David J. Madden and Zachary A. Monge
Age-related decline occurs in several aspects of fluid, speed-dependent cognition, particularly those related to attention. Empirical research on visual attention has determined that attention-related effects occur across a range of information processing components, including the sensory registration of features, selection of information from working memory, controlling motor responses, and coordinating multiple perceptual and cognitive tasks. Thus, attention is a multifaceted construct that is relevant at virtually all stages of object identification. A fundamental theme of attentional functioning is the interaction between the bottom-up salience of visual features and top-down allocation of processing based on the observer’s goals. An underlying age-related slowing is prominent throughout visual processing stages, which in turn contributes to age-related decline in some aspects of attention, such as the inhibition of irrelevant information and the coordination of multiple tasks. However, some age-related preservation of attentional functioning is also evident, particularly the top-down allocation of attention. Neuroimaging research has identified networks of frontal and parietal brain regions relevant for top-down and bottom-up attentional processing. Disconnection among these networks contributes to an age-related decline in attention, but preservation and perhaps even increased patterns of functional brain activation and connectivity also contribute to preserved attentional functioning.
Human visual development is a complex dynamic psychological/neurobiological process, being part of the developing systems for cognition, action, and attention. This article reviews current knowledge and methods of study of human visual development in infancy and childhood, in relation to typical early visual brain development, and how it can change in developmental disorders, both acquired (e.g., related to at-risk births) and genetic disorders. The newborn infant starts life with a functioning subcortical visual system which controls newborn orienting to nearby high contrast objects and faces. Although visual cortex may be active from birth, its characteristic stimulus selectivity and control of visual responses is generally seen to emerge around six to twelve weeks after birth. By age six months the infant has adequate acuity and contrast sensitivity in nearby space, and operating cortical mechanisms for discriminating colors, shapes, faces, movement, stereo depth, and distance of objects, as well as the ability to focus and shift attention between objects of interest. This may include both feedforward and feedback pathways between cortical areas and between cortical and subcortical areas. Two cortical streams start to develop and become interlinked, the dorsal stream underpinning motion, spatial perception and actions, and the ventral stream for recognition of objects and faces. The neural systems developing control and planning of actions include those for directed eye movements, reaching and grasping, and the beginnings of locomotion, with these action systems being integrated into the other developing subcortical and cortical visual networks by one year of age. Analysis of global static form (pattern) and global motion processing allows the development of dorsal and ventral streams to be monitored from infancy through childhood. The development of attention, visuomotor control and spatial cognition in the first years show aspects of function related to the developing dorsal stream, and their integration with the ventral stream.
The milestones of typical visual development can be used to characterize visual and visuo-cognitive disorders early in life, such as in infants with perinatal brain injuries and those born very prematurely. The concept of “dorsal stream vulnerability” is outlined. It was initially based on deficits in global motion sensitivity relative to static form sensitivity, but can be extended to the planning and execution of visuomotor actions and problems of attention, together with visuospatial and numerical cognition. These problems are found in the phenotype of children with both genetic developmental disorders (e.g., Williams syndrome, autism, fragile-X, and dyslexia), and in acquired developmental disorders related to very preterm birth, or in children with abnormal visual input such as congenital cataract, refractive errors, or amblyopia. However, there are subtle differences in the manifestation of these disorders which may also vary considerably across individuals. Development in these clinical conditions illustrates the early, but limited, plasticity of visual brain mechanisms, and provides a challenge for the future in designing successful intervention and treatment.
Ekaterina Zavershneva and René van der Veer
Lev Semyonovich Vygotsky (real name Lev Simkhovich Vygodsky; Orsha 1896–Moscow 1934) was a Russian psychologist who created cultural-historical theory, which proved influential in developmental psychology and other psychological disciplines. Vygotsky characterized his approach as “height psychology” (as opposed to “depth psychology”) and posited that the higher forms of mind should be the starting point for the study of human development. In his view it was essential to study psychological processes in their historical dynamics; these dynamics could be unraveled with the causal-genetic approach he developed, which involved the guided formation of mind in the course of its study or the experimental unfolding of ontogeny. Vygotsky claimed that the mechanisms of human development are not genetically determined and that we must find its source in culture and the social environment. Human development is mediated by cultural artifacts and sign systems, which are mastered in a dialogue with other people in spontaneous or guided interaction, which stimulates development by creating a zone of proximal development. The major means of the transformation of innate mind into higher mind is language, which enables us to preserve and transmit the experience of generations. In this process of cultural development the person develops a system of higher psychological functions that are social in origin, voluntary and mediated in nature, and form part of a systemic whole. The process of ontogeny goes through a series of stable periods and crises that correspond with specific conditions of the social situation of development and the developmental tasks. Age periods are completed with the development of neoformations, which do not just form results but are also prerequisites for further development. With the development of verbal thinking and the mastery of cultural means of behavior the person masters her/his innate mind and becomes a personality, whose main characteristic is freedom of behavior.
Working memory as a temporary buffer for cognitive processing is an essential part of the cognitive system. Its capacity and select aspects of its functioning are age sensitive, more so for spatial than verbal material. Assumed causes for this decline include a decline in cognitive resources (such as speed of processing), and/or a breakdown in basic control processes (resistance to interference, task coordination, memory updating, binding, and/or top-down control as inferred from neuroimaging data). Meta-analyses suggest that a decline in cognitive resources explains much more of the age-related variance in true working memory tasks than a breakdown in basic control processes, although the latter is highly implicated in tasks of passive storage. The age-related decline in working memory capacity has downstream effects on more complex aspects of cognition (episodic memory, spatial cognition, and reasoning ability). Working memory remains plastic in old age, and training in working memory and cognitive control processes yields near transfer effects, but little evidence for strong far transfer.