The level of rate remapping due to mechanism A (ηA), which is based on the change of the sum of direct
excitatory inputs, is the absolute difference in the mean sum of the input at the positions of the place field normalized by λSR. The level of rate remapping due to mechanism B (ηB), which is based on the change in the level of inhibition, is the absolute difference in the mean global inhibition level at the positions of the place field, normalized by λSR. The ratio of the impact of the two mechanisms (γ) is ηB divided by ηA + ηB. ηR(p)=∑rr⊂p|λi1(r)−λi0(r)|∑rr⊂pλSR ηA(p)=∑rr⊂p|Ii1(r)−Ii0(r)|∑rr⊂pλSR ηB(p)=∑rr⊂p|0.9⋅maxjDG(Ij1(r))−0.9⋅maxjDG(Ij0(r))|∑rr⊂pλSR γ(p)=ηBηA+ηB We thank Paul Miller for an insightful conversation and Licurgo de Almeida for his assistance. This work was supported by European Community FP7/2007-2013 Grant 217148 – SF and by NIH/NIMH Grant P50 MH060450. “
“The medial find more entorhinal cortex (MEC) is a six-layered cortex and is part of the medial temporal lobe. It is implicated in physiological processes underlying navigation, learning, and memory and is often the site for early insults during pathophysiological conditions such as epilepsy and Alzheimer disease (Canto et al., 2008 and Witter and Amaral, 2004). The superficial layers of the MEC contain two morphologically distinct
excitatory projection neurons: the stellate and Androgen Receptor antagonist the pyramidal cells. Layer 2 (L2) contains both stellate and pyramidal cells (L2Ss and L2Ps respectively; Alonso and Klink, 1993), whereas layer 3 (L3) is exclusively composed of pyramidal cells (L3Ps) as projection neurons (Dickson et al., 1997 and Gloveli et al., 1997). MEC is the main input relay to the hippocampus. The main excitatory cells in the superficial layers project in a region-specific manner to the hippocampus. Although such ADP ribosylation factor interregional connectivity has long been studied, not much is known about the intrinsic organization of the microcircuitry in the
MEC. Microcircuits are characterized by the cell-specific ratios of intralaminar and interlaminar connections and the spatial distribution of inputs (Lübke and Feldmeyer, 2007, Mountcastle, 1997 and Schubert et al., 2007). Anatomical and electrophysiological studies have distinguished two different patterns of associative connectivity in superficial layers of the MEC: intralaminar recurrent connections (Köhler, 1986 and Dhillon and Jones, 2000) and ascending interlaminar feedback connections (Iijima et al., 1996, Kloosterman et al., 2003 and Köhler, 1986). Those studies, however, have not revealed the target-cell-specific functional connectivity patterns with respect to the layer-specific weight and spatial organization of the microcircuitry for all three classes of superficial excitatory cells. Using scanning photostimulation with caged glutamate (Callaway and Katz, 1993), we mapped the microcircuitry of the excitatory cells in the L2-3 MEC.