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Neuronal Ensembles (neuronal + ensembles)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

Attention , oscillations and neuropharmacology

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2009
Gustavo Deco
Abstract Attention is a rich psychological and neurobiological construct that influences almost all aspects of cognitive behaviour. It enables enhanced processing of behaviourally relevant stimuli at the expense of irrelevant stimuli. At the cellular level, rhythmic synchronization at local and long-range spatial scales complements the attention-induced firing rate changes of neurons. The former is hypothesized to enable efficient communication between neuronal ensembles tuned to spatial and featural aspects of the attended stimulus. Recent modelling studies suggest that the rhythmic synchronization in the gamma range may be mediated by a fine balance between N -methyl- d -aspartate and ,-amino-3-hydroxy-5-methylisoxazole-4-propionate postsynaptic currents, whereas other studies have highlighted the possible contribution of the neuromodulator acetylcholine. This review summarizes some recent modelling and experimental studies investigating mechanisms of attention in sensory areas and discusses possibilities of how glutamatergic and cholinergic systems could contribute to increased processing abilities at the cellular and network level during states of top-down attention. [source]

Multiple functions of GABAA and GABAB receptors during pattern processing in the zebrafish olfactory bulb

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2008
Rico Tabor
Abstract ,-Aminobutyric acid (GABA)ergic synapses are thought to play pivotal roles in the processing of activity patterns in the olfactory bulb (OB), but their functions have been difficult to study during odor responses in the intact system. We pharmacologically manipulated GABAA and GABAB receptors in the OB of zebrafish and analysed the effects on odor responses of the output neurons, the mitral cells (MCs), by electrophysiological recordings and temporally deconvolved two-photon Ca2+ imaging. The blockade of GABAB receptors enhanced presynaptic Ca2+ influx into afferent axon terminals, and changed the amplitude and time course of a subset of MC responses, indicating that GABAB receptors have a modulatory influence on OB output activity. The blockade of GABAA receptors induced epileptiform firing, enhanced excitatory responses and abolished fast oscillations in the local field potential. Moreover, the topological reorganization and decorrelation of MC activity patterns during the initial phase of the response was perturbed. These results indicate that GABAA receptor-containing circuits participate in the balance of excitation and inhibition, the regulation of total OB output activity, the synchronization of odor-dependent neuronal ensembles, and the reorganization of odor-encoding activity patterns. GABAA and GABAB receptors are therefore differentially involved in multiple functions of neuronal circuits in the OB. [source]

Theta rhythm of navigation: Link between path integration and landmark navigation, episodic and semantic memory

HIPPOCAMPUS, Issue 7 2005
György Buzsáki
Abstract Five key topics have been reverberating in hippocampal-entorhinal cortex (EC) research over the past five decades: episodic and semantic memory, path integration ("dead reckoning") and landmark ("map") navigation, and theta oscillation. We suggest that the systematic relations between single cell discharge and the activity of neuronal ensembles reflected in local field theta oscillations provide a useful insight into the relationship among these terms. In rats trained to run in direction-guided (1-dimensional) tasks, hippocampal cell assemblies discharge sequentially, with different assemblies active on opposite runs, i.e., place cells are unidirectional. Such tasks do not require map representation and are formally identical with learning sequentially occurring items in an episode. Hebbian plasticity, acting within the temporal window of the theta cycle, converts the travel distances into synaptic strengths between the sequentially activated and unidirectionally connected assemblies. In contrast, place representations by hippocampal neurons in 2-dimensional environments are typically omnidirectional, characteristic of a map. Generation of a map requires exploration, essentially a dead reckoning behavior. We suggest that omnidirectional navigation through the same places (junctions) during exploration gives rise to omnidirectional place cells and, consequently, maps free of temporal context. Analogously, multiple crossings of common junction(s) of episodes convert the common junction(s) into context-free or semantic memory. Theta oscillation can hence be conceived as the navigation rhythm through both physical and mnemonic space, facilitating the formation of maps and episodic/semantic memories. © 2005 Wiley-Liss, Inc. [source]

Firing properties and functional connectivity of substantia nigra pars compacta neurones recorded with a multi-electrode array in vitro

THE JOURNAL OF PHYSIOLOGY, Issue 10 2010
Nicola Berretta
Dopamine (DA) neurones of the substantia nigra pars compacta (SNc) are involved in a wide variety of functions, including motor control and reward-based learning. In order to gain new insights into the firing properties of neuronal ensembles in the SNc, we recorded extracellular single units from spontaneously active neurones, using a multi-electrode array (MEA) device in midbrain slices. The majority of neurones (50.21%) had a low firing frequency (1,3 Hz) and a stable pacemaker-like pattern, while others (44.84%) were irregular, but still firing at a low rate. The remaining population (4.95%) comprised neurones with a regular higher firing rate (5,10 Hz). High rate neurones, on the whole, were insensitive to DA (30 ,m), while low rate neurones were mostly inhibited by DA, although responding either with a prominent or a weak inhibition. However, we recorded low rate regular neurones that were insensitive to DA, or irregular low rate neurones excited by DA. Interestingly, we found pairs of active neurones (12.10 ± 3.14%) with a significant proportion of spikes occurring synchronously. Moreover, the crosscorrelation probability in each pair tended to increase in response to DA. In conclusion, MEA recordings in midbrain slices reveal a much more complex picture than previously reported with regard to the firing pattern and DA sensitivity of spontaneously active SNc neurones. Moreover, the study opens new prospectives for the in vitro investigation of functional connectivity in the midbrain dopaminergic system, thus proposing new targets for the pharmacological treatment of DA-dependent neurological disorders. [source]