Changes In Light Reflectance Research Articles

What's in a “Smile?” Intra-operative Observations of Contralateral Smiles Induced by Deep Brain Stimulation

Objective: To descirbe smiling and euphoria induced by deep brain stimulation (DBS). Background and Significance: The brain systems inducing emotional experiences and displays are not entirely known, but the ventral striatum including the nucleus accumbens have been posited to play a critical role in mediating emotions with positive valence. DBS has been successfully employed for the treatment of movement disorders, and most recently obsessive compulsive disorder (OCD). The purpose of this report is to describe the emotional changes associated with stimulation of the ventral striatum. Methods: A single patient with intractable OCD had electrode arrays placed in the right and left anterior limbs of the internal capsule and region of the nucleus accumbens. Changes in facial movement during stimulation were quantified by video recording. Ten video segments, time locked to the onset of stimulation, were digitized and changes in pixel intensity that occurred over both sides of the lower face, on a frame by frame basis, following stimulation onset were computed. These summed changes in pixel intensity represented the dependent variable of “entropy” and directly corresponded to changes in light reflectance that occur during facial movement. Results: During stimulation on both the right and left side, the patient consistently developed a half smile on the side of the face contralateral to the stimulating electrode, and also became euphoric. The effect ceased when DBS was discontinued. Conclusions: DBS in the region of the nucleus accumbens produced smile and euphoria suggesting that alterations in the ventral striatum may result in emotional experience and displays. We hypothesize the existence of a limbic-motor network responsible for such changes. This observation suggests that DBS may be useful as a therapy for mood disorders.

Optic nerve and retinal reflectance changes in response to physiological stimuli

An ocular fundus reflectometer to measure non-invasively the light reflectance changes in response to diffuse flicker stimulation at two wavelengths (569 and 600nm) simultaneously is presented. Image registration to minimize the effect of involuntary eye motion is described. Two-dimensional maps of reflectance changes of the optic disc and peripapillary retinal tissues in healthy volunteers are presented. These functional maps suggest increases in blood volume during stimulation, with changes in the optic disc as large as 10.7% at 569nm and 3.5% at 600nm.

Analysis of red blood cell aggregation in cardio-pulmonary bypass (CPB) surgery.

Not much is known about red cell aggregation during cardio-pulmonary bypass surgery (CPB). Blood samples from 19 patients undergoing CPB were anticoagulated with EDTA. Hematocrit was adjusted to 40%. A red blood cell aggregometer (LORCA) measured changes in light reflection from each blood sample after cessation of the rotation, and calculated an aggregation index (AI). Reflection measurements were stored. Because LORCA software failed for 87 of 171 samples, we developed new software, and applied it to the stored reflection measurements. This software failed only in 7 out of 171 cases and showed that all LORCA failures occurred for AI < 40%. The new calculations revealed that the aggregation index significantly decreased from 46.6 +/- 10.1 (mean +/- standard deviation) baseline to 22.8 +/- 8.3 at the end of CPB and recovered to 37.1 +/- 13.5 at day 1. It is concluded that the new software can be used to study decreased red cell aggregation during CPB.

Functional imaging of the human papilla and peripapillary region based on flicker-induced reflectance changes

A non-invasive functional imaging technique of the nervous tissue of the human eye fundus based on two wavelength light reflectance changes (Δ R %) is presented. The effect of 30° diffuse luminance flicker field made of two spectral components (569 and 600 nm) on Δ R was studied in six normal volunteers. Group averaged Δ R was significant and similar in all quadrants of the optic disc at 569 nm with a mean equal to −10.7% for the tissue of the optic disc and −3.6% for the peripapillary regions. At 600 nm, the Δ R were also significant but smaller, i.e. −3.5% for the disc tissue and −1.7% for the peripapillary region. The changes at 569 and 600 nm represent most probably blood volume changes. The 600 nm reflectance did not show evident features suggesting the presence of flicker-induced oxygenation changes.

