This study investigates howĚýcerebrospinal fluid (CSF)—the fluid that surrounds and cushions the brain and spinal cord—moves within the brain, and how this movement is influenced by the body’s automatic (autonomic) functions, such as heart rate and breathing. CSF flow is important because it helps remove waste and maintain brain health. While previous research has linked CSF movement to sleep and brain activity, the researchers wanted to isolate the role of theĚýautonomic nervous systemĚý(the system that controls involuntary processes like heartbeat and respiration).

To do this, they used fMRI scans to observe fluid-related signals in the brain while changing levels of carbon dioxide (COâ‚‚) in participants’ blood—a method that affects blood vessel tone, breathing, and heart function without directly altering brain activity. They found that changes in CSF movement could not be explained simply by physical or mechanical factors. Instead, variations inĚýheart-rate variabilityĚý(natural fluctuations in the time between heartbeats) played a key role in driving slow CSF flow, independent of breathing. Additionally, changes in COâ‚‚ levels mainly affected how frequently heart rate and breathing patterns fluctuated, rather than how strong those fluctuations were.

Overall, the findings suggest that CSF movement is strongly influenced by autonomic regulation, and that both higher and lower-than-normal CO₂ levels can disrupt this process. This highlights a new way to study and potentially control brain fluid dynamics—by adjusting CO₂ levels—without relying on sleep or direct neural activity, offering potential insights into brain health and disease.

Ěý

Fig 1: The predictions of CSF flow dynamics across capnias is based on three different physiological pathways: vascular tone, sympathetic tone, and neuronal activity. According to the vascular-tone theory, CSF fluctuations should be maximal at normocapnia. According to the neuronal-activity theory, CSF fluctuations should be maximized at hypocapnia. Lastly, according to the sympathetic-tone theory, CSF fluctuations should be maximized at hypercapnia. These theories will be tested using empirical data involving different capnias, at which all three variables will be altered.

]]> /valiant/2026/03/26/functional-magnetic-resonance-imaging-insights-into-nociceptive-signal-processing-network-in-rat-lumbar-spinal-cord/ Thu, 26 Mar 2026 19:07:00 +0000 /valiant/?p=6324 Xuerong Zhang; Chaoqi Mu; Arabinda Mishra; Feng Wang; Pai-Feng Yang; Xinqiang Yan; Ming Lu; John C. Gore; Li Min Chen (2026).Ěý.ĚýPain Reports, 11(2), e0000000000001368.Ěý

This study used high-resolution functional MRI (fMRI), a technique that measures brain or spinal cord activity by detecting changes in blood flow (called the BOLD signal), to better understand how pain from heat is processed in the spinal cord. Specifically, the researchers focused on the lumbar (lower back) region of the spinal cord in rats. They applied a painful heat stimulus (47.5°C) to one hind paw and recorded activity in spinal cord segments L3 to L5, while also collecting data during rest to examine how different regions communicate with each other.

The results showed that painful heat triggered increased activity in specific areas of the spinal cord’s gray matter, particularly in theĚýdorsal hornĚý(a region that processes sensory information like pain) and theĚýintermediate zoneĚý(a region involved in integrating and relaying signals). These responses were strongest in segments L3 and L4, suggesting these areas play a key role in processing heat-related pain. Additionally, when the animals were at rest, the researchers found strong functional connectivity (synchronized activity) between similar regions on both sides of the spinal cord—specifically between dorsal horns and between ventral horns (the latter being more involved in motor control)—but not between different spinal segments. Based on these findings, the authors propose that a part of the L3 segment, known as the intermediate zone, may act as a central hub that helps regulate how pain signals are processed within the spinal cord.

Figure 1.:

High-resolution magnetization transfer contrast (MTC)-weighted anatomical images of the L3–L5 spinal cord from a representative rat. (A) Left: schematic illustration of the research interest of lumbar spinal cord. Right: A typical axial slice of MTC image of lumbar spinal cord with the gray–white matter boundary outlined by yellow lines. (B) Left: 5 axial MTC images acquired with slice 3 centered at the L3/L4 segment. Right: the corresponding axial slice positions overlaid on the coronal image in the middle line. (C) Schematics of 1 imaging session timeline and noxious heat stimulus presentation paradigm. D, dorsal; L, left; R, right; V, ventral.

In people withĚýmultiple sclerosis (MS), imaging techniques likeĚýdiffusion tensor imaging (DTI)Ěýcan detect damage in the spinal cord before major symptoms appear, but these methods are not very specific.ĚýDiffusion tensor tractographygoes a step further by mapping the paths of nerve fibers, and while it’s widely used in the brain, it hasn’t been fully explored in the spinal cord of people with relapsing-remitting MS (pwRRMS).

