A Prosthesis to Fix Broken Memories

Neuroscience

By: Daniel Hass, 2nd year PhD candidate in the Neuroscience Graduate Program

ibm_human_brainThe Defense Advanced Research Projects Agency (DARPA) has been a major funding source for the development of unique and innovative technologies under its motto of “driving technological surprise.”  Some of DARPA’s current projects include designing bullets that can adjust their course in-flight, novel techniques to investigate brain function (see my previous post on CLARITY), and brain-controlled prosthetic limbs.

As if the line between reality and science fiction was not blurred enough, aid is now being given to researchers for the development of a prosthetic device that will improve the recall and formation of long-term memories.

This program is titled Restoring Active Memory (RAM) and is designed to help individuals who have suffered from traumatic brain injury that may have disrupted their ability to properly form and retrieve memories.  Normally, memory formation occurs in a region of the brain called the hippocampus, where brain circuits corresponding to sensations and thoughts stimulate brain cells in the dentate gyrus, CA3, and CA1 areas to form memories.  The specific groups of brain cells (neurons) that are stimulated are unique for each memory, and connect to the frontal cortex for storage as long term memories.

Memory retrieval is also believed to occur through a sequential activation of neurons that are spread out over the whole cerebral cortex.  However, in each of these cases, a memory signal cannot be formed or retrieved if the connections between these neurons forming a “circuit” are broken.  Traumatic brain injury may disrupt some of these circuits, and therefore some of the neurons in this circuit cannot be activated, resulting in difficulties forming and retrieving memories.

Screen Shot 2014-07-25 at 12.16.45 AMThe goal of RAM is to create an implantable device that can (1) read signals in one part of the brain corresponding to an earlier neuron in a memory circuit, (2) wirelessly transmit this input to another part of the brain past a break in the circuit corresponding to traumatic injury, and (3) stimulate neural activity for remembering a skill or event.  This setup will theoretically allow the brain to bypass damaged neural circuitry and reestablish normal function.

In theory, it sounds pretty easy, right?

Unfortunately, there are several major roadblocks to overcome first.  It is important that we understand the cellular and molecular basis of how memories and their components are stored in the brain.

Although we are familiar with many of the regions associated with establishing a memory, long-term memory formation and storage is not yet well understood.  One of the initiatives of the RAM project is to better understand long-term memory by constructing computational models of the connections in brain areas associated with memories in order to understand how the signals coming from this brain device should “look.”

Other roadblocks are logistical, such as engineering a device which will properly fit inside the skull and can properly mimic brain activity.  To overcome these hurdles, DARPA will be working with biotechnology companies such as NeuroPace to construct a device that fits these exacting parameters.

Though there are many difficulties that scientists will need to overcome for the development of a functional human memory prosthetic, proof of concept devices have already been made that restore function in disrupted somatosensory and motor pathways in rat brains.  While rat brains are not as complex as their human counterparts, DARPA funded research aims to test similar devices in human subjects that may directly benefit from the prosthetic.

This research will be carried out by teams at UCLA and the University of Pennsylvania, which will receive $47.5 million dollars over 4 years with funding being contingent upon reaching specific research milestones in three different areas devoted to computationally modeling long term memory in the brain, constructing a functional device that can be used in the human brain, and using the computational model and device to quantify and understand how neural activity over time results in specific long term memories.

Although the device was designed with traumatic brain injury in mind, it may also be able to assist with the treatment of symptoms in other disorders that damage memory recall such as epilepsy and Alzheimer’s disease, making this new prosthesis one to watch for in the near future.  If this project achieves such an astonishing goal within its projected timeline, there really won’t be a limit to the wonders that can be accomplished in even the next decade.

RAM project information and announcement:

http://www.darpa.mil/Our_Work/BTO/Programs/Restoring_Active_Memory_RAM.aspx

http://www.darpa.mil/NewsEvents/Releases/2014/07/09.aspx

Proof of concept for implantable wireless device for restoring brain function:

http://www.pnas.org/content/110/52/21177.long

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