Neuronal Plasticity: Beyond the Critical Period Mark Hübener, Tobias Bonhoeffer  Cell  Volume 159, Issue 4, Pages 727-737 (November 2014) DOI: 10.1016/j.cell.2014.10.035 Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 1 Map Plasticity in Sensory Areas of the Adult Neocortex (A) In the adult somatosensory cortex, surgically connecting two fingers (syndactyly) leads to receptive fields (in the gray region) that can be activated by either of the two fingers. Note that, normally, there is an abrupt transition from the representation of one finger to the next (digit 2/3 and digit 4/5). Reprinted with permission from Clark et al. (1988). (B) In the adult auditory cortex, behavioral training leads to overrepresentation of those frequencies (2.5 kHz) that are important for the behavioral task that the monkey was trained on. Reprinted with permission from Recanzone et al. (1993). (C) Retinal lesions lead, initially, to a zone in the visual cortex, which receives no visual input anymore (left). After some time, neurons in this zone start responding to locations in the visual field that lie outside of the visual scotoma (“filling-in,” right). This process occurs in the adult visual cortex of monkeys, cats (left), mice (right) and presumably many other mammals. Reprinted with permission from Gilbert (1992) (left) and Keck et al. (2008) (right). Cell 2014 159, 727-737DOI: (10.1016/j.cell.2014.10.035) Copyright © 2014 Elsevier Inc. Terms and Conditions

Figure 2 Interventions Promoting OD Plasticity in the Visual Cortex of Adult Rodents (A) Three days of MD do not change OD in adult rats, shown here as the ratio between contra- and ipsilateral eye visually evoked potential (VEP) amplitudes, which normally ranges between 2 and 2.5. In contrast, contralateral eye MD following dark rearing (DR, 10 days) causes a strong shift toward the ipsilateral eye. Each symbol represents one animal. Modified from He et al. (2006). (B) Adult rats kept in an enriched environment (EE) before and during a 7 day MD show a clear shift in OD, whereas rats in standard cages (SC) do not. Modified from Baroncelli et al. (2010). (C) Adult mice kept as pairs during the MD period display strong OD plasticity, which is not seen in mice housed individually. The ocular dominance index (ODI) represents a scaled version of the contra/ipsi response strength ratio, with lower values indicating a shift toward the non-deprived eye. Data were obtained with intrinsic optical imaging, each symbol representing one mouse. Modified from Balog et al. (2014). (D) Strong visual stimulation with drifting gratings during the deprivation period induces clear shifts in OD after as little as 2 days. Gray box indicates ODI range of non-deprived controls. Modified from Matthies et al. (2013). (E) Recovery from long-term MD is strongly facilitated by daily, head-fixed running on an air-suspended trackball during the presentation of visual stimuli (VS). Data show the strength of cortical responses elicited through the previously closed eye, assessed with intrinsic optical imaging. Gray box indicates values for non-deprived controls. Modified from Kaneko and Stryker (2014). (F) Three days of MD are insufficient to change OD in naive mice but cause a strong shift in animals that had experienced an OD shift earlier in life. Data were obtained with intrinsic optical imaging. Modified from Hofer et al. (2006). Note that the schematics do not necessarily reflect the actual rearing or experimental condition. Rather, they depict the critical parameter that was different between the control and test groups. Cell 2014 159, 727-737DOI: (10.1016/j.cell.2014.10.035) Copyright © 2014 Elsevier Inc. Terms and Conditions