Calcium Sensors for Better Brain Imaging
Using fMRI, functional magnetic resonance imaging, to create colorful maps of brain activity has pervaded almost every area of neuroscience research, not to mention the fledgling field of neuromarketing. Conventional fMRI, though, has significant limitations in its spatial resolution. We recently reported on some advances in high resolution fMRI systems as well as high-res PET scanners. Now, according to an article in the MIT Technology Review, Tracking Information Flow in the Brain, nano-scale calcium sensors may eventually provide far greater resolution by tracking cell-to-cell communications in the brain.
Alan Jasanoff and his team at the Francis Bitter Magnet Lab and McGovern Institute of Brain Research have found that tracking calcium, a key messenger in the brain, may be a more precise way of measuring neural activity, compared with current imaging techniques, such as traditional functional magnetic resonance imaging (fMRI).
…fMRI, as it is used today, has a major drawback: it measures blood flow, or hemodynamics, which is an indirect measure of neural cell activity. “It turns out hemodynamics basically introduces a delay of five seconds,” says Jasanoff. “It keeps you from being able to detect fast variation [in neural activity].” Since neurons typically fire on the order of milliseconds, current fMRI techniques provide only a rough estimate of what the brain is doing at any given moment. FMRI scans also have a relatively low spatial resolution, measuring activity in areas of 100 microns, a volume that typically contains 10,000 neurons, each with varying activation patterns. Efforts to fine-tune fMRI have focused on developing stronger magnets and a better understanding of blood flow and its relationship to brain activity.
But Jasanoff believes there’s a better, more precise way of tracking neural activity. He and his team are looking at calcium as a direct measure of neuronal firing. When a neuron sends an electrical impulse to another neuron, calcium-specific channels in the neuron’s membrane instantaneously open up, letting calcium flow into the cell. “It’s a very dramatic signal change,” says Jasanoff.
The actual tools to apply this technology on actual subjects remains to be developed. Nevertheless, both neuroscientists and neuromarketers can be encouraged that there is yet another technology with the potential to greatly enhance our understanding of brain activity. In his book, The Singularity is Near, Ray Kurzweil predicted an exponential improvement in spatial and temporal resolution in brain imaging. With the plethora of different approaches to better imaging that are under development, Kurzweil’s prediction may prove to be one of the most achievable in a book filled with aggressive extrapolation of exponential trends.