Axons, CCKexpressing interneuron types are recognized as basket cells, proximal dendritic innervating cells (Schaffer collateralassociated cells in CA1) and perforant ARQ-092 custom synthesis path-associated cells, which can be further divided on the basis of molecular SB 203580 supplier expression profiles. In vivo recordings show several differences between the same cell type in CA1 and CA3. In general, CCK/CB1R-expressing interneurons in CA3 [32] show more cell-type-dependent diversity in their theta phase coupling than in CA1, where most of them have a mean phase preference to the ascending phase of the pyramidal layer theta LFP [38]. In CA3, the basket and the proximal dendritic layer innervating interneurons fire maximally when the local pyramidal cell firing is minimal, on the CA1 theta LFP peak. By contrast, the strongly phase-modulated perforant path-associated CCK/CB1Rexpressing CA3 interneurons fire maximally 1808 phase shifted, on CA1 theta troughs. Thus, CA3 pyramidal cells, unlike their CA1 counterparts receive counter-phased GABAergic input from different types of CCK/CB1R-expressing GABAergic cells. During SWRs, single CCK/CB1R-expressing interneurons in CA1 and CA3 are sometimes activated, or do not change their firing rate relative to non-SWR periods, or are inhibited [32,38]. However, in CA3, some types of CCK/CB1R-expressing interneuron were mostly activated, whereas others were mostly inhibited, showing greater diversity of participation in SWRs than in CA1. In summary, based mostly on experiments under anaesthesia, only some of the brain-state-dependent firing dynamics of the same interneuron type can be predicted in the CA3 area from the previously described activity patterns of the same cell type in the CA1 area.in vivo [62,105] and in vitro [22,106?09]. These changes are probably key contributors to the formation and maintenance of cell assemblies related to navigation. Stimulation of glutamatergic pathways at theta frequency is a particularly efficacious method for changing synaptic weights [110]. Recording unidentified interneurons in novel environment showed a temporary suppression of firing [111,112], while the rats learned the new environment. A recent elegant study [113] demonstrated differential effects on the activity of individual interneurons during a goal-directed spatial navigation task involving learning. In this task, the firing patterns of pyramidal cell assemblies flickered between the representation of the new and the old maps across theta cycles; some interneurons associated their firing with the new assemblies, whereas others dissociated their activity from these. The firing associations of interneurons resulted from a local change in the efficacy of spike transmission from pyramidal cells to interneurons, either increasing or decreasing, possibly as a result of synaptic plasticity. Such association of some individual interneurons with specific cell assemblies emerged during the learning process, and remained stable in sleep and subsequent awake memory retention test [113]. It remains to be established whether the role of interneurons that increased their association with the new assembly was to suppress other assemblies, i.e. prevent their expression and/or to keep a temporal structure within the new assemblies, i.e. to maintain them, and/or prevent interference between competing assemblies by allowing their fine temporal coordination. The interneurons were recorded in and near the pyramidal cell layer with tetrodes [113] and could in.Axons, CCKexpressing interneuron types are recognized as basket cells, proximal dendritic innervating cells (Schaffer collateralassociated cells in CA1) and perforant path-associated cells, which can be further divided on the basis of molecular expression profiles. In vivo recordings show several differences between the same cell type in CA1 and CA3. In general, CCK/CB1R-expressing interneurons in CA3 [32] show more cell-type-dependent diversity in their theta phase coupling than in CA1, where most of them have a mean phase preference to the ascending phase of the pyramidal layer theta LFP [38]. In CA3, the basket and the proximal dendritic layer innervating interneurons fire maximally when the local pyramidal cell firing is minimal, on the CA1 theta LFP peak. By contrast, the strongly phase-modulated perforant path-associated CCK/CB1Rexpressing CA3 interneurons fire maximally 1808 phase shifted, on CA1 theta troughs. Thus, CA3 pyramidal cells, unlike their CA1 counterparts receive counter-phased GABAergic input from different types of CCK/CB1R-expressing GABAergic cells. During SWRs, single CCK/CB1R-expressing interneurons in CA1 and CA3 are sometimes activated, or do not change their firing rate relative to non-SWR periods, or are inhibited [32,38]. However, in CA3, some types of CCK/CB1R-expressing interneuron were mostly activated, whereas others were mostly inhibited, showing greater diversity of participation in SWRs than in CA1. In summary, based mostly on experiments under anaesthesia, only some of the brain-state-dependent firing dynamics of the same interneuron type can be predicted in the CA3 area from the previously described activity patterns of the same cell type in the CA1 area.in vivo [62,105] and in vitro [22,106?09]. These changes are probably key contributors to the formation and maintenance of cell assemblies related to navigation. Stimulation of glutamatergic pathways at theta frequency is a particularly efficacious method for changing synaptic weights [110]. Recording unidentified interneurons in novel environment showed a temporary suppression of firing [111,112], while the rats learned the new environment. A recent elegant study [113] demonstrated differential effects on the activity of individual interneurons during a goal-directed spatial navigation task involving learning. In this task, the firing patterns of pyramidal cell assemblies flickered between the representation of the new and the old maps across theta cycles; some interneurons associated their firing with the new assemblies, whereas others dissociated their activity from these. The firing associations of interneurons resulted from a local change in the efficacy of spike transmission from pyramidal cells to interneurons, either increasing or decreasing, possibly as a result of synaptic plasticity. Such association of some individual interneurons with specific cell assemblies emerged during the learning process, and remained stable in sleep and subsequent awake memory retention test [113]. It remains to be established whether the role of interneurons that increased their association with the new assembly was to suppress other assemblies, i.e. prevent their expression and/or to keep a temporal structure within the new assemblies, i.e. to maintain them, and/or prevent interference between competing assemblies by allowing their fine temporal coordination. The interneurons were recorded in and near the pyramidal cell layer with tetrodes [113] and could in.
