“Sensitive Periods in the Development of the Brain and Behavior.”

Department of Neurobiology, Stanford University School of Medicine, Sherman Fairchild Sciences Building, Stanfrord, CA 94305-5125, USA.
Journal of Cognitive Neuroscience (Impact Factor: 4.09). 11/2004; 16(8):1412-25. DOI: 10.1162/0898929042304796
Source: PubMed


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.

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    • "However, this pattern changes as experience with categorical exemplars accumulate. Brain responses become stronger, more efficient, and automatic as the boundaries of relevant stimuli becomes narrower, while responses to non-experienced stimuli are dampened (Greenough et al., 1987; Knudsen, 2004; Stiles, 2008; Leppanen and Nelson, 2009; Werker and Hensch, 2015). Interestingly, while the timing of the opening and closing of sensitive windows has generally been considered an internally mediated phenomenon with pre-determined timing parameters, under some conditions, environmental experiences can also affect the timing and pace of the period of heightened sensitivity. "
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    • "As a rule, circuits that process lower level information mature earlier than those that process higher level information (Scherf, Behrmann, Humphreys, & Luna, 2007). For example, in the neural hierarchy that analyzes visual information, low-level circuits that analyze the color, shape, or motion of stimuli are fully mature long before the high-level circuits that analyze or identify biologically important stimuli, such as faces, food, or frequently used objects (Knudsen, 2004; Scherf et al., 2007). The process by which initial learning leads to a constraint on later learning is termed entrenchment, and is equally apparent in the development of speech (Munakata & Pfaffly, 2004; Seidenberg & Zevin, 2006). "

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