the activity of VIP and SST-expressing cells result in the disinhibition of pyramidal neurons. Then, by inhibiting only certain dendritic branches of these now dis-inhibited pyramidal neurons, the neuromodulation-activated cells allow select sensory inputs to excite the pyramidal neurons and be represented in the brain circuitry. Thus, in a landscape of global inhibition by maturing inhibitory signaling, neuromodulation allows windows of dis-inhibition, temporally and spatially, that allow behaviorally important sensory inputs the opportunity to influence the brain. Linguistics First language acquisition The critical period hypothesis (CPH) states that the first few years of life constitute the time during which language develops readily and after which (sometime between age 5 and puberty) language acquisition is much more difficult and ultimately less successful. The hypothesis that language is acquired during a critical period was first proposed by neurologists Wilder Penfield and Lamar Roberts in 1959 and popularized by linguist Eric Lenneberg in 1967. Lenneberg argued for the hypothesis based on evidence that children who experience brain injury early in life develop far better language skills than adults with similar injuries. Dr. Maria Montessori was one of the earlier educators who brought attention to this phenomenon and called it "Sensitive Periods", which is one of the pillars of her philosophy of education. The two most famous cases of children who failed to acquire language after the critical period are Genie and the feral child Victor of Aveyron. However, the tragic circumstances of these cases and the moral and ethical impermissibility of replicating them make it difficult to draw conclusions about them. The children may have been cognitively disabled from infancy, or their inability to develop language may have resulted from the profound neglect and abuse they suffered. Many subsequent researchers have further developed the CPH, most notably Elissa Newport and Rachel Mayberry. Studies conducted by these researchers demonstrated that profoundly deaf individuals who are not exposed to a sign language as children never achieve full proficiency, even after 30 years of daily use. While the effect is most profound for individuals who receive no sign language input until after the age of 12, even those deaf people who began learning a sign language at age 5 were significantly less fluent than native deaf signers (whose exposure to a sign language began at birth). Early language exposure also affects the ability to learn a second language later in life: profoundly deaf individuals with early