Abstract and Keywords
This chapter provides a summary of what has been reviewed in this volume. It is all too common to hear in neuroscience and psychology that attention is a vague concept not amenable to a truly scientific explanation; or that, even if we did have an understanding of the mechanisms of attention, this would do little to illuminate the problems that arise in psychology or social neuroscience. The goal of this volume is to argue that both of these assertions are false. Although certainly there is much more to be learned, attention is an organ system and thus can be studied network by network, even though—as in all systems—there are interactions among the constituent parts. Attention networks have anatomical and functional independence, but they also interact in many practical situations. Damage to a node of these networks, irrespective of the source, produces distinctive neuropsychological deficits.
It is all too common to hear in neuroscience and psychology that attention is a vague concept not amenable to a truly scientific explanation; or that, even if we did have an understanding of the mechanisms of attention, they would do little to illuminate the problems that arise in psychology or social neuroscience. My goal in this volume has been to argue that both of these assertions are false. Although certainly there is much more to be learned, attention is an organ system and thus can be studied network by network, even though—as in all systems—there are interactions among the constituent parts.
As I have argued, attention networks have anatomical and functional independence, but they also interact in many practical situations. Damage to a node of these networks, irrespective of the source, produces distinctive neuropsychological deficits. This principle has been best established with respect to damage to the parietal lobe. Studies have shown that damage to parietal neurons (occurring in stroke, degeneration in Alzheimer's disease, blocking of cholinergic input, lesions of nucleus basalis, temporary damage from transcranial magnetic stimulation, direct injections of scopolamine, or closed head injury) all lead to difficulties in using cues to process targets in the visual field opposite the damage. Normal subjects who have one or two copies of the APOE4 (p.157) gene, which increases the risk of Alzheimer's disease, have also been shown to have increased difficulty in orienting attention and in adjusting the spatial scale of attention; however, they have no difficulty with maintaining the alert state. In one sense, the convergence between imaging, lesions, and pharmacology in terms of cognitive effect is obvious. If computations of parietal neurons lead to shifts of visual attention, damage to these neurons should produce difficulties. Yet there has been the notion in neuropsychology that localization is not as important as the cause of the lesion. Moreover, there has also been the argument that imaging does not provide a good account of the computations that can predict the effect of damage (Utall, 2001). Throughout this book, we have seen that imaging results provide clear evidence of the importance of areas of the parietal lobe in orienting of attention, and that damage to these areas—regardless of cause—interferes with aspects of orienting.
In the case of self-regulation, our effort to derive its physical basis (Posner & Rothbart, 2009) depended on the rather surprising relationship between a measure of executive attention derived from the attention network test (ANT) and parental reports of effortful control. This allowed us to discuss how the many nodes of the neural network that carry out resolution of conflict are crucial to self regulation and the important role of anterior cingulate connectivity in influencing many brain areas involved in cognition and emotion. This work has produced a putative brain circuitry underlying self-regulation. The anterior cingulate proved to have an important evolutionary history, including the presence of special cells unique to areas involved in self-regulation in large-brained mammals, notably humans and great apes. Specialization in this area could well be an important part of the unique human ability to delay gratification and to otherwise regulate behavior (p.158) in the service of long-term goals. This finding provides a renewed opportunity to explore differences between the brains of humans and other primates.
The association of genetic variations with individual differences in the efficiency of networks provides a method for discovery of those genes that serve to build the nodes and connections of the attentional network during development. This link provides a molecular perspective to the physical basis of a complex psychological construct. The ability to find candidate genes related to the attentional network rested on pharmacological findings linking different neuromodulators to the various networks. This opportunity is not present in a majority of the networks shown in Table 1.1. However, other methods, such as the use of full genome scans, the study of brain pathologies, and the use of hints from comparative studies of animals, can be used to provide appropriate candidate genes for other networks.
What illumination will this molecular perspective provide? The conservation of genetic mechanisms along the phylogenetic scale provides a basis for relating developments in human evolution to the more general issues of evolution of our species. As studies of the DRD4 gene suggest, human evolution continues to play a central role in behavior. Evidence for positive selection of alleles of this gene within recent human history has led us to propose the possibility that this and perhaps other alleles may increase the influence of cultural factors, such as parenting, on the child and thus provide for improved reproductive success and enhanced positive selection. This connection between genetic variation and cultural influence shows that the molecular perspective can deepen our understanding of human nature in ways that may be unanticipated. Even though we are very far from a deep understanding of the physical basis of many psychological concepts (p.159) central to human nature, the tools currently available can foster this effort.
Because attentional networks can influence the operation of other networks, they provide a link between brain mechanisms of attention and what might be called our voluntary behavior. Although this volume does not seek to answer the philosophical question about whether, in principle, all our actions are determined, it does provide critical knowledge of the mechanisms by which we exercise will.
In the preface to this volume I expressed the hope that reading it would help students of social neuroscience in their research. Chapters 5 and 6 summarized how attention may illuminate a wide variety of issues involved in social life. From the socialization of children to the understanding of antisocial behavior (psychopathy) and acquiring expertise, the volume has sought to foster an understanding of the role of attention in human life. Moreover, a tool kit of methods discussed in this volume provides us with the possibility of obtaining further knowledge and thus a firmer basis for the construction of psychology and social neuroscience.