The impact of poverty on the development of brain networks

Although the study of brain development in non-human animals is an old one, recent imaging methods have allowed non-invasive studies of the gray and white matter of the human brain over the lifespan. Classic animal studies show clearly that impoverished environments reduce cortical gray matter in relation to complex environments and cognitive and imaging studies in humans suggest which networks may be most influenced by poverty. Studies have been clear in showing the plasticity of many brain systems, but whether sensitivity to learning differs over the lifespan and for which networks is still unclear. A major task for current research is a successful integration of these methods to understand how development and learning shape the neural networks underlying achievements in literacy, numeracy, and attention. This paper seeks to foster further integration by reviewing the current state of knowledge relating brain changes to behavior and indicating possible future directions.

Neural correlates of establishing, maintaining, and switching brain states

Although the study of brain states is an old one in neuroscience, there has been growing interest in brain state specification owing to MRI studies tracing brain connectivity at rest. In this review, we summarize recent research on three relatively well-described brain states: the resting, alert, and meditation states. We explore the neural correlates of maintaining a state or switching between states, and argue that the anterior cingulate cortex and striatum play a critical role in state maintenance, whereas the insula has a major role in switching between states. Brain state may serve as a predictor of performance in a variety of perceptual, memory, and problem solving tasks. Thus, understanding brain states is critical for understanding human performance.

Imaging attention networks

The study of attention has largely been about how to select among the various sensory events but also involves the selection among conflicting actions. Prior to the late 1980s, locating bottlenecks between sensory input and response dominated these studies, a different view was that attentional limits involved the importance of maintaining behavioral coherence rather than resulting from a bottleneck. In both cases ideas of resource limits taken over from economics were important. Early evidence relating to the anatomy of attention came from neurological investigations of lesioned patients, but the major impetus for the anatomical approach came from neuroimaging studies that provided evidence of brain networks related to orienting to sensory events and control of response tendencies. The presence of a functional anatomy has supported studies of the development of attention networks and the role of neuromodulators and genetic polymorphisms in their construction. Together these developments have enhanced our understanding of attention and paved the way for significant applications to education, pathology and prevention of mental illness.

The attention system of the human brain: 20 years after

Here, we update our 1990 Annual Review of Neuroscience article, "The Attention System of the Human Brain." The framework presented in the original article has helped to integrate behavioral, systems, cellular, and molecular approaches to common problems in attention research. Our framework has been both elaborated and expanded in subsequent years. Research on orienting and executive functions has supported the addition of new networks of brain regions. Developmental studies have shown important changes in control systems between infancy and childhood. In some cases, evidence has supported the role of specific genetic variations, often in conjunction with experience, that account for some of the individual differences in the efficiency of attentional networks. The findings have led to increased understanding of aspects of pathology and to some new interventions.

Attentional networks and consciousness

The term consciousness is an important one in the vernacular of the western literature in many fields. It is no wonder that scientists have assumed that consciousness will be found as a component of the human brain and that we will come to understand its neural basis. However, there is rather little in common between consciousness as the neurologist would use it to diagnose the vegetative state, how the feminist would use it to support raising male consciousness of the economic plight of women and as the philosopher would use it when defining the really hard question of the subjective state of awareness induced by sensory qualities. When faced with this kind of problem it is usual to subdivide the term into more manageable perhaps partly operational definitions. Three meanings that capture aspects of consciousness are: (1) the neurology of the state of mind allowing coherent orientation to time and place (2) the selection of sensory or memorial information for awareness and (3) the voluntary control over overt responses. In each of these cases the mechanisms of consciousness overlap with one or more of the attentional networks that have been studied with the methods of cognitive neuroscience. In this paper we explore the overlap and discuss how to exploit the growing knowledge of attentional networks to constrain ideas of consciousness.

