{"id":267825,"date":"2019-03-12T17:33:23","date_gmt":"2019-03-12T21:33:23","guid":{"rendered":"https:\/\/news.harvard.edu\/gazette\/?p=267825"},"modified":"2023-11-08T20:39:48","modified_gmt":"2023-11-09T01:39:48","slug":"harvard-neuronlike-brain-implants-may-help-treat-disease-mental-illness","status":"publish","type":"post","link":"https:\/\/news.harvard.edu\/gazette\/story\/2019\/03\/harvard-neuronlike-brain-implants-may-help-treat-disease-mental-illness\/","title":{"rendered":"Sensors go undercover to outsmart the brain"},"content":{"rendered":"\n\t
\"Charles

Charles Lieber and his colleagues published a paper on neural probes that are less detectable by the human brain and may be more effective in treatment.<\/p>

Rose Lincoln\/Harvard file photo<\/p><\/figcaption><\/figure>\n\n\t

\n\t\t\t\n\t\t\tScience & Tech\t\t<\/a>\n\t\t\n\t\t

\n\t\tSensors go undercover to outsmart the brain\t<\/h1>\n\n\t\n\t\t\t<\/div>\n\t\t\n\t
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\n\t\tCaitlin McDermott-Murphy\t<\/p>\n\t\t\t

\n\t\t\tHarvard Correspondent\t\t<\/p>\n\t\t\t\t\t<\/address>\n\t\t<\/div>\n\n\t\t

\n\t\t\tDevices used in mice offer a more accurate way to study the brain, potential treatment for disease, damage, mental illness\t\t<\/h2>\n\t\t\n<\/header>\n\n\n\n
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Like a well-guarded fortress, the human brain attacks intruders on sight. Foreign objects, including neural probes used to study and treat the brain, do not last long. But now, researchers have designed a probe that looks, acts, and feels so much like a real neuron that the brain cannot identify it as an imposter. According to Charles M. Lieber<\/a>, this breakthrough \u201cliterally blurs the ever-present and clear dissimilarities in properties between man-made and living systems\u201d \u2014 in other words, between human and machine.<\/p>\n

Lieber, the Joshua and Beth Friedman University Professor at Harvard, and his lab members are authors on a new paper published in Nature Materials that presents a bioinspired design for neural probes. Implanted directly into brain tissue, the probes are designed to survive as long as possible in the organ\u2019s warm, humid, inhospitable environment. Sensors hidden within protective casings send data back to researchers about how and when individual neurons fire and neural circuits communicate. This information could help scientists treat neurological disorders like Parkinson\u2019s, reverse neural decay from Alzheimer\u2019s and aging, and even enhance cognitive capabilities.<\/p>\n

But current implants cannot trick the brain \u2014 they cause a foreign-body response. Large and stiff compared with real neurons and neural tissue, traditional implants have two major impediments to sustained monitoring. During the initial placement in brain tissue \u2014 which usually requires surgery \u2014 neurons flee the impacted area. Previous studies have shown that the brain\u2019s immune system senses the foreign object and gets to work, causing inflammation and scar tissue to isolate the device. Even if they can capture signals beyond the scar tissue, rigid probes can shift position and end up replacing one neural signal for another, closer one.<\/p>\n

\u201cThis will ultimately make the recorded signal unstable,\u201d said first author Xiao Yang, a fourth-year graduate student in the Lieber lab. She moved her cupped hands together, then apart, then together again as she explained how she and her team built a probe that inspires a negligible immune response, records neural signals within a day post-implantation, and may even encourage tissue regeneration.<\/p>\n

\u201cThe stereotype of the neural probe is that they are giant compared to the neuron targets that they\u2019re interrogating,\u201d she explained. \u201cBut in our case, they are essentially the same.\u201d The team\u2019s probe mimics three features that have previously been impossible to achieve in a lab: the shape, size, and flexibility of an actual neuron.<\/p>\n\r\n

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Neuronlike electronics (red) mimic the shape, size, and flexibility of neurons (green), enabling them to act in concert with native brain tissue.<\/p><\/figcaption>\r\n\t\t\t<\/div>\n\t\t\t\n\t\t\t\t\t\n\t\t\t

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Neurons look a bit like tadpoles, with round \u201cheads\u201d \u2014 actually the soma, or cell body \u2014 and long, flexible tails. So Yang and her colleagues created a minuscule compartment the same size as the neuron\u2019s soma to house the\u00adir metal recording electrode. Its wires interconnect \u2014 which attaches to input\/output pads positioned on the outside of the mouse\u2019s skull to collect and store data from individual sensors \u2014 snake through an ultra-flexible polymer \u201ctail,\u201d resembling the neuron\u2019s neurite. According to Yang, their neuron-like electronics (NeuEs) are \u201cfive to 20 times more flexible than the most flexible probes reported to date.\u201d The ones they bested were their own mesh electronics<\/a>, developed last year.<\/p>\n

The width of a typical neuron soma is about the same as a very fine strand of hair (20 microns), and the \u201ctail\u201d can be 10 to 20 times finer. Measuring the same or even thinner widths, the neuron-like electronic is the smallest probe yet. To craft their microscopic tools, Yang and her colleagues relied on photolithography, which uses light to transfer a pattern onto material and constructs the probe\u2019s four distinct layers of metal and polymer one at a time.<\/p>\n

Once the devices are built, the team uses a syringe to inject 16 of their cell imitators into the hippocampus region \u2014 chosen for its central role in learning, memory, and aging \u2014 of a mouse brain. There, the NeuEs unfold to create a porous web, imitating the brain\u2019s crisscrossing neural network.<\/p>\n

Bigger, less-flexible probes \u2014 the next-smallest, created by the same team, are five to 50 times larger than the NeuEs \u2014 displace native cells from their territory and can disrupt the neural circuits that researchers are trying to study. Yang\u2019s probes allow cells to integrate fully, and take up less than 1 percent of the volume where they are implanted. Starting from as early as a day to months later, real neurons integrate with the artificial network, forming a harmonious hybrid. This assimilation explains why the team achieved stable data collection even months post-implantation. They did not lose even one neuron signal. Instead, they actually gained some.<\/p>\n\r\n

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