Related Experiment Video
Updated: Jul 11, 2026
05:59
New Framework for Understanding Cross-Brain Coherence in Functional Near-Infrared Spectroscopy (fNIRS) Hyperscanning Studies
Published on: October 6, 2023
Functional contrast based on intermolecular double-quantum coherences: influence of the correlation distance
Andreas Schäfer1, Harald E Möller
1Max Planck Institute for Human Cognitive and Brain Sciences, Leipzig, Germany.
Magnetic Resonance in Medicine
|September 28, 2007
Summary
This study used functional MRI (fMRI) with intermolecular double-quantum coherences to detect brain activation. Researchers found that optimizing the correlation distance significantly enhanced signal changes compared to conventional BOLD fMRI.
Area of Science:
- Neuroimaging
- Magnetic Resonance Imaging
- Biophysics
Background:
- Conventional functional MRI (fMRI) relies on the blood oxygen level-dependent (BOLD) contrast, which has limitations in sensitivity and specificity.
- Intermolecular double-quantum coherences (IDQC) offer a potential alternative contrast mechanism for fMRI.
- Optimizing acquisition parameters is crucial for maximizing the signal-to-noise ratio and sensitivity in fMRI.
Purpose of the Study:
- To investigate the utility of intermolecular double-quantum coherences (IDQC) for functional MRI (fMRI) at 3 Tesla.
- To evaluate the impact of varying correlation distance (d(c)) and evolution time (tau) on fMRI activation.
- To compare the performance of IDQC-based fMRI with conventional BOLD fMRI.
Main Methods:
- A 3 Tesla fMRI study was conducted on healthy subjects during visual stimulation.
- Intermolecular double-quantum coherences were exploited as the contrast mechanism.
- The correlation distance (d(c)) was systematically varied (60-300 microm) and evolution times (tau = 15, 20 ms) were tested.
Main Results:
- Robust brain activation was observed across all experiments, with signal changes exceeding conventional BOLD fMRI.
- The number of activated voxels increased with d(c) up to approximately 120 microm, reaching a plateau.
- Signal attenuation due to diffusion and signal fluctuations impacted sensitivity at shorter d(c) values.
Conclusions:
- IDQC-based fMRI demonstrates superior signal changes compared to conventional BOLD fMRI.
- Optimizing the correlation distance is critical for maximizing activation detection in IDQC fMRI.
- Further research is needed to fully elucidate the potential of IDQC for advanced neuroimaging applications.
Related Concept Videos
03:00Intermolecular vs Intramolecular Forces
Intermolecular forces (IMF) are electrostatic attractions arising from charge-charge interactions between molecules. The strength of the intermolecular force is influenced by the distance of separation between molecules. The forces significantly affect the interactions in solids and liquids, where the molecules are close together. In gases, IMFs become important only under high-pressure conditions (due to the proximity of gas molecules). Intermolecular forces dictate the physical properties of...
01:182D NMR: Overview of Heteronuclear Correlation Techniques
Heteronuclear correlation spectroscopy is an analytical technique that investigates the coupling between different types of nuclei, often a proton and an X-nucleus, such as carbon-13 or nitrogen-15. This method is commonly used in nuclear magnetic resonance (NMR) spectroscopy to gain insights into complex chemical compounds' structural and compositional aspects. A typical heteronuclear correlation spectrum displays X-nucleus chemical shifts on one axis and a proton spectrum on the other axis.
01:02¹H NMR: Interpreting Distorted and Overlapping Signals
Spin systems where the difference in chemical shifts of the coupled nuclei is greater than ten times J are called first-order spin systems. These nuclei are weakly coupled, and their chemical shifts and coupling constant can generally be estimated from the well-separated signals in the spectrum.
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
As Δν decreases and the signals move closer, the doublets appear increasingly distorted. The intensities of the inner lines increase at the cost of those of the outer lines as the signals are slanted or...
01:162D NMR: Overview of Homonuclear Correlation Techniques
Homonuclear correlation spectroscopy (COSY) is a powerful technique used in Nuclear Magnetic Resonance (NMR) spectroscopy to study the correlations between nuclei of the same type within a molecule. It provides information about scalar couplings between adjacent nuclei, which helps determine connectivity and structural information. There are several COSY variants, each with its unique strengths and experimental parameters.
COSY90 is the standard two-dimensional (2D) COSY experiment that...
COSY90 is the standard two-dimensional (2D) COSY experiment that...
02:36Molecular Geometry and Dipole Moments
The VSEPR theory can be used to determine the electron pair geometries and molecular structures as follows:
01:27¹H NMR: Long-Range Coupling
The coupling interactions of nuclei across four or more bonds are usually weak, with J values less than 1 Hz. While these are usually not observed in spectra, the presence of multiple bonds along the coupling pathway can result in observable long-range coupling.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.
In alkenes, spin information is communicated via σ–π overlap, as seen in allylic (four-bond) and homoallylic (five-bond) couplings. These coupling interactions are stronger when the σ bond is parallel to the alkene π orbitals.