The prefrontal cortex (PFC) receives input from all other cortical regions and functions to plan and direct motor, cognitive, affective, and social behavior across time. It has a prolonged development, which allows the acquisition of complex cognitive abilities through experience but makes it susceptible to factors that can lead to abnormal functioning, which is often manifested in neuropsychiatric disorders. When the PFC is exposed to different environmental events during development, such as sensory stimuli, stress, drugs, hormones, and social experiences (including both parental and peer interactions), the developing PFC may develop in different ways. The goal of the current review is to illustrate how the circuitry of the developing PFC can be sculpted by a wide range of pre-and postnatal factors. We begin with an overview of prefrontal functioning and development, and we conclude with a consideration of how early experiences influence prefrontal development and behavior.neural plasticity | dendritic spines | prenatal stress | psychoactive drugs | metaplasticity T he development of the cerebral cortex reflects more than a simple unfolding of a genetic blueprint; rather, it represents a complex dance of experiential and genetic factors that mold the emerging cerebrum. Pre-and postnatal environmental events, such as sensory stimuli, hormones, parent-child relationships, stress, and psychoactive drugs, modify cerebral development and, ultimately, adult behavior. Although all cerebral regions are influenced by early experience, the effects of experience are significantly different in specific cortical regions. The goal of this article is to review the ways in which one specific region, the prefrontal cortex (PFC), is sculpted by a wide range of pre-and postnatal factors. We begin with an overview of the nature and function of the PFC, followed by a review of experience-dependent modification of prefrontal organization and function. What Is the PFC?Kaas (1) proposed that a few basic areas of cerebral cortex are present in all mammals. These include primary and secondary visual and somatosensory areas (i.e., V1, V2, S1, S2), at least one auditory area and one taste area, a motor area, a transitional strip of cortex that relates the amygdala and hippocampus to other cortical areas (i.e., perirhinal cortex, entorhinal cortex), and a region referred to as the PFC. The definition of the sensory regions is relatively straightforward insofar as they receive unimodal input from the sensory receptor systems (e.g., eye, ear, tongue), and the outputs of the motor cortex are ultimately directed via polysynaptic pathways to effector organs. The outputs of all cortical regions are also components of feedback loops through which the cortex and subcortical regions of the brain mutually influence each other. Although there is no universally acceptable definition of the PFC, it can be regarded to be the region of the cortex that receives its principal thalamic inputs from the mediodorsal nucleus of the thalamus (e.g., 2). This cor...

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Memory formation is hypothesized to involve the generation of event-specific neural activity patterns during learning and the subsequent spontaneous reactivation of these patterns. Here, we present evidence that these processes can also be observed in urethane-anesthetized rats and are enhanced by desynchronized brain state evoked by tail pinch, subcortical carbachol infusion, or systemic amphetamine administration. During desynchronization, we found that repeated tactile or auditory stimulation evoked unique sequential patterns of neural firing in somatosensory and auditory cortex and that these patterns then reoccurred during subsequent spontaneous activity, similar to what we have observed in awake animals. Furthermore, the formation of these patterns was blocked by an NMDA receptor antagonist, suggesting that the phenomenon depends on synaptic plasticity. These results suggest that anesthetized animals with a desynchronized brain state could serve as a convenient model for studying stimulus-induced plasticity to improve our understanding of memory formation and replay in the brain.

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