ABSTRACT

Neuroscientists have long recognized that the brain is an open, adaptive system and that the organism's experiences are environmentally contextualized. However, the proposition that sociocultural contexts may exert reciprocal influences on neurobiological mechanisms is rarely considered and could not be empirically explored until very recently. This chapter reviews an emerging trend of interdisciplinary research aimed at exploring the effects of sociocultural influences on human brain functioning. Viewed through the lens of a cross-level biocultural co-constructive framework, human development is co-constructed by biology and culture through a series of reciprocal interactions between developmental processes and plasticity at different levels.

INTRODUCTION

For more than a century, neuroscientists have been interested in how neural mechanisms implement mental experiences and how experiences may exert reciprocal influences on the neurobiological substrates of the mind. Ramón y Cajal enunciated what today is known as the “activity-dependent synaptic plasticity and memory hypothesis.” Since the formulation and discoveries of synaptic processes of memory and learning, a great variety of neurochemical mechanisms involved in tuning synaptic efficacy have been identified (see Bliss, Collingridge, & Morris, 2003, for a recent review).

ABSTRACT

It is well established that brain development depends on the interaction between the basic components of the nervous system (nature) and the environment (nurture). This interaction, however, relies on a number of rules that could modify not only the organization of neural systems, but also their function. In this chapter, we report results on the plasticity of the visual system in animal and human models, using a variety of methodological approaches. In particular, we describe major findings regarding plasticity that result from modifications of the visual input through lesions in the various stages of the visual pathway (peripheral and central). Possible mechanisms for such neural reorganization are also discussed.

NATURE VERSUS NURTURE: ENVIRONMENTAL EFFECTS ON BRAIN PLASTICITY

One of the oldest issues in modern psychology and biology concerns the nature versus nurture conundrum. Miscellaneous inquiries have been explored in this topic, such as “to what extent can genetic dispositions endow behaviors?” and “to what degree can the environment shape these?” It is well established that brain development depends on the interaction between the basic components of the nervous system (nature) and the stimulating environment (nurture). However, this interaction relies on a number of rules that could modify not only the organization of neural systems, but also their function. As we consider the main principles of evolution, we focus on the characteristics of the brain that are inheritable.

ABSTRACT

Although aging is broadly characterized by decline, the potential for new learning and plasticity persists well into the later decades of life. Scientific advances are yielding a deeper understanding of the limitations that biological aging imposes on cognitive function, as well as new insights into how the human mind and brain respond adaptively to the aging process. Neurocognitive investigations of the reciprocity between mind and brain reveal new avenues to influence and shape neural processes that underlie mental fitness, especially in the golden years. We explore these ideas to illustrate the co-constructivist framework in operation across neural, cognitive, behavioral, and cultural dimensions as they influence late-life development.

OVERVIEW

The persistence of behavioral adaptation and plasticity (i.e., modifiability) in later life has been recognized by the field of cognitive aging for several decades (e.g., Baltes, 1997). Training procedures of various sorts have been shown to enhance cognitive performance and produce long-term gains, even for older adults well into their seventies (e.g., Willis & Nesselroade, 1990). With the recent advances in genetics, in the basic neurosciences, and in brain imaging technologies, the scope and potential of age-related reorganizational processes have attained a new level of analysis and persuasion, especially for researchers whose theoretical orientation is closely linked to brain correlates of plasticity (Park, Polk, Mikels, Taylor, & Marshuetz, 2001; Reuter-Lorenz, 2002).

ABSTRACT

Contrary to widely held belief, a small number of new neurons are generated in the adult brain and even in the aging brain. Although this adult neurogenesis is minute compared with the vast number of neurons in our brains, and although adult neurogenesis does not lead to substantial regeneration in cases of neuronal loss, the new neurons may serve an important function in learning and memory processes. Adult neurogenesis is neuronal development in nucleo and is controlled by genetic and environmental factors. It exemplifies that, throughout life, brain development is activity and experience dependent, and, more important, that it never ends.

