Sensitive Periods in the Development of the Brain and Behavior

Abstract

Experience exerts a profound influence on the brain and, therefore, on behavior. When the effect of experience on the brain is particularly strong during a limited period in development, this period is referred to as a sensitive period. Such periods allow experience to instruct neural circuits to process or represent information in a way that is adaptive for the individual. When experience provides information that is essential for normal development and alters performance permanently, such sensitive periods are referred to as critical periods. Although sensitive periods are reflected in behavior, they are actually a property of neural circuits. Mechanisms of plasticity at the circuit level are discussed that have been shown to operate during sensitive periods. A hypothesis is proposed that experience during a sensitive period modifies the architecture of a circuit in fundamental ways, causing certain patterns of connectivity to become highly stable and, therefore, energetically preferred. Plasticity that occurs beyond the end of a sensitive period, which is substantial in many circuits, alters connectivity patterns within the architectural constraints established during the sensitive period. Preferences in a circuit that result from experience during sensitive periods are illustrated graphically as changes in a ''stability landscape,'' a metaphor that represents the relative contributions of genetic and experiential influences in shaping the information processing capabilities of a neural circuit. By understanding sensitive periods at the circuit level, as well as understanding the relationship between circuit properties and behavior, we gain a deeper insight into the critical role that experience plays in shaping the development of the brain and behavior.

Sensitive periods for the functional specialization of the neural system for human face processing

“…Our data for the human face processing system seem to be incompatible with the proposal (1) that a lack of appropriate input to a neural system for an extended period after birth results in a random organization of these neural circuits (1). Moreover, our data argue against the assumption that degraded basic visual functions predominantly cause face processing deficits in cc individuals (13).…”

“…These epochs are called "sensitive phases." They are named "critical periods" if neural systems are irreversibly shaped during this time (1,2). The mechanisms of sensitive periods have often been investigated in animal research using a visual deprivation approach (see pioneering work in ref.…”

“…Testing this hypothesis with a neural marker is crucial, because the same overt behavior might arise from different neural circuits, e.g., as a result of functional reorganization or strategy change (1). Here, we made use of the high temporal resolution of noninvasive event-related potentials (ERPs) in humans to test whether the development of the human face-specific neural processing system depends on visual…”

Multi-competence and first language attrition

“…During this over-production of synapses, the extensive growth and elimination of axons and dendrites, and the forming and breaking of the connections between pre-and postsynaptic neurons leads to the development and stabilization of neural circuits (Knudsen 2004). A significant reduction of synapses plus an increase in stabilized synapses may be contributing to the critical or sensitive period that is often referred to in general learning, as well as -for our purposes -in L2 acquisition research.…”

Effects of habitat enrichment and food availability on the foraging behaviour of juvenile Atlantic Cod (Gadus morhua L)

“…It has been reported for many species, over several taxa, that early experience plays an important role in shaping adult behaviour (Sackett et al 1999;Rosenzweig 2003;Knudsen 2004;Poirier et al 2004;Braithwaite and Salvanes 2005). The kinds of early experience that can have an effect include social interactions, exposure to predators, experience of foraging on live prey and, more generally, interacting with structural complexity such as enrichment in the captive environment.…”