1,721,139 research outputs found
Direct and indirect communication between functionally different regions of the rat striatum
Full text linkGroenewegen, H.J. [Promotor]Pennartz, C.M.A. [Promotor
Episodic memory and the role of the brain's default-mode network
Full text linkItem does not contain fulltextThis thesis provides a number of new insights into episodic memory and the role of the default-mode network. First, it provides the first direct evidence for the contrasting role of DMN during encoding and retrieval. Secondly, the experimental findings eliminate several possible explanations for the role of the DMN, including a simple reallocation account and the orienting of attention account. Moreover, the present work sheds light on the contribution of different processes - including respiratory - to the fMRI signal. Finally, the work clarifies the flexible nature of the DMN, for example, the distinct role of the hippocampus during encoding. Overall, the work within this thesis clearly indicates that the individual DMN regions provide distinct contributions to learning and remembering.Universiteit van Amsterdam, 17 december 2010Promotor : Pennartz, C.M.A. Co-promotor : Daselaar, S.M.139 p
Cellular mechanisms underlying spontaneous firing rat suprachiasmatic nucleus: involvement of a slowly inactivating component of sodium current.
Full text link Pennartz, C.M.A., M. A. Bierlaagh, and A.M.S. Geurtsen. Cellular mechanisms underlying spontaneous firing in rat suprachiasmatic nucleus: involvement of a slowly inactivating component of sodium current. J. Neurophysiol. 78: 1811–1825, 1997. Neurons constituting the pacemaker of circadian rhythms, located in the suprachiasmatic nucleus, generate spontaneous firing patterns that change across the day-night cycle. Their average spontaneous firing rate is considered an important functional marker of clock activity because it is highest during daytime and low at night. In this study we investigate the ionic mechanisms underlying spontaneous firing in acutely prepared slices and dissociated neurons of the suprachiasmatic nucleus. In current-clamp mode, spontaneous action potentials were consistently preceded by depolarizing ramps. These ramps were Na+ dependent, were sensitive to tetrodotoxin (TTX), and disappeared on hyperpolarization. Ramps and associated spikes were not abolished by blockers of the H current (1 mM cesium) or calcium currents (50 μM nickel or 200 μM cadmium). In voltage-clamped neurons in slices or dissociated neurons, TTX-sensitive and Na+-dependent inward current was observed to activate well below firing threshold (−60 to −50 mV). The low-threshold component of Na+ current inactivated slowly as compared with the fast component that mediates action potentials. However, its inactivation proceeded more rapidly than has been reported for the persistent Na+ current in cortical structures. Persistent Na+ current was generally absent or small in amplitude. The voltage dependence and kinetics of the slowly inactivating component of Na+ current are consistent with the hypothesis that it is partially deinactivated during spike afterhyperpolarizations and contributes significantly to subsequent depolarizing ramps. These observations implicate the slowly inactivating component of Na+ current in ionic mechanisms governing spontaneous firing in suprachiasmatic nucleus neurons. </jats:p
Plasticity of neuronal firing in deep layers of the medial prefrontal cortex in rats engaged in operant conditioning.
No full textElectrophysiology of the rat nucleus accumbens : local circuitry, neuromodulation and synaptic plasticity
No full textIdentification and integration of sensory modalities: Neural basis and relation to consciousness
No full textA key question in studying consciousness is how neural operations in the brain can identify streams of sensory input as belonging to distinct modalities, which contributes to the representation of qualitatively different experiences. The basis for identification of modalities is proposed to be constituted by self-organized comparative operations across a network of unimodal and multimodal sensory areas. However, such network interactions alone cannot answer the question how sensory feature detectors collectively account for an integrated, yet phenomenally differentiated experiential content. This problem turns out to be different from, although related to, the binding problem. It is proposed that the neural correlate of an enriched, multimodal experience is constituted by the attractor state of a dynamic associative network. Within this network, unimodal and multimodal sensory maps continuously interact to influence each other's attractor state, so that a feature change in one modality results in a fast re-coding of feature information in another modality. In this scheme, feature detection is coded by firing-rate, whereas firing phase codes relational aspects
Postsynaptic modulation of AMPA- and NMDA-receptor currents by Group III metabotropic glutamate receptors in rat nucleus accumbens
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