Near-infrared Optical Topography Research Articles

Early Diagnosis and Perioperative Therapeutic Management of Cerebral Ischemia in Cerebral Vasospasm Using Oxygen-pulse Near-infrared Optical Topography

Early Diagnosis and Perioperative Therapeutic Management of Cerebral Ischemia in Cerebral Vasospasm Using Oxygen-pulse Near-infrared Optical Topography

P4-16 Brain imaging in Karuta players with near-infrared optical topography and event-related potential

P4-16 Brain imaging in Karuta players with near-infrared optical topography and event-related potential

Shortened Dental Arch and Cerebral Regional Blood Volume: An Experimental Pilot Study with Optical Topography

A shortened dental arch without posterior occlusal support has been thought to maintain sufficient oral function. The mechanism of occlusal adaptation with a shortened dental arch is unclear. For a better understanding of the effects of molar teeth on brain function, the authors combined experimentally- shortened dental arches and a neuro-imaging technique. Regional cerebral blood volume was measured using near-infrared optical topography during maximum voluntary clenching tasks from 10 subjects on individually fabricated oral appliances, which can create experimentally complete and shortened dental arches. Results suggested that clenching on the complete dental arch showed a significantly higher brain blood volume than that on the shortened dental arch. Moreover, there were no differences between the two splints in the latency to the maximum oxyhemoglobin concentration. These findings suggest that occlusal status is closely related to brain blood flow and lack of occlusal molar support rapidly reduces cerebral blood volume in the maximum voluntary clenching condition.

Signal filtering algorithm for depth-selective diffuse optical topography

A compact filtered backprojection algorithm that suppresses the undesirable effects of skin circulation for near-infrared diffuse optical topography is proposed. Our approach centers around a depth-selective filtering algorithm that uses an inverse problem technique and extracts target signals from observation data contaminated by noise from a shallow region. The filtering algorithm is reduced to a compact matrix and is therefore easily incorporated into a real-time system. To demonstrate the validity of this method, we developed a demonstration prototype for depth-selective diffuse optical topography and performed both computer simulations and phantom experiments. The results show that the proposed method significantly suppresses the noise from the shallow region with a minimal degradation of the target signal.

Extrauterine environment affects the cortical responses to verbal stimulation in preterm infants

Using optical topography, changes in the cerebral oxygenation were compared in the parieto-temporal lobe of preterm and term infants of equal postconceptional age in response to verbal stimulation. Eight preterm infants of gestational age 23-34 weeks were studied at postconceptional term age (38-46 weeks). Ten term infants were studied at 2-11 days after birth. Twenty-four-channel near-infrared optical topography (NIOT) was used to measure changes in concentration of oxyhemoglobin ([oxyHb]), deoxyhemoglobin ([deoxyHb]) and total hemoglobin ([totalHb]) in the bilateral temporal cortices. Verbal stimulation was provided by a recording of a Japanese fairy tale. The latency in response to verbal stimulation was significantly shorter in the preterm infants than in the term infants. This time is thought to reflect brain development, particularly the development of the neuro-vascular coupling mechanisms in the cerebral cortex. The present results indicate that the number of days after birth is more closely related to development of auditory system and neuro-vascular coupling than is postconceptional age. Thus, this suggests that early extrauterine environment affects the cortical responses to verbal stimulation in preterm infants.

Selectivity and localization of cortical response to auditory and visual stimulation in awake infants aged 2 to 4 months

To better understand the development of multimodal perception, we examined selectivity and localization of cortical responses to auditory and visual stimuli in young infants. Near-infrared optical topography with 24 channels was used to measure event-related cerebral oxygenation changes of the bilateral temporal cortex in 15 infants aged 2 to 4 months, when they were exposed to speech sounds lasting 3 s and checkerboard pattern reversals lasting 3 s, which were asynchronously presented with different alternating intervals. Group analysis revealed focal increases in oxy-hemoglobin and decreases in deoxy-hemoglobin in both hemispheres in response to auditory, but not to visual, stimulation. These results indicate that localized areas of the primary auditory cortex and the auditory association cortex are involved in auditory perception in infants as young as 2 months of age. In contrast to the hypothesis that perception of distinct sensory modalities may not be separated due to cross talk over the immature cortex in young infants, the present study suggests that unrelated visual events do not influence on the auditory perception of awake infants.

The right hemisphere of sleeping infant perceives sentential prosody

Behavioral studies proposed that prosodic information in speech sounds plays important roles for human infants to acquire their native languages. Here, we examined the neural basis of prosodic processing in 3-month-old infants. In order to obtain hemodynamic responses with high signal-to-noise ratio, we used near-infrared optical topography in the infants while they were in quiet sleep. First, we observed bilateral activation under each of the normal and flattened speech conditions. The flattened speech sound was created by eliminating changes in the pitch contours of the original utterance. In a direct comparison between the two conditions, the right temporoparietal region showed more prominent activation to normal speech sounds than to flattened speech sounds. This result demonstrates that the localized region of the right hemisphere in 3-month-old infant is involved in the processing of pitch contours. Our findings suggest that prosodic processing in the right hemisphere may facilitate the acquisition of lexical or syntactic knowledge in the early stages of language development.

