Mapping the Brain

Freiburg Researchers Use Signals from Natural Movements to Identify Brain Regions

Whether we run to catch a bus or reach for a pen: Activities that involve the use of muscles are related to very specific areas in the brain. Traditionally, their exact location has only been determined through electrical stimulation or unnatural, experimental tasks. A team of scientists in Freiburg has now succeeded for the first time in mapping the brain’s surface using measurements of everyday movements.
Attributing abilities to specific brain regions and identifying pathological areas is especially important in the treatment of epilepsy patients, as severe cases require removal of neural tissue. Until now, such “mapping” involved stimulating individual regions of the brain’s surface with electric currents and observing the reaction or sensation. Alternatively, patients were asked to perform the same movements again and again until the physicians isolated the corresponding patterns in brain activity. However, these methods required for the patient to cooperate and to provide detailed answers to the physicians’ questions. This is a prerequisite that small children or patients with impaired mental abilities can hardly meet, and hence there is a need for other strategies.

Scientists from the group of Dr. Tonio Ball at the Cluster of Excellence “BrainLinks-BrainTools” and the Bernstein Center Freiburg report in the current issue of NeuroImage that the brain’s natural activity during everyday movements can also be used to reliably identify the regions responsible for arm and leg movements.

The researchers examined data from epilepsy patients who had electrodes implanted under their skull prior to surgery. Using video recordings, the team captured the spontaneous movements of their patients, searching for concurrent signals of a certain frequency in the data gathered on the surface of the brain. They succeeded in creating a map of the brain’s surface for arm and leg movements that is as accurate as those created through established experimental methods.

A big hope for the team of researchers is also to gain new insights into the control of movements in the brain, as their method allows them to explore all manner of behaviors and is no longer limited to experimental conditions. Last but not least, the scientists explain that this new method of analyzing signals from the brain will contribute to the development of brain-machine interfaces that are suitable for daily use.

Brain Activation in Motor Sequence Learning Is Related to the Level of Native Cortical Excitability

Cortical excitability may be subject to changes through training and learning. Motor training can increase cortical excitability in motor cortex, and facilitation of motor cortical excitability has been shown to be positively correlated with improvements in performance in simple motor tasks. Thus cortical excitability may tentatively be considered as a marker of learning and use-dependent plasticity. Previous studies focused on changes in cortical excitability brought about by learning processes, however, the relation between native levels of cortical excitability on the one hand and brain activation and behavioral parameters on the other is as yet unknown. In the present study we investigated the role of differential native motor cortical excitability for learning a motor sequencing task with regard to post-training changes in excitability, behavioral performance and involvement of brain regions. Our motor task required our participants to reproduce and improvise over a pre-learned motor sequence. Over both task conditions, participants with low cortical excitability (CElo) showed significantly higher BOLD activation in task-relevant brain regions than participants with high cortical excitability (CEhi). In contrast, CElo and CEhi groups did not exhibit differences in percentage of correct responses and improvisation level. Moreover, cortical excitability did not change significantly after learning and training in either group, with the exception of a significant decrease in facilitatory excitability in the CEhi group. The present data suggest that the native, unmanipulated level of cortical excitability is related to brain activation intensity, but not to performance quality. The higher BOLD mean signal intensity during the motor task might reflect a compensatory mechanism in CElo participants.

Rats’ brains are more like ours than scientists previously thought

Neuroscientists face a multitude of challenges in their efforts to better understand the human brain. If not for model organisms such as the rat, they might never know what really goes on inside our heads.

The brain is a phenomenal processor that in a year’s time can generate roughly 300,000 petabytes of data — 30,000 times the amount generated by the Large Hadron Collider. Trying to decipher its signals is a daunting prospect.

But particularly for individuals who have lost a limb or been partially or fully paralyzed, such research has potentially life-changing results because it can enable such biotechnological advances as the development of a brain-computer interface for controlling prosthetic limbs.

Such devices require a detailed understanding of the motor cortex, a part of the brain that is crucial in issuing the neural commands that execute behavioral movements. A recent paper published in the journal Frontiers in Neural Circuits by Jared Smith and Kevin Alloway, researchers at the Penn State Center for Neural Engineering and affiliates of the Huck Institutes of the Life Sciences, details their discovery of a parallel between the motor cortices of rats and humans that signifies a greater relevance of the rat model to studies of the human brain than scientists had previously known.

"The motor cortex in primates is subdivided into multiple regions, each of which receives unique inputs that allow it to perform a specific motor function," said Alloway, professor of neural and behavioral sciences. "In the rat brain, the motor cortex is small and it appeared that all of it received the same type of input. We know now that sensory inputs to the rat motor cortex terminate in a small region of the motor cortex that is distinct from the larger region that issues the motor commands. Our work demonstrates that the rat motor cortex is parcellated into distinct subregions that perform specific functions, and this result appears to be similar to what is seen in the primate brain."

