One of the most significant trends in treating neurological diseases and disorders in recent years has been the increasing acceptance of the phenomenon of cortical plasticity. This refers to the inherent capability of the central nervous system to modify existing connections, making them either stronger or weaker, and to form new connections.
Cortical plasticity has been put to use first to treat stroke, but applications in a number of other areas are on the horizon. One of the foremost researchers in the field is Michael Merzenich at the W.M. Keck Center for Integrative Neuroscience at the University of California, San Francisco. In the 1970s and 80s, Merzenich headed one of the first research teams to develop a cochlear implant.
In 1996, Merzenich and colleague Paula Tolal at Rutgers University founded a company called Scientific Learning Corp., which has targeted language learning impaired children with a series of educational software and diagnostic tools. Merzenich and his colleagues discovered that many language learning impaired children were deficient at frequency discrimination of short-duration (under 50 ms) tones, a deficiency he traced to an area of auditory cortex.
The premise behind Scientific Learning’s intellectual property is that a training regimen of specific types of auditory stimuli can help overcome these deficiencies by progressively accentuating or expanding in time the troublesome frequency discrimination. The company has achieved positive results in tens of thousands of children with a training program as short as eight weeks.
Merzenich has recently formed a new company in San Francisco called Neuroscience Solutions, to address a more mature market, specifically older people. Neuroscience Solutions will license patents from Scientific Learning as it develops treatments for disorders such as Parkinson’s disease, dystonia, Alzheimer’s disease, and psychiatric disorders. Jeff Zimman, a San Francisco management and investment specialist, serves as president of the new firm. Merzenich said that he has investors lined up for the new venture, though he did not name them. Warburg Pincus was the lead investor in Scientific Learning.
Neuroscience Solutions has not announced specific products as yet, but it is likely that cortical plasticity will figure prominently in the mix. Merzenich believes that the market potential for cortical plasticity applications is at least as great as with advances in neuropharmacology and biotech approaches to treating disorders of the nervous system. He also believes that psychiatric disorders such as schizophrenia can be successfully treated with an intensive training program that targets destabilized neuronal processes.
There are several other firms and research institutions who are looking at cortical plasticity as a treatment for neurological diseases and disorders. Colorado-based Stroke Recovery Systems, Inc. is currently marketing a device called the NeuroMove 900 in the treatment of stroke. The device applies surface stimulation to muscles that are undergoing rehabilitation training whenever an integrated electromyographic electrode detects that the user is making an attempt to move the affected muscle. According to SRSI, this “neural re-education” process results in dramatic improvements in stroke rehabilitation. The NM 900 received FDA approval in 2001.
A number of research institutions, including the Alfred Mann Institute for Biomedical Engineering at the University of Southern California, are investigating “constraint-induced therapy,” which requires hemiplegic stroke patients to attempt to use the limb on the affected side, rather than relying on the unaffected limb.
And a host of neurostimulation and neural prostheses manufacturers, including NESS Ltd. of Israel and Vertis Neuroscience of Seattle, WA, are hoping to take advantage of cortical plasticity with their stimulation products targeted at the stroke market. NESS markets a series of orthosis-integrated surface stimulation devices.
Researchers collaborating with Vertis have reported promising results from studies with rats and primates who received cortical stimulation in conjunction with physical exercise after receiving stroke-like lesions. Moreover, several studies have shown that functional mapping of the cerebral cortex after training-induced improvements in cognitive and motor tasks confirms that distinct changes in the organization and mapping of cortical areas accompanies these improvements.
While it’s too early to say whether commercial efforts that rely primarily on training and re-education regimens will do better than firms incorporating cortical or neuromuscular stimulation, it is clear that as more is learned about plasticity in the central nervous system, prospects for restoring function to individuals with neurological diseases and disorders will be greatly enhanced.