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1、Anatomy of the Hippocampus ComputationalModelsofNeuralSystems Lecture3.2 DavidS.Touretzky September,2013 09/25/13 ComputationalModelsofNeuralSystems 2 Human Hippocampus 09/25/13 ComputationalModelsofNeuralSystems 3 Human Hippocampus 09/25/13 ComputationalModelsofNeuralSystems 4 Hippocampus Means “Se
2、ahorse” Dissectedhumanhippocampusnexttoaspecimenofhippocampusleria,one ofseveraldozenspecies. 09/25/13 ComputationalModelsofNeuralSystems 5 Rat Hippocampal Formation From(AmaralPOR:postrhinalcortex;EC:entorhinalcortex;PrS:presubiculum;PaS: parasubiculum;DG:dentategyrus;CA:Cornuamonis;S:subiculum;RSP
3、:retrosplenialcortex; Par/Oc:parietal/occipitalcortex 09/25/13 ComputationalModelsofNeuralSystems 17 Three Major Fiber Systems Angular bundle from EC: perforant path (and more) Fimbria/fornix to subcortical areas fimbria: red fornix: yellow Dorsal and ventral commissures link hippocampi dorsal: purp
4、le ventral: green 09/25/13 ComputationalModelsofNeuralSystems 18 Alveus/Fimbria/Fornix Second input/output pathway for hippocampus (first is via angular bundle from EC) Communicates with subcortical structures: septal nuclei and mammillary bodies 09/25/13 ComputationalModelsofNeuralSystems 19 (commi
5、ssural pathway) (perforantpath) 09/25/13 ComputationalModelsofNeuralSystems 20 Dendritic Arborization of Principal Cells suprapyramidalblade infrapyramidalblade 09/25/13