title: Examining the Role of the Human Hippocampus in Approach-Avoidance Decision Making Using a Novel Conflict Paradigm and Multivariate Functional Magnetic Resonance Imaging.
abstract: Rodent models of anxiety have implicated the ventral hippocampus in approach-avoidance conflict processing. Few studies have, however, examined whether the human hippocampus plays a similar role. We developed a novel decision-making paradigm to examine neural activity when participants made approach/avoidance decisions under conditions of high or absent approach-avoidance conflict. Critically, our task required participants to learn the associated reward/punishment values of previously neutral stimuli and controlled for mnemonic and spatial processing demands, both important issues given approach-avoidance behavior in humans is less tied to predation and foraging compared to rodents. Participants played a points-based game where they first attempted to maximize their score by determining which of a series of previously neutral image pairs should be approached or avoided. During functional magnetic resonance imaging, participants were then presented with novel pairings of these images. These pairings consisted of images of congruent or opposing learned valences, the latter creating conditions of high approach-avoidance conflict. A data-driven partial least squares multivariate analysis revealed two reliable patterns of activity, each revealing differential activity in the anterior hippocampus, the homolog of the rodent ventral hippocampus. The first was associated with greater hippocampal involvement during trials with high as opposed to no approach-avoidance conflict, regardless of approach or avoidance behavior. The second pattern encompassed greater hippocampal activity in a more anterior aspect during approach compared to avoid responses, for conflict and no-conflict conditions. Multivoxel pattern classification analyses yielded converging findings, underlining a role of the anterior hippocampus in approach-avoidance conflict decision making.
  
  
  CONCLUSIONS
  Approach-avoidance conflict has been linked to anxiety and occurs when a stimulus or situation is associated with reward and punishment. Although rodent work has implicated the hippocampus in approach-avoidance conflict processing, there is limited data on whether this role applies to learned, as opposed to innate, incentive values, and whether the human hippocampus plays a similar role. Using functional neuroimaging with a novel decision-making task that controlled for perceptual and mnemonic processing, we found that the human hippocampus was significantly active when approach-avoidance conflict was present for stimuli with learned incentive values. These findings demonstrate a role for the human hippocampus in approach-avoidance decision making that cannot be explained easily by hippocampal-dependent long-term memory or spatial cognition.
authors.affiliation: Department of Psychology (St. George and Scarborough), University of Toronto, Toronto M5S 3G3/M1C 1A4, Canada.
authors.forename: Edward B
authors.identifier: http://orcid.org/0000-0001-7899-3573
authors.initials: EB
authors.lastname: O'Neil
authors.affiliation: Department of Psychology (St. George and Scarborough), University of Toronto, Toronto M5S 3G3/M1C 1A4, Canada.
authors.forename: Rachel N
authors.initials: RN
authors.lastname: Newsome
authors.affiliation: Department of Psychology (St. George and Scarborough), University of Toronto, Toronto M5S 3G3/M1C 1A4, Canada.
authors.forename: Iris H N
authors.initials: IH
authors.lastname: Li
authors.affiliation: Department of Psychology (St. George and Scarborough), University of Toronto, Toronto M5S 3G3/M1C 1A4, Canada.
authors.forename: Sathesan
authors.identifier: http://orcid.org/0000-0003-3011-9021
authors.initials: S
authors.lastname: Thavabalasingam
authors.affiliation: Department of Psychology (St. George and Scarborough), University of Toronto, Toronto M5S 3G3/M1C 1A4, Canada, Department of Cell and Systems Biology, University of Toronto, Toronto M5S 3G5, Canada, and andych.lee@utoronto.ca rutsuko.ito@utoronto.ca.
authors.forename: Rutsuko
authors.identifier: http://orcid.org/0000-0003-1769-5470
authors.initials: R
authors.lastname: Ito
authors.affiliation: Department of Psychology (St. George and Scarborough), University of Toronto, Toronto M5S 3G3/M1C 1A4, Canada, Rotman Research Institute, Baycrest Centre for Geriatric Care, Toronto M6A 2E1, Canada andych.lee@utoronto.ca rutsuko.ito@utoronto.ca.
authors.forename: Andy C H
authors.identifier: http://orcid.org/0000-0002-8546-5311
authors.initials: AC
authors.lastname: Lee
mesh_terms: D000328:Adult; D001362:Avoidance Learning / Q000502:physiology*; D003220:Conflict, Psychological; D003657:Decision Making / Q000502:physiology*; D005260:Female; D006624:Hippocampus / Q000502:physiology*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D015999:Multivariate Analysis; D010775:Photic Stimulation / Q000379:methods*; D011930:Reaction Time / Q000502:physiology; D055815:Young Adult
keywords: approach–avoidance conflict; decision making; functional magnetic resonance imaging; hippocampus; memory