Effects of a single dose of cortisol on the neural correlates of episodic memory and error processing in healthy volunteers.

RATIONALE

Neuropsychological impairments seen in depression may be secondary to hypercortisolaemia. Repeated cortisol administration impairs episodic memory with an alteration in event-related potentials (ERPs) recorded during information retrieval. It is unclear whether such ERP effects are specific to episodic memory, or whether repeated cortisol administration is required.

OBJECTIVE

To investigate the effect of a single dose of hydrocortisone on the neural correlates of episodic memory and error detection.

METHODS

Twenty healthy subjects were treated with hydrocortisone (100 mg) or placebo orally, in a double-blind, two-way crossover study. ERPs were recorded during an episodic memory and a Stroop task, 1-3 h following the medication.

RESULTS

Cortisol increased error rates during the Stroop task but had no effect on episodic memory. The magnitude of ERPs associated with incorrect response in the Stroop task between -250 ms and +500 ms post-response was increased by cortisol, with no effect on correct-response ERPs. There was no effect of cortisol on episodic memory-retrieval-dependent ERPs.

CONCLUSIONS

Cortisol can impair not only episodic memory but also processes involved in error detection. In contrast to repeated cortisol administration, a single dose of cortisol does not alter the behavioural performance or the electrophysiological correlates of episodic memory. However, it increases error rates in a choice response task with associated quantitative changes in incorrect-response ERPs. This probably reflects an alteration in anterior cingulate cortex activity. Such changes may contribute to the neuropsychological impairment seen in depression. This study also demonstrates the utility of ERPs for investigating the effect of neuroendocrine manipulations on the neural correlates of neuropsychological function.