Intraoperative optical intrinsic signal imaging: a clinical tool for functional brain mapping

Optical imaging of intrinsic signals (OIS) is a well-established neuroimaging modality by which functional cortical activity is mapped by detecting activity-related changes in cortical light reflectance. Light reflectance changes are detected by a charged-coupled device camera that captures images of the exposed cortex both at rest and during activity. Although to date OIS has only been used for research purposes, intraoperative OIS (iOIS) holds promise as a clinical mapping tool. In general, iOIS demonstrates good spatial correlation with electrocortical stimulation mapping (ECSM) and other electrophysiological modalities. Additionally, iOIS offers high spatial resolution (in microns), does not make contact with the surface of the brain, and introduces no potentially harmful compounds. Moreover, mapping is relatively rapid. The authors review the potential contribution of iOIS to the intraoperative environment. Specifically, they review iOIS methodology, discuss signal origin, compare OIS with other functional mapping modalities, and explain its potential benefits and limitations. They propose that iOIS may, in the future, be used in conjunction with ECSM to improve the resolution and accuracy of intraoperative mapping, decrease total time of intraoperative mapping, and possibly improve neurological outcomes. Additional studies will be required to quantify the sensitivity and specificity of optical maps relative to ECSM before it can be implemented clinically.

Spontaneous and stimulus-evoked intrinsic optical signals in primary auditory cortex of the cat.

Spontaneous and tone-evoked changes in light reflectance were recorded from primary auditory cortex (A1) of anesthetized cats (barbiturate induction, ketamine maintenance). Spontaneous 0.1-Hz oscillations of reflectance of 540- and 690-nm light were recorded in quiet. Stimulation with tone pips evoked localized reflectance decreases at 540 nm in 3/10 cats. The distribution of patches "activated" by tones of different frequencies reflected the known tonotopic organization of auditory cortex. Stimulus-evoked reflectance changes at 690 nm were observed in 9/10 cats but lacked stimulus-dependent topography. In two experiments, stimulus-evoked optical signals at 540 nm were compared with multiunit responses to the same stimuli recorded at multiple sites. A significant correlation (P < 0.05) between magnitude of reflectance decrease and multiunit response strength was evident in only one of five stimulus conditions in each experiment. There was no significant correlation when data were pooled across all stimulus conditions in either experiment. In one experiment, the spatial distribution of activated patches, evident in records of spontaneous activity at 540 nm, was similar to that of patches activated by tonal stimuli. These results suggest that local cerebral blood volume changes reflect the gross tonotopic organization of A1 but are not restricted to the sites of spiking neurons.

Visualizing and quantifying evoked cortical activity assessed with intrinsic signal imaging

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.

Imaging the dorsal hippocampus: light reflectance relationships to electroencephalographic patterns during sleep

We assessed the correspondence of 660 nm light reflectance changes from the dorsal hippocampus with slow wave electroencephalographic (EEG) activity during quiet sleep (QS) and rapid eye movement (REM) sleep in four cats. An optic probe, attached to a charge-coupled-device (CCD) video camera, was placed on the dorsal hippocampal surface to collect reflectance images simultaneously with EEG, which was measured by macroelectrodes placed around the probe circumference. Spectral estimates of EEG and light reflectance amplitude indicated that reflectance changes occurred in a similar frequency range as EEG changes. Dividing the image into 10 subregions revealed that reflectance changes at the rhythmical slow wave activity band (RSA, 4–6 Hz) persisted in localized regions during QS and REM sleep, but regional changes showed considerable wave-by-wave independence between areas and from slow wave electrical activity. Peak frequencies for reflectance changes corresponded to fast RSA frequencies observed in the EEG. Optical changes most likely derive from fast-acting physical phenomena, rather than from alterations in blood perfusion, and provide increased spatial resolution over that offered by electrical measurements.

Annual Meeting of the American Laryngological, Rhinological, and Otological Society

This meeting was held at Marriott's Desert Springs Hotel, Palm Desert, Calif, May 1 through 3, 1995. (2) Using magnetic resonance imaging cross-sectional area to calculate the volume of acoustic neuromas in patients with neurofibromatosis type 2, Mona Abaza, MD , and coauthors, San Antonio, Tex, studied the growth characteristics and associated audiologic parameters of these tumors. While the average growth rate of acoustic neuromas in patients with neurofibromatosis type 2 was 0.30 cm/y, the rate was significantly higher in older patients and in patients with spinal tumors. For these two groups, Dr Abaza recommends close follow-up with baseline magnetic resonance imaging and serial audiograms and aggressive treatment. (3) An exciting new computer system designed to quantitatively and objectively assess facial paralysis expresses facial surface deformation as a dimensional variable based on light reflectance changes. J. Gaily Neely, MD

