In a laboratory at St. Jude Children's Research Hospital and Columbia University, researchers set out to chart the brain's familiar machinery of movement and instead noticed something quiet that had been waiting in plain sight. When mice rested, sensory regions pulsed in rhythm with small patches of the secondary motor cortex, and those patches, taken together, revealed a body map no one had drawn before. It is a reminder that the brain often shows its structure most clearly when it appears to be doing nothing at all, and that the path toward understanding how children's nervous systems falter
Optical Imaging Reveals a Hidden Body-Part Map in the Mouse Secondary Motor Cortex
The map began with a pause, not a movement.
Mark
Why does a map of body parts in the mouse brain matter?
Mimi
Because motor cortex activity has been hard to read. This map shows that M2 isn't one uniform thing. Small subregions line up with different body parts.
Mark
And they found it by accident?
Mimi
Roughly. They were looking for primary movement regions, then noticed sensory areas fluctuating strongly at rest, each in sync with a small patch of M2.
Luke
So the map came from resting synchrony, not from watching movement directly?
Mimi
That's how it was first noticed. They then checked neuronal activity in the subregions and found it depended on which body part was in use.
Mark
What did they learn about complex movements?
Mimi
M2 activated more strongly when several body parts moved in a coordinated way. At rest it fluctuates, in simple movements it engages briefly, and in complex ones it sustains.
Luke
Worth saying this is mouse work. Nothing here tells us what a human map looks like.
Mimi
Right, the source doesn't claim that.
Luke
And the disease angle?
Mimi
It's a stated hope. Hillman wants to study mechanisms, biomarkers and therapies for pediatric conditions, but no results there are reported yet.
Mark
So the real shift is the method?
Mimi
Partly. Continuous whole-brain imaging revealed pathways that averaging over repeated movements had hidden.
The Pulse
- Researchers expected to find the main drivers of movement and instead saw sensory regions fluctuating strongly while the mice were at rest.
- Small patches of the mouse secondary motor cortex synchronized with those sensory fluctuations, and fitted together they formed an unexpected body-part map.
- Activity surges as movements grow more complex, with multiple body parts engaged at once, pushing the region from brief engagement into sustained activity.
- Continuous whole-brain optical imaging has exposed hidden communication pathways, and the team is now aiming that method at disease, biomarkers and therapies for pediatric conditions.
In a laboratory at St. Jude Children's Research Hospital and Columbia University, researchers set out to chart the brain's familiar machinery of movement and instead noticed something quiet that had been waiting in plain sight. When mice rested, sensory regions pulsed in rhythm with small patches of the secondary motor cortex, and those patches, taken together, revealed a body map no one had drawn before. It is a reminder that the brain often shows its structure most clearly when it appears to be doing nothing at all, and that the path toward understanding how children's nervous systems falter may run through such unexpected small discoveries.
The discovery began with a pause. Researchers at St. Jude Children's Research Hospital and Columbia University were mapping the regions that drive movement in the mouse brain when they noticed something unexpected: while the animals rested, sensory areas showed strong waves of activity.
Elizabeth Hillman, chair of the St. Jude Department of Imaging Sciences and corresponding author, explained that each sensory area's resting rhythm lined up with a small patch of the secondary motor cortex, known as M2. Put together, those patches formed a neat body-part map. The team had been searching for something else, and the finding surprised them.
The map, published in Nature Communications, showed distinct regions tied to different body parts. Further analysis confirmed that activity in each subregion depended on which body part was moving. The region also responded to complexity: it engaged more strongly during coordinated movements involving several body parts at once.
Hillman saw in these shifting states an explanation for why motor cortex activity has been so hard to read. Once the pattern was recognized, she said, it became far easier to interpret, like picking out the instruments in an orchestra.
The method matters as much as the map. Hillman's wide-field optical imaging watches neural activity across the whole brain in real time, rather than averaging many repetitions in a small region. That view revealed communication pathways between regions that earlier techniques had missed, and it offers a way to see how movement control fails in neurological disease or brain injury.
She hopes to apply the approach to disease mechanisms, biomarkers and therapies for a range of pediatric conditions affecting movement, behavior and cognition. Whether the path from mouse map to clinical research holds is the next question.
The discovery began with a pause. Researchers at St. Jude Children's Research Hospital and Columbia University were imaging the mouse brain, looking for the main regions that drive movement. What caught their attention was what happened when the animals were at rest: sensory areas of the brain showed strong fluctuations in activity.
Elizabeth Hillman, PhD, chair of the St. Jude Department of Imaging Sciences and corresponding author of the study, said each sensory area's resting activity was synchronized with a small patch of the secondary motor cortex, known as M2. When the team fitted all of those patches together, they formed what she described as a neat little body-part map. She called the finding unexpected, since the group had been searching for something else.
The result, published in Nature Communications, is a previously unknown map inside the mouse secondary motor cortex, with distinct regions tied to different parts of the body. The researchers then looked at neuronal activity within those subregions and confirmed that activation depended on which body part was in use.
They also compared activity patterns across different kinds of movement. Secondary motor cortex activated more strongly during complicated, coordinated movements that involved several body parts at once.
Taken together, the observations describe a region that changes state. At rest, its subregions fluctuate in synchrony with sensory areas. During simple movements, it engages briefly. During more complex movements involving multiple body parts, its activity is sustained. Hillman said these shifting states help explain why motor cortex activity has been so hard to interpret during movement. Once the team recognized the pattern, she said, the activity became much easier to read, like recognizing which instruments are playing in an orchestra.
The method matters as much as the map. Hillman has pioneered the wide-field optical mapping approach used here, which gives real-time readouts of neural activity across the brain during spontaneous movements. She noted that neuroscience studies have typically averaged many repetitions of the same movement or stimulus, often within a small brain region. By imaging continuously across the whole brain, her team saw regions fluctuate together at rest and go quiet when movement began. Analyzing those patterns exposed communication pathways between multiple regions that earlier imaging approaches had hidden.
The work could help researchers understand how these processes are disrupted by neurological disease or brain injury. Hillman said that because the approach lets the team watch the brain control movement in real time, they can also analyze how and when that system fails.
She hopes to use the technique to explore disease mechanisms and biomarkers, and to evaluate therapies for a range of pediatric conditions that affect movement, behavior and cognition. The next question is whether that path from mouse map to disease research bears out.
Notable Quotes
Finding this map was unexpected.— Elizabeth Hillman, PhD, St. Jude Department of Imaging Sciences chair
Because we can visualize how the brain controls movements in real time, we can also analyze how and when that system fails.— Elizabeth Hillman (paraphrased)
Want the full story?
Read the original at News-Medical ↗