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An elephant walks into the room, and you will surely have a reaction of some kind. Depending, perhaps, on your relationship with elephants, you may choose to stay and feed him peanuts or you may run in fear.

One way or another it is an event in response to which no human brain is likely to be quiescent. But, in fact, the brain is always saying, in effect, “Ah, ha!” to the flood of stimuli – aural or visual, dramatic and not so dramatic – around us all the time. Such “Ah, ha!” moments are the brain's electrophysiological response to environmental stimuli, and it is a response that can be measured by researchers, and recorded as “event-related potentials” (ERPs).

Experts who spoke with Neurology Today say ERPs have potential for understanding neurobehavioral responses to external stimuli, with current or potential applications in education, medicine, and – most recently – in forensic science. Though not widely used clinically, ERPs have sometimes been used to help assess Alzheimer disease or even multiple sclerosis, Parkinson disease, and other conditions.

“ERP technology may be a powerful tool to study changes in brain-behavior relations and functions across the life span,” said neuropsychologist Spencer Kelly, PhD, Assistant Professor of Psychology and Neuroscience at Colgate University in Hamilton, NY.

“Research over the last century has demonstrated that the ERP can be used to effectively study both general and specific aspects of the organism's response to events in the environment. The ERP can also be used to study an individual's perceptions and decisions during tasks or following a learning situation.”


ERP technology uses electrodes placed on the scalp to study electrical brain waves emitted in response to specific stimuli at specific points in time. Brain waves can have a positive or negative voltage potential and are categorized according to their “latency,” or the amount of time that has elapsed from the occurrence of the stimuli.

Since the 1960s, the brain wave with a positive voltage potential occurring at a latency of 300 milliseconds – called the P300 brainwave – has emerged as especially important – as the brain's electrical signature indicating that it has recognized and taken note of something in the environment.

Neurologist Marc R. Nuwer, MD, PhD, Professor of Neurology at the University of California-Los Angeles, said the P300 ERP has been of most interest to researchers seeking to study the process by which the brain recognizes, remembers, or coordinates tasks that involve visual or motor coordination.

More rarely, ERP technology has been used clinically to aid in the assessment of Alzheimer dementia. Dr. Nuwer explained that the timing of the P300 brain wave to rise to its peak is slow in Alzheimer disease, while the time to peak does not slow in persons with benign age-related memory problems.


Dr. Lawrence Farwell, shown here, tests brain fingerprinting – using event related potentials – with model D. Turner.

Other studies measuring the amplitude of the P300 brain wave in assessment of Alzheimer disease – as opposed to timing – appear to be less successful. In a study appearing in the March 2004 Journal of the International Neuropsychological Society, researchers from the Center for Research in Human Development at Concordia University in Montreal, Canada, investigated the sensitivity of the P300 ERP to memory function in patients with dementia of the Alzheimer type (DAT), those with mild cognitive impairment (MCI), and normal elderly controls.

The study also evaluated how well measures of delayed verbal memory performance and measures of hippocampal volume distinguished the three study groups. Fourteen patients with DAT, 16 with MCI, and 15 age- and education-matched controls were tested.

The researchers found that P300 amplitude was reduced in DAT subjects, but did not distinguish between MCI and control subjects. Moreover, delayed verbal memory performance was found to best discriminate DAT from MCI and control subjects, while delayed verbal memory performance and hippocampal volume best discriminated MCI subjects from controls.

“These results support the utility of neuropsychological and neuroanatomical measures in diagnosing dementia and do not support the notion that P300 amplitude is sensitive to mild memory dysfunction …,” the researchers wrote.


One area where ERP technology has potential is the neuropsychological study of early infant and child language development. Dr. Kelly was co-author of a 2001 paper in Learning Disability Quarterly with researchers Dennis L. Molfese, PhD, and Victoria J. Molfese, PhD, on the use of brain electrophysiology techniques to study language.

That paper described studies showing that ERP technology could be used in infants as young as a day old to successfully predict learning difficulties years later when the infants were school children.

For instance, Dr. Molfese recorded ERPs in 48 infants within 36 hours of birth, elicited in response to spoken syllables. The same group – tested again within two weeks of their eighth birthday using the same ERP procedure as well as a variety of language and cognitive measures – included 17 dyslexics, seven poor readers, and 24 controls.

Remarkably, analysis of the latency and amplitude of ERPs recorded at infancy successfully distinguished all seven of the poor readers, 13 of the 17 dyslexics, and 19 of the 24 controls.

