1. ¹Department of Psychiatry, University of Michigan, Ann Arbor, Ann Arbor, MI, USA
2. ²Department of Radiology, University of Michigan, Ann Arbor, Ann Arbor, MI, USA
3. ³Neuroscience Program, University of Michigan, Ann Arbor, Ann Arbor, MI, USA
4. ⁴Psychiatry Service, Ann Arbor VAMC, Ann Arbor, MI, USA

Correspondence: Dr KL Phan, Department of Psychiatry, University of Michigan, UH9D, University Hospital, Box 0118, 1500 E. Medical Center Dr, Ann Arbor, MI 48109-0118, USA. Tel: +1 734 936 9280; Fax: +1 734 936 7868; E-mail: luan@umich.edu

Received 20 November 2002; Revised 5 February 2003; Accepted 10 February 2003; Published online 23 April 2003.

Abstract

Habituation of the neural response to repeated stimuli has been well demonstrated for subcortical limbic regions responding to emotionally salient stimuli. Although the rostral or affective division of the anterior cingulate cortex (rACC) is also engaged during emotional processing, little is known about the temporal dynamics of this region in sustained evaluation of emotional salience. Using a test/retest design, the present study assessed habituation in the human brain with functional magnetic resonance imaging. Eight healthy subjects were exposed to two repeated runs of aversive, neutral, and blank images. Activation of the rACC to negatively valenced pictures occurred only in the first session, and this activation was significantly greater in the first relative to the second session. Additionally, medial prefrontal cortex, hippocampal, and amygdalar activations were noted during the first, but not second, presentation of aversive pictures. These findings highlight the phasic activity of the rACC in emotional processing consistent with habituation.