INTRODUCTION

“Adult neurogenesis” is the generation of new nerve cells in the adult brain (Fig. 4.1), a process that was long believed to be impossible, although it occurs in both nonhuman primates (Gould et al., 1999) and humans (Eriksson et al., 1998). Today, adult neurogenesis has become a prime topic in biomedical research because of its implications for the treatment of neurodegenerative disorders and essentially all diseases that involve a loss of nerve cells (neurons). Because it is the stem cells residing in the adult brain from which new neurons originate in adult neurogenesis, many researchers believe that we might learn from adult neurogenesis how to “grow” stem cells into new neurons for transplantation – in cases of Parkinson's disease, for example (Bjorklund & Lindvall, 2000).

ABSTRACT

Biocultural co-constructivism is a concept new to the field of developmental neuroscience, and thus there is no precedent for modeling how cultural processes are incorporated into the developing or developed brain. In this chapter, I offer a number of suggestions for how one might think about and study the relations among brain, culture, and development. I begin by providing a brief overview of brain development, followed by a discussion of neural plasticity. I conclude by speculating as to how culture might be incorporated into neural substrate, and subsequently and conversely, how such a remodeled brain might lead to changes in behavior.

BACKGROUND

In 1997, Bloom and I published a paper in which we lamented the lack of communication among those studying behavioral development and those studying brain development (Nelson & Bloom, 1997). We argued that the impressive advances being made on both fronts – brain and behavioral development – and our knowledge of children in general would expand exponentially if there was greater cross-fertilization across disciplines. We illustrated a few examples, emphasizing most how advances in brain imaging and in our knowledge of neural plasticity may ultimately come to revolutionize our thinking about brain–behavior relations.

The arguments in favor of studying “neurobehavioral” development are as true today as when Bloom and I first proposed this in 1997. I still contend that our knowledge of the developing brain would best be grounded in knowledge of child development, and conversely, that our knowledge of child development could be vastly improved were we to explicate the neural mechanisms that underlie behavioral development.

The main objective of this book is to advance research and theory in the study of brain–culture relationships. Contentwise, our primary arena is the study of human behavior, in general, and human development, in particular. When speaking of human development, we refer to the view that human development is a lifelong process, extending from conception into old age. When we speak of culture in this context, we use it in its most general sense and mean to include all aspects of the environment – physical, material, social, and symbolic.

On the one hand, we note the already existing and recently strengthened connections between researchers and scholars in the neuro, behavioral, social, and cultural sciences that give testimony to a new level of “interdisiplinarity.” It is increasingly recognized that such collaborative work, aimed at a more explicit treatment of the brain–culture interface, is necessary to better understand the interactive systems that shape the human mind and its development.

On the other hand, we also suggest that there are lacunae or misunderstandings in recognizing the full reciprocal nature of the brain–culture interaction. One example is the occasionally high emphasis that brain researchers place on brain determinism. A similar one-sidedness exists among some social scientists when they engage themselves in demonstrating the exclusive role of social-cultural environmental conditions. To counteract such lacunae or one-sided perspectives, we introduce a new “metatheoretical” paradigm as a guiding principle. This is the principle of developmental biocultural co-constructivism.

ABSTRACT

The human brain is formed by two interactive systems: the genetic-biological and the sociocultural systems. The brain, in turn, regulates behavior and thereby acts on the societal environment. This chapter examines how experience shapes the brain and describes the interaction of brain, behavior, and culture under conditions of extreme and traumatic stress as present in many of the world's war-torn regions. Traumatic events massively change the brain's structure and function. Within our model of biological-cultural interaction, we analyze how these experiences foster violent behavior and deal with the societal consequences of the traumatization of large parts of the population.

INTRODUCTION

In this day and age, humans are raised and live in a complex sociocultural environment with increased demands for the brain, the body, and the social structures to adapt. More information at increasingly complex levels has to be processed than ever before at an ever-increasing velocity and over an extended lifespan. This places high pressure on the individual and society to continuously adjust to new environmental conditions, resulting in a stream of continuous microstressors. At the same time, modern societies are becoming increasingly aware of the effects of macrostressors, including traumatic stress, which, although seemingly transient, may be changing the brain's processing machinery, resulting in characteristic behavioral, physiological, and psychological (mal)adaptations to environmental conditions and – when a whole community is affected – changes in the local culture.