Rehabilitation with dental prosthesis can increase cerebral regional blood volume

Treatment with denture for edentulous people is highly important for maintaining quality of life. However, its effect on the brain is unknown. In this experimental study, we hypothesized that dental prosthesis can recover not only the physical condition of mastication system but also the regional brain activity. We evaluated functional brain imaging of edentulous subjects fixed by dental implant prosthesis with clenching tasks by multi-channel near-infrared optical topography. Results revealed a significantly (P<0.001; paired t-test) increased cerebral regional blood volume during maximum voluntary clenching task by implant-retained prosthesis. There were no statistically significant differences between patients with and without prosthesis in the latency to the maximum regional blood volume after the task. Conclusively, clenching can be effective for increasing cerebral blood volume; accordingly maintenance of normal chewing might prevent the brain from degenerating.

Novel Motor and Somatosensory Activity Is Associated With Increased Cerebral Cortical Blood Volume Measured by Near-Infrared Optical Topography

Recent reports suggest that learning is enhanced by emotion, spontaneity, and play. The mechanisms of this enhancement are unclear and might involve increased cortical stimulation by the limbic system. Since neuronal activity is tightly coupled to changes in cerebral blood flow and volume, the demonstration of increased cortical blood volume during playful versus routine motor and somatosensory activity would imply enhanced neuronal activity and provide insight into the complex interaction between play and learning. Near-infrared spectroscopy was used to detect changes in cortical blood volume during performance of (1) rudimentary visual, motor, and speech tasks; (2) integration of the tasks in a familiar routine manner; and (3) integration of the tasks in a novel, spontaneous, playful manner. No significant differences in cortical blood volume were found during the performance of the individual rudimentary tasks and their routine integration. However, the novel integration activity was associated with a significantly greater increase in frontal lobe oxyhemoglobin, deoxyhemoglobin, and total hemoglobin, as well as parietal lobe total hemoglobin. This small pilot study provides a limited measure of physiologic support for a relationship between play and learning.

A frequency multiplexed near-infrared topography system for imaging functional activation in the brain

We have developed a novel near-infrared optical topography system that can acquire images of functional activation in the human brain at 10 frames per second using 32 detectors. The image acquisition rate is inversely proportional to the number of detectors, so the maximum acquisition rate using four detectors is 80Hz. 16 laser diode sources (8 at 785 and 8 at 850nm) are illuminated simultaneously, and each of 8 avalanche photodiode detectors records light from several sources at the same time. The contribution from each source is demultiplexed in software using fast Fourier transforms. This allows for a more flexible, smaller, and less complex system than is achievable using traditional hardware demodulation techniques, such as lock-in amplifiers. The system will eventually incorporate a total of 64 sources and 32 detectors, enabling the entire adult cortex to be imaged. The system is designed to be as flexible as possible, and to be applicable to a wide variety of experimental and clinical needs. To this end, it can operate in two distinct modes: As a frequency multiplexed system and as a time multiplexed system. We describe phantom and in vivo investigations that have been undertaken using the new instrument in its frequency multiplexed operating mode.

Near-infrared optical topography to assess activation of the parietal cortex during a visuo-spatial task

Multi-channel near-infrared spectroscopy (NIRS) is a relatively new method to investigate the brain activation, based on changes in oxygenated haemoglobin (O 2Hb) and deoxygenated haemoglobin (HHb). Recently, it has been shown that NIRS seems to be able to detect even small changes in O 2Hb and HHb concentration due to cognitive demands. This study aimed at investigating the changes in O 2Hb and HHb concentrations of the parietal cortex during a spatial task, a modified version of the Benton Line Orientation Task [Gur, R. C., Alsop, D., Glahn, D., Petty, R., Swanson, C. L., Maldjian, J. A., et al. (2000). An fMRI study of sex differences in regional activation to a verbal and a spatial task. Brain & Language, 74(2), 157–170.]. Twenty-four subjects were measured with NIRS while they had to estimate the orientation of a given line or to name the colour of the line in the control condition. Both conditions consisted of three activation phases each lasting 30 s, with a 10 s baseline and a 20 s post resting period. For assessing the changes in O 2Hb and HHb concentrations, we measured with 24 NIRS channels over the parietal cortex using the NIRS apparatus ETG-100 (Hitachi Medical Ltd.). O 2Hb concentration significantly increased during the active phase compared to the baseline for both conditions, but was significantly higher in the active phase for the line orientation condition compared to the colour naming condition bilaterally parieto-occipital. For the HHb concentrations, we only found significant decreases for both conditions but no differences between the conditions. The results of our study underscore the value of multi-channel NIRS for assessing cortical activation during cognitive tasks.

