Traumatic brain injury (TBI) is a serious cause of disability in the United States. Diagnosed in more than 270,000 military servicemembers since 2000 and affecting an estimated 1.7 million U.S. civilians each year1, TBI frequently results in an impaired ability to retrieve memories formed prior to injury and a reduced capacity to form or retain new memories following injury. Despite the scale of the problem, few effective therapies currently exist to mitigate the long-term consequences of TBI on memory. Through the Restoring Active Memory (RAM) program, DARPA seeks to accelerate the development of technology able to address this public health challenge and help servicemembers and others overcome memory deficits by developing new neuroprosthetics to bridge gaps in the injured brain.
The end goal of RAM is to develop and test a wireless, fully implantable neural-interface medical device for human clinical use, but a number of significant advances will be targeted on the way to achieving that goal. To start, DARPA will support the development of multi-scale computational models with high spatial and temporal resolution that describe how neurons code declarative memories—those well-defined parcels of knowledge that can be consciously recalled and described in words, such as events, times, and places. Researchers will also explore new methods for analysis and decoding of neural signals to understand how targeted stimulation might be applied to help the brain reestablish an ability to encode new memories following brain injury. “Encoding” refers to the process by which newly learned information is attended to and processed by the brain when first encountered.
Building on this foundational work, researchers will attempt to integrate the computational models developed under RAM into new, implantable, closed-loop systems able to deliver targeted neural stimulation that may ultimately help restore memory function. These studies will involve volunteers living with deficits in the encoding and/or retrieval of declarative memories and/or volunteers undergoing neurosurgery for other neurological conditions.
In addition to human clinical efforts, RAM will support animal studies to advance the state-of-the-art of quantitative models that account for the encoding and retrieval of complex memories and memory attributes, including their hierarchical associations with one another. This work will also seek to identify any characteristic neural and behavioral correlates of memories facilitated by therapeutic devices.
RAM and related DARPA neuroscience efforts are informed by members of an independent Ethical, Legal, and Social Implications (ELSI) panel. Communications with ELSI panelists supplement the oversight provided by institutional review boards that govern human clinical studies and animal use.
RAM is part of a broader portfolio of programs within DARPA that support President Obama’s brain initiative.
The goal of the RAM Replay program is to develop new closed-loop, non-invasive systems that leverage the role of neural “replay” in the formation and recall of memory to help individuals better remember specific episodic events and learned skills. The RAM Replay program aims to non-invasively detect, model, and facilitate real-time correlates of replay in humans, leveraging not only neurophysiology, but also other factors including physiological state and external elements in the surrounding environment. This 24-month fundamental research program is designed to develop novel intervention strategies to help investigators determine not only which neural, physiological, and environmental components matter for memory formation and recall, but also how much they matter. To ensure real-world relevance, RAM Replay researchers will validate their assessments and intervention strategies through performance on DoD-relevant tasks, rather than relying on conventional behavioral paradigms commonly used to assess memory in laboratory settings. Using the new knowledge and paradigms for assessing memory formation and recall, the program seeks to improve performance of complex skills by healthy humans.
1Source: Faul M, Xu L, Wald MM, Coronado VG. Traumatic Brain Injury in the United States: Emergency Department Visits, Hospitalizations and Deaths 2002–2006. Atlanta (GA): Centers for Disease Control and Prevention, National Center for Injury Prevention and Control; 2010.
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