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Tommas Ellender, James Harwood, Polina Kosillo, Marco Capogna and Paul Bolam report in the latest issue of the Journal of Physiology (591: pages 257-272, 2013) for the first time the heterogeneous synaptic properties of the two main thalamic projections to the striatum which originate in the rostral central lateral (CL) and the caudal parafascicular (Pf) nucleus. Building on previous work of the Unit showing that the thalamostriatal neurons in these nuclei differ in their morphology, firing properties, as well as their striatal targets (Lacey et al. 2007), we set out to test the hypothesis that synapses formed in the striatum by neurons originating in either nucleus have different functional properties. To address this we isolated and selectively activated the thalamostriatal projections using targeted viral delivery of channelrhodopsin-2 (ChR2). Whole-cell patch-clamp recordings of neurochemically identified medium-spiny neurons (MSN) together with optical activation of specific thalamic inputs enabled us to identify the properties of the two types of thalamic synapse in the adult mouse striatum. We found that thalamostriatal synapses differ significantly in their peak amplitude responses, short-term dynamics, expression of ionotropic glutamate receptor subtypes and potential to exhibit spike timing-dependent plasticity. Our results reveal a hitherto unidentified heterogeneity in the thalamostriatal projection and suggest they subserve different roles in striatal function. More specifically they suggest that CL synapses may act as drivers of MSN spiking activity whereas Pf synapses may subserve the role of modulators of the activity of MSNs.

Alan Cowey (life), FRS, FMedSci, Emeritus Professor of Experimental Psychology, Oxford and Honorary Associate of the Unit, passed away on the 19th of December 2012 after being diagnosed with cancer on the 24th of September. Alan was one of Peter Somogyi’s closest friends and past collaborator, a pioneer of visual neuroscience, an unflinching supporter of the Unit, a true gentleman and an example to us all as a scientist and as a person. Alan was elected an Honorary Fellow of the Hungarian Academy of Sciences in 2010 and gave his inaugural lecture at Budapest in April 2011 (see picture). He lectured in the symposium at the Hungarian Embassy in London on the 27th of February 2012: Visions, links and opportunities in Hungarian and British neuroscience.

He is sorely missed.

Dr. Stéphanie Trouche joins the Unit as an MRC Investigator Scientist. Stéphanie’s previous research has focused on the neural circuits underlying memory processes and has employed system-neuroscience approach combining behavioural, neuroanatomical and imaging tools. In September 2009, Stéphanie obtained her Ph.D. in Neuroscience at the University of Toulouse, France, where she examined the contribution of new hippocampal neurons to spatial memory processes. She moved in January 2010 as a Fyssen postdoc fellow at Tufts University School of Medicine (Department of Neuroscience, Boston, USA) in the group of Dr. Leon Reijmers where she studied the role of the inhibitory circuits during memory extinction. She will now work in the group of Dr. David Dupret where she will be studying how the assembly firing patterns in the hippocampus contribute to the formation and expression of spatial memory traces.

Miroslawa Manko, Thomas Bienvenu, Yannis Dalezios and Marco Capogna report in the last issue of the Journal of Physiology (590.22:5611-5627, 2012) a novel interneuron type of the amygdala, termed neurogliaform cell, and study its function by a combination of in vivo and in vitro techniques. They used a mouse line expressing a green fluorescent protein (GFP) under the neuropeptide Y (NPY) promoter. Paired recordings between presynapticNPY-GFP-expressing (+) cells and postsynaptic principal neurons (PNs) of the basolateral amygdala (BLA) were performed. The NPY-GFP+ neurons displayed small somata and short dendrites embedded in a cloud of highly arborized axon, suggesting a neurogliaform cell (NGFC) type. A NPY-GFP+ cell evoked a GABA-A receptor-mediated slow inhibitory postsynaptic current (IPSC) in a PN and an autaptic IPSC. The slow kinetics of these IPSCs was likely caused by the low concentration and spillover of extracellular GABA. They also report that NGFCs of the BLA fired action potentials phase-locked to hippocampal theta oscillations in anaesthetized rats. When this firing was re-played in NPY+-NGFCs in vitro, it evoked a transient depression of the IPSCs. Presynaptic GABA-B receptors and functional depletion of synaptic vesicles determined this short-term plasticity. Synaptic contacts made by recorded NGFCs showed close appositions, and rarely identifiable classical synaptic structures. Thus, they report a novel interneuron type of the amygdala that generates volume transmission of GABA. The peculiar functional mode of NGFCs makes them unique amongst all GABAergic cell types of the amygdala identified so far.