TMA) in the extracellular space, these IOS correlate with the extent and time course of the change of the extracellular space size. They have a high signal to noise ratio and allow measurements of IOS changes in the order of a few percent. Under conditions of reduced net KCl uptake (low Cl solution) a directed spatial buffer mechanism (K syphoning) can be demonstrated in the neocortex with widening of the extracellular space in superficial layers associated with a reduced light transmission and an increase of extracellular K concentration. The nature of the IOS under pathophysiological conditions is less clear. Spreading depressions first cause an increase of light transmission, then a decrease. Such a decrease has also been observed following application of NMDA where it was associated with structural damage. Pharmacological analyses suggest that under physiological conditions changes of extracellular space size are mainly caused by astrocytic volume changes while with strong stimuli and under pathophysiological conditions also neuronal swelling occurs. With reflected light usually signals opposite to those observed with transmitted light are seen. Recording of IOS from interface slices gives very complex signals since under these conditions an increase of light transmission has been reported to be superimposed by a decrease of the signal due to mechanical lensing effects of the slice surface. Depending on the method of measurement and the exact conditions, several mechanisms may contribute to IOS. Under well defined conditions IOS are a useful supplementary tool to monitor changes of extracellular volume both in space and time.

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“…Optical imaging techniques such as intrinsic optical signal (IOS) [4][5][6][7], diffuse optical tomography (DOT) [8][9][10], and spatial frequency domain imaging (SFDI) [11] overcome these limitations by achieving high-resolution, minimally invasive, imaging of the occurrence and propagation of neuronal and epileptic activity through changes in intrinsic tissue optical properties.…”

Section: Introductionmentioning

confidence: 99%

Localization of cortical tissue optical changes during seizure activity in vivo with optical coherence tomography

Eberle¹,

Hsu²,

Rodriguez³

et al. 2015

Biomed. Opt. Express

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Optical coherence tomography (OCT) is a high resolution, minimally invasive imaging technique, which can produce depth-resolved cross-sectional images. In this study, OCT was used to detect changes in the optical properties of cortical tissue in vivo in mice during the induction of global (pentylenetetrazol) and focal (4-aminopyridine) seizures. Through the use of a confidence interval statistical method on depth-resolved volumes of attenuation coefficient, we demonstrated localization of regions exhibiting both significant positive and negative changes in attenuation coefficient, as well as differentiating between global and focal seizure propagation. Holzwarth, H. A. Reitsamer, J. E. Morgan, and A. Cowey, "Imaging ex vivo and in vitro brain morphology in animal models with ultrahigh resolution optical coherence tomography," J. ©2015 Optical Society of America

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Use of Intrinsic Optical Signals to Monitor Physiological Changes in Brain Tissue Slices

Cited by 133 publications

References 34 publications

Beyond the Visible—Imaging the Human Brain with Light

Beyond the Visible—Imaging the Human Brain with Light

Cell swelling and ion redistribution assessed with intrinsic optical signals

Localization of cortical tissue optical changes during seizure activity in vivo with optical coherence tomography

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