Cortisol And Working Memory

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Research has shown that there is a definite connection between cognitive function and hormones that are released in the human body during moments of exacerbated stress or emotion. It has been suggested that an individual's working memory, "the cognitive mechanism that allows us to keep a limited amount of information active for a limited period of time," (Elzinga & Roelofs, 2005; Baddeley, 1996) is significantly affected by the release of cortisol. "Recent findings from studies in animals suggest that that influence of GC's on memory functioning depends on the level of training-induced emotional arousal and/or adrenergic activity during memory performance." (Okuda, Roozendall, & McGaugh, 2004; Elzinga & Roelofs, 2005) Intrigued by these findings, the authors decided to conduct a study to determine whether or not cortisol released in humans during stressful or emotional situations requires adrenergic activity to have an effect on working memory. They believed their research would indicate that working memory is impaired during "acute psychosocial stress" (Elzinga & Roelofs, 2005), which casues both elevated cortisol levels and more significant amounts of adrenergic activity.

Methods: Elzinga & Roelofs recruited a total of 44 college students, who were either paid or given course credit for participating in the study. Participants were screened for psychiatric disorders, substance abuse, clinically signigicant medical disease, and use of medication. All participants were between the ages of 18 and 37. Female participants were only allowed if they were in days 21-25 of their menstrual cycle; "there are indications that during this phase, stress-induced cortisol levels do not differ between men and women." (Kirschbaum, Kudielka, Gaab, Schommer, & Hellhammer, 1999; Elzinga & Roelofs, 2005). Participants were instructed to

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refrain from physical exercise, large meals, smoking, and ingesting coffee or low pH beverages, as these things are known to influence cortisol levels.

Participants were given a version of the Trier Social Stress Test (TSST). The TSST is an exercise that consists mainly of public speaking and mental arithmetic tasks in front of an audience. Heart rate, blood pressure, and salivary cortisol are usually measured to determine the subject's stress level. Participants in this study were told that they would be pretending to apply for a research assistant position at a university. They were given 5 minutes to prepare, and were expected to deliver a 5 minute speech to an audience of 3 psychologists. They were told that their speech would be videotaped, they were to speak for the entire 5 minutes, that the psychologists were trained to monitor nonverbal behavior related to speech, that a voice frequency analysis would be performed, and that their speech would be judged based on its content and the way in which it was presented. For the mental arithmetic task, participants were asked to subtract 13 from 1587 serially (1587-13, 1574-13, etc.). When any mistake was made, participants were instructed by a member of the judging panel to repeat the task from the beginning.

Working memory was tested by use of the Digit Span subtest of the Wechsler Adult Intelligence Scale - Revised (Wechsler, 1987). Five series of numbers, increasing in length, were read to the participant at the rate of one digit per second. The participant was then asked to repeat the sequence of numbers both in the original order given and backwards. This test was administered three times: once for a baseline reading without an audience present, once

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immediately following the TSST with the audience still present, and once after the TSST without an audience.

Starting 45 minutes prior to the introduction of the first stressor, and again every 15 minutes thereafter until 50 minutes after the last stressor, salivary cortisol samples, heart rates, and blood pressure readings were taken.

Results: After collecting all the data, the authors found that all participants demonstrated higher heart rates and blood pressure levels during the highest stress phase of the study and were back to baseline levels by 50 minutes later. Average cortisol levels increased significantly over time in the stress group, while they decreased over time in the control group. Additionally, the stress group showed a marked variance between cortisol levels right before the TSST and right after the TSST, with the readings afterward being much higher, whereas the control group showed a significant decrease in cortisol levels. These findings lead the authors to divide the stress group of participants into two categories: cortisol responders and nonresponders. "Responders showed elevated cortisol levels from right after the TSST until the end of the experiment." (Elzinga & Roelofs, 2005) Prior to the TSST, the two groups did not exhibit any differences.

The authors found that cortisol responders did not perform as well using working memory during the TSST. During baseline and recovery phases of the experiment, responders and nonresponders were considered equal in terms of working memory performance. Therefore, the authors concluded that the increase