"You have to take into account the animal’s natural behaviors to best understand how its brain is structured for sensory and motor processing," said Jared Smith, graduate student in the Huck Institutes’ neuroscience program and the first author of the paper. "For primates like us, that means a strong reliance on visual information from the eyes, but for rats it’s more about the somatosensory inputs from their whiskers."

In fact, nearly a third of the rat’s sensorimotor cortex is devoted to processing whisker-related information, even though the whiskers’ occupy only one-third of one percent of the rat’s total body surface. In humans, nearly 40 percent of the entire cortex is devoted to processing visual information even though the eyes occupy a very tiny portion of our body’s surface.

To understand the structure and function of the rat motor cortex, Smith and Alloway conducted a series of experiments focused on the medial agranular region, which responds to whisker stimulation and elicits whisker movements when stimulated.

"Our research," said Smith, "was conducted in two stages to investigate the functional organization of the brain: first tracing the neuronal connectivity, and then measuring how the circuits behave in terms of their electrophysiology. Just like in any electrical circuit, the first thing you need to do is trace the wires to see how the different components are connected. Then you can use this information to make sense of the activity going on at any particular node. In the end, you can step back and see how all the circuits work together to achieve something more complex, such as motor control."

"We discovered different sensory input regions that were distinct from the region that issued the motor commands to move the whiskers," said Alloway. "In this respect, we were fortunate to have Patrick Drew [assistant professor of engineering science and mechanics and neurosurgery at Penn State] help us analyze the EMG signals produced by microstimulation because this showed that the sensory input region was significantly less effective in evoking whisker movements."

As a result of Smith and Alloway’s discovery, previously published data on the rat motor cortex can be revisited with a new degree of specificity, and more similarities between the brains and neural processes of rats and humans may eventually come to light, perhaps even informing studies of other model organisms. This discovery is also likely to advance the study of the human brain.

"This study opens up avenues for studying some very complex neural processes in rodents that are more like our own than we had previously thought," said Smith. "The tools now available for studying activity in the rodent brain are improving at a remarkable pace, and the findings are even more interesting as we discover just how similar these mammalian relatives are to us. This is a very exciting time in neuroscience."

Stroke Damage in Mice Overcome by Training that ‘Rewires’ Brain Centers

Johns Hopkins researchers have found that mice can recover from physically debilitating strokes that damage the primary motor cortex, the region of the brain that controls most movement in the body, if the rodents are quickly subjected to physical conditioning that rapidly “rewires” a different part of the brain to take over lost function.

Their research, featuring precise, intense and early treatment, and tantalizing clues to the role of a specific brain area in stroke recovery, is described online in the journal Stroke.

"Despite all of our approved therapies, stroke patients still have a high likelihood of ending up with deficits," says study leader Steven R. Zeiler, M.D., Ph.D., an assistant professor of neurology at the Johns Hopkins University School of Medicine. "This research allows us the opportunity to test meaningful training and pharmacological ways to encourage recovery of function, and should impact the care of patients."

With improved acute care for stroke, more patients are surviving. Still, as many as 60 percent are left with diminished use of an arm or leg, and one-third need placement in a long-term care facility. The economic cost of disability translates to more than $30 billion in annual care.

The Science of Storytelling: Why Telling a Story is the Most Powerful Way to Activate Our Brains

We all enjoy a good story, whether it’s a novel, a movie, or simply something one of our friends is explaining to us. But why do we feel so much more engaged when we hear a narrative about events?

It’s in fact quite simple. If we listen to a powerpoint presentation with boring bullet points, a certain part in the brain gets activated. Scientists call this Broca’s area and Wernicke’s area. Overall, it hits our language processing parts in the brain, where we decode words into meaning. And that’s it, nothing else happens.

When we are being told a story, things change dramatically. Not only are the language processing parts in our brain activated, but any other area in our brain that we would use when experiencing the events of the story are too.

Cognitive signals for brain–machine interfaces in posterior parietal cortex include continuous 3D trajectory commands

Cortical neural prosthetics extract command signals from the brain with the goal to restore function in paralyzed or amputated patients. Continuous control signals can be extracted from the motor cortical areas, whereas neural activity from posterior parietal cortex (PPC) can be used to decode cognitive variables related to the goals of movement. Because typical activities of daily living comprise both continuous control tasks such as reaching, and tasks benefiting from discrete control such as typing on a keyboard, availability of both signals simultaneously would promise significant increases in performance and versatility. Here, we show that PPC can provide 3D hand trajectory information under natural conditions that would be encountered for prosthetic applications, thus allowing simultaneous extraction of continuous and discrete signals without requiring multisite surgical implants. We found that limb movements can be decoded robustly and with high accuracy from a small population of neural units under free gaze in a complex 3D point-to-point reaching task. Both animals’ brain-control performance improved rapidly with practice, resulting in faster target acquisition and increasing accuracy. These findings disprove the notion that the motor cortical areas are the only candidate areas for continuous prosthetic command signals and, rather, suggests that PPC can provide equally useful trajectory signals in addition to discrete, cognitive variables. Hybrid use of continuous and discrete signals from PPC may enable a new generation of neural prostheses providing superior performance and additional flexibility in addressing individual patient needs.