Functions of the neural "valuation network": neuroimaging and lesion evidence

In recent years, functional neuroimaging studies have delineated a network consisting of the ventromedial prefrontal cortex / medial orbitofrontal cortex and ventral striatum that is involved in representing subjective reward values ("valuation" network). My talk focuses on this network, and is split into two parts. In the first part, I will present data from an ongoing fMRI study on how homeostatic changes (e.g. hunger vs. satiety) modulate responses in this "valuation" network to different classes of rewards. Homeostatic hormone levels (e.g. Leptin/Ghrelin) have been linked to neural processing in this network. Human participants took part in two counter-balanced fMRI sessions, once following 8hrs of fasting, and once following normal food intake. We explored parametric reward representation in response to monetary and food-related reward cues. In the second part on my talk I will show findings on decision-making and reward valuation impairments in patients with focal damage to this network. Patients with lesions to the medial orbitofrontal cortex / ventromedial prefrontal cortex (n=9) and controls (n=19) where tested on decision-making (risky and inter-temporal choice) and reward valuation tasks to explore the possibility that self-control impairments in this patient group might be associated with impairments in reward-valuation. Findings revealed considerable heterogeneity in the pattern of decision-making and valuation impairments observed in the patient group: Some patients showed striking impairments in self-control, whereas others where indistinguishable from controls. Potential reasons for this heterogeneity and implications for models of self-regulation are discussed.