Diversity beyond variance: modulation of firing rates and network coherence by GABAergic subpopulations

Földy, Csaba; Aradi, Ildikó; Howard, Allyson; Soltész, Iván

doi:10.1046/j.1460-9568.2003.03096.x

Cited by 27 publications

(23 citation statements)

References 52 publications

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“…Both experimental and modeling studies have demonstrated that stable oscillatory activity can emerge in networks of heterogeneous inhibitory neurons. Furthermore, the stability of network oscillations increases with larger variation in physiological parameters (Aradi and Soltesz, 2002;Foldy et al, 2004). Our results, together with data showing remarkable heterogeneity in a given neurochemicalmorphological neuron type (Pawelzik et al, 2002;Monyer and Markram, 2004), raise the possibility that the variability in firing pattern can contribute to the stabilization of theta oscillation in the septal network, whereas phase difference may be determined from the interaction of mutually connected PV-IR neurons (see below).…”

Section: Discussionmentioning

confidence: 51%

Phase Segregation of Medial Septal GABAergic Neurons during Hippocampal Theta Activity

et al. 2004

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Septo-hippocampal GABAergic neurons immunoreactive for parvalbumin are thought to play a crucial role in the generation of hippocampal theta oscillations associated with a specific stage of memory formation. Here we use in vivo juxtacellular recording and filling in the medial septum followed by immunocytochemical identification of the recorded cells containing parvalbumin to determine their firing pattern, phase relationship with hippocampal theta, morphology, and to thereby reveal their involvement in the generation of hippocampal theta activity. We have demonstrated that GABAergic medial septal neurons form two distinct populations exhibiting highly regular bursting activity that is tightly coupled to either the trough (178°) or the peak (330°) of hippocampal theta waves. Additionally, different types of bursting as well as nonbursting activity patterns were also observed. The morphological reconstruction of theta-bursting neurons revealed extensive axon arbors of these cells with numerous local collaterals establishing symmetrical synapses; thus, synchrony among the septal pacemaker units may be brought about by their recurrent collateral interactions. Long projecting axons could also be found running dorsally toward the hippocampus and ventrally in the direction of basal forebrain regions. We conclude that GABAergic neurons in the medial septum, which are known to selectively innervate hippocampal interneurons, are in a position to induce rhythmic disinhibition in the hippocampus and other theta-related subcortical areas at two different phases of hippocampal theta.

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Section: Discussionmentioning

confidence: 51%

Phase Segregation of Medial Septal GABAergic Neurons during Hippocampal Theta Activity

et al. 2004

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“…By themselves, changes in the relative proportions of different interneuron subtypes can cause significant alterations in the properties of a modelled neuronal network [51], but in this case there is an increase in some of the populations as well as changes in the relative proportions of each subtype.…”

Section: Discussionmentioning

confidence: 99%

Altered Distribution of Hippocampal Interneurons in the Murine Down Syndrome Model Ts65Dn

et al. 2014

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Down Syndrome, with an incidence of one in 800 live births, is the most common genetic alteration producing intellectual disability. We have used the Ts65Dn model, that mimics some of the alterations observed in Down Syndrome. This genetic alteration induces an imbalance between excitation and inhibition that has been suggested as responsible for the cognitive impairment present in this syndrome. The hippocampus has a crucial role in memory processing and is an important area to analyze this imbalance. In this report we have analysed, in the hippocampus of Ts65Dn mice, the expression of synaptic markers: synaptophysin, vesicular glutamate transporter-1 and isoform 67 of the glutamic acid decarboxylase; and of different subtypes of inhibitory neurons (Calbindin D-28k, parvalbumin, calretinin, NPY, CCK, VIP and somatostatin). We have observed alterations in the inhibitory neuropil in the hippocampus of Ts65Dn mice. There was an excess of inhibitory puncta and a reduction of the excitatory ones. In agreement with this observation, we have observed an increase in the number of inhibitory neurons in CA1 and CA3, mainly interneurons expressing calbindin, calretinin, NPY and VIP, whereas parvalbumin cell numbers were not affected. These alterations in the number of interneurons, but especially the alterations in the proportion of the different types, may influence the normal function of inhibitory circuits and underlie the cognitive deficits observed in DS.

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“…These alterations in the number of cortical interneurons can influence the normal function of inhibitory circuits and may underlie the cognitive deficits observed in different pathologies, including DS. In fact, changes in the relative proportions of different interneuron subtypes can cause significant alterations in the properties of a modelled neuronal network (Foldy et al 2004).…”

Section: Discussionmentioning

confidence: 99%

Alteration of inhibitory circuits in the somatosensory cortex of Ts65Dn mice, a model for Down’s syndrome

et al. 2010

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Down's syndrome (DS), with an incidence of one in 800 live births, is the most common genetic disorder associated with mental retardation. This trisomy on chromosome 21 induces a variable phenotype in which the only common feature is the presence of mental retardation. The neural mechanisms underlying mental retardation might include defects in the formation of neuronal networks and neural plasticity. DS patients have alterations in the morphology, the density and the distribution of dendritic spines in the pyramidal neurons of the cortex. Our hypothesis is that the deficits in dendritic arborization observed in the principal neurons of DS patients and Ts65Dn mice (a model for DS that mimics most of the structural alterations observed in humans) may be mediated to some extent by changes in their inhibitory inputs. Different types of interneurons control different types of inhibition. Therefore, to understand well the changes in inhibition in DS, it is necessary to study the different types of interneurons separately. We have studied the expression of synaptophysin, Glutamic acid decarboxylase-67 (GAD-67) and calcium-binding protein-expressing cells in the primary somatosensory cortex of 4-5 month old Ts65Dn mice. We have observed an increment of GAD67 immunoreactivity that is related mainly to an increment of calretinin-immunoreactive cells and among them the ones with bipolar morphology. Since there is a propensity for epilepsy in DS patients, this increase in interneurons might reflect an attempt by the system to block overexcitation rather than an increment in total inhibition and could explain the deficit in interneurons and principal cells observed in elderly DS patients.

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Diversity beyond variance: modulation of firing rates and network coherence by GABAergic subpopulations

Cited by 27 publications

References 52 publications

Phase Segregation of Medial Septal GABAergic Neurons during Hippocampal Theta Activity

Phase Segregation of Medial Septal GABAergic Neurons during Hippocampal Theta Activity

Altered Distribution of Hippocampal Interneurons in the Murine Down Syndrome Model Ts65Dn

Alteration of inhibitory circuits in the somatosensory cortex of Ts65Dn mice, a model for Down’s syndrome

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