Development of neural mechanisms of working memory

Working memory (WM), the ability to hold and manipulate information online, improves during childhood as shown by an increase in WM capacity and a positive correlation between age and measures of WM performance. Intact function of WM is essential in many forms of complex cognition such as learning, reasoning, problem solving and language comprehension. WM function has a strong impact on academic achievement and is related to adaptive functioning at school. Children with deficits in WM have learning difficulties that are often accompanied by behavioural problems. The neural processes subserving WM performance and brain structures supporting this system continue to develop throughout childhood till adolescence and early adulthood. The prefrontal cortex (PFC), that is one of the last brain regions to mature, has a central role in the function of WM. WM network involves also distributed areas in parietal, temporal and striatal regions. It has been suggested that neuroanatomical brain development occurs in parallel with behavioural and cognitive maturation during childhood and adolescence. In this chapter, we focus on the neural mechanisms that support the function of WM, their developmental trajectories and relation of their development to the maturation of cognitive abilities. We will also discuss the development of the brain's "default-mode" network that isactive in the absence of cognitive task performance, i.e. during a resting state and shows attenuation of activation (deactivation) when the brain becomes engaged in attention requiring cognitive task performance. Deactivation mechanisms are important in the performance of WM tasks: inability to deactivate is associated with impaired task performance and is evident in patients with certain neuropsychological disorders.