updated 9/21/2009 3:58:49 PM ET 2009-09-21T19:58:49

The CIA's harsh interrogation program likely damaged the brain and memory functions of terrorist suspects, diminishing their physical ability to provide the detailed information the spy agency sought, according to a new scientific paper.

The paper by an Irish academic scrutinizes the harsh techniques used by the CIA under the Bush administration through the lens of neurobiology. Researchers concluded that the harsh methods were biologically counterproductive to eliciting quality information because prolonged stress harms the brain's ability to retain and recall information.

"Solid scientific evidence on how repeated and extreme stress and pain affect memory and executive functions (such as planning or forming intentions) suggests these techniques are unlikely to do anything other than the opposite of that intended by coercive or enhanced interrogation," according to the paper published Monday in the scientific journal Trends in Cognitive Sciences.

In the paper, Shane O'Mara, a professor at Ireland's Trinity College Institute of Neuroscience, wrote that the severe interrogation techniques appear based on "folk psychology" — a layman's idea of how the brain works as opposed to science-based understanding of memory and cognitive function.

O'Mara told The Associated Press on Monday he reviewed the scientific literature about the effect of stress on memory and brain function after reading descriptions of the CIA's Bush-era interrogation methods. The methods were detailed in previously classified legal memos released in April.

"The assumption is that the (methods) are without effect on memory, or indeed facilitate the retrieval of information from memory," O'Mara said.

But overwhelmingly, scientific literature shows the opposite: Chronic stress and trauma — the likely result of the CIA's methods, particularly for long-term prisoners, according to O'Mara — can damage the hippocampus, the part of the brain that integrates memory.

The list of techniques the CIA used included prolonged sleep deprivation — six days in at least one instance — being chained in painful positions, exploiting prisoners' phobias, and waterboarding, a form of simulated drowning that President Barack Obama has called torture. Three CIA prisoners were waterboarded, two of them extensively.

Stress hormones released
Those methods cause the brain to release stress hormones that, if their release is repeated and prolonged, may result in compromised brain function and even tissue loss, O'Mara wrote.

He warned that this could lead to brain lobe disorders, making the prisoners vulnerable to confabulation — the pathological production of false memories based on suggestions from an interrogator. Those false memories mix with true information in the interrogation, making it difficult to distinguish between what is real and what is fabricated.

Waterboarding is especially stressful "with the potential to cause widespread stress-induced changes in the brain, especially when these are repeated frequently and intensively," O'Mara wrote.

"The fact that the detrimental effects of these techniques on the brain are not visible to the naked eye makes them no less real," O'Mara wrote.

The paper also asserted that forcibly exposing prisoners to what they are afraid of — the CIA got approval to use a suspect's fear of insects against him — is actually a method used to cure phobias.

Copyright 2009 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

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