Remote effect of repetitive transcranial magnetic stimulation on the cerebellum of spinocerebellar degeneration patients

In order to investigate the effect of repetitive transcranial magnetic stimulation (rTMS) on the cerebellum of spinocerebellar degeneration (SCD) patients, the hemodynamic changes of the brain during rTMS was measured using noninvasive dynamic multi-channel near-infrared optical topography (OT). Two SCD patients diagnosed as OPCA participated in this study. Both had been having rTMS administered to their cerebellum once a week for more than 2 years for therapeutic purposes under the permission of the local ethical committee. Three sessions of 15 times application of 1 Hz rTMS were applied at 3-min intervals. OT probes were set on the scalp and the hemodynamic changes of the fronto-paretal lobe were measured during each session. Changes in hemoglobin were recorded at 15-s prestimulus intervals and consecutively 195 s during and after stimulus. Increased blood flow around the premotor area was observed during rTMS, and the effects were prolonged for more than at least a couple of minutes after rTMS. These results suggest that rTMS administered to the cerebellum of SCD patients may have a remote effect on the frontal lobe and that the blood flow of the frontal lobe may change during and after rTMS.

Hemodynamic responses to visual stimulation in occipital and frontal cortex of newborn infants: a near-infrared optical topography study

A near-infrared optical topography (OT) was used to reveal spatio-temporal changes in the cerebral oxygenation of newborn infants in response to brief visual stimulation. Newborn infants were presented 3 s stroboscopic light flashing at 14 Hz during spontaneous sleep. Event-related changes in oxy- and deoxyhemoglobin ([oxy-Hb] and [deoxy-Hb]) were observed over the occipital and frontal cortex. The visual stimulus produced statistically significant increases in oxyhemoglobin not only in the occipital cortex but also in the prefrontal cortex. These results suggest that the cerebrovascular coupling is already functioning in newborn’s brain. The prefrontal activation implies that it may contribute to early processing of sensory signals.

Brain Function Measurement System, Near-infrared Light Optical Topography

Brain Function Measurement System, Near-infrared Light Optical Topography

Hemodynamic responses to visual stimulation in occipital and frontal cortex of newborn infants: a near-infrared optical topography study

A near-infrared optical topography (OT) was used to reveal spatio-temporal changes in the cerebral oxygenation of newborn infants in response to brief visual stimulation. Newborn infants were presented 3-s stroboscopic light flashing at 14 Hz during spontaneous sleep. Event-related changes in oxy- and deoxyhemoglobin ([oxy-Hb] and [deoxy-Hb]) were observed over the occipital and frontal cortex. The visual stimulus produced statistically significant increases in oxyhemoglobin not only in the occipital cortex but also in the prefrontal cortex. These results suggest that the cerebrovascular coupling is already functioning in newborn's brain. The prefrontal activation implies that it may contribute to early processing of sensory signals.

Brain imaging in awake infants by near-infrared optical topography.

Studies of young infants are critical to understand perceptual, motor, and cognitive processing in humans. However, brain mechanisms involved are poorly understood, because the use of brain-imaging methods such as functional magnetic resonance imaging in awake infants is difficult. In the present study we show functional brain imaging of awake infants viewing visual stimuli by means of multichannel near-infrared spectroscopy, a technique that permits a measurement of cerebral hemoglobin oxygenation in response to brain activation through the intact skull without subject constraint. We found that event-related increases in oxyhemoglobin were evident in localized areas of the occipital cortex of infants aged 2-4 months in response to a brief presentation of a checkerboard pattern reversal while they maintained fixation to attention-grabbing stimuli. The dynamic change in cerebral blood oxygenation was qualitatively similar to that observed in the adult brain. This result introduces near-infrared optical topography as a method for investigating the functional development of the brain in early infancy.

Development of noninvasive measurement techniques for the human brain

This paper proposes optical topography using near-infrared light as a new noninvasive measurement method for higher brain function. The brain activity accompanying human finger movement is measured by the proposed method. By static optical topography, the activation, of the primary motor area in connection with contralateral finger movement side is observed, which is consistent with established knowledge, and indicates the validity of the proposed method. By using dynamic optical topography, the hemodynamic changes accompanying the activation of the brain function are temporally and spatially analyzed. As a result, the change of the blood volume in the neighborhood of the motor area as a whole is observed at the start and immediately after the movement, as a characteristic event in common to both ipsilateral and contralateral finger movements. The increase of the local blood volume in the primary motor area is observed in the movement period as a characteristic event of the finger movement on the contralateral side. Near-infrared optical topography is a practical noninvasive method of measurement for the higher brain function, which has high portability and can be used in various environments. © 1997 Scripta Technica, Inc. Electron Comm Jpn Pt 3, 80(4): 42–50, 1997