These findings are also interesting as well.

Childhood abuse and other extreme stressors can have lasting effects on brain areas involved in memory and emotion. The hippocampus is a brain area involved in learning and memory that is particularly sensitive to stress.^8,9 As reviewed in greater detail by Bruce McEwen in other Cyberounds high levels of glucocorticoids (cortisol in the human) released during stress were associated with damage to neurons in the CA3 region of the hippocampus, and a loss of neurons and dendritic branching.^10,11,12 Glucocorticoids disrupt cellular metabolism and increase the vulnerability of hippocampal neurons to excitatory amino acids like glutamate.¹³ Other neurochemical systems interact with glucocorticoids to mediate the effects of stress on memory and the hippocampus, including serotonin¹⁴ and brain-derived neurotrophic factor (BDNF).^15,16 Stress also results in deficits in new learning that are secondary to damage to the hippocampus.^17,18 Exciting recent research has shown that the hippocampus has the capacity to regenerate neurons and that stress inhibits neurogenesis in the hippocampus.¹⁹

Studies in animals showing glucocorticoid-mediated hippocampal toxicity and memory dysfunction with stress raised the question: Does early stress, such as childhood abuse, result in similar deficits in human subjects? With this in mind, we used neuropsychological testing to measure declarative memory function in PTSD. We selected measures that were validated in studies of patients with epilepsy to be specific probes of hippocampal function. These neuropsychological measures (including delayed paragraph recall and word list learning) were correlated with a loss of neurons in the hippocampus in patients who underwent surgical resection of the hippocampus for the treatment of epilepsy.²⁰ We initially found verbal declarative memory deficits using similar measures in Vietnam combat veterans with PTSD.²¹

In the first report to use brain imaging in PTSD, combat veterans were found to have an 8% reduction in right hippocampal volume, measured with magnetic resonance imaging (MRI), with no difference in comparison regions including caudate, amygdala and temporal lobe (Figure 1).