Short-term meditation increases network efficiency of the anterior cingulate cortex

Previous studies have found that short-term integrative body-mind training (IBMT) has positive effects on the brain structure and function in the anterior cingulate cortex. Here, we determined whether 11 h of IBMT alters topological properties of the anterior cingulate cortex in brain functional networks. We applied network analysis to resting-state functional connectivity between 90 cortical and subcortical regions before and after IBMT and relaxation training. The results demonstrated a significant increase in the network efficiency and connectivity of the anterior cingulate cortex after IBMT, but not after relaxation training. These findings indicated that the change in network topology might occur by altering the brain or psychological state. IBMT might be an intervention tool for improvement of self-regulation.

Control networks and neuromodulators of early development

In adults, most cognitive and emotional self-regulation is carried out by a network of brain regions, including the anterior cingulate, insula, and areas of the basal ganglia, related to executive attention. We propose that during infancy, control systems depend primarily upon a brain network involved in orienting to sensory events that includes areas of the parietal lobe and frontal eye fields. Studies of human adults and alert monkeys have shown that the brain network involved in orienting to sensory events is moderated primarily by the nicotinic cholinergic system arising in the nucleus basalis. The executive attention network is primarily moderated by dopaminergic input from the ventral tegmental area. A change from cholinergic to dopaminergic modulation would be a consequence of this switch of control networks and may be important in understanding early development. We trace the attentional, emotional, and behavioral changes in early development related to this developmental change in regulative networks and their modulators.

Brain states and hypnosis research

Research in cognitive neuroscience now considers the state of the brain prior to the task an important aspect of performance. Hypnosis seems to alter the brain state in a way which allows external input to dominate over internal goals. We examine how normal development may illuminate the hypnotic state.

Developing Mechanisms of Self-Regulation in Early Life

Children show increasing control of emotions and behavior during their early years. Our studies suggest a shift in control from the brain's orienting network in infancy to the executive network by the age of 3-4 years. Our longitudinal study indicates that orienting influences both positive and negative affect, as measured by parent report in infancy. At 3-4 years of age, the dominant control of affect rests in a frontal brain network that involves the anterior cingulate gyrus. Connectivity of brain structures also changes from infancy to toddlerhood. Early connectivity of parietal and frontal areas is important in orienting; later connectivity involves midfrontal and anterior cingulate areas related to executive attention and self-regulation.

Functional MRI evidence for inefficient attentional control in adolescent chronic cannabis abuse

Control of attention is a key mechanism underlying behavior regulation. In this study we detail the aspects of attention that covary with the chronic use of cannabis throughout adolescence. We compared performance and brain activation differences in tasks involving attention between young adults with a history of chronic cannabis use during adolescence and matched non-user control subjects. Two tasks were used to activate attention networks: the Attention Network Task (ANT) and the use generation task. In the ANT, chronic users (N=14) differed from controls (N=14) in showing poorer performance (longer reaction time and more errors) on tasks requiring processing of incongruent stimuli reflecting the executive attention network, but not in networks related to alerting or orienting components of attention. Functional MRI of brain activity showed stronger activation within the right prefrontal cortex in chronic users compared to the control group specifically on ANT trials requiring executive attention. The use generation task also revealed significantly stronger activation of the same right prefrontal area in users compared to controls. These results suggest that chronic cannabis users have less efficient executive attention in conflict resolution tasks, demanding more activation in the right prefrontal areas to resolve conflict.

Theta synchrony supports Weber-Fechner and Stevens' Laws for error processing, uniting high and low mental processes

Human brain theta rhythm has been related to the operation of a generic mechanism involved in error detection processes of different types (e.g., detecting incorrect motor responses or incorrect arithmetic equations). This theta activity seems to be sensitive to error salience or magnitude, that is, stronger theta activity is found with larger or more deviant errors (e.g., 1+2=8) than with smaller or less deviant ones (e.g., 1+2=4). A time-frequency decomposition analysis indicated that theta activity is modulated by the magnitude of erroneous information in a nonlinear fashion, which can be characterized using Weber-Fechner's law of logarithmic function and Stevens' law of power function. The present study suggests that the generic mechanisms for error detection and evaluation may share similar fundamental neural schemes with primary cognitive and sensory or perceptual processes, which are directly involved in processing the specific type of input.

