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Contact the MEG Lab

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About Us

Scientists:

• Dr. Bernhard Ross
  

Programmer/Physicist:

Current Post-doctoral Fellows:

• Dr. Takako Fujioka

Graduate Students:

• Shahab Jamali Gharetape
• Becca Charron

Undergraduate Students:

• Michelle Nurwandi
• Jessica Thompson
  

Research Assistants:

• Panteha Razavi

Recent Graduates:

• Antoine Shahin
• Tim Bardouille
• Dr. Hao Luo

Current Research

Neuromagnetic studies of musical training effects on auditory-motor functions

Bernhard Ross, Fujioka Takako, Ween Jon, Alain Claude, Stuss Donald

• By providing music-supported training to stroke rehabilitation treatment, we shall reproduce and evaluate behavioural improvements. We will examine changes in cortical and muscle activities and integrity of motions before, throughout, and after the training. These physiological and behavioural data will tell how much the music-supported training can benefit motor rehabilitation. At the same time we shall examine healthy age-matched subjects for potential benefits in cognitive and motor functions. We use MEG recording when the subjects perform simple auditory or motor tasks which will be overlayed on an individual's MRI (listening or tapping to auditory beats, or passively perceiving somatosensory stimulation). The physiological indices (evoked responses and accompanying oscillatory activities) are usually sensitive to yield differences within subject across multiple measurements, thus suitable for assessing training-induced changes.
  

Magnetoencephalography as a possible diagnostic tool for traumatic brain injury: Cortical oscillations during retrieval from working memory

Bernhard Ross

• Mild head injury, concussion or ‘mild traumatic brain injury’ is an important public health concern with an estimated annual incident rate of 150, 000 cases in Canada. About 15-30% of mild traumatic brain injury cases will have persistent physical, emotional, and cognitive symptoms, referred to as ‘postconcussion symptoms’ over months and years following the injury. The analysis of electromagnetic neural activity is a sensitive tool, which can reveal abnormal brain function. My novel approach is to the analyse specific brain activity related to cognitive processing, which may be impaired after mild traumatic brain injury.

Improved characterization of human somatosensory cortex using simultaneous vibro-tactile stimulation of multiple digits

Bernhard Ross, Shahab Jamali Gharetape

• Tactile sensation is encoded in the primary somatosensory cortex in topographical maps accordingly to the body surface. This topographical representation can be modified as the result of training and experience. This brain plasticity results from newly expressed or strengthened synaptic connections. The effect can be measured in humans noninvasively using magnetoencephalography (MEG) as increased activation, or larger activated area on the cortical surface. Brain plasticity is an important factor for successful recovery from a stroke. We shall develop a new method for objectively monitoring of plastic reorganization in somatosensory cortex by measuring the size of the somatotopic hand area as indicated by the distance between finger representation.
  

Auditory cortex activation indicating audiovisual integration during listening and reading the speakers lips

Bernhard Ross, Hao Luo

• Simultaneous use of visual and auditory information when listening and seeing the speaker’s lips results in better speech understanding than listening alone. Both normal-hearing and hearing impaired listeners benefit from lipreading. Training lipreading potentially facilitates compensatory mechanisms to overcome communication deficits, which especially the elderly population experiences in noisy environments. However, the neurobiological basis of lipreading is widely unknown. Therefore, we shall investigate the effects of lipreading on auditory evoked and oscillatory cortical activity. We shall record brain activity with whole head magnetoencephalography (MEG) and localize underlying sources in auditory, visual, and multi-sensory cortices. Source activity in those identified areas will be analyzed with respect to various stimulus conditions This method will serve as an objective tool for assessing functional changes during audiovisual training and thus should help to develop efficient training programs. Moreover, we shall gain the basic knowledge about human cross-modal sensory processing.

Functional magnetic resonance imaging (fMRI) and magnetoencephalography (MEG) in human somatosensory cortex

Michael Marxen, Tara Dawon, Tim Bardouille, Bernhard Ross, Fred Tam, Simon Graham

• Motivation: Stroke is one of the most significant causes of impaired brain function. Non-invasive imaging techniques allow the mapping of brain activity in space and time with great potential for a better understanding of normal brain functions and their impairments. However, all non-invasive techniques image brain activity indirectly. Functional magnetic resonance imaging (fMRI) is sensitive to changes in blood flow and oxygenation following neuronal activation. Magnetoencephalography (MEG), in comparison, measures the very small magnetic fields outside of the skull generated by neuronal activity. Both fMRI and MEG will be used in conjunction in this study to develop models of neuronal activity within the brain consistent with the spatiotemporal signals obtained with both modalities.

