A seemingly simple action, such as picking up a pencil, actually involves complex communication between many parts of the central nervous system. Information about the pencil and its location enters the body through the eye, and eventually reaches a part of the brain called the somatosensory cortex.
There, this information seems to be encoded as two types of brain waves: gamma waves, which oscillate 30–80 times per second, and very fast oscillations (VFOs), which oscillate 80–160 times per second. These brain rhythms may then be conveyed to other parts of the brain to initiate and control the action of reaching out an arm to pick up the pencil.
If other parts of the brain also produce gamma waves and VFOs, it is possible that these brain regions could receive these signals from the somatosensory cortex, and communicate with this or other portions of the cerebral cortex to control movements. In fact, recent work measuring brain waves from the cerebellum, the part of the brain responsible for motor learning, indicates that the cerebellum may communicate with the cerebral cortex to regulate movement. A team of researchers, including Steven Middleton and Thomas Knöpfel from the RIKEN Brain Science Institute (BSI), Wako, Miles Whittington from Newcastle University, United Kingdom, and Roger Traub, now at IBM in New York, report these findings in the journal Neuron.
Tapping into brain waves
In slices from the mouse cerebellum that they had treated with nicotine, the researchers measured the frequency of oscillations using two methods: electrode recordings, and visualization of a voltage-sensitive dye. By both methods, they found that the cerebellar oscillations were a mixture of gamma waves and VFOs. These waves were almost identical in frequency to oscillations others had measured in the cerebral cortex during the same experimental conditions. This frequency match suggests that the cerebellum and cerebral cortex may exchange signals to control movement.
The cerebral cortex contains many types of neurons that are both excitatory and inhibitory. The excitatory neurons, which use glutamate as their chemical neurotransmitter, play an important role in regulating the oscillations of the cerebral cortical neuronal network. The cerebellum also contains some excitatory (granule) cells, while the rest consists of inhibitory neurons, which use GABA (γ-aminobutyric acid) as their neurotransmitter. The researchers demonstrated that the granule cells were not involved in generating the brain waves, so it was surprising that they observed these oscillations at all, since they had to have been generated by inhibitory neuronal populations only. The findings therefore indicate that brain areas with vastly different neuronal compositions can still produce similar rhythms.
Middleton, Knöpfel and colleagues also found another important difference between the cerebellum and the cerebral cortex. Oscillations in both brain regions can be triggered by activation of receptors for the neurotransmitter acetylcholine; however, the receptors in the cortex are so-called muscarinic receptors, which are not activated by nicotine, whereas the receptors in the cerebellum are triggered by nicotine. Furthermore, the cerebellar nicotine receptor that is acting to induce the brain waves seemed to be a ‘nonclassical’ nicotine receptor.
Unraveling neuronal communication
The network oscillations in the cerebral cortex occur due, in part, to gap junctions between cortical neurons, in which electrical activity in one cell can spread through channels that connect that neuron directly to its partner. The researchers also found many pieces of evidence that suggest that electrical connections also exist between cerebellar neurons.
First, they showed that a dye injected into a cerebellar output neuron, called the Purkinje cell, could diffuse to its neighboring local cerebellar interneuron, called a basket cell or a stellate cell. Then, they blocked all chemical communication that occurs in the spaces between neurons, called ‘synaptic neurotransmission’, by removing calcium ions from the solution bathing the cerebellar slices, and still observed VFOs. Finally, they blocked gap junctions with a drug, and this manipulation was sufficient to block both the gamma waves and the VFOs. Their results suggest that direct electrical connections between cerebellar neurons may be one mechanism by which network oscillations are regulated.
Visualizing the source of brain waves
Middleton, Knöpfel and colleagues then used electrical and optical recordings to pinpoint the area of the cerebellum which was responsible for generating the gamma waves and the VFOs. “Optical voltage imaging is a technique for which the RIKEN BSI Laboratory for Neuronal Circuit Dynamics attains world-wide recognition,” says Knöpfel. ”We are expecting that the use of optical voltage imaging in this research field will increase over the coming years.”
The researchers also confirmed their findings in slices from the human cerebellum, suggesting that the data could also be relevant to motor function in humans. Because the oscillations were stimulated by nicotine, the findings imply that nicotine from cigarette smoking may have effects on motion—such as tremor—owing to effects on network oscillations in the cerebellum.
This research provides insight into how the cerebellum and cerebral cortex may communicate with each other to create, organize, and control movements. The researchers believe that their work establishes a new approach to the understanding of how the cerebellum handles information, suggesting that, as in cerebral cortex, oscillations are used for temporal coding of information.
“Startup of this exciting new research was made possible through a generous one-year grant from the directors’ fund of former BSI director Shunichi Amari,” explains Knöpfel. “While we have established the mechanisms underlying cerebellar oscillation generation, we now aim to study the behavioral correlates of these rhythms,” say Middleton and Knöpfel.
1. Middleton, S.J., Racca, C., Cunningham, M.O., Traub, R.D., Monyer, H., Knöpfel, T., Schofield, I.S., Jenkins, A. & Whittington, M.A. High-frequency network oscillations in cerebellar cortex. Neuron 58, 763–774 (2008).
The corresponding authors for this highlight are based at the RIKEN Laboratory for Neuronal Circuit Dynamics
Strong, steady forces at work during cell division
20.10.2016 | University of Massachusetts at Amherst
20.10.2016 | Max Delbrück Center for Molecular Medicine in the Helmholtz Association
Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.
"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...
In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.
A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...
By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.
"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...
COMPAMED has become the leading international marketplace for suppliers of medical manufacturing. The trade fair, which takes place every November and is co-located to MEDICA in Dusseldorf, has been steadily growing over the past years and shows that medical technology remains a rapidly growing market.
In 2016, the joint pavilion by the IVAM Microtechnology Network, the Product Market “High-tech for Medical Devices”, will be located in Hall 8a again and will...
'Ferroelectric' materials can switch between different states of electrical polarization in response to an external electric field. This flexibility means they show promise for many applications, for example in electronic devices and computer memory. Current ferroelectric materials are highly valued for their thermal and chemical stability and rapid electro-mechanical responses, but creating a material that is scalable down to the tiny sizes needed for technologies like silicon-based semiconductors (Si-based CMOS) has proven challenging.
Now, Hiroshi Funakubo and co-workers at the Tokyo Institute of Technology, in collaboration with researchers across Japan, have conducted experiments to...
14.10.2016 | Event News
14.10.2016 | Event News
12.10.2016 | Event News
20.10.2016 | Physics and Astronomy
20.10.2016 | Physics and Astronomy
20.10.2016 | Physics and Astronomy