“If language interventions designed to prevent reading problems were attempted shortly after birth on the basis of these data, 22 of 24 children in need of intervention at eight years of age could have been targeted to receive intervention beginning at birth while only 5 of 24 children who did not require intervention would have received it,” Drs. Molfese and Kelly wrote in the 2001 paper.

“Thus, ERP measures shortly after birth demonstrate high accuracy, identifying nearly 92 percent of children in need of intervention by eight years and general relatively few false positives in predicting reading problems eight years later.”

Dr. Kelly's own research has used ERPs to look at how people integrate verbal and non-verbal information in their understanding of language. And he has found that verbal information is only a component of a larger and more complex system, involving a variety of other contextual cues including hand and facial gestures by which the brain processes and understands language – a finding that he said has important implications for education.

Dr. Kelly believes the technology used by Dr. Molfese to study ERPs in infants can be adopted for use with school age children to tailor teaching to the needs of individual students.

“The science is real,” Dr. Kelly told Neurology Today. “I don't think this is science fiction. In the near future, this technology could be available to schools to distinguish and treat children with language disorders and other learning problems.”


ERP technology is also being considered in forensic cases. Brain Fingerprinting Laboratories, Inc., a Seattle-based company, has generated a lot of attention in the press – with stories on CBS's “60 Minutes” and Time magazine – for its claims that the technology can be used as a piece of objectively quantifiable evidence – a “footprint in the brain” – that can distinguish the guilty from the innocent or identify a member of a terrorist cell.

Lawrence Farwell, PhD, President and Chief Executive Officer of Brain Fingerprinting Laboratories, said the company's technology has been accurate in tests funded by the CIA and in tests for the FBI and the US Navy. Brain fingerprinting testing is admissible in court as scientific evidence in the state of Iowa, and Dr. Farwell believes it will be ruled as admissible evidence in other states.

What brain fingerprinting does, he claims in a Q-and-A on the company Web site – – is provide “scientific evidence in answer to a scientific question: Does a person have particular crime-relevant information stored in his brain, or not?”


Dr. Spencer Kelly: “ERP technology may be a powerful tool to study changes in brain-behavior relations and functions across the life span.”

Dr. Farwell explained that knowledge of the details of a crime is something only the perpetrator of that crime retains, an “Ah, ha!” moment stored in the brain of a criminal not unlike the memory of the elephant that walks in your room – something he is not likely to forget.

In ERP testing, suspects in a criminal investigation are shown words or pictures that may be relevant to the crime under investigation – the name or picture of the crime location, for example, or a picture or description of a weapon. A subject who has knowledge of the information being tested will produce a recordable ERP, while a subject who lacks this record in his brain will not.

Moreover, Dr. Farwell said he has refined the measurement of P300 ERPs to include what he believes is a negative peak that occurs in addition to the positive peak of a P300 brain wave. This more refined measurement, which he calls the P300 MERMER (memory and encoding related multifaceted electro-encephalographic response), further distinguishes the neuro-electrical response of a perpetrator from that of an innocent person when confronted with details of the crime.


“The science about the P300 itself is well established,” said Dr. Nuwer. “Regarding brain fingerprinting, Dr. Farwell has a reasonable chance at having this actually work out the way he says it will. I will stay tuned, but I am not going to bet on it until I see it independently corroborated.”

“The idea behind it is well grounded in scientific ERP research,” agreed Dr. Kelly. But he noted that the effects seen in tests may not always generalize to actual situations, and the technology could produce false positives if images of a crime scene – reminiscent, say, of something one has seen in a movie – evoke the same positive response in an innocent person.

Dr. Farwell is quick to acknowledge that brain fingerprinting does not solve crimes; rather, it adds one element of objective data to the adjudicative process.

Dr. Farwell added: ''One thing I don't claim is that brain fingerprinting tells us what to look for. I don't say on the basis of this technology that this guy is a murderer or is innocent. What I can say is that this brain has particular information and this brain does not.

“The fundamental difference between a perpetrator and an innocent person is that the perpetrator, having committed the crime, has those details stored in his brain and the innocent person does not. Neuroscience has progressed to the point where we can objectively detect that difference.”


✓ The article discusses the potential application of event related potentials – an electrophysiological response to environmental stimuli – in education, neurology, and forensic science.


• Molfese DL, Molfese VJ, Kelly S. The use of brain electrophysiology techniques to study language: A basic guide for the beginning consumer of electrophysiology information. Learning Disab Q 2001;24(3):177–188.
    • Phillips NA, Chertkow H, Leblanc MM. Functional and anatomical memory indices in patients with or at risk for Alzheimer's disease. J Int Neuropsychol Soc 2004;10(2):200–210.