Medial prefrontal cortex (MPFC) activation has been observed in studies of many types related to emotion regulation, self and familiar other-knowledge, mentalizing, morality, reward, and uncertainty. Furthermore, the anterior cingulate cortex (ACC) and the lateral prefrontal cortex (LPFC), which have reciprocal connections with MPFC, are considered necessary for cognitive regulation. Based on these findings, Nakao, Takezawa, and Miyatani (2006) proposed an integrative explanation for MPFC function: MPFC has a function of representing a benchmark that reduces conflict among many possible answers by biasing either choice of behavior. In this article, we review studies related to MPFC function and the benchmark hypothesis with recent new findings. Additionally, we discuss emotion regulation, which was not described in Nakao et al. (2006), in relation to the benchmark hypothesis.

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Late luteal phase behavioural changes (LLBC) have been reported for humans and some other primates, and encompass a wide spectrum of behaviours. Several studies have estimated that a majority of women manifest some LLBC. At a more extreme end of the spectrum, in a small minority of women, LLBC have been classified as major emotional disturbances or medical conditions (although not without controversy), for example, as part of premenstrual dysphoric disorder. In this report, an attempt is made to place LLBC in an evolutionary context; some of these behaviours, in particular at a less extreme end of the spectrum, may have co-evolved with reproductive physiology. Evolutionary perspectives upon human reproductive behaviour are often complex (and controversial) issues; in this context, specific and more isolated mechanisms for possible evolutionary stability of some LLBC—e.g., related to male-female behavioural interactions—are suggested for further discussion. Overall, it is proposed that qualitative and quantitative changes in hormones and hormonal activities during the menstrual cycle evolved to optimize reproductive success through neurophysiological responses that include behavioural components, perhaps some LLBC.

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Current literature on preattentive detection of significant emotional faces in visual search tasks show that these results require an explanation within the theories devoted to explaining similar results obtained for features like orientation and color in the attention literature, the best known candidate for which so far is the feature integration theory (FIT) proposed by Treisman and Gelade. This paper attempts to bridge such a gap between the attention and the emotion theories by proposing that `emotional features' should be proposed within the FIT due to their resemblance with the other features of the theory like their preattentive detection. Within such a scheme the amygdala will act as a substitute for the cells in the striate cortex that are shown to be responsible for processing the visual features, as amygdala has been shown to process faces with significant emotional value preattentively. The paper also proposes an experimental paradigm that can provide empirical support for such emotional features.

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Human decision-making has been investigated under two frameworks: cognitive and emotional decision-making. Cognitive decision-making is a choice behavior in the risky situation, in which the payoff and the probability of each option are explicit and calculable. This form of decision-making has been considered to be performed without emotional influence. Although recent works have revealed the importance of the emotion in human decision-making, emotional effect on cognitive decision-making is yet unknown. To examine whether cognitive decision-making is affected by emotional distracters, we implemented a secondary task requiring short-term memory of an emotional word in the Cambridge gambling task (CGT). Although the quality and the quickness of decision-making were not affected by emotional distracters, the amount of bet was significantly higher in trials requiring positive word memorization. These results indicate that some processes of cognitive decision-making are affected by emotion.

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It is unclear whether behavioral inhibition leads to heightened brain activation in response to reward or punishment incentives. In this study, we utilized near-infrared spectroscopy (NIRS) to evaluate right ventrolateral prefrontal cortex (VLPFC) activity during a reward/punishment Go/No-go task. As hypothesized, the activation of the right VLPFC was modulated according to different incentive outcomes during the Go/No-go task. Under the reward-only condition, oxyhemoglobin (oxy-Hb) concentrations in the right VLPFC significantly increased as compared with those under the punishment-only condition. In addition, the percentage of commission errors under the punishment-only condition was negatively correlated with neuroticism. These results provide new evidence that the role of the right VLPFC is modulated according to the reward/penalty outcomes, and the relation between motor inhibition and personality traits.

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Positive feeling is derived not only from biologically significant causes but also from biologically non-significant causes (e.g., seeing preferred stimuli). To neurobiologically examine whether or not the preference for biologically non-significant neutral stimuli is related to positive emotion which arises when monkeys see preferred stimuli, we first determined whether monkeys exhibit preference for biologically non-significant fractal stimuli. We presented 2 fractal stimuli simultaneously and asked monkeys to select one of them by eye movements and look at the selected stimulus for up to 12 sec. Monkeys exhibited different percentages of correct performances to different stimuli. The rank orders of the stimuli estimated by the percentage of correct performance were maintained throughout many sessions. The rank orders of the stimuli were not related to the exposure effect or stimulus-reward association. These results indicate that monkeys exhibited preference for fractal stimuli and that the rank orders of the stimuli estimated by the percentage of correct performance reflect the strength of monkey's preference for the stimuli. This method allows us to determine monkey's preference for biologically non-significant neutral stimuli to perform neurobiological experiments for examining whether this preference is related to positive emotion.

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