experience shapes receptive field structure during distinct critical periods of development (Daw et al., 1992, Fox, 1992, Stern et al., 2001 and Wiesel and Hubel, 1963). Changing the whisker complement alters receptive fields in the barrel cortex (Wallace and Fox, 1999) and altering visual input can change ocular dominance in the visual cortex (Wiesel and Hubel, 1963). These adaptive processes are thought to tune sensory neurons to the features they detect in the environment. In adulthood, plasticity persists in visual and somatosensory cortex chiefly in extragranular layers (LII/III and LV) (Daw et al., 1992, Diamond et al., 1994 and Fox, 1992). Most of the functional studies on experience-dependent plasticity KPT-330 ic50 to date have either investigated
plasticity in LIV or the superficial layers of cortex (LII/III), while relatively little is known of the functional plasticity in LV cells (Beaver et al., 2001, Diamond et al., 1994, Erchova et al., 2003 and Wilbrecht et al., 2010). Conversely, most of the studies on structural plasticity to date have investigated spine plasticity 3-deazaneplanocin A of LV neurons (Hofer et al., 2009, Trachtenberg et al., 2002 and Wilbrecht et al., 2010). LV is a major output projection layer of the cortex and in the somatosensory system sends connections to a variety of subcortical targets including trigeminal, pontine, thalamic, striatal, and collicular locations as well as other cortical areas (see Fox, 2008). The relative paucity of studies on LV plasticity makes it difficult
both to relate spine plasticity to functional plasticity and to gain some understanding of how cortical plasticity affects intracortical circuits and subcortical targets. LV contains a major subdivision between LVa and LVb and these Tryptophan synthase layers are engaged by distinct cortical circuits (Manns et al., 2004, Schubert et al., 2006, Shepherd et al., 2005 and Shepherd and Svoboda, 2005). Within LVb, pyramidal cells have diverse soma sizes, dendritic morphologies and synaptic targets (Chagnac-Amitai et al., 1990, Hattox and Nelson, 2007, Larkman et al., 1992, Mason and Larkman, 1990 and Tsiola et al., 2003). The intrinsic bursting (IB) and regular spiking (RS) cells within LVb can be distinguished by their intrinsic firing patterns and their somatic and dendritic morphology (Agmon and Connors, 1992, Chagnac-Amitai et al., 1990 and Zhu and Connors, 1999), although it has been argued that the morphological distinctions may represent two ends of a continuous spectrum rather than discrete categories of cell type. IB cells fire bursts of spikes in response to steady somatic current injection and tend to have complex dendritic arbors and large somata. RS cells fire adapting trains of spikes in response to steady current injection and tend to have relatively simple dendritic arbors and small somata. The intracortical circuits for IB and RS cells are different (Schubert et al.