Preface

During early childhood, mental and neurocognitive illnesses are highly prevalent. To understand these illnesses, researchers have to know things about genetics and about environmental factors that influence the brain. This article discusses the existing knowledge about maternal care and mother-child interactions. The research question in the article is:  Do fragmentation and unpredictability of maternal cues during fetal and early postnatal life contribute to unfavorable cognitive and emotional outcomes and to changes in underlying brain structures?

Studies with humans

The literature, which is strongly influenced by Bowlby's research, suggests that the quality of the parent-child relationship affects developmental outcomes of the child. Research by Bowlby also shows that the child's relationship with the parents and especially the relationship with the mother at a young age is an important predictor for the extent to which the child individual develops cooperative relationships, trusts someone and safely attaches to someone. Children who develop a secure attachment are often children with a history of sensitive (accurate responses to children's signals) and responsive (consistency of responses to the child's signals) parents. A secure attachment style offers is also a predictor for higher independence, better emotional regulation skills and better social adjustment. Children with unsafe bonding due to poor maternal care quality are more vulnerable to risk factors and suffer from poorer mental health.

Studies with animals

Certain research cannot be done with humans. This is why researchers test on animals. The influence of maternal behavior on offspring has been investigated during animal studies. Studies with rodents support Bowlby's assumption that sensory signals from mothers are one of the mechanisms by which the environment influences brain development. The environment influences maternal behavior and maternal behavior influences the brain. A stressful environment for the mother not only leads to stress, but also to abnormal parenting behavior towards their offspring. The timing of the abnormal signals and the sex of the offspring also influence the outcomes.

Quantity and quality of maternal care

Both quantitative and qualitative aspects of maternal care have been validated as important frameworks that can change brain function in offspring. Increasing quantitative maternal care leads to attenuation of the stress hormone gene expression, a reduced stress response and more resilience, while minimal care leads to cognitive and emotional problems. Maternal sensitivity and responsiveness are determinants of the quality of maternal care.

Fragmentation and unpredictability

In human behavior, fragmented behavior is behavior that consists of many consecutive simple patterns. In rodents, fragmentation focuses on the extent to which care behavior occurs in numerous short episodes. For both humans and rodents, unpredictable maternal behavior focuses on patterns of behavior and measures the occurrence of consistent compared to inconsistent prevention of behavior.

Fragmentary and unpredictable maternal signals: pre and postnatal

It is not yet fully understood how sensory input is transmitted from the mother to the fetus. Recent research shows that a consistent emotional state of the mother leads to better mental development in children who are one year of age. It might be that the mother passess on emotional information to her fetus through physical parameters such as hormone levels or heart rate, but this has not yet been proven.

With the help of video recordings, specific sensory signals from the mother to the child have been identified. Qualitative and quantitative aspects in rodents have been evaluated by reducing a group's nesting material (this is a simulation of poverty). Fragmentation of maternal care causes cognitive and emotional problems in puppies, of which the consequences become visible later in life and persist into middle age. Learning difficulties were associated with loss of hippocampal synapses and dendrites. Emotional problems resulted in anxious behavior and increases the vulnerability to depression. If predictable and consistent sensory input from the mother diminishes excitement and gene expression, it seems likely that fragmentary and unpredictable sensory signals have the opposite effect.

Discussion & Conclusion

The patterns and especially the degree of fragmentation and unpredictability of maternal signals have an important influence on the neuropsychiatric outcomes of the child, both pre- and postnatally. Little is known yet about how maternal care affects the brain of the fetus and about the mechanisms by which these influences take place.