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Whatdoyounotice?
Thetanetworks
Abrainregion important forlearning
(linking events)andspatialnavigation
ThetainRatCA1
modified fromRamonyCajal,1909
Colgin, Ann.Rev.Neurosci,2013
Thetanetworks
Multiplemechanismsforthetageneration:
CA1pyramidalneurons havearesonancefrequency atthetawhenslightly depolarized orhyperpolarized:
duetohyperpolarization-activated
non-specific cation HCNchannels
Membranevoltage:
duetovoltage-gatedpersistent
Na+andM-channels(K+)
ZAPcurrent:
Huetal.,JournalofPhysiology, 2002
Thetanetworks
Multiplemechanismsforthetageneration:
GABAergic pacemakercellsinthemedialseptum (which projectstothehippocampus):
Thisthetarhythmic activityisalso
dependent upon HCNchannels
Varga etal.,JournalofPhysiology, 2008
Thetanetworks
Multiplemechanismsforthetageneration:
1) Theresonancepropertiesofhippocampalneurons
2) Theresonancepropertiesofneuronsinthemedialseptum
Therearelikemany morecontributorstothehippocampalthetarhythm.
Theresultinahighlyinterconnectednetworkisthelarge-scalecoordination
ofhippocampalactivityinathetarhythm.
Functionalconsequencesofthethetarhythm
Hypothesizedto“package”informationsenttootherbrain regions:
Dotanddashonly
Withspaces(start-stop
punctuation)
Morsecodereads:“Segmentationofinformation istheessenceofcoding”
Buzsaki,Neuron,2010
Twoconnectedneuronsareoftendescribedas“communicating.”
Ifneuronsweretospeaktoeachotherinwordsandsentences,what
rolemightrhythmsplay(pacingofwords,ordering,sentence
structure,etc.)inhelpingneuronscommunicate?
Linkstobehaviorandcognitiveprocesses
Lesionorinactivationofthemedialseptumreducethetaoscillationsanddisrupt learning andspatialnavigation:
Mitchelletal.,J.Neurosci.,1982
Linkstobehaviorandcognitiveprocesses
Eachthetacyclecontainsacompactrepresentation ofalargerpath(thetasequences):
Triangle=ratposition
A singlethetacyclecontainsinformation
aboutwheretherathasbeenandwhere
heisgoing
Guptaetal.,NatureNeuro.,2012
Linkstobehaviorandcognitiveprocesses
Administration of cannabinoids disrupts thetasequencesandspatialmemory performance:
Thedistancebetweentwoplacefieldsiscorrelatedwiththetimelagbetween
spikesinathetacycle,butthedrug removesthisrelationship
Thecorrelationisrelatedtospatial
memory performance
Robbe andBuzsaki,J.Neurosci,2009
Linkstobehaviorandcognitiveprocesses
Administration of cannabinoids disrupts thetasequencesandspatialmemory performance:
Robbe andBuzsaki,J.Neurosci,2009
Twoconnectedneuronsareoftendescribedas“communicating.”
Ifneuronsweretospeaktoeachotherinwordsandsentences,what
rolemightrhythmsplay(pacingofwords,ordering,sentence
structure,etc.)inhelpingneuronscommunicate?