A brain area responsible for grasping

April 4, 2014 by Silvia Arber
A brain area responsible for grasping

(Medical Xpress)—The research group led by Silvia Arber at the Friedrich Miescher Institute for Biomedical Research and the Biozentrum of the University of Basel has shown that limb motor control is regulated by a selective synaptic connectivity matrix between the brainstem and the spinal cord. In particular, the researchers have pinpointed a brainstem area responsible for the control of grasping. This is the first time it has been possible to link defined neuronal circuit elements unequivocally to a specific phase of movement. The findings were published in Nature.

For most people who try to grasp a small ball with their toes, the difference between the motor skills of the hands and feet is immediately obvious. But for scientists looking at the neurons that control limb movements, the reason for why this is the case has not been so apparent. In the case of both hand and foot, circuits in the brain connect to spinal , which in turn control the various limb muscles. It has not been clear however where specialization occurs, which neuronal circuits account for the differences between hand and foot motor control and how they do so. Silvia Arber and her team at the Friedrich Miescher Institute for Biomedical Research and the Basel University Biozentrum have now investigated the circuits in the brain underlying these differences.

Connectivity matrix between brainstem and spinal cord

In a study published in Nature today, the Basel-based neurobiologists show that the mouse brainstem comprises a number of areas controlling movement via highly specialized connections to the spinal cord.

The work involved the use of state-of-the art methods for visualizing connections between neurons. The researchers were thus able to reveal the three-dimensional connectivity matrix between the brainstem and motor neurons. They found that brainstem neurons connected to motor neurons innervating the mouse forelimb (corresponding to the human arm) reside in part in different areas than those targeting hindlimb-innervating motor neurons. Forelimb control was particularly pronounced in an area known as the brainstem nucleus medullary reticular formation ventral part – or MdV for short.

But there are not only differences between the hind- and forelimbs in general. The researchers also found that neurons residing in particular brainstem areas show connection biases towards motor neurons with different functions. Thus, neurons in certain areas have preferential connections to biceps and others to triceps motor neurons, while others again are connected to both. "This means that there is a specific connectivity matrix for brainstem input to numerous functionally distinct motor neurons," says Silvia Arber.

A brainstem area for grasping

To assess the importance of this connectivity matrix for movements, the researchers analyzed neurons in one of the brainstem areas – the MdV – in more detail. Having first determined that MdV neurons control fine, but not gross, motor tasks, they studied each individual phase of a skilled motor task – retrieval of a single food pellet – in isolation. They found that MdV neurons control only the phase of grasping a pellet, and not the phases of initial reaching or subsequent transfer of the food to the mouth.

Arber comments: "If we want to understand how movements arise and are controlled, then we first have to understand the structure of the various neural circuits involved. In our study, we've identified a first level of connections controlling a clearly defined movement. We assume that an elaborate matrix responsible for a wide range of movements will ultimately be revealed at the level of the ."

Explore further: How neurons control fine motor behavior of the arm

More information: Esposito MS, Capelli P, Arber S (2014) "Brainstem nucleus MdV mediates skilled forelimb motor tasks." Nature, 2014.

Related Stories

How neurons control fine motor behavior of the arm

January 31, 2014

Motor commands issued by the brain to activate arm muscles take two different routes. As the research group led by Professor Silvia Arber at the Basel University Biozentrum and the Friedrich Miescher Institute for Biomedical ...

Brainstem discovered as important relay site after stroke

February 25, 2014

Around 16,000 people in Switzerland suffer a stroke every year. Often the result of a sudden occlusion of a vessel supplying the brain, it is the most frequent live-threatening neurological disorder. In most cases, it has ...

Anatomical blueprint for motor antagonism identified

October 20, 2011

(Medical Xpress) -- Walking or movement in general, comes so naturally to us, yet it results from a sophisticated interplay between the nervous system and muscles. Little is known about the neuronal blueprint that ensures ...

Recommended for you

Scientists identify neurons devoted to social memory

September 30, 2016

Mice have brain cells that are dedicated to storing memories of other mice, according to a new study from MIT neuroscientists. These cells, found in a region of the hippocampus known as the ventral CA1, store "social memories" ...

Throwing light on the brain's perception of transparency

September 30, 2016

Researchers have created a new optical illusion that helps reveal how our brains determine the material properties of objects – such as whether they are transparent, shiny, matte or translucent – just from looking at ...

Scientists track unexpected mechanisms of memory

September 29, 2016

Do you remember Simone Biles's epic gymnastics floor routine that earned her a fifth Olympic medal? Our brains hold on to memories like these via physical changes in synapses, the tiny connections between neurons.

Some brains are blind to moving objects

September 28, 2016

As many as half of people are blind to motion in some part of their field of vision, but the deficit doesn't have anything to do with the eyes.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.