Researchers model how neurons work together

June 18, 2014, University of Cambridge
Neurons. Image credit: Denis Burdakov

A newly-developed, highly accurate representation of the way in which neurons behave when performing movements such as reaching could not only enhance understanding of the complex dynamics at work in the brain, but aid in the development of robotic limbs which are capable of more complex and natural movements.

Researchers from the University of Cambridge, working in collaboration with the University of Oxford and the Ecole Polytechnique Fédérale de Lausanne (EPFL), have developed a new model of a neural network, offering a novel theory of how work together when performing complex movements. The results are published in the18 June edition of the journal Neuron.

While an action such as reaching for a cup of coffee may seem straightforward, the millions of neurons in the 's must work together to prepare and execute the movement before the coffee ever reaches our lips. When reaching for the much-needed cup of coffee, the millions of neurons in the brain's motor cortex spring into action, sending a series of signals from the brain to the hand. These signals are transmitted across synapses – the junctions between neurons.

Determining exactly how the neurons work together to execute these movements is difficult, however. The new theory was inspired by recent experiments carried out at Stanford University, which had uncovered some key aspects of the signals that neurons emit before, during and after the movement. "There is a remarkable synergy in the activity recorded simultaneously in hundreds of neurons," said Dr Guillaume Hennequin of the University's Department of Engineering, who led the research. "In contrast, previous models of cortical circuit dynamics predict a lot of redundancy, and therefore poorly explain what happens in the motor cortex during movements."

Better models of how neurons behave will not only aid in our understanding of the brain, but could also be used to design prosthetic limbs controlled via electrodes implanted in the brain. "Our theory could provide a more accurate guess of how neurons would want to signal both movement intention and execution to the robotic limb," said Dr Hennequin.

The behaviour of neurons in the motor cortex can be likened to a mousetrap or a spring-loaded box, in which the springs are waiting to be released and are let go once the lid is opened or the mouse takes the bait. As we plan a movement, the 'neural springs' are progressively flexed and compressed. When released, they orchestrate a series of neural activity bursts, all of which takes place in the blink of an eye.

The signals transmitted by the synapses in the motor cortex during complex movements can be either excitatory or inhibitory, which are in essence mirror reflections of each other. The signals cancel each other out for the most part, leaving occasional bursts of activity.

Using control theory, a branch of mathematics well-suited to the study of complex interacting systems such as the brain, the researchers devised a model of neural behaviour which achieves a balance between the excitatory and inhibitory synaptic signals. The model can accurately reproduce a range of multidimensional movement patterns.

The researchers found that neurons in the motor cortex might not be wired together with nearly as much randomness as had been previously thought. "Our model shows that the inhibitory synapses might be tuned to stabilise the dynamics of these brain networks," said Dr Hennequin. "We think that accurate models like these can really aid in the understanding of the incredibly complex dynamics at work in the human brain."

Future directions for the research include building a more realistic, 'closed-loop' model of movement generation in which feedback from the limbs is actively used by the brain to correct for small errors in movement execution. This will expose the new theory to the more thorough scrutiny of physiological and behavioural validation, potentially leading to a more complete mechanistic understanding of complex movements.

Explore further: Motor cortex shown to play active role in learning movement patterns

More information: "Optimal Control of Transient Dynamics in Balanced Networks Supports Generation of Complex Movements" Neuron, June 18, 2014.

Related Stories

Motor cortex shown to play active role in learning movement patterns

May 4, 2014
Skilled motor movements of the sort tennis players employ while serving a tennis ball or pianists use in playing a concerto, require precise interactions between the motor cortex and the rest of the brain. Neuroscientists ...

Study sheds light on how our brains move limbs

January 16, 2013
(Medical Xpress)—A Queen's University study is giving new insight into how the neurons in our brains control our limbs. The research might one day help with the design of more functional artificial limbs.

Brain's motor cortex uses multiple frequency bands to coordinate movement

February 21, 2014
Synchrony is critical for the proper functioning of the brain. Synchronous firing of neurons within regions of the brain and synchrony between brain waves in different regions facilitate information processing, yet researchers ...

Complex neural circuitry keeps you from biting your tongue

June 3, 2014
Eating, like breathing and sleeping, seems to be a rather basic biological task. Yet chewing requires a complex interplay between the tongue and jaw, with the tongue positioning food between the teeth and then moving out ...

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 ...

Isolating the circuits that control voluntary movement

May 7, 2014
(Medical Xpress)—Extraordinarily complex networks of circuits that transmit signals from the brain to the spinal cord control voluntary movements. Researchers have been challenged to identify the controlling circuits, but ...

Recommended for you

Brain zaps may help curb tics of Tourette syndrome

January 16, 2018
Electric zaps can help rewire the brains of Tourette syndrome patients, effectively reducing their uncontrollable vocal and motor tics, a new study shows.

A 'touching sight': How babies' brains process touch builds foundations for learning

January 16, 2018
Touch is the first of the five senses to develop, yet scientists know far less about the baby's brain response to touch than to, say, the sight of mom's face, or the sound of her voice.

Researchers identify protein involved in cocaine addiction

January 16, 2018
Mount Sinai researchers have identified a protein produced by the immune system—granulocyte-colony stimulating factor (G-CSF)—that could be responsible for the development of cocaine addiction.

Neuroscientists suggest a model for how we gain volitional control of what we hold in our minds

January 16, 2018
Working memory is a sort of "mental sketchpad" that allows you to accomplish everyday tasks such as calling in your hungry family's takeout order and finding the bathroom you were just told "will be the third door on the ...

Brain imaging predicts language learning in deaf children

January 15, 2018
In a new international collaborative study between The Chinese University of Hong Kong and Ann & Robert H. Lurie Children's Hospital of Chicago, researchers created a machine learning algorithm that uses brain scans to predict ...

Preterm babies may suffer setbacks in auditory brain development, speech

January 15, 2018
Preterm babies born early in the third trimester of pregnancy are likely to experience delays in the development of the auditory cortex, a brain region essential to hearing and understanding sound, a new study reveals. Such ...

0 comments

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.