Functional MRS with J-edited lactate in human motor cortex at 4 T

Area of Science:

• Neuroimaging
• Metabolic Neuroscience
• Magnetic Resonance Spectroscopy

Background:

• Functional MRI (fMRI) identifies brain activation sites, while functional MRS (fMRS) elucidates metabolic processes.
• Previous fMRS studies faced challenges in accurately quantifying lactate due to overlapping signals, particularly with short echo-time protocols.
• Long echo-time J-difference 1H-MRS offers improved specificity for lactate detection, reducing susceptibility to signal overlap.

Purpose of the Study:

• To investigate the reliability of a J-edited fMRS protocol for detecting metabolic changes in the human motor cortex during a finger-tapping task.
• To assess the sensitivity and specificity of J-edited fMRS in measuring task-induced lactate modulation.
• To establish a method for studying metabolic underpinnings of cognitive functions using lactate dynamics.

Main Methods:

• A 4-Tesla (4T) J-edited fMRS protocol was employed, guided by fMRI for precise voxel placement in the motor cortex.
• The study utilized a finger-tapping paradigm to induce task-related metabolic changes.
• Both lactate and beta-hydroxybutyrate (BHB) were monitored due to similar J-evolution profiles.

Main Results:

• The J-edited fMRS protocol successfully detected both lactate and BHB.
• Only lactate exhibited reproducible task-induced modulation, increasing by 0.07 mM from a baseline of 0.82 mM.
• The results demonstrated good sensitivity and specificity for detecting task-induced lactate modulation.

Conclusions:

• J-edited fMRS is a sensitive and specific method for quantifying task-induced lactate dynamics in the human motor cortex.
• This technique enables the investigation of metabolic underpinnings of human cognition and brain function.
• J-edited fMRS can be applied across various brain regions at magnetic fields lower than 7T, complementing fMRI paradigms.