In this study, we examined the paths of nerve fibers in theĚýcervical spinal cordĚýof 56 pwRRMS and 46 healthy controls using a 3T MRI scanner. We looked not only at overall lesion load but also at lesions and diffusion patterns within specific white matter columns and along individual fiber paths. We found thatĚýfractional anisotropy (FA), a measure of microstructural integrity, was lower in women and older participants, though this effect was less pronounced along the fiber paths themselves. We also found no significant links between these imaging measures and clinical symptoms.

Overall, while spinal cord tractography may be useful for visualizing nerve fiber paths, it did not provide clear advantages over conventional imaging methods in detecting MS-related damage.

Fig.1. In addition to the single shell diffusion acquisition (15 directions, b = 750 s/mm²) centered between cervical levels C3 and C4, the protocol included a sagittal T2-weighted turbo spin echo and mFFE axial anatomical scan (A). The mFFE, diffusion b0, and FA maps are included for a 27.5-year-old HC and 26.4-year-old pwRRMS with a lesion identified via the yellow arrow (B). (C) Tractography is included for a 23.6-year-old HC (C1) as visualized via MI-Brain and FiberNavigator. The white matter fiber tracts are split into six bundles (left and right ventral, lateral, and dorsal) with a gray matter mask overlaid on the axial view of the anatomic mFFE image (C2). For a 29.8-year-old pwRRMS, two streamline bundles (right dorsal, right lateral) are highlighted in blue, with the streamlines touching lesions highlighted in pink. The right dorsal tract demonstrates low streamline bundle load, while the right lateral tract demonstrates high streamline bundle load (C3). The right lateral lesion can be easily visualized on the axial view of the anatomic mFFE (yellow arrow) (C4).

When the spinal cord is injured, the damage and healing processes are complex and involve many different biological changes. To better understand and track these changes, especially in studies that test treatments in animals before trying them in people, scientists are looking for reliable and noninvasive ways to measure what’s happening inside the body. This study focused on using a special type of MRI scan to find signals, or “biomarkers,” that reflect the severity of spinal cord injury, the loss and repair of protective nerve coverings (called myelin), and inflammation in the nervous system.Ěý

Researchers used two advanced MRI techniques—chemical exchange saturation transfer (CEST) and quantitative magnetization transfer (qMT)—to study rats that had a moderate spinal cord injury. Some of the rats were treated with a drug called riluzole, which may protect nerve cells, while others received a control treatment. Over the course of eight weeks, the scientists monitored changes in the rats’ spinal cords using these MRI methods and then compared the results to lab tests and how well the animals could move and feel.Ěý

They found that rats treated with riluzole had signs of better myelin repair in their spinal cords, and less inflammation, compared to untreated rats. These findings were backed up by tissue analysis after the animals were studied. The MRI measurements also matched up with how well the rats recovered, suggesting that the scans were picking up meaningful signs of healing.Ěý

Overall, this research shows that these advanced MRI techniques can be powerful tools for tracking spinal cord injury and recovery. They help researchers understand how treatments like riluzole are working, and could make it easier to apply what’s learned in animal studies to help people in the future.Ěý

FIGURE 1Ěý

Comparison of qMT PSR maps and values along the spinal cord in riluzole-treated versus HBC vehicle-treated SCI rats. (A,B) Representative PSR maps acquired from injury epicenter, rostral, and caudal to the injury at Week 1 and Week 2 to Week 4 post-injury in rats that received riluzole (A) versus HBC vehicle (B) treatment. (C–E) Average white matter PSR values comparison between treatment and vehicle groups, at (C) injury epicenter, (D) rostral, and (E) caudal, from Week 1 to Week 4. *p < 0.05, **p < 0.005, non-parametric Wilcoxon rank-sum test.Ěý

Researchers are addressing challenges in spinal cord imaging using diffusion MRI, which often suffers from issues like geometric distortion due to magnetic field irregularities and motion artifacts from biological movements. A recent study evaluated techniques to improve image quality, focusing on correcting distortions and using cardiac triggering to reduce motion effects. The findings suggest that while distortion correction methods align images better with structural scans, they do not consistently enhance the clarity or contrast within the spinal cord itself. Additionally, experiments showed that omitting cardiac triggering, which typically synchronizes image capture with heartbeats to minimize motion blur, did not degrade image quality significantly. This suggests that forgoing this technique can shorten the imaging process without sacrificing much in terms of image fidelity. The study highlights the need for further refinement in spinal cord imaging methods, particularly those adapted from brain imaging technologies.