Project

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Functional Assessment of Brain Tissue by Near-Infrared Imaging and EEG

Applicant Wolf Martin
Number 120727
Funding scheme Interdisciplinary projects
Research institution Klinik für Neonatologie UniversitätsSpital Zürich
Institution of higher education University of Zurich - ZH
Main discipline Electrical Engineering
Start/End 01.08.2008 - 31.12.2010
Approved amount 230'237.00
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All Disciplines (7)

Discipline
Electrical Engineering
Embryology, Developmental Biology
Neurophysiology and Brain Research
Biomedical Engineering
Psychology
Other disciplines of Physics
Biophysics

Keywords (16)

near infrared imaging & spectroscopy; neuronal activity; high time resolution spectroscopy; absorption; scattering; oxygenation; brain function; brain development; hemodynamic activity; Near infrared imaging; Electroencephalography; Neonate; Preterm infant; Brain activity; Intensive care

Lay Summary (English)

Lead
Lay summary
The main aim of this project is to shed new light on the brain using near-infrared imaging (NIRI). NIRI is a technique with considerable potential that determines and images non-invasively functional parameters of tissue such as oxygenation and potentially neuronal activity. NIRI could be a valuable clinical tool, because it is applicable at the bedside and causes no pain and allows long term measurements (monitoring).
Neuronal activity is a small signal compared to optical changes due to functional or physiological variations such as e.g. the arterial pulsation. Additionally, the time resolution of 100 Hz required to detect the neuronal signal is two orders of magnitudes higher than the one used in conventional NIRI. Both factors make it difficult to detect the neuronal signal. However, due to the fast time course, the response to a thousand stimuli or more can be averaged and thus it may be possible to detect the neuronal signal.
Previous results suggest that NIRI is able to directly and non-invasively detect neuronal activity of the brain in human adults. In a currently ongoing SNF project, the reproducibility of such measurements in adults is tested and NIRI is compared to EEG. So far the measurement of neuronal activity in neonates and preterm infants has not been investigated. Therefore, the aim of this continuation of the project is to test the reproducibility of the optical detection of the neuronal activity in neonates and preterm infants and to compare it to EEG. We expect that neuronal activity can reproducibly be detected.
If NIRI is able to detect neuronal activity, it will be the only method capable of simultaneously studying the neuronal and hemodynamic activity. Thus, it would allow non-invasively investigating the relation between neuronal activity and the blood circulation and oxygenation of the brain. In this project this relation will be examined in any case, because EEG measures neuronal activity and NIRI blood circulation and oxygenation. Unique information about the development of the seeing and hearing abilities of neonates will be obtained.
In the future we will introduce NIRI as a clinical tool to study brain function, particularly in unconscious neonatal intensive care patients, where information about the integrity of the brain is of high clinical interest.
Direct link to Lay Summary Last update: 21.02.2013

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
112677 Functional imaging of brain tissue by near-infrared spectroscopy 01.05.2006 Project funding (Div. I-III)

Abstract

The main aim of this project is to shed new light on the brain using near-infrared imaging (NIRI). NIRI is a technique with considerable potential that determines and images non-invasively functional parameters of tissue such as oxygenation and potentially neuronal activity. This opens new dimensions for tissue characterization. Moreover, NIRI could be a valuable clinical tool, because it is applicable at the bedside and causes no pain and allows long term measurements (monitoring).Our previous results suggest that NIRI is able to directly and non-invasively detect cerebral functional neuronal activity in human adults. Although an increasing number of research groups have confirmed the results, they are still controversial. Therefore, in a currently ongoing, preceding SNF project, the reproducibility of such measurements in adults is tested and NIRI is compared to EEG. So far the detectability of neuronal activity in neonates and preterm infants has not been investigated. Their neuronal signals are expected to be easier to detect, because their head is more transparent and brain closer to the surface compared to adults. Therefore, the aim of the proposed continuation of the project is to test the reproduci-bility of the optical detection of the neuronal activity in neonates and preterm infants and to compare it to EEG. The hypothesis is that neuronal activity can reproducibly be detected.If NIRI is able to detect neuronal activity, it will be the only method capable of simultaneously studying the neuronal and hemodynamic activity. Thus, it would allow non-invasively investigating neurovascular coupling and brain function in vivo. The neuronal signal is a small signal, i.e. the optical changes are approximately 100 times smaller than the optical changes due to the hemodynamic signal or physiological variations such as e.g. the arterial pulsation. Additionally, the time resolution of 100 Hz required to detect the neuronal signal is two orders of magnitudes higher than the one used in conventional NIRI. Both factors make it difficult to detect the neuronal signal. However, due to the fast time course, the response to a thousand stimuli or more can be averaged and thus it may be possible to detect the neuronal signal. By a multimodal set-up using NIRI and EEG simultaneously functional measurements of the visual and auditory cortex will be carried out three times on different days to determine the reproducibility in 15 neonates and 15 preterm infants. The set-up, procedures and data analysis will be specifically developed for these infants. If NIRI is able to detect the neuronal activity, we will determine the reproducibility and the detailed optical properties. In addition, the optical signal will be compared to standard evoked potentials measured by EEG. This will give a firm basis for the understanding of its nature. Also even if NIRI is not able to detect neuronal activity, our multimodal set-up will enable us to detect both the neuronal activity by EEG and the hemodynamic signals by NIRI. Thus, in any case the neurovascular coupling, i.e. the interaction of neuronal and hemodynamic activity, will be examined with regard to the spatial collocation and habituation. Unique information about the development of the visual and auditory cortex of neonates and the neurovascular coupling will be obtained. In the future we will introduce NIRI as a clinical tool to study brain function, particularly in unconscious adult and neonatal intensive care patients, where information about the integrity of the brain is of high clinical interest. For the design of a new clinical NIRI instrument it is indispensable to know, whether the neuronal signal can be detected or not. This novel imaging instrument will be applicable in many other fields to study the brain (neurology, neuroscience, psychiatry, rehabilitation), but will also be useful to study other tissues such as e.g. muscle and liver. A whole new scope of clinical applications can be envisioned.
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