Saturday, May 24, 2008

Es gibt (It gives / There is) a question of innateness as moot

[from the final pages of The Fundamentals of Brain Development: integrating nature and nurture, Joan Stiles, Harvard UP 2008]

“The view of brain development presented here is dynamic, interactive, and adaptive. Complex signaling cascades [of produced cellular-environmental proteins] direct the formation and fate of cell populations, specify the migratory pathways and final destinations of new neurons, direct the formation of connections, and even signal cell death [e.g., for neural net pruning] in targeted populations [having overexuberant neuronal genesis]. The developmental process can adjust to contingencies and even to direct insult [i.e., injury] to brain structure. Yet there does not appear to be a blueprint, an executive, or even a homunculus [So it goes, Terence Deacon] directing the continuous changes in the complex array of elements, systems, and processes that emerge, expand, change, and sometimes just disappear across [a] period of development... [379].

At first, “[i]nteractions are governed by intrinsic signaling cascades that function to define primary cell lines and the primitive spatial organization of the embryo. Later in development, the system is structurally more complex, but the developmental process has produced greater compartmentalization and regionalization of systems, as well as increasing commitment of neural elements to specific structures [e.g., sensory areas] with particular functions [e.g., connecting sensed edges and sensed colors in the perception of an object]. Thus the process of development introduces levels of structure and function that constrain the range of possible developmental trajectories for the organism. In that sense, development is, in part, a self-organizing process[..., an i]dea [that...] has a long and varied history in disciplines as diverse as evolutionary biology, psychology, anthropology, and computational modeling... [381].

“[O]n the question of innateness, within this model of biological brain development, innate factors [my emph. - G], that is, inherited factors, are inextricably linked to experience [in, for example, the sense of embryonically-cellular excitation of signal-expectant responsiveness, as well as later neuroelectric excitation of further neurogenesis], and together inheritance and experience define and direct the developmental process. This presents a very different view of what it means for something to be innate than is typically presented in psychological models. In this view, everything that develops has an innate aspect [my emph. - G]. It must because all developmental processes rely, fundamentally, on the information encoded in the genes and on the cellular mechanisms that provide access to that information[, beginning with the given, generative mechamisms of the fertilized ovum—that intergenerational start-up environment “genomically” produced from a mature ovary—then, the environment of every cell division in embryogenesis and beyond]. Genes themselves do not participate in developmental processes; rather, it is the products of gene expression, the proteins, that are the active agents [my emph. -G] in development. But gene products do not by themselves create neural structures or functions. Rather, they participate in complex signaling cascades that over time serve to direct the [regional] fate of cells, the organization of systems, and the establishment of signaling pathways. Indeed, the same gene product can have markedly different effects depending on the developmental context[, earlier vs later in a process of development] in which it is expressed....This is a very different way of thinking about what it means for something to be innate. It renders any attempt to classify things as innate or learned[, i.e., as one or the other,] moot....Innate factors and environmental context act in concert to direct the processes that generate the developing neural system. The question, by this model[—which, by the way, is strictly based on the past 370+ pages of integrated empirical research, involving hundreds of resources—], becomes, what is the nature of the developmental process that gives rise to a particular biological structure, neural function, learning mechanism, or concept?” [384].

The question of innateness dissolves or translates into the question of the emergent “act[ing] in concert to direct...processes that generate...that gives rise.”