The ability to process emotional stimuli with increased efficacy depends on neural mechanisms that allow detection, identification, and processing of stimuli and situations that are important for survival (e.g., finding food, avoiding predators) (Anderson & Phelps, 2001
; LeDoux, 1996
; Ohman, Flykt, & Ludqvist, 2000
). These mechanisms have evolved during evolution and are continuously modelled during ontogeny. At a basic level, these mechanisms overlap with those involved in the generalised response to stressful situations, which consist of coordinated neurohormonal changes that are set in motion when a stressor of any kind exceeds specific thresholds (Arnsten, 1998
; Selye, 1985
). The engagement of the stress system as a result of exposure to uncontrollable stressful situations sets off a chain of events that not only ensure immediate adaptive responses but also trigger mechanisms that will determine our responses in future similar situations.
Emotions may affect various aspects of our cognition and behaviour, by enhancing or hindering them and by exerting both transient and long-term influences. Possibly as a result of their relevance for survival, emotional stimuli tend to capture our attention more easily than none-motional stimuli, and thus may affect different levels of our cognition, from lower level (e.g., perceptual) to higher level (e.g., mnemonic and executive) cognitive processes. The enhanced significance of emotional stimuli can benefit cognitive processes (e.g., better memory for emotional events) (Dolcos, 2010
; Dolcos & Denkova, 2008
; Dolcos, LaBar, & Cabeza, 2006
; McGaugh, 2004
; Phelps, 2004
), but can also have detrimental effects on behaviour (e.g., increased distractibility to task-irrelevant emotional stimuli) (Dolcos, Diaz-Granados, Wang, & McCarthy, 2008
; Dolcos, Kragel, Wang, & McCarthy, 2006
; Dolcos & McCarthy, 2006
). Also, although some of these effects are transient, influencing online perceptual and executive processes, others produce long-term effects (Dolcos, LaBar, & Cabeza, 2005
) that can last for a lifetime (Markowitsch, 2008
; Moscovitch, Nadel, Winocur, Gilboa, & Rosenbaum, 2006
; Rubin, 2005
). Evidence concerning these aspects will be discussed in the first section of this review.
Emotion processing is also susceptible to cognitive influences, as complex behaviour involves reciprocal interactions between affective and cognitive processes. Indeed, the neurobiological theories of cognitive–affective interactions would not be complete without an account of the mechanisms underlying the effect of cognitive processes on emotional processing. Particularly important in this context is the ability to promptly deploy cognitive control of emotion in order to resist momentary emotional distraction and, in a longer run, the ability to cope with emotional responses as a result of recollecting memories of unpleasant events. The engagement of these mechanisms can occur automatically, probably as a result of gradual development during ontogeny, and depend on the attributed personal significance to the potentially emotional situations. For instance, when witnessing a tragic accident some individuals may be more distressed and hence experience and express intense emotions, whereas others are better able to control their emotions (e.g., by reappraising the situation, or by concealing their emotions), and hence overall reduce their emotional experience. Because emotion regulation strategies have a substantial impact on one's emotional experience, leading to different behavioural, cognitive, and neural results (Gross, 2008
; Ochsner & Gross, 2005
; Richards, 2004
), they are an important part of emotion–cognition interactions. Evidence concerning these aspects will be discussed in the second section.
Understanding the mechanisms underlying the reciprocal interactions between emotion and cognition is critical for understanding fundamentals of healthy functioning, as well as changes associated with psychological and emotional disorders. An important aspect in this context concerns the role of individual differences in emotion–cognition interaction, and, related to this, individual variations in the vulnerability to affective disorders, as even within the realm of healthy emotional responses some individuals may tend to be more emotionally responsive and “anxious,” whereas others can control better their emotions. Understanding the role of individual differences can provide insights into the factors that may influence the susceptibility to affective disorders, in which unbalanced interactions between emotion and cognition may lead to devastating effects, such as those observed in depression and anxiety. For example, the tendency to ruminate on negative emotions and memories observed in depressed patients and the intrusive recollection of traumatic memories observed in patients with posttraumatic stress disorder affect tremendously the way these patients think and behave. Therefore, it has become apparent that finding cures for these disorders depends on understanding the brain mechanisms that are responsible for such dramatic changes in the ways emotion interfaces with cognition, as well as on identifying the role of individual differences in mediating these interactions. Evidence concerning these aspects will be discussed in the third section.
To summarise, the present review analyses the reciprocal interactions between emotion and cognition, as derived from brain imaging investigations focusing on the three main topics highlighted earlier: (1) the impact of emotion on cognition, (2) the impact of cognition on emotion, and (3) the role of individual differences in emotion–cognition interactions. First, we will discuss evidence concerning the neural circuitry underlying the enhancing/beneficial and impairing/detrimental impact of emotion on cognitive processes, by considering findings from studies focusing on both lower level perceptual processing and higher level executive functions, and on both transient and longer lasting effects of emotion. Conversely, we will consider the reverse side of these effects, namely the impact of cognition on affective processing, by addressing evidence concerning the neural correlates of emotion regulation and coping with emotional distraction. Finally, we will also discuss the reciprocal interactions between emotion and cognition in the context of highlighting the role of individual differences (i.e., related to personality, sex, and age).