Topic: pyramidal cells

Inhibition has long been thought to stabilize the activity of cortical networks at low rates, and to shape significantly their response to sensory inputs. In this talk, I will describe three recent collaborative projects that shed light on these issues. (1) I will show how optogenetic excitation of inhibition neurons is consistent with cortex being inhibition stabilized even in the absence of sensory inputs, and how this data can constrain the coupling strengths of E-I cortical network models. (2) Recent analysis of the effects of optogenetic excitation of pyramidal cells in V1 of mice and mon

Accurate perception requires the integration of external (bottom-up) and internally generated (top-down) information. The main recipient of top-down projections in cortex is layer 1, which houses the dendrites of pyramidal cells (PC; Schuman et al., 2021). While layer 1 is devoid of excitatory cell bodies, it contains a variety of interneurons, including neurogliaform cells expressing neuron-derived neurotrophic factor (NDNF; Abs et al., 2018). NDNF interneurons are unique in that they provide slow inhibition, partially via non-synaptic volume release of GABA (Pardi et al. 2020). Yet, their co

In understanding circuit operations, a key issue is the extent to which neuronal spiking reflects local computation or responses to upstream inputs. Because pyramidal cells in CA1 do not have local recurrent projections, it is currently assumed that firing in CA1 is inherited from its inputs – thus, entorhinal inputs provide communication with the rest of the neocortex and the outside world, whereas CA3 inputs provide internal and past memory representations. Several studies have attempted to prove this hypothesis, by lesioning or silencing either area CA3 or the entorhinal cortex and examinin

Recent chronic imaging experiments in mice have revealed that the hippocampal code exhibits non-trivial turnover dynamics over long time scales. Specifically, the subset of cells which are active on any given session in a familiar environment changes over the course of days and weeks. While some cells transition into or out of the code after a few sessions, others are stable over the entire experiment. The mechanisms underlying this turnover are unknown. Here we show that the statistics of turnover are consistent with a model in which non-spatial inputs to CA1 pyramidal cells readily undergo p

There is little consensus on the level of spatial complexity at which dendrites operate. On the one hand, emergent evidence indicates that synapses cluster at micrometer spatial scales. On the other hand, most modelling and network studies ignore dendrites altogether. This dichotomy raises an urgent question: what is the smallest relevant spatial scale for understanding dendritic computation? We have developed a method to construct compartmental models at any level of spatial complexity. Through carefully chosen parameter fits, solvable in the least-squares sense, we obtain accurate reduced co

Rapidly changing inputs such as visual scenes and auditory landscapes are transmitted over several synaptic interfaces and perceived with little loss of detail, but individual neurons are typically “noisy” and cortico-cortical connections are typically “weak”. To understand how information embodied in spike train is transmitted in a lossless manner, we focus on a single synaptic interface: between pyramidal cells and putative interneurons. Using arbitrary white noise patterns injected intra-cortically as photocurrents to freely-moving mice, we find that directly-activated cells exhibit precisi

Successful integration of feedforward and feedback signals play a major role in cortical processing [1]. Pyramidal cells are thought to be the main sites to perform this integration locally. Signals from the two different pathways are integrated at distinct sites of the pyramidal cell [2]. Information originating up-stream, closer to primary sensory input, is integrated at basal peri-somatic dendrites and drives the cell's firing. Contextual information from down-stream sources is integrated at distal apical dendrites and amplifies the cell's firing only if coinciding with basal input. Importa

Left-right asymmetry is a fundamental feature of higher-order brain structure and function. Within the mouse hippocampus, properties of synapses between pyramidal cells depend on the hemispheric origin of presynaptic inputs. In the CA3-CA1 connection, right-input synapses in stratum radiatum have larger postsynaptic density (PSD) and higher perforation ratio, expressing lower NR2B subunit density, than left-input synapses. The major histocompatibility complex class I (MHCI) and Paired immunoglobulin-like receptor B (PirB) contribute to this asymmetry, suggesting potential trans-synaptic signal