Imaging cell volume changes and neuronal excitation in the hippocampal slice

Brain cell swelling is a consequence of Scizure, ischemia or excitotoxicity. Changes in light reflectance from cortical surface are now used to monitor brain activity but these intrinsic signals are poorly understood. The objectives of this study were first, to show that changes in light transmittance were correlated with cell volume and second, to image increases in light transmittance as they related to neuronal activation. Transverse hippocampal slices from the rat were used for the study. Brief exposure (4–6 min) to hypo-osmotic artificial cerebrospinal fluid (−40 mOsm) elevated light transmittance consistently and reversibly in most regions of the slice and particularly in CA1 dendritic regions. Neither zero-Ca 2+ artificial cerebrospinal fluid nor tetrodotoxin altered the transmittance increase and its subsequent reversal, suggesting that it was dependent on osmolality but independent of synaptic transmission and neuronal firing. The amplitude of the CA1 population spike evoked from Schafler collaterals increased concomitantly with the hypo-osmotic increase in light transmittance, providing evidence that the extracellular tissue resistance increased. Hyper-osmotic artificial cerebrospinal fluid (+40 mOsm) containing impermeant mannitol consistently lowered light transmittance and the amplitude of the population spike. Glycerol (+40mOsm), which is cell permeant, did not have an affect. Taken together these observations indicate that osmotic challenge alters light transmittance by inducing changes in cell volume. Transmittance increases induced by hypo-osmotic artificial cerebrospinal fluid or 10μ M kainate were small in the CA1 cell body region compared to dendritic regions. Similarly, orthodromic stimulation of axons terminating in stratum oriens or in stratum radiatum evoked transmittance increases only in their respective postsynaptic areas. In contrast, the cell body region and its adjacent proximal-apical dendrites (both sites of action potential initiation) could display dramatic increases in light transmittance upon brief exposure to 20 mM K +. The response, which may represent neuronal damage, was blocked in tetrodotoxin. Antidromic stimulation evoked a weak response in these same proximal areas. We conclude that activity-dependent increases in light transmittance across brain slices primarily reveal glial and neuronal swelling associated with excitatory synaptic input and action potential discharge. The signal can be imaged in real time to reveal neuronal activation, not only among hippocampal areas, but among neuronal regions. Cell swelling is a known consequence of excessive neuronal discharge. Therefore, the imaging of changes in light transmittance across brain slices should prove useful in monitoring epileptiform and excitotoxic states.

Ventilatory CO2-induced optical activity changes of cat ventral medullary surface

We examined neuronal activation of the ventral medullary surface (VMS) during hypercapnic challenges using optical recording procedures. With a coherent imaging probe, we assessed reflected 700-nm light from 18 VMS sites in 11 spontaneously breathing adult cats and from the suprasylvian cortex in two cats. Video frames were acquired during a baseline period, hypercapnic (3, 5, and 10% CO2 in O2) exposure, and recovery. Hypercapnic exposure elicited overall reflectance changes in all VMS sites, but no changes in the suprasylvian cortex. Light reflectance changes, suggesting altered neuronal activity, were reproducible, occurred as early as 30 s after CO2 exposure, and were dose dependent. The changes persisted approximately 20-25 min beyond the stimulus, but respiratory responses consistently recovered within 2-3 min. Although more rostral VMS sites tended to be associated with decreased activity and caudal regions with increased excitation, no uniform topographical organization was apparent across animals. The variability in VMS optical reflectance patterns across animals during CO2 stimulation may reflect the heterogeneous topographical distribution of responsive neurons in the structure.

Theoretical estimates of light reflection and transmission by spatially complex and temporally varying sea ice covers

The reflection, absorption, and transmission of light at visible and near‐infrared wavelengths by snow and ice covers is important for a number of geophysical problems. The focus of this paper is on the reflection and transmission of light by spatially inhomogeneous and temporally varying sea ice covers. This is investigated using a two‐stream, multilayer radiative transfer model in the wavelength region from 400 to 1000 nm. The model is computationally simple and utilizes the available experimental data on the optical properties of sea ice. The ice cover is characterized as a layered medium composed of selections from nine distinct snow and ice types. Three case studies are presented illustrating values of spectral albedo, transmittance, and transmitted photosynthetically active radiation (PAR) for (1) a spatially inhomogeneous ice cover, (2) a uniform ice cover as it undergoes a melt cycle, and (3) a temporally changing spatially variable ice cover. Results indicate that small‐scale horizontal variations in snow depth and ice thickness can cause light transmission to change over 3 orders of magnitude. Dramatic changes in light reflection and transmission are predicted in the early part of the melt season as the ice cover evolves from an opaque, snow‐covered medium to translucent bare or ponded ice.

