Abstract

The primary aim of the present experiment was to distinguish and map the hemodynamic
correlates of hedonic experience using functional magnetic resonance imaging (fMRI).
To accomplish this, we exploited a functional distinction between thermosensory
perception and hedonic valuation. We used a water-perfused suit, both to deviate core
temperature and to deliver thermal stimulation to the skin. We acquired two fMRI scans
of each participant, under opposite core temperature deviations, in a single experimental
session. During each scan we alternated the temperature of the circulating water in the
suit from hot to cold every 2.25 minutes, for 18 minutes. Participants rated their thermal
comfort and the suit temperature on 11-point Likert scales during alternating nine-second
epochs. The critical feature of our design is that the hedonic sequence was the same in the
two scans whereas the sequence of peripheral thermal stimuli and the core temperature
deviations were opposite. We present behavioral evidence that the opposite sequences of
thermal stimuli induced a common pattern of hedonic experience. Concurrent hedonic
ratings tracked the blood oxygenation level dependent (BOLD) signal recorded from
spatially conjoint volume elements in pairs of scans from the same individuals. In cross
subject mixed effects analyses, we grouped the functional scans acquired under each core
temperature deviation. We then used a conjunction analysis of the group statistical maps to
identify common hemodynamic correlates of the pattern of hedonic experience in bothscans.
Spatially conjoint (i.e., co-localized) BOLD signal correlates of the hedonic ratings were
observed in bilateral subregions of the orbitomedial prefrontal cortex (OMPFC). A second
analysis, based on a normative model of hedonic response, yielded spatially conjoint BOLD
signal correlates in a more broadly distributed area of the OMPFC,including the subgenual
cingulate and bilateral temporal poles.