title: Connectivity patterns revealed by mapping of active inputs on dendrites of thalamorecipient neurons in the auditory cortex.
abstract: Despite being substantially outnumbered by intracortical inputs on thalamorecipient neurons, thalamocortical projections efficiently deliver acoustic information to the auditory cortex. We hypothesized that thalamic projections may achieve effectiveness by forming synapses at optimal locations on dendritic trees of cortical neurons. Using two-photon calcium imaging in dendritic spines, we constructed maps of active thalamic and intracortical inputs on dendritic trees of thalamorecipient cortical neurons in mouse thalamocortical slices. These maps revealed that thalamic projections synapse preferentially on stubby dendritic spines within 100 microm of the soma, whereas the locations and morphology of spines that receive intracortical projections have a less-defined pattern. Using two-photon photolysis of caged glutamate, we found that activation of stubby dendritic spines located perisomatically generated larger postsynaptic potentials in the soma of thalamorecipient neurons than did activation of remote dendritic spines or spines of other morphological types. These results suggest a novel mechanism of reliability of thalamic projections: the positioning of crucial afferent inputs at optimal synaptic locations.
authors.affiliation: Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Richardson
authors.forename: Jay A
authors.initials: JA
authors.lastname: Blundon
authors.forename: Ildar T
authors.initials: IT
authors.lastname: Bayazitov
authors.forename: Stanislav S
authors.initials: SS
authors.lastname: Zakharenko
mesh_terms: D015763:2-Amino-5-phosphonovalerate / Q000494:pharmacology; D000818:Animals; D001303:Auditory Cortex / Q000166:cytology*; D001931:Brain Mapping; D002118:Calcium / Q000378:metabolism; D003712:Dendrites / Q000502:physiology* / Q000648:ultrastructure; D049229:Dendritic Spines / Q000145:classification / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D005971:Glutamates / Q000494:pharmacology; D066298:In Vitro Techniques; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D009415:Nerve Net / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D018408:Patch-Clamp Techniques / Q000379:methods; D011984:Sensory Receptor Cells / Q000166:cytology* / Q000187:drug effects; D055366:Synaptic Potentials / Q000502:physiology; D013788:Thalamus / Q000166:cytology
chemical_list: D018691:Excitatory Amino Acid Antagonists; D005971:Glutamates; C082764:alpha-(4,5-dimethoxy-2-nitrobenzyl) glutamate; D015763:2-Amino-5-phosphonovalerate; D002118:Calcium