The response of the light reflex of retinal vessels to reduced blood pressure in hypertensive patients

The response of retinal arteries and veins to 3 months of antihypertensive medication was studied in 10 patients (39-56 years old) with essential hypertension. We used computerized microdensitometry on fundus photographs, a technique allowing for objective and simultaneous measures of the caliber of blood columns and the width and intensity of their central 'light reflex'. A moderate lowering of diastolic and systolic blood pressures (P less than 0.001) resulted in a significant reduction in the intensity of reflection from retinal arteries (38.6%; P less than 0.005). An increase in the width of the blood column (2.8%; n.s.) and the reflex (8.6%; n.s.) was indicated. Traditionally, changes in light reflectivity has been associated with arteriosclerosis of the vessel wall. The study shows, however, that the vascular reflex is most sensitive to changes in the systemic blood pressure. This signals a need for critical reviewal of interpretation and usefulness of classical grading systems of ophthalmoscopic signs of hypertensive retinopathy.

Influence of PaO2 on cerebral macro- and microcirculation as observed by light reflection: time course of changes.

A silicon intensified target camera was used to study cerebral cortical vessels of the cat through a skull window implant, and red cell content changes were measured by light reflectance. Red cell content changes were observed in cerebral arterioles, capillaries, and venules when the PaO2 was decreased by lowering the PiO2. The time course of change in the diameter of the arterioles and venules was measured by selecting a cross section of the vessel plus some surrounding tissue. From the averaged cross-sectional reflectance signal, the change in vessel diameter was followed as a function of time following the PiO2 change. All vessels of greater than 10 microns were observed in focus. Substantial areas where no vessels could be discriminated would contain only capillaries, and changes in light reflectance from such areas would indicate changes in capillary red cell content. The time course of these changes following a step decrease in PiO2 was recorded. Results show that the sequence of red cell content increase in cerebral microcirculation during hypoxia is capillary before venule and arteriole. The times of initial red cell content increase are 37.9 +/- 7 s, 59.7 +/- 7.9 s, and 60.8 +/- 9.1 s, respectively. These results suggest an increase in the capillary bed red cell content as the initial response to hypoxia, but venules and arterioles change only on longer exposure to hypoxia. The sequence of the increase in red cell content suggests the capillaries rather than the arterioles are the vessels which respond to the oxygen autoregulation signal.

Group transmission of predator avoidance behaviour in a marine insect: The trafalgar effect

The approach of a predator model induces rapid changes in the locomotory behaviour of individuals at the periphery of flotillas of a marine insect, the ocean skater Halobates robustus Barber. There is an abrupt and substantial increase in velocity, frequency of turning, the number of apparently random encounters between individuals and also the frequency of changes in light reflection from the body surfaces. These behavioural responses are postulated to cause predator confusion and, less frequently, to initiate rapid, synchronous dispersal of the flotillas. Interactions between individuals in the flotillas mediate a rapid transmission of avoidance behaviour through the flotilla which, in our field experiments, greatly exceeded the speed of approach of a predator model. This behaviour (named the Trafalgar Effect) enables individuals to initiate avoidance behaviour before the approaching predator can be seen.

Food Storage Effects, Changes in Light Reflectance and Ascorbic Acid Content of Foods During Frozen Storage

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTFood Storage Effects, Changes in Light Reflectance and Ascorbic Acid Content of Foods During Frozen StorageN. B. GuerrantCite this: J. Agric. Food Chem. 1957, 5, 3, 207–212Publication Date (Print):March 1, 1957Publication History Published online1 May 2002Published inissue 1 March 1957https://doi.org/10.1021/jf60073a006RIGHTS & PERMISSIONSArticle Views79Altmetric-Citations4LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (548 KB) Get e-Alerts Get e-Alerts

The Spectrophotometric Determination of the Color of Milk

Summary 1. The Beckman spectrophotometer provides basic data for spectral composition of energy reflected from a sample and when it is combined with standard colorimetric data (as the I.C.I. Standard Observer and one of the I.C.I. Standard Illuminants) it provides a good means of estimating the color. 2. A convenient index for routine estimations of the darkening in color of evaporated milk can be determined by noting changes in reflectance of light of 520 mμ wave length.