Emotion in motion

It has been, until recently, all too easy to consider understanding of emotions the preserve of popular magazines. Whereas understanding of other higher-level brain functions such as language and memory has been investigated intensively, emotions have not been considered worthy of scientific endeavour. In The Emotional Brain, Joseph LeDoux has succeeded in providing the reader with a personal and comprehensive account of the development of scientific research in emotion perception. LeDoux also conveys the information in a style which allows the reader to understand and appreciate fully the ideas that acted as a basis for progress in this fascinating area of cognitive or "mind" science.

In the first chapter, these ideas or hypotheses are presented as themes that run throughout the book, including the fact that emotions are conserved across different animal species and in different human cultures, and the knowledge that emotions are represented in patterns of behaviour in addition to feelings. Several chapters are also devoted to explanations of the brain mechanisms underlying perception of emotions, with the emphasis on the description of that most basic emotion, fear.

A central question is whether emotions can be considered to be similar to other higher-level brain functions. Are there similar regions of the brain associated with the performance of all such higher functions, or are emotions special, with specific areas of the brain associated with perception of emotion but not other brain functions? LeDoux provides a compelling argument for the inclusion of emotions in the field of cognitive neuroscience in chapter two: emotions, like other higher brain functions, can be understood in terms of underlying unconscious processes which eventually produce a conscious output. Based on several lines of evidence from the study of animals and humans when processing emotional information, LeDoux is, however, quick to state his "desire to protect emotion from being consumed by the cognitive monster". The presence of bodily feedback during emotional experiences, but not during other higher brain functions, appears to be of central importance in distinguishing the two processes. The reader is left in no doubt that emotion and other higher brain functions (the latter termed cognition) should be considered as "separate but interacting mental functions".

At this point, the reader may be forgiven for being slightly confused as to the direction of emotion research. If emotions are different from other higher brain functions (cognition), then can we expect to apply to the study of emotions similar scientific principles to those applied to the study of cognition? If we can, then why are emotions so different from these other higher-level brain functions? In reviewing the research to date on regions of the brain implicated in perception of emotions, and, in particular, those regions involved in perception of fear, LeDoux manages to convey the idea that there exist interacting brain systems for emotion on the one hand and cognition on the other. Thus, although similar types of model can be constructed to help us understand brain function during emotion perception and cognition, the important point is that different areas of the brain, or pathways, are involved in these two processes. A good example of this is the perception of a fearful object. LeDoux refers to "the low and the high road" when describing the regions of the brain that are involved during our response to fear, with the "low road" referring to the fast pathway involved in the immediate or "emotional" response to a fearful object, and the "high road" to the slower pathway whose function is to process the details of the object at a more "cognitive" level.

A substantial section of the book highlights the role of the amygdala, a small, almond-shaped region of the brain, in the perception of fear. Several studies are described in which perception of fearful objects was investigated in humans and animals. It becomes clear to the reader that the amygdala is important for perception of fear not only in humans, but in several different animal species.

LeDoux has been particularly ambitious in the content of the book. There are further chapters devoted to the description of emotional memory and the role of emotion, especially that of fear, in the development of specific psychiatric conditions such as phobias, post-traumatic stress disorder and panic. It is a credit to the author that these complicated subjects are discussed in a concise and yet informative fashion, so that the reader is left with the overriding view that intact perception of emotion is central to mental health.

In the final chapter, the emphasis is on the development of a theory to describe the function of the brain during conscious experience of emotion. The difficulty here is that consciousness itself remains an extremely difficult subject for scientific research, with little known to date about the brain regions involved in the formation of conscious experiences per se. LeDoux, however, manages to construct a plausible model to describe the various brain regions and their specific functions which together allow us to experience an emotional feeling, in addition to the bodily responses accompanying such a feeling. It is even argued that humans may, at some stage in the future, be able to control emotions more successfully than at present by means of adaptation of these existing pathways in the brain.

Emotions by their very nature are complex phenomena and difficult to study in laboratory settings. In describing the major areas of emotion research in The Emotional Brain, LeDoux manages not only to convince the reader that the study of emotion perception is worthwhile, but also engages the reader in a compelling narrative describing the growth and development of several themes underlying our understanding of emotion.

How do we convey our emotions to others? One obvious way we have of doing this is by making specific facial expressions. We smile when we are happy, we frown when angry, and we may appear tearful when sad. It is remarkable that relatively small movements of the facial musculature can alter dramatically the emotion which we display to others. Our ability to both make and recognise different facial expressions is clearly an extremely important social skill.

It is even more remarkable that over one hundred years ago, Charles Darwin wrote a ground-breaking book, The Expression of the Emotions in Man and Animals, which not only described the various different emotional expressions in man and animals in detail, but also attempted to explain the reason for the association of a particular expression with a specific emotion, for example why we blush when we are embarrassed, or why we make a characteristic mouth movement when disgusted. Darwin went further than this, however, and provided evidence that facial expressions of emotion are universal, ie that facial expressions for specific emotions are similar in many different cultures. He also, controversially, provided evidence for the presence of these expressions in other animals.

In producing the third edition of Darwin's book, Paul Ekman, an expert in the neuropsychology of facial expression, has been able to improve on previous editions by incorporating changes to the text which Darwin himself had wanted. In addition, new photographic illustrations are included to replace some of the woodcuts and engravings of previous editions. Ekman has also provided the reader with excellent commentaries throughout the text in order to clarify specific issues.

He points out in his introduction that although the book was a bestseller when first published in 1872, with 9,000 copies selling in the first four months, its popularity diminished quickly and it was "studiously ignored" for nearly 100 years afterwards. Why was this? Ekman suggests several reasons, the most important of which he believes to be the controversy surrounding Darwin's theory of the innate nature of facial expressions, ie that we are born with the ability to make and recognise facial expressions, rather than learning this as a result of the effects of culture. This theory was opposed by leading psychologists and anthropologists of the last century. In his afterword, Ekman describes his personal struggle and determination to prove Darwin correct, describing several exchanges which occurred between himself and leading scientists in opposition to Darwin's view.

Ekman, in true scientific fashion, does make some criticisms of Darwin. He criticises the methods which Darwin employed to collect the data to support his theories, in particular, the use of anecdotal information obtained from a small number of English observers who had travelled overseas in support of the theory of universality of facial expression across different cultures. In today's scientific community, peers would require substantially more empirical evidence before being persuaded to accept the theory. Ekman then describes his elegant experiments in the field, which were conducted over several years in many different countries, and which succeeded in providing further evidence for Darwin's theory.

The Emotional Brain and The Expression of the Emotions in Man and Animals both succeed in conveying the importance of emotions and the expression of these for communication, and also serve to highlight the recent increase in interest in performing emotion research. These are fascinating books which should appeal to readers not only with a background in natural science, but to all interested in understanding more about the nature of an essential function of the animal brain, emotion.

Mary L. Phillips is lecturer in psychological medicine, Institute of Psychiatry, London.