Variations in catechol-O-methyltransferase gene interact with parenting to influence attention in early development

Attention influences many aspects of cognitive development. Variations in the catechol-O-methyltransferase (COMT) gene, known to affect dopamine neurotransmission, have frequently been found to influence attention in adults and older children. In this paper we examined 2 year old children and found that variation in the COMT gene influenced attention in a task involving looking to a sequence of visual stimuli. Because the influence of another dopamine-related gene (DRD4) has been shown to interact with parenting quality at this age, we explored parenting in relation to variations in the COMT gene. Variations in COMT interacted with parenting quality to influence our attention measure. The Val(108/158)Met polymorphism of COMT is commonly used to determine allelic groups, but recently haplotypes of several polymorphisms within this gene have been shown to be more strongly associated with perceived pain. Since attention and pain both involve the activation of the anterior cingulate gyrus in imaging studies, we compared the Val(108/158)Met influence with the COMT haplotypes and found the latter to be more predictive of attention. Our results confirm that important aspects of cognitive development including attention depend on the interaction of genes and early environment.

Genetic variation influences on the early development of reactive emotions and their regulation by attention

INTRODUCTION

Individual differences in temperament and attention provide an important link between normal and pathological development. Previous studies suggest that during infancy, orienting of attention is associated with higher levels of positive affect and lower levels of negative affect. For older children and adults, self-regulation, as measured by ratings of effortful control, is consistently associated with lower levels of negative affect such as sadness and distress.

METHODS

In the current paper we use a longitudinal study of children at ages 6-7 months (Time 1) and 18-20 months (Time 2) to examine how variations in candidate genes relate to emotional and self-regulatory aspects of temperament.

RESULTS

In accord with previous findings, parent ratings of orienting were positively related to positive affect only during infancy. Genetic variation in COMT was related to positive affect at Time l but not Time 2. Negative affect at both Time 1 and Time 2 was related to genetic variation in SNAP25. Genetic variation in CHRNA4 was related to Effortful Control at Time 2.

CONCLUSIONS

These findings lend support to the early modulation of emotion by aspects of orienting (Time 1) and executive attention (Time 2), and indicate that emotional reactivity and its regulation are modulated by different genes.

Toward a physical basis of attention and self regulation

The concept of self-regulation is central to the understanding of human development. Self-regulation allows effective socialization and predicts both psychological pathologies and levels of achievement in schools. What has been missing are neural mechanisms to provide understanding of the cellular and molecular basis for self-regulation. We show that self-regulation can be measured during childhood by parental reports and by self-reports of adolescents and adults. These reports are summarized by a higher order factor called effortful control, which reflects perceptions about the ability of a given person to regulate their behavior in accord with cultural norms. Throughout childhood effortful control is related to children's performance in computerized conflict related tasks. Conflict tasks have been shown in neuroimaging studies to activate specific brain networks of executive attention. Several brain areas work together at rest and during cognitive tasks to regulate competing brain activity and thus control resulting behavior. The cellular structure of the anterior cingulate and insula contain cells, unique to humans and higher primates that provide strong links to remote brain areas. During conflict tasks, anterior cingulate activity is correlated with activity in remote sensory and emotional systems, depending upon the information selected for the task. During adolescence the structure and activity of the anterior cingulate has been found to be correlated with self-reports of effortful control.Studies have provided a perspective on how genes and environment act to shape the executive attention network, providing a physical basis for self-regulation. The anterior cingulate is regulated by dopamine. Genes that influence dopamine levels in the CNS have been shown to influence the efficiency of self-regulation. For example, alleles of the COMT gene that influence the efficiency of dopamine transmission are related to the ability to resolve conflict. Humans with disorders involving deletion of this gene exhibit large deficits in self-regulation. Alleles of other genes influencing dopamine and serotonin transmission have also been found to influence ability to resolve conflict in cognitive tasks. However, as is the case for many genes, the effectiveness of COMT alleles in shaping self-regulation depends upon cultural influences such as parenting. Studies find that aspects of parenting quality and parent training can influence child behavior and the efficiency of self-regulation.During development, the network that relates to self-regulation undergoes important changes in connectivity. Infants can use parts of the self-regulatory network to detect errors in sensory information, but the network does not yet have sufficient connectivity to organize brain activity in a coherent way. During middle childhood, along with increased projection cells involved in remote connections of dorsal anterior cingulate and prefrontal and parietal cortex, executive network connectivity increases and shifts from predominantly short to longer range connections. During this period specific exercises can influence network development and improve self-regulation. Understanding the physical basis of self-regulation has already cast light on individual differences in normal and pathological states and gives promise of allowing the design of methods to improve aspects of human development.

