Mapping neuron activity in live animals is a key step for researchers,
But one significant hurdle to date has been successfully applying the technique to live animals, and using it to visualize the neural processes and networks involved when a living subject interacts with its environment and makes decisions.
The answer could be a lightweight and miniaturized microscopy platform developed by California-basedInscopix, which has successfully been used in trials on rodent animal models and could ultimately be used on humans.
Now marketed as the nVista system, the platform also demonstrates that the time is right for greater industrial involvement in ongoing neuroscience research, according to Inscopix founder and CEO Kunal Ghosh.
"Epifluorescence is a workhorse microscopy modality in the field, and has proven to be ideal at recording activity across large numbers of neurons, so that researchers can better understand how the brain works," he commented. "The challenge has always been that epifluorescence platforms to date are certainly not amenable to being used for imaging in an animal model, such as a freely behaving rodent."
Ghosh was part of a project at Stanford University addressing that problem, and which published its solution in the journal Nature Methods in 2011. The team designed a working integrated microscopy platform contained in a housing of around 2.4 cm3, with a mass of less than 2 grams. Its compact optical system included a blue LED mounted on a customized 6 mm2 PCB, along with a 640x480 pixel CMOS sensor.
"Designing an integrated microscope of a suitable size and weight for live-animal experiments required miniaturization of a range of system elements, leveraging advances in micro-optics, solid state sensors and lens technology," said Ghosh. "And it was remarkable how advances in the consumer space were the key to making this possible, now that technologies around LEDs and image sensors have become ubiquitous in cell phones and mobile platforms."
Technical advances and economies of scale have led to drastic reductions in the sizes of these components, alongside significant enhancements in performance for mass-market applications - all of which Inscopix, spun-out from Stanford in 2011, has been able to exploit when bringing its integrated microscope platform to market.
Image restoration techniques
"At Inscopix we are interested in enabling high throughput in vivo assays," Ghosh said. "These are important for pharmaceutical researchers examining the course of diseases in living animals, trying to understand how those diseases manifest themselves in autistic or depressed animal models. Today, scientists really have no ideal tool for that, and no ability to look into the living brain while the subject is as normal as it can be other than having the disease."
At present the most common animal models are rodents, although some groups are testing neuronal imaging in songbirds to examine learning and vocalization. Ghosh describes avian studies as being something of a niche, but the guiding principle behind nVista has been to develop a system suitable for as wide a variety of models as possible.
"Inscopix has a long-term perspective of enabling a platform suitable for imaging and recording large scale neural circuit activity that is agnostic of the animal model," he commented. "Rodent research in probably the largest sector today, but the intention is to transfer this system into higher order animal models, and eventually into humans. I don't think that's inconceivable."
Data processing plays its part in the kind of large-scale neuronal imaging that Inscopix aims to enable - the company also markets Mosaic, an analysis suite optimized for processing large-scale calcium imaging data sets of the kind captured by nVista.
"One of our revelations was that we did not necessarily have to design highly complex optics, but could use less sophisticated optical design that might not approach the best optics-limited resolution, and then get to the finer structure through signal processing," commented Ghosh. "And in our platform we can develop these image restoration techniques very precisely, because we know the entire transfer function of the device."
One consequence is that the nVista device has a modest optical magnification of ~5.0x, effectively circumventing the traditional trade-off between magnification level, resolution, and field of view, as Ghosh noted.
"In our design, a low magnification can still yield a high resolution, by taking advantage of modern CMOS sensor technology and its small pixels. If the sensor is close to the specimen plane, a low magnification can be enough."
Industry to the forefront
But Ghosh also commented that for this to happen successfully, industrial photonics developers would need to become more involved than they have been to date.
"The parallels with genomics are quite striking, but what's currently missing - perhaps understandably since the field is young - is the industrial dimension," he said. "So far neuroscience has been a component-driven industry, and even the few systems players that do exist have been somewhat divorced from the science and its applications. It has been left to researchers to figure out how to use the components, in order to carry out meaningful science."
A solution would be industrial developers integrating across the various workflows involved, much as Illumina did in the genomics field - a crucial step towards turning gene sequencing into an affordable, even routine, operation.
"This philosophy has to date been missing from neuroscience as a field," said Ghosh. "Now is the time for larger photonics companies to help build the ecosystem; to start engaging with the companies in this space and also address it within their internal R&D programs. This will be a long term strategic play - it took a decade for a genomics industry to form, with photonics equally at the heart of that effort - but my fear is that at the moment the photonics industry is missing the opportunity to help enable and catalyze the revolution that's at hand. Ultimately, they will benefit."
Posted by Tim Hayes - 03.30.2016