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In Combat Veterans with PTSD, Memory Deficits Associated with Decreased Frontotemporal Activity

ARTICLE IN BRIEF

  • ✓ In the first ever functional magnetic resonance imaging (fMRI) study of the neural correlates of learning and memory in patients with post-traumatic stress disorder, Dutch researchers reported that memory deficits were associated with decreased activity in frontotemporal areas during both the encoding and retrieval of memory processing.

SAN DIEGO—Post-traumatic stress disorder (PTSD) — whether experienced by war veterans or non-combat individuals after a life-threatening event — is manifested by serious problems coping and functioning in everyday life. The hallmarks of PTSD are heterogeneous and include anxiety, depression, disturbed sleep, and cognitive impairment.

At the November Society for Neuroscience (SfN) annual meeting, two independent research teams presented new insights on PTSD based on imaging studies and memory tests.

In the first ever functional magnetic resonance imaging (fMRI) study of the neural correlates of learning and memory in PTSD patients, Dutch researchers reported in a poster that memory deficits were associated with decreased activity in frontotemporal areas during both the encoding and retrieval of memory processing. The study is currently in press in the Journal of Psychiatric Research.

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Dr. Elbert Geuze: “These neurobiological alterations witnessed in veterans with PTSD provide some acknowledgement that their problems are not just figments of the imagination but very real neurobiological consequences of traumatic stress.”

“These neurobiological alterations witnessed in veterans with PTSD provide some acknowledgement that their problems are not just figments of the imagination but very real neurobiological consequences of traumatic stress,” said the study's first author Elbert Geuze, PhD, a senior researcher at the Military Mental Healthcare Research Centre and University Medical Center, Utrecht, in the Netherlands. “Patients seem to use a wrong part of the brain: the superior temporal cortex instead of the medial temporal cortex, where the hippocampus is.”

BRAIN DIFFERENCES IN MEMORY TASKS

The Geuze team studied 24 men who were combat veterans — all Dutch men who had served in United Nations peacekeeping missions in Lebanon, Cambodia, and Bosnia. Half of them had PTSD, a condition associated with impaired attention and memory; those who did not have PTSD served as controls matched for age, handedness, year of deployment, and country of deployment. None of the veterans in the study had been physically injured at the time of deployment.

The subjects were given 12 word pairs to remember and were scanned by MRI. The words were back-projected onto a screen that was visible inside the scanner via a mirror. The subjects were asked to remember unrelated word pairs such as “rose” and “car.” The words were presented in the same order three times for the encoding condition. About 20 minutes after the encoding run, the volunteers were asked to silently recall the second word in response to the first word being shown.

Veterans with PTSD had less activity in the left frontal cortex and left middle temporal gyrus during the memorization phase, as well as increased activity in the left superior temporal gyrus. During the recall process, there was decreased activation in both the temporal and frontal areas.

“It's as though patients with PTSD use the wrong part of the brain, the lateral temporal cortex instead of the medial temporal cortex,” Dr. Geuze said. “Apparently, patients are unable to fully recruit the frontal cortex, an area important for working memory processing.”

‘AN IMPORTANT ADDITION’

Commenting on the study, Bruce McEwen, PhD, head of the Harold and Margaret Milliken Hatch Laboratory of Endocrinology at the Rockefeller University in New York City, said: “We know that the prefrontal cortex is involved in working memory, attention, decision making, control of impulsive behavior, as well as control of the amygdala regarding fear and emotions and autonomic neuroendocrine release. Thus, the findings of Geuze and colleagues that there is altered prefrontal cortex function in PTSD are meaningful and imply that these functions may also be altered.”

“However,” he added, “many psychiatric disorders, including schizophrenia and depression, are linked to impaired prefrontal cortex function, and the field is not yet able to specify the neuroanatomical deficits for each disorder.”

Noting that the prefrontal cortex is a complex structure that communicates with the rest of the brain, he said, “Other brain areas such as the amygdala and hippocampus also are likely to change in these disorders.” fMRI provides the possibility of defining the specific circuitry that is altered in PTSD, he said, so the study by Dr. Geuze and colleagues is an important addition to understanding this condition.

Dr. Geuze and colleagues noted that future research should include patients with PTSD after civilian trauma. In addition, they said that future studies might include the addition of functional outcome measures to help determine the clinical importance of these findings.

Additionally, the team from the Military Mental Healthcare Research Centre is testing soldiers in the Netherlands, prior to military deployment, using fMRI, blood and saliva samples, and questionnaires. The researchers plan a 10-year follow-up with the soldiers.

REFERENCE

• Geuze, et al. Neural correlates of associative leaning and memory in veterans with posttraumatic stress disorder. J Psychiatric Res (in press).