Critical Period Window for Spectral Tuning Defined in the Primary Auditory Cortex (A1) in the Rat

University of California, Berkeley, Berkeley, California, United States
The Journal of Neuroscience : The Official Journal of the Society for Neuroscience (Impact Factor: 6.34). 02/2007; 27(1):180-9. DOI: 10.1523/JNEUROSCI.3227-06.2007
Source: PubMed


Experience-dependent plasticity during development results in the emergence of highly adapted representations of the external world in the adult brain. Previous studies have convincingly shown that the primary auditory cortex (A1) of the rat possesses a postnatal period of sensory input-driven plasticity but its precise timing (onset, duration, end) has not been defined. In the present study, we examined the effects of pure-tone exposure on the auditory cortex of developing rat pups at different postnatal ages with a high temporal resolution. We found that pure-tone exposure resulted in profound, persistent alterations in sound representations in A1 only if the exposure occurred during a brief period extending from postnatal day 11 (P11) to P13. We also found that postnatal sound exposure in this epoch led to striking alterations in the cortical representation of sound intensity.

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Available from: Etienne de Villers-Sidani, Jan 14, 2015
    • "Pups are born with a functional sense of smell (Alberts 1984) but their hearing and vision senses only appear later in life (PN13-14; Blatchley et al. 1987; de Villers-Sidani et al. 2007; Freeman et al. 1999). Pups engage in somatosensory learning , especially associated with the whisker system for nipple location and nursing (Landers & Sullivan 1999; Sullivan et al. 2003). "
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    ABSTRACT: Pavlovian fear or threat conditioning, where a neutral stimulus takes on aversive properties through pairing with an aversive stimulus, has been an important tool for exploring the neurobiology of learning. In the past decades, this neurobehavioral approach has been expanded to include the developing infant. Indeed, protracted postnatal brain development permits the exploration of how incorporating the amygdala, prefrontal cortex and hippocampus into this learning system impacts the acquisition and expression of aversive conditioning. Here we review the developmental trajectory of these key brain areas involved in aversive conditioning and relate it to pups' transition to independence through weaning. Overall, the data suggests that adult-like features of threat learning emerge as the relevant brain areas become incorporated into this learning. Specifically, the developmental emergence of the amygdala permits cue learning and the emergence of the hippocampus permits context learning. We also describe unique features of learning in early life that block threat learning and enhance interaction with the mother or exploration of the environment. Finally, we describe the development of a sense of time within this learning and its involvement in creating associations. Together these data suggest that the development of threat learning is a useful tool for dissecting adult-like functioning of brain circuits, as well as providing unique insights into ecologically relevant developmental changes.
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    • "During this period, the cortical region responsive to tonal stimuli contracts and the juvenile overrepresentation of high frequencies is converted to a mature, more balanced frequency map [4]. Further, during the sensitive period, passive exposure to frequency-specific, pulsed tones results in competitive overrepresentation of those frequencies in A1, with the most dramatic changes occurring around PD 11– 13 [3] [4]. The observation that a single, brief (8 to 25 min) exposure to broadband noise on PD 14 can impair the ability of rats to perform acoustic frequency discrimination in adulthood further emphasizes that there are important functional consequences of exposure to specific sounds during this period of auditory development [5]. "
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    • "We studied vocal behavior during the first 4 weeks of life, a period in which the onset of dystonic symptoms in homozygote dt rats overlaps with a significant growth spurt (5 g at birth to about 25 g at P15) and at least three neurophysiological maturation processes. Pups begin to hear, and auditory experiences have long-lasting impacts on adult brain sound representation starting at P10 (e.g., Geal-Dor et al. 1993; de Villers-Sidani et al. 2007), adult respiratory patterns crystallizes between P10 and P15 (Paton and Richter 1995; Dutschmann et al. 2009), and the ingestive behavior transforms from suckling to mastication of hard food starting on P12 (Iriki et al. 1988; Westneat and Hall 1992). All four processes can affect vocal production, some in a predictable way (larger vocal organs likely lower pitch), whereas others are not fully understood. "
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