Regulation of learned vocal behavior by an auditory motor cortical nucleus in juvenile zebra finches.

In the process of song learning, songbirds such as the zebra finch shape their initial soft and poorly formed vocalizations (subsong) first into variable plastic songs with a discernable recurring motif and then into highly stereotyped adult songs. A premotor brain area critically involved in plastic and adult song production is the cortical nucleus HVC. One of HVC's primary afferents, the nucleus interface of the nidopallium (NIf), provides a significant source of auditory input to HVC.

Spikes and bursts in two types of thalamic projection neurons differentially shape sleep patterns and auditory responses in a songbird.

In mammals, the thalamus plays important roles for cortical processing, such as relay of sensory information and induction of rhythmical firing during sleep. In neurons of the avian cerebrum, in analogy with cortical up and down states, complex patterns of regular-spiking and dense-bursting modes are frequently observed during sleep. However, the roles of thalamic inputs for shaping these firing modes are largely unknown.

Group I metabotropic glutamate receptors enable two distinct forms of long-term depression in the rat dentate gyrus in vivo.

The existence of long-term depression (LTD) in the dentate gyrus of freely moving rats, as well as the contribution of different types of metabotropic glutamate receptors (mGluRs) to this form of plasticity, has been the subject of much debate. Here, we describe two distinct forms of mGluR-dependent hippocampal LTD in the dentate gyrus of freely moving adult rats. LTD, induced by low-frequency stimulation (LFS) of the medial perforant path (LFS-LTD), was prevented by antagonism of the phospholipase C-coupled receptors, mGluR1 but not mGluR5.

Group III metabotropic glutamate receptor-mediated, chemically induced long-term depression differentially affects cell viability in the hippocampus.

In vivo, activation of group III metabotropic glutamate (mGlu) receptors leads to a reduction of basal synaptic transmission in the hippocampus, and depending on the experimental conditions in vitro, leads to neuroprotection or neurotoxicity. Here, the cellular response to cerebral application of L(+)-2-amino-4-phosphonobutanoic acid (AP4) was investigated in the CA1 region and dentate gyrus of freely moving rats. Drugs were applied via the lateral ventricle, and electrophysiological measurements were obtained via chronically implanted electrodes.

Investigations of the protein synthesis dependency of mGluR-induced long-term depression in the dentate gyrus of freely moving rats.

Hippocampal long-term depression (LTD) comprises an activity-dependent weakening of synaptic strength. In this study we compared persistent LTD induced by the group I mGluR agonist, DHPG, or the group III mGluR agonist, AP4, in the dentate gyrus of freely moving rats. The role of protein translation, using the translation inhibitors, anisomycin and emetine, was also investigated.

Pharmacological antagonism of metabotropic glutamate receptor 1 regulates long-term potentiation and spatial reference memory in the dentate gyrus of freely moving rats via N-methyl-D-aspartate and metabotropic glutamate receptor-dependent mechanisms.

Group I metabotropic glutamate receptors (mGluRs) are critically required for multiple forms of hippocampal synaptic plasticity in vivo. The role of the receptor subtype mGluR1 in long-term potentiation (LTP) and learning is unclear. We examined the contribution of mGluR1 to hippocampal LTP and spatial learning using the selective antagonist (S)-(+)-alpha-amino-4carboxy-2-methylbenzene-acetic acid (LY367385).

Regulation by metabotropic glutamate receptor 5 of LTP in the dentate gyrus of freely moving rats: relevance for learning and memory formation.

Group I metabotropic glutamate (mGlu) receptors play a critical role in the regulation of hippocampal long-term potentiation (LTP) in vivo. Little is known, however, about the contribution of the individual subtypes mGlu1 and mGlu5 to learning processes and LTP. We investigated the involvement of mGlu5 in hippocampal LTP and spatial learning using the selective antagonist 2-methyl-6-(phenylethynyl)pyridine (MPEP).