December 30, 20134:04 PM ET
Affect is the experience of feeling or emotion. Affect is a key part of the process of an organism‘s interaction with stimuli. The word also refers sometimes to affect display, which is “a facial, vocal, or gestural behavior that serves as an indicator of affect” (APA 2006).
The affective domain represents one of the three divisions described in modern psychology: the cognitive, the conative, and the affective. Classically, these divisions have also been referred to as the “ABC of psychology”, in that case using the terms “affect”, “behavior“, and “cognition”. In certain views, the cognitive may be considered as a part of the affective, or the affective as a part of the cognitive.
Affective states are psycho-physiological constructs. According to most current views, they vary along three principal dimensions: valence, arousal, and motivational intensity.Valence is the subjective positive-to-negative evaluation of an experienced state. Emotional valence refers to the emotion’s consequences, emotion-eliciting circumstances, or subjective feelings or attitudes. Arousal is objectively measurable as activation of the sympathetic nervous system, but can also be assessed subjectively via self-report. Arousal is a construct that is closely related to motivational intensity but they differ in that motivation necessarily implies action while arousal does not. Motivational intensity refers to the impulsion to act. It is the strength of an urge to move toward or away from a stimulus. Simply moving is not considered approach motivation without a motivational urge present.
All three of these categories can be related to cognition when considering the construct of cognitive scope. Initially, it was thought that positive affects broadened cognitive scope whereas negative affects narrowed cognitive scope. However, evidence now suggests that affects high in motivational intensity narrow cognitive scope whereas affects low in motivational intensity broaden cognitive scope. The cognitive scope has indeed proven to be a valuable construct in cognitive psychology.
Emotions are thought to be related to activity in brain areas that direct our attention, motivate our behavior, and determine the significance of what is going on around us. Pioneering work by Paul Broca (1878), James Papez (1937), and Paul D. MacLean (1952) suggested that emotion is related to a group of structures in the center of the brain called the limbic system, which includes the hypothalamus, cingulate cortex, hippocampi, and other structures. Research has shown that limbic structures are directly related to emotion, but non-limbic structures have been found to be of greater emotional relevance. The following brain structures are currently thought to be involved in emotion:
In its broadest sense, cognition refers to all mental processes. However, the study of cognition has historically excluded emotion and focused on non-emotional processes (e.g., memory, attention, perception, action, problem solving and mental imagery). As a result, the study of the neural basis of non-emotional and emotional processes emerged as two separate fields: cognitive neuroscience and affective neuroscience. The distinction between non-emotional and emotional processes is now thought to be largely artificial, as the two types of processes often involve overlapping neural and mental mechanisms. Thus, when cognition is taken at its broadest definition, affective neuroscience could also be called the cognitive neuroscience of emotion.
Main structures of the limbic system
- Amygdala — The amygdalae are two small, round structures located anterior to the hippocampi near the temporal poles. The amygdalae are involved in detecting and learning what parts of our surroundings are important and have emotional significance. They are critical for the production of emotion, and may be particularly so for negative emotions, especially fear. Multiple studies have shown amygdala activation when perceiving a potential threat; various circuits allow the amygdala to use related past memories to better judge the possible threat.
- Thalamus– The thalamus is involved in relaying sensory and motor signals to the cerebral cortex, especially visual stimuli. The thalamus also plays an important role in regulating states of sleep and wakefulness.
- Hypothalamus– The hypothalamus is located below the thalamus. It plays a role in emotional responses by synthesizing and releasing neurotransmitters which can affect mood, reward and arousal.
- Hippocampus – The hippocampus is a structure of the medial temporal lobes that is mainly involved in memory. It works to form new memories and also connecting different senses such as visual input, smell or sound to memories. The hippocampus allows memories to be stored long term and also retrieves them when necessary. It is this retrieval that is used within the amygdala to help evaluate current affective stimulus.
- Fornix The fornix is the main output pathway from the hippocampus to the mammillary bodies. It has been identified as a main region in controlling spatial memory functions, episodic memory and executive functions.
- Mammillary body – Mammillary bodies are important for recollective memory.
- Olfactory bulb– The olfactory bulbs are the first cranial nerves, located on the ventral side of the frontal lobe. They are involved in olfaction, the perception of odors.
- Cingulate gyrus– The cingulate gyrus is located above the corpus callosum and is usually considered to be part of the limbic system. The different parts of the cingulate gyrus have different functions, and are involved with affect, visceromotor control, response selection, skeletomotor control, visuospatial processing, and in memory access. A part of the cingulate gyrus is the anterior cingulate cortex, that is thought to play a central role in attention and behaviorally demanding cognitive tasks. It may be particularly important with regard to conscious, subjective emotional awareness. This region of the brain may also play an important role in the initiation of motivated behavior.
- Basal ganglia – Basal ganglia are groups of neuclei found on either side of the thalamus. Basal ganglia play an important role in motivation.
- Orbitofrontal cortex – Is a major structure involved in decision making and the influence by emotion on that decision.
- Prefrontal cortex — The term prefrontal cortex refers to the very front of the brain, behind the forehead and above the eyes. It appears to play a critical role in the regulation of emotion and behavior by anticipating the consequences of our actions. The prefrontal cortex may play an important role in delayed gratification by maintaining emotions over time and organizing behavior toward specific goals.
- Ventral striatum — The ventral striatum is a group of subcortical structures thought to play an important role in emotion and behavior. One part of the ventral striatum called the nucleus accumbens is thought to be involved in the experience of goal-directed positive emotion. Individuals with addictions experience increased activity in this area when they encounter the object of their addiction.
- Insula — The insular cortex is thought to play a critical role in the bodily experience of emotion, as it is connected to other brain structures that regulate the body’s autonomic functions (heart rate, breathing, digestion, etc.). This region also processes taste information and is thought to play an important role in experiencing the emotion of disgust.
- Cerebellum – Recently, there has been a considerable amount of work that describes the role of the cerebellum in emotion as well as cognition, and a “Cerebellar Cognitive Affective Syndrome” has been described. Both neuroimaging studies as well as studies following pathological lesions in the cerebellum (such as a stroke) demonstrate that the cerebellum has a significant role in emotional regulation. Lesion studies have shown that cerebellar dysfunction can attenuate the experience of positive emotions. While these same studies do not show an attenuated response to frightening stimuli, the stimuli did not recruit structures that normally would be activated (such as the amygdala). Rather, alternative limbic structures were activated, such as the ventromedial prefrontal cortex, the anterior cingulate gyrus, and the insula. This may indicate that evolutionary pressure resulted in the development of the cerebellum as a redundant fear-mediating circuit to enhance survival. It may also indicate a regulatory role for the cerebellum in the neural response to rewarding stimuli, such as money, drugs of abuse, and orgasm.