Testing the behavioral interaction and integration of attentional networks

One current conceptualization of attention subdivides it into functions of alerting, orienting, and executive control. Alerting describes the function of tonically maintaining the alert state and phasically responding to a warning signal. Automatic and voluntary orienting are involved in the selection of information among multiple sensory inputs. Executive control describes a set of more complex operations that include detecting and resolving conflicts in order to control thoughts or behaviors. Converging evidence supports this theory of attention by showing that each function appears to be subserved by anatomically distinct networks in the brain and differentially innervated by various neuromodulatory systems. Although much research has been dedicated to understanding the functional separation of these networks in both healthy and disease states, the interaction and integration among these networks still remain unclear. In this study, we aimed to characterize possible behavioral interaction and integration in healthy adult volunteers using a revised attention network test (ANT-R) with cue-target interval and cue validity manipulations. We found that whereas alerting improves overall response speed, it exerts negative influence on executive control under certain conditions. A valid orienting cue enhances but an invalid cue diminishes the ability of executive control to overcome conflict. The results support the hypothesis of functional integration and interaction of these brain networks.

Executive attention and self-regulation in infancy

This study investigates early executive attention in infancy by studying the relations between infant sequential looking and other behaviors predictive of later self-regulation. One early marker of executive attention development is anticipatory looking, the act of looking to the location of a target prior to its appearance in that location, a process that involves endogenous control of visual orienting. Previous studies have shown that anticipatory looking is positively related to executive attention as assessed by the ability to resolve spatial conflict in 3-4-year-old children. In the current study, anticipatory looking was positively related to cautious behavioral approach in response to non-threatening novel objects in 6- and 7-month-old infants. This finding and previous findings showing the presence of error detection in infancy are consistent with the hypothesis that there is some degree of executive attention in the first year of life. Anticipatory looking was also related to the frequency of distress, to looking away from disturbing stimuli, and to some self-regulatory behaviors. These results may indicate either early attentional regulation of emotion or close relations between early developing fear and later self-regulation. Overall, the results suggest the presence of rudimentary systems of executive attention in infants and support further studies using anticipatory looking as a measure of individual differences in attention in infancy.

Failure of frontolimbic inhibitory function in the context of negative emotion in borderline personality disorder

OBJECTIVE

The authors sought to test the hypothesis that in patients with borderline personality disorder, the ventromedial prefrontal cortex and associated regions would not be activated during a task requiring motor inhibition in the setting of negative emotion. Such a finding would provide a plausible neural basis for the difficulty borderline patients have in modulating their behavior during negative emotional states and a potential marker for treatment interventions.

METHOD

A specifically designed functional magnetic resonance imaging (fMRI) activation probe was used, with statistical parametric mapping analyses, to test hypotheses concerning decreased prefrontal inhibitory function in the context of negative emotion in patients with borderline personality disorder (N=16) and healthy comparison subjects (N=14). 3-T fMRI scanning was used to study brain activity while participants performed an emotional linguistic go/no-go task.

RESULTS

Analyses confirmed that under conditions associated with the interaction of behavioral inhibition and negative emotion, borderline patients showed relatively decreased ventromedial prefrontal activity (including medial orbitofrontal and subgenual anterior cingulate) compared with healthy subjects. In borderline patients, under conditions of behavioral inhibition in the context of negative emotion, decreasing ventromedial prefrontal and increasing extended amygdalar-ventral striatal activity correlated highly with measures of decreased constraint and increased negative emotion, respectively.

CONCLUSIONS

These findings suggest specific frontolimbic neural substrates associated with core clinical features of emotional and behavioral dyscontrol in borderline personality disorder.