Introduction

The social brain undergoes many changes during adolescence. Research shows that changes in social behaviour are caused by sociocultural factors and innate characteristics. Both ensure that the brain adjusts naturally on a social level. In addition, abnormal emotional responses to social situations are also important for mood and anxiety disorders during adolescence.

Social information processing

Social information processing requires complex neuronal systems. One must quickly identify a particular stimulus as being 'social' and then integrate this stimulus into a larger, already existing, emotional and cognitive network. This requires communication between brain areas that deal with social detection and brain areas that process affective and cognitive information.

The following model is discussed in this article: Social Information Processing Network (SIPN). This model consists of three key points:

1. Detection. Here it is determined whether or not a stimulus can be seen as 'social'. Various brain structures are involved, such as the inferior occipital cortex, the intraparietal sulcus and the fusiform face area. The various brain areas involved include perceptual functions.

2. Affection. These are areas of the brain that deal with reward and punishment, including the amygdala, the septum, and the hypothalamus. For example, this determines whether the social stimulus should be approached or avoided. In addition, autonomous and cognitive processes are arranged here in order to be able to respond adequately to the social stimulus.

3. Cognitive regulation. This involves three different processes:

• Processing of the mental state of the other (Theory of Mind) by the dorsomedial prefrontal cortex.

• Inhibition of violent reactions by the ventral prefrontal cortex.

• Facilitate goal-oriented behaviour by the dorsal and ventral prefrontal cortex. It is important to achieve goals to control emotional behaviour. Motivation to achieve a goal also plays a role here.

The ventral cortex plays a role in both affection and cognitive regulation.

The SIPN model assumes that the aforementioned processes take place one after the other. However, when looking at the brain, one can see that the three processes are part of an interactive network. For example, the detection areas receive information from the affection areas to be able to interpret a stimulus as social.

Changes in the SIPN model in adolescence

There are many changes in social behaviour during adolescence. Three major changes are sexuality, being more focused on peers and less focused on parents.

• Detection. The associated brain structures mature early in life. Thus, there are no known changes to these brain structures during adolescence since the structures are already mature.

• Affection. During puberty, there are both functional and anatomical changes in the corresponding brain structures. This is caused by sex steroids (i.e. sex hormones). This steroid regulates other neurotransmitter systems, for example, the systems of dopamine, serotonin and oxytocin, all involved in social behaviour. Sex steroids are involved in behavioural changes in social responses. The most striking is the sexual reactivity. Some studies have also found that steroids play a role in dominant behaviour and conflicts with parents during puberty. Other studies find links between sex hormones and sexual behaviour, parental behaviour, social bonding and social memory. Functional changes in the areas of the brain related to affection have an effect on the amount of sex hormone that is released. There are also studies that show the link between hormones and new stimuli, which makes the adolescence period very important for developing patterns of social behaviour.

• Cognitive regulation. People with damage to the prefrontal cortex have problems with social awareness and making social decisions. The earlier in development these areas are damaged, the more intense the effects are. Parts of the prefrontal cortex have not matured until the end of the teenage years or early twenties, which means that for example, inhibition control is very difficult for younger people. More myelin and the pruning of existing networks leads to changes in the field of cognitive regulation. These changes are slower than the changes in the affective areas. The hormones also play no role in this. Interaction with the affective areas can, however, ensure that hormone levels play a secondary role in the changes in the brain involved in cognitive regulation.

Neuroimaging techniques and changes in the SIPN model

The central nervous system mediates changes in the social brain areas during adolescence. Very little is known about which changes are taking place within the areas as discussed in the SIPN model. A recent study shows that different activation patterns are visible in the brain in response to social stimuli when comparing young adults with adolescents. We looked at the areas associated with affection and cognitive regulation. The activation in the amygdala, orbitofrontal cortex and anterior cingulate is higher in adolescents when they see frightened faces than in young adults.

When we look at important changes at the behavioural level during adolescence, contact with peers should provide more and more reward as the adolescent gets older. When contacting the parents this is exactly the other way around. In the brain, this should be reflected in increased activation in the brain areas associated with affection, when stimuli from peers are offered. In addition, these stimuli should have a stronger effect on attention and memory processes. The same should also happen with potential sexual partners. These assumptions can be investigated with fMRI.

Studies show that adolescents are very sensitive to peer acceptance and rejection. Neuroimaging techniques could also be used for this. In the areas of the brain related to affection, activation should be seen in terms of motivation, self-confidence, and social acceptance and rejection.

Although the Theory of Mind is a well-known phenomenon, very little research has been done about the changes during adolescence. This is probably because the Theory of Mind originates in early childhood. Recent research implies that regions in the dorsomedial cortex play an important role in the Theory of Mind. Changes take place in this area until early adulthood. fMRI tasks in which one subject (thinks he) interacts with another can play a role in understanding the changes in Theory of Mind during adolescence.

The brain development according to the SIPN model and affective disorders

During adolescence, the number of people with an affective or specific anxiety disorder increases considerably. Changes in the processing of social stimuli as stated in the SIPN model seem important here. In adolescence, people seem to be very responsive to social stimuli and social events. Changes in emotional motivation play a role here. For some adolescents, these emotions are so strong that there is psychopathology.

Rejection by a possible romantic partner or by peers also plays an important role in the development of psychopathology during adolescence. Difficulties regarding social relationships are also related to suicide risk. During early adolescence, suicide risk is more closely related to the relationship with parents, while suicide risk is more closely related to romantic relationships during late adolescence. This suggests changes in the brain areas related to affect.

Especially in women, there is a large correlation between stress and emotion during adolescence.

The extra stress during adolescence contributes to psychopathology. We know that a good social network can serve as a buffer for stress-related events. In adolescents, however, the social network is undergoing a change (fewer parents and direct family, more peers), while the amount of stress (for example due to academic achievement) increases. Social integration in a renewed social network is largely dependent on the brain areas involved in the SIPN model.

During the adolescence period, there appears to be a 'mismatch' between the affective systems and the systems involved in cognitive regulation. This is because the affective systems mature quickly, while the cognitive regulation systems lag behind, due to their slow development. As a result, some adolescents experience intense emotional reactions, while their inhibitory capacity, for example, cannot yet mediate.

During adolescence, women suffer from mood and anxiety disorders twice as often as men. Gender differences in social behaviour are present throughout life, but reach a peak during adolescence. The reason that women are more often confronted with psychopathology is probably the fact that women rely more on social support and suffer more from rejection than men. Recent research, however, shows that there are more complicated mechanisms behind it, and the type of stressor, among other things, needs to be considered. The areas as discussed in the SIPN model are more sensitive to stress in women than in men.

Recent research seems to indicate abnormalities in structures that are part of the SIPN model when there is an anxiety or mood disorder. This relates to the superior temporal gyrus, the ventral prefrontal cortex and the amygdala. The level of white matter in the frontal areas and the levels of choline in the orbitofrontal cortex also play a role.

New fMRI tasks are desperately needed to expose psychopathology in the brain during adolescence. For example, one could look at social rejection, where a very strong negative reaction should occur in women with mood or anxiety disorders.

Conclusion

The social behaviour of adolescents undergoes many changes. This is caused by neuronal changes, caused by hormones, maturation and learning processes. It is important to expose these changes with neuroimaging techniques such as fMRI. Among other things, this helps us to understand the increased risk of psychopathology in adolescence. There seems to be a strong relationship between psychopathology in adolescence and the SIPN model.