|Other Abstract||In old age, a special time in our life, people face a range of progressive decline of physiological functions and possible bereavement in life. Whether the elderly can maintain self-care, independence and positive emotions at this stage is crucial to their physical and mental health. The sense of touch plays a vital role in keeping with activities of daily living and emotional regulation. Meanwhile, dispositional optimism was beneficial to cope with loneliness and stress, depression resistance, improve daily life adaptability. Therefore, it is necessary to investigate dispositional optimism, touch process and their relationship.
Compared with other sensory perception, touch, as the fifth sense of human, has received relatively less attention. On the one hand, the significant role of social affective touch in promoting interpersonal relationship, physical and psychological well-being of healthy people has been preliminarily confirmed; on the other hand, in clinical and subclinical groups, the avoidance attitude towards social affective touch is significantly associated with various mental disorders such as social anxiety, post-traumatic stress disorder, autism spectrum disorder and depression. There are few studies on the elderly group and more data are needed.
Optimism affects how individuals view themselves and environment, process afferent information, and guide the actions. People's expectations of the future are good or bad, which is closely related to the core process of behavior. Optimism acts as a powerful cognitive filter, which can change the individual's view of the world and influence the way they react and adapt to new situations. The individual difference of optimism is also related to clinical psychological disorders and psychopathological risk.
Social affective touch is influenced by top-down factors, what is the relationship among dispositional optimism, as a top-down personality trait, and the elderly's attitude towards social affective touch and its perception evaluation? What is its performance at the level of cerebral cortex? Compared with touch on forearm and palm, how does another form of social affective touch---embrace perform differently in sensory evaluation and neural activity? In addition, we hope to answer some important issues related to social affective touch: is there emotionality in the palm touch and embrace of Chinese elderly people? Are there similarities and differences between forearm and palm touch processing? Do sociality and animacy affect real social affective touch? In this study, we will use general propensity measurement, behavioral experiments and neural activity data to answer these questions.
The present study includes three studies. In the first study, the reliability and validity of the Chinese version of social touch scale were tested, and the relationship between the elderly's dispositional optimism and their attitude to social affective touch was investigated. The second study used behavioral experiment method to investigate the relationship between dispositional optimism and sensory evaluation of social affective touch and the role of active and passive touch, touch position, sociality and animacy. In the third Study, behavioral experiments and functional near-infrared spectroscopy techniques were used to investigate the influence of dispositional optimism on social affective touch (touch on forearm and embrace) perception and its cerebral cortex performance, the differences of neural activities between touch and embrace and the roles of sociality and animacy were compared in the elderly.
In study 1, the results showed that psychometric properties confirmed the adaptation of the STQ to the Chinese culture. It is a reliable and valid tool to assess attitudes towards social affective touch. The dispositional optimism is significantly related to the attitude of social affective touch, and the level of high and low dispositional optimism is well differentiated in the social affective touch questionnaire in old age.
In study 2, the results investigated that the level of optimism has a certain impact on the comfort of social affective touch on forearm, which the positive effects of social attributes (positive emotions of social attributes are greater than non-social attributes) disappeared in the high level optimism group under the condition of passive touch; touch on the forearm (with unmyelinated C-type tactile fiber) and palm (without unmyelinated C-type tactile fiber) of the elderly produce positive emotional experience; the positive main effect of sociality exists in forearm and palm; animacy affect the perception of real touch.
In study 3, the results demonstrated that active touch and embrace produce positive emotions in old age, which belongs to social affective touch processing; the elderly's dispositional optimism affects the tactile perception evaluation and neural activity; animacy and sociality influences perception experience and neural activity of touch and embrace. In addition, the bilateral frontal eye fields area (Brodmann 8) is also an important brain area involved in social affective touch. Compared with the resting baseline state, the activated brain areas of the prefrontal cortex in the touch and embrace task present overlap in most areas and different in a small part; In the dorsolateral prefrontal cortex and frontal polar region, the activated brain areas of the touch task do not have left and right hemisphere preference, which does not support the lateralization theory; while the cortical activation of the embrace task may support the tactile lateralization theory, but also the right hemisphere hypothesis of emotion theory.
In general, three studies showed that the dispositional optimism and social affective touch are related in attitude report, perception evaluation and neural activation in the elderly. On the attitude level, the higher the level of optimism, the higher the acceptance of social affective touch. In terms of the perception level of touch as a whole, the elderly's dispositional optimism, active and passive touch patterns and social attributes jointly affect the social affective touch at the forearm; In terms of active touch and embrace, the higher the level of dispositional optimism, the higher the tactile temperature of forearm. In addition, on the level of neural activation, the elderly's dispositional optimism and animacy and social attributes jointly affect the neural processing of frontal polar region, and the high optimism group has higher activation for interpersonal contact.
In addition, the forearm (with CT afferent) and palm (without CT afferent) perception of touch and embrace of the elderly produce positive emotional experience under the optimal 3cm / s; animacy and sociality also play an important role in the perception and neural activation of embrace and touch; in addition to the dorsolateral prefrontal cortex and frontal polar area, the frontal eye fields area (Brodmann 8) produce positive emotional experience, which also was an important brain area of prefrontal cortex involved in social affective tactile processing.|