Elsevier

International Congress Series

Volume 1226, January 2002, Pages 17-26
International Congress Series

Multimodality brain imaging

https://doi.org/10.1016/S0531-5131(01)00493-9Get rights and content

Abstract

To study human brain function noninvasively, a number of techniques have been developed. Each can be valuable, but see the function from only a selective point of view. Putting a number of techniques together can be synergistic. This principle is illustrated with two examples. Making finger-tapping movements at different frequencies leads to activation of the primary sensorimotor area (SM1) and supplementary motor area (SMA) as can be demonstrated with positron emission tomography (PET) and functional magnetic resonance imaging (fMRI). The time course of activity of these regions cannot be specified by neuroimaging nor can the dynamic interaction of these structures. EEG studies of power in specific frequency bands can show the timing of regional activation, and correlation studies can show the timing of interregional communication. In this situation, such studies show changes with each movement and different behavior at slow and fast rates, explaining the different behavior at different rates. In the no-go task of a go/no-go experiment, fMRI does not show the activation of SM1. SM1 activation is seen with EEG power changes; however, the pattern is similar to that seen with the go task. Transcranial magnetic stimulation (TMS) clarifies that the no-go task is associated with active inhibition. Each modality contributes to the final understanding.

Section snippets

Background: neuroimaging of self-paced movement

To introduce the methodology, the findings with self-paced movements will be reviewed. Functional neuroimaging studies with positron emission tomography (PET) and fMRI show increased metabolism mainly in three cortical areas with simple self-paced movements [1], [2]. PET using O-15 water measures regional cerebral blood flow; this is a reasonable measure since synaptic activity increases local metabolism and stimulates changes in perfusion. fMRI most commonly uses the BOLD technique which

Example 1: brain activity associated with movements at different frequencies

Work by Kunesch et al. [9] has demonstrated that manipulative serial hand movements show a clear distribution of their temporal characteristics into two distinct groups. When the hand was used as a sense organ during active touch, the finger movements across objects were restricted to a slow performance range below 2 Hz. In contrast, manual skills not associated with the collection of sensory information like handwriting, typing or pencil shading, were performed rapidly at frequencies close to

Example 2: motor cortex activity in a no-go task

The go/no-go task is a popular experimental design, for the study of reaction time and studies of cognitive function and the motor system. It is basically a two-choice reaction time experiment. Subjects wait for one of two stimuli and then either move or do not move depending on which it is. The issue to be discussed here is what happens in the motor cortex in the no-go situation. There are several possibilities, but the two most likely are that the cortex does just nothing, or that it is

Conclusion

These examples demonstrate that multimodal brain imaging is much better than the use of only a single modality. In fact, a single modality might be actively misleading. Regions of the brain can be active and not show with PET or fMRI. EEG findings can be similar for excitation and inhibition. Putting all the methods together is not easy, and further methodological development is required, but it is already apparent that the multimodal approach will be very helpful in understanding human brain

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