Researchers Daniel McKim, Anzela Niraula, Andrew Tarr, and Eric Wohleb at Ohio State University (OSU) and observing the hippocampus of mice, found that chronic stress erodes memory functioning. Mice with documented learned knowledge “forgot” critical information after stress induction.
According to their research published in The Journal of Neuroscience and supported by the National Institutes of Health, the National Institute of Aging and the National Institute of Dental and Craniofacial Research, the immune system also plays a key role in the manifestation of cognitive impairment.
The hippocampus organ in the brain’s medial temporal lobe is a small and crucial part of the limbic system that regulates emotions. The hippocampus is particularly associated long-term memory and spatial skills. Damage to the hippocampus can cause memory loss and inability to establish new memories as commonly seen in Alzheimer’s patients.
Thankfully, not all learning processes are governed by the hippocampus. This fact is evidenced in the ability of patients to learn certain types of new skills such as learning to play an instrument, after suffering damage to the hippocampal region.
This examination of sustained stress effects is unique in its focus on the relationship between short-term memory and prolonged stress. The purpose of `the research is to discover the seeds and roots of stress and cognitive and mood interruptions and to identify ways of supporting patients suffering from anxiety, depression, and chronic stress conditions such as Post-Traumatic Stress Disorder (PTSD).
Implications of this study could allow development of mental health treatments aimed specifically at combatting effects of sustained stress such as that induced by bullying and stressful work conditions.
In this study, mice observed in a maze setting, were repeatedly exposed to the stimulus of a larger, more aggressive, intruding mouse. The intimidation of the larger mouse is an instance of “social defeat – basically dominance by an alpha mouse”. This scenario mimics the chronic psychosocial stress that humans experience on the job and when under duress.
Resulting from social defeat, intimidated mice avoided social contact and exhibited depressive-like behavior lasting into four weeks of monitoring.
Lead Researcher Jonathan Godbout , Associate Professor of Neuroscience at Ohio State University (OSU) told the OSU news that the stressed mice (fearing the intruder) had difficulty with spatial memory for a period of 28 days in which they did not recall the location of an “escape hole” although they had successfully located and used it in prior trials where the intruding mouse was not introduced. The mice who were not suffering from stress, recalled the location of the escape hole every time.
By the above measurement, it can take at least a month to recover from a stressful stimulus, with the recovery beginning only after the stressor is withdrawn. Thus, a sustained stressor that does not allow the recovery period to begin, prolongs memory vulnerability and may increase the requisite recovery period.
Most importantly, the research team was able to confirm a cause and effect relationship in which short-term memory loss was the result of the brain inflammation induced by the immune system’s stress overload reaction.