Neuroimaging studies of auditory perception and attention

Sylvain Moreno, Ellen Bialystok Claude Alain

• Bilinguals have been shown to perform better than monolinguals in executive function tasks involving conflict (for a review, see Bialystok, 2001). These findings have been attributed to bilinguals' need to switch constantly between their two languages and inhibit interference from the other language. Frequent recruitment of these processes forces bilinguals to develop executive function skills differently than monolinguals. Research with children has shown that bilinguals performed better than monolinguals in executive function tasks (Bialystok et al, 2004; 2005). Our project is to test children who were either English monolingual or English bilingual while they performed a control task.

What is Magnetoencephalography (MEG)

Your Brain is a Magnet?

When you perform any activity, different areas of your brain communicate with each other through electrical impulses. These impulses can also be thought of as electric currents. The famous physicists Maxwell and Faraday showed that any current will generate electric and magnetic fields. Thus, when your brain is active it creates tiny magnetic fields inside and around your head. This goes on all the time - when you are walking, talking, or even sleeping - but the fields are very small, so we don't notice them. For comparison, the ticking of an analog clock generates a magnetic field which is one million times larger! Our scientists are very interested in determining which areas of your brain are working while you perform different tasks. This is where Magnetoencephalography (MEG) comes in. As explained, we can think of patterns of brain activity as a number of sources of electro-magnetic fields. MEG allows us to measure the magnetic fields outside of your head. MEG is a non-invasive and passive way to measure the magnetic fields that your brain generates naturally. This method is non-invasive because it does not require making measurements inside your body. It is passive because it simply measures a signal that your brain generates, and does not act upon your body in any way. This method is used in hospitals and medical centers, is very low-risk, and has no known short or long term side effects.

For What Are We Looking?

The study of pictures of brain activity is a discipline known as Neuroimaging. In general, to generate a neuroimage, a person is placed within an imaging device (for example, MEG or MRI), and asked to observe some visual, auditory, or tactile stimulus. The person may be asked to perform a task, to think about the stimulus, or to do nothing. In some cases, the person is simply required to go to sleep! At our site, the magnetic field around the head is recorded at 151 locations at speeds up to 2500 samples per second. These 151 sets of magnetic field information (MEG data) are put through some mathematical modelling to estimate the location of the activity within the brain.

In the simplest cases, we may be trying to locate the brain centres associated with perceiving different types of objects with our eyes and ears, or by touch. More complex information processing such as melody and language can also be explored. Furthermore, we can look at which regions of the brain are involved in decision making, emotion, learning, and more.

Is MEG the Same as MRI?

Magnetic Resonance Imaging (MRI) is a much more well-known type of neuroimaging method. Basically, this method generates a 3-D picture of the density of brain matter. In essence, it is like removing the skull, and looking directly at the brain (as an X-ray allows us to look at bone structure under the skin). In order to achieve this, the person's upper body is placed in the centre of a large magnet. The magnet is rotated around the body and we observe the manner in which brain matter interacts with this large changing magnetic field. This is an "active" form of imaging, since we must apply a force on the person being measured.

In many ways, MEG is the opposite of MRI. Rather than applying a magnetic field to the brain and observing its effects, MEG measures naturally occuring magnetic fields generated by the brain. An MRI image gives us information about structure of brain matter, and sometimes how the blood-oxygen level of brain tissue changes over time. From these changes in blood-oxygen level, we can determine where blood flow changes are occuring in the brain. However, MEG allows us to localise the electrical impulses of brain activity directly. Thus, in many ways, MEG and MRI are complimentary forms of neuroimaging. The information about the structure of an individual's brain (obtained by MRI) can be combined with the brain activity location information (obtained by MEG) to generate a picture of which part of the brain is responsible for a given task.

So Who Makes These Machines Anyway?

The Rotman Research Institute MEG device is designed, manufactured, and maintained by CTF Systems Inc. CTF is a Canadian company based in Port Coquitlam, British Columbia. The device is most often and most accurately described as a "very large hair-dryer". A person sits on a adjustable hydraulic chair. The bottom of the device is shaped like the inside of a helmet. This is where the person's head is situated. One hundred and fifty-one magnetic field sensors are contained within the helmet. The electronic equipment which measures and amplifies the magnetic sensor information is contained in a large dewar above the helmet which holds almost 100L of Liquid Helium.

In order to measure the miniscule magnetic fields generated by the brain, the equipment in the dewar must be kept at very low temperatures (about -269 degrees Celsius). Helium is always at this temperature in its liquid state, so the dewar is filled with Liquid Helium to keep the electronic equipment cold. Because of the cryogenic design of the dewar, the inside of the dewar is only four degrees above absolute zero, but the outside of the dewar is quite comfortable to touch.

MEG Links

Distributors

• VSM MedTech Ltd. - MEG system designers based in British Columbia, Canada - charge to 737201830 (MEG Operations)

• Elekta - MEG system designers


• Vitalaire Healthcare - 905-595-0170 to order Medical Air and cylinders of gas - charge to 737201830 (MEG Operations)