There's been a lot of hype coming out of Silicon Valley in recent months about technology that can meld the human brain with machines. But how will this tech help society, and which companies are leading the charge?

Tesla and SpaceX CEO Elon Musk made waves in March when he announced his latest venture, Neuralink, which will design so-called brain-computer interfaces (BCIs). Initially, the BCIs will be used for medical research, but the ultimate goal is to prevent humans from becoming obsolete, by enabling people to merge with artificial intelligence.

While these may seem like lofty goals, Musk is not the only one who's trying to bring humans closer to machines. Here are five companies that have doubled down on hacking the brain. [Super-Intelligent Machines: 7 Robotic Futures]

Neuralink

According to Musk, the main barrier to human-machine cooperation is communication "bandwidth."

This means that using a touch screen or a keyboard is a slow way to communicate with a computer. Musk's new venture aims to create a direct "high-bandwidth" link between the human brain and machines.

What that system would actually look like is not entirely clear yet. Words like "neural lace" and "neural dust" have been bandied about, but all that has really been revealed is a business model. Neuralink has been registered as a medical research company, and Musk said the firm will produce a product to help people with severe brain injuries within four years.

This will lay the groundwork for developing BCIs for healthy people, thus enabling humans to communicate by "consensual telepathy," which could be ready within five years, Musk said. Some scientists, particularly those in the neuroscience community, are skeptical of Musk's ambitious plans.

Facebook

Not to be outdone, just a few weeks after Musk launched Neuralink, Facebook announced that it is working on a way to let people type with their thoughts.

The goal is to build a device that would allow people to "type" up to 100 words per minute, according to Regina Dugan, head of the company's secretive Building 8 research group. Dugan also suggested that the device could work as a "brain mouse" for augmented reality (AR), removing the need to track hand movements to control cursors, The Verge reported.

Facebook has also been light on the details of its plans. The company has said it does not think implants are feasible in the long term, so it's focusing on developing some kind of cap that could track brain activity noninvasively, most likely using optical imaging.

But this technology doesn't exist yet. So, in the meantime, Facebook said that, within two years, it plans to create a prototype medical implant that would pave the way for future devices.

Kernel

Musk wasn't the first wealthy entrepreneur to dive into the underdeveloped neurotechnology space. Last August, Bryan Johnson, founder of the online payments company Braintree, invested $100 million into the startup called Kernel.

The company's initial goal was to develop a chip that could record memories and redeliver them to the brain, based on research by Theodore Berger, a biomedical engineer and neuroscientist at the University of Southern California. But six months later, the two parted ways due to the long timescales involved, reported MIT Technology Review, and the company is now focusing on technology similar to Neuralink.

Kernel plans to build a flexible platform for recording and stimulating neurons, with the goal of treating diseases such as depression and Alzheimer's. But like Musk, Johnson is not afraid to discuss the prospect of using the technology to augment human abilities and merge with machines.

"There's this huge potential to co-evolve with our technology," Johnson told CNBC.

Emotiv

Unlike some other companies in this burgeoning industry, Emotiv actually makes products — electroencephalography headsets that record brain activity noninvasively.

The technology is lower fidelity than the kinds of neural implants other companies, such as Neuralink, are considering, but it is more established. The company has a research-grade device, called EPOC+, which sells for $799. But it also produces a more consumer-oriented headset, called Insight, which retails for $299.

Emotiv also produces a variety of software products that allow users to visualize their brain activity in 3D; measure their brain fitness; and even control drones, robots and video games, reported The Daily Dot. The company was selected to be part of the Disney Accelerator program in 2015, with the aim of creating a "wearable for the brain."

DARPA

Although it's not a company itself, the U.S. military's Defense Advanced Research Projects Agency announced a $60 million program last year to develop an implantable neural interface in collaboration with a consortium of private companies.

The project, which is a part of former President Barack Obama's BRAIN Initiative, is ambitious. DARPA wants a device that can record 1 million neurons simultaneously and stimulate at least 100,000 neurons in the brain. DARPA also wants the device to be wireless, the size of a nickel and ready in four years, which is an incredibly aggressive deadline, according to MIT Technology Review.

Potential applications include compensating for sight or hearing problems because the device could feed digital auditory or visual information directly into the brain. The exact technological approach is unclear at this stage, but the project has the heft of some major engineering giants, such as Qualcomm, behind it, Quartz reported.

Original article on Live Science.