The neural basis of feelings
Recent progress in the elucidation of the neural basis of feelings has been just as remarkable. Historically, it was thought that emotion would occur when a causative object first triggered a feeling state as a result of which the body would be aroused emotionally. Feeling states elicited by a situation produced bodily manifestations, in the face and in the viscera. Late in the nineteenth century William James proposed to invert this sequence, as outlined in his 1884 paper: “Our natural way of thinking about these emotions is that the mental perception of some fact excites the mental affection called the emotion, and that this latter state of mind gives rise to the bodily expression.My thesis on the contrary is that the bodily changes follow directly the PERCEPTION of the exciting fact and that our feeling of the same changes as they occur IS the emotion”. James was proposing something along the lines of the current view. Each emotion is a collection of bodily actions so well differentiated that the overall perception of the particular action program of a given emotion yields a distinct pattern. There were early attacks on this position and claims that the body engagement was not differentiated enough to generate distinct feelings. It was said that the body component consisted of a non-specific arousal state, no different for fear than for sadness or happiness.
Current evidence suggests, however, that the body state associated with each kind of emotion is distinctive and capable of supporting distinctive representations of emotion even if those representations are probably transformed by subcortical stations charged with transmitting signals from the body to cerebral cortex. The objections to James would not have found an audience if it were not for the unfortunate wording he used. When James stated that the feeling of the changed body is the emotion, he conflated emotions and feelings of emotions and opened the door to the arguments that undermined his position. Once it was possible to conceive of emotions-proper and feelings of emotion as distinctive components of a functional sequence, and once the mechanisms behind the triggering and execution of emotions gained clarity, the search for a physiological platform for feelings of emotion turned to somato-sensing brain regions.
At the level of the cerebral cortex the insula offered itself as a main candidate and indeed a large number of studies have shown that numerous emotional feeling states, positive as well as negative, simple or complicated, activate the insular cortex. The fact that the insula is the main cortical target of signals hailing from the body’s interior — the viscera and the internal milieu — is the likely reason for this differential activity (Damasio et al, 2000; Craig, 2002). But the neural basis of feeling states is not to be found only at the level of the cerebral cortex. We know now that complete destruction of the insula in both cerebral hemispheres does not abolish feelings, indicating that the feeling process probably begins at the level of the brain stem in nuclei which bring together at any moment information about the ongoing state of the body and can elaborate on that information. It has been suggested that the brainstem provides the most basic level of feelings — primordial feelings — whose modification would give rise to emotional feelings (Damasio, 2010). I
n brief, feelings of emotions are the perceptions of the action program that constitutes an emotion as it unfolds together with the salient representation of the causative object and with thoughts related to the situation. Organisms with simple brains need not perceive the unfolding of an emotional program for the emotional behavior to be effective. In organisms with complex brains, however, and with elaborate consciousness and memory, aspects of the feeling process are recorded and can be used for future planning and for optimized decision-making. In other words, feelings play a practical role in adaptive behavior and extend the advantages of emotions to the realm of conscious behavior. Feelings are not a useless reflection of the emotion process. Although the brain devices required to process emotions and feelings are put in place by the genome early in development, individual experience and learning introduce variations in the performance of emotions. As a consequence there is a subtle customization that makes an individual’s expressive patterns distinctive, in spite of their basic stereotypy. We laugh and cry with partially distinctive expressions. The fact that the emotional competence of objects and situations varies from individual to individual further undermines the possibility of genetic determinism.
We all generate fear responses to a number of comparable situations, but each of us has learned to fear certain objects and situations that others will not. Individual experience alters the stereotypy that might result from genomic instruction. Finally, different individuals exhibit different degrees of emotional regulation, yet another source of customization of the emotion and feeling cycle (Davidson et al, 2010). Over the course of biological evolution, emotions have allowed organisms to cope with threats originating within the body or in the environment and to take advantage of opportunities related to nutrition or mating. Emotional action programs increase survival by delivering an advantageous standard response to particular circumstances in the absence of thinking and deliberation. For species with limited cognitive abilities this is a spectacular advantage. For humans the advantages vary with the circumstances.
A rapid and comprehensive response can be beneficial, although on numerous occasions suppressing emotions and substituting a deliberated response constitutes the best response. But deliberated responses depend not only on an accumulation of factual knowledge and on the exercise of logic, but also on the past experience of emotional feelings relative to prior objects and situations.
- source: Scholarpedia.org
