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Leslie Ramos

(Paragraphs supposed to combine with/ part of other plasticity paragraphs)

Auditory Plasticity

Neural circuits are shaped by experience during periods of heightened brain plasticity in early postnatal life. The tonotopic patterning of the auditory cortical circuitry forms during the developmental window and remodels to adapt to the surrounding environment during this period

Recent studies found that release of the neurotransmitter norepinephrine is required for critical period plasticity in the auditory cortex, however intrinsic tonotopic patterning of the auditory cortical circuitry occurs independently from norepinephrine release [4].

A recent toxicity study showed that in-utero and postnatal exposure to polychlorinated biphenyl (PCB) altered overall primary auditory cortex (A1) organization, including tonotopy and A1 topography. Early PCB exposure also changed the balance of excitatory and inhibitory inputs, which altered the ability of the auditory cortex to plastically reorganize  after changes in the acoustic environment, thereby altering the critical period of auditory plasticity [5]

Adult plasticity

Studies in mature A1 have focused on neuromodulatory influences and have found that direct and indirect vagus nerve stimulation, which triggers neuromodulator release, promotes adult auditory plasticity [6]. Cholinergic signaling has been shown to engage 5-HT3AR cell activity across cortical areas and facilitate adult auditory plasticity [7]. Furthermore, behavioral training using rewarding or aversive stimuli, commonly known to engage cholinergic afferents and 5-HT3AR cells, has also been shown to alter and shift adult tonotopic maps [8].

Shepard, K., Liles, L., Weinshenker, D., & Liu, R. (2015). Norepinephrine is necessary for experience-dependent plasticity in the developing mouse auditory cortex. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience,35(6), 2432-7. [4]

T. Kenet, R. C. Froemke, C. E. Schreiner, I. N. Pessah, & M. M. Merzenich. (2007). Perinatal exposure to a noncoplanar polychlorinated biphenyl alters tonotopy, receptive fields, and plasticity in rat primary auditory cortex. Proceedings of the National Academy of Sciences, 104(18), 7646-7651.[5]

Navzer D. Engineer, Jonathan R. Riley, Jonathan D. Seale, Will A. Vrana, Jai A. Shetake, Sindhu P. Sudanagunta,. . . Michael P. Kilgard. (2011). Reversing pathological neural activity using targeted plasticity. Nature, 470(7332), 101-4. [6]

Takesian, A. E., Bogart, L. J., Lichtman, J. W., & Hensch, T. K. (2018). Inhibitory circuit gating of auditory critical-period plasticity. Nature neuroscience, 21(2), 218–227. doi:10.1038/s41593-017-0064-2 [7]

Polley, D., Steinberg, E., & Merzenich, M. (2006). Perceptual learning directs auditory cortical map reorganization through top-down influences. The Journal of Neuroscience : The Official Journal of the Society for Neuroscience, 26(18), 4970-4982. [8]