Neurotransmitters and Electrophysiological Changes Might Work as Biomarkers for Diagnosing Affective Disorders

Abstract

Affective disorders are the leading causes of human disability worldwide; however, the diagnosis is still hard to define, because emotion is the least study subjects in psychology. Recent emotional studies suggest that human emotions are developed from basic emotions, which are evolved for fundamental human lives. Even though most psychologists agree upon the idea that there are some basic emotions, there is little agreement on how many emotions are basic, which emotions are basic, and why they are basic. In our previous papers, we suggested that there are three basic emotions: joy, fear, and disgust. These basic emotions depend on the peptides and monoamines: dopamine-joy (peptides-reward), norepinephrine-fear (anger), and serotonin-disgust (sadness). Further tests with event-related potentials (ERP) found that joy, fear, and disgust showed the fastest response compared with other emotions, suggesting that they are fast automatic responses, which confirmed that these three emotions are prototypical emotions. Other basic emotions, anger and sadness, are due to object induced behaviors instead of sensation of object, so they developed secondary to prototypical emotions. Thus, we concluded that only joy, fear, and disgust are prototypical emotions, which can mix into other emotions, like the primary colors. In all, the neural substrates for all emotions, including the affections, are possibly monoamine neuromodulators: joy-dopamine (peptides), fear (anger)-norepinephrine, and disgust-serotonin. We hope these basic emotional studies will offer some neural mechanisms for emotional processing and shed lights on the diagnosis of affective disorders.

Figure 1

Only three basic emotions can be activated by object pictures. (a) The distributions of responses from the object pictures from IAPS and CAPS show that joy, fear, and disgust are three major basic emotions. (b) Number of pictures for each categorized emotion. Pictures were categorized according to the emotion that gained more than half of the responses. (c) The average accuracy for each emotion is 67.3 ± 5.1% (n = 63) for neutral, 76.5 ± 3.9% (n = 32) for joy, 55.4 ± 3.7% (n = 16) for fear, and 71.4 ± 4.3% (n = 12) for disgust, respectively. (d) The averaged percentage of emotional responses (top label) for categorized neutral, joy, fear, and disgust pictures (left label).

Figure 2

The three prototypical emotions showed the fastest responses. (a) The procedure for the “Winner-takes-all” approach experiment. (b) The accuracy of the responses for each group of pictures. The side labels mean the group of pictures, and the top labels mean the responses for the 6 kinds of emotions. (c, d) The reaction times for joy, fear, and disgust are significantly shorter than those of the other three basic emotions (p < 0.01, one-way ANOVA). (e) The procedure for the “go/no-go protocol” experiment. The emotion picture was presented until the participant choose the space bar.

Figure 3

ERP studies of 6 basic emotions. (a) Typical ERP recordings at Pz. (b) Statistical analysis of averaged amplitudes of ERP recordings at P1, P2, and P3. (c) Relative amplitude ([relative peak = (categorized − neutral)/neutral) of ERP recordings at Pz. Statistical analysis showed that fear, joy, and disgust induced the earliest responses.

Figure 4

ERP studies of 6 basic emotions. (a) Topological distribution of ERP recordings at P1 shows that fear, joy, and disgust have the strongest P1 response at Pz points. (b) Valence and arousal distributions of the 6 categorized pictures showed that sadness and disgust overlapped, surprise and joy overlapped, and fear and anger overlapped. (c) Statistical analysis of valence and arousal showed that disgust and sadness have similar negative valence; fear and anger have similar arousal.

Figure 5

A schema shows that joy, fear, and disgust are three prototypical emotions. Emotions are developed at two major levels: unconscious and conscious. Like what Lazarus [14] said “I distinguish between two modes of appraisal: one automatic, unreflective, and unconscious; the other deliberate and conscious.” The lower level animals may not experience emotions consciously; they do have the prototypical emotions. The prototypical emotions are due to automatically sensation/perception about the objects, such as dizzy at height (fear), or nausea at a stool (disgust), or arousal at a sex nude body (joy). These three prototypical emotions fit for two primary needs: physiological need (valence: like–joy; dislike–disgust) and safety needs (arousal–fear) [19]. The unconscious appraisal can be divided into three levels: sensation-opinion-behaviors (S-O-R). Surprise is due to perception about the ways the object appears, while anger or sadness is due to behaviors that deals with the object.