, 1989, Galli and Maffei, 1988, Garaschuk et al., 1998, O’Donovan et al., 1994, Wong et al., 1995 and Yuste et al., 1992). Frequently, this form of activity travels across brain regions as waves activating neighboring neurons simultaneously. This particular property of intrinsically generated activity in developing networks is thought to be an important component of the activity-dependent establishment of specific brain circuits. For example, the high degree of correlation between neighboring neurons helps maintaining their spatial relationship through ascending neuronal pathways and thus establishing a topographic organization at

all levels (e.g., Triplett et al., 2009). Although the patterns MK-2206 ic50 of spontaneous activity at the level of

networks and individual neurons have been described in great detail, the activity patterns at the level of individual synapses within the dendritic arborization of single neurons are not known. It has been clear for some time that—within one neuron—spontaneous network events are frequently manifested as barrages or bursts of coincident synaptic inputs (Ben-Ari et al., 1989). However, how these synaptic inputs are distributed click here across the dendritic tree has not been investigated, mostly due to the fact that electrophysiological measurements do not allow identifying the dendritic locations of synaptic inputs. In mature neurons, the location of synaptic inputs within the dendritic arborization is most likely Calpain crucial for processing and storing information. For example, in tadpoles the dendrites of individual tectal neurons receive topographically organized afferent inputs (Bollmann and Engert, 2009). In mice, pyramidal neurons of the visual and auditory cortex receive functionally diverse synaptic inputs that are integrated by the postsynaptic cell to generate highly specific output (Chen et al., 2011 and Jia et al., 2010). Dendritic integration in pyramidal neurons has been shown to be supra-linear and—as

a consequence—the simultaneous activation of several synapses that are located close to each other on the same dendrite have a stronger influence on neuronal firing than the activation of the same number of synapses on different branches (Branco and Häusser, 2010, Larkum and Nevian, 2008, Losonczy and Magee, 2006 and Polsky et al., 2004). Furthermore, theoretical work demonstrated that such a local integration scheme where information is computed in dedicated dendritic subunits can boost the information processing capacities of neurons dramatically (Häusser and Mel, 2003, Poirazi and Mel, 2001 and Spruston, 2008). Here, we asked whether the patterns of synaptic input that developing hippocampal pyramidal neurons receive during spontaneous network bursts may already reflect such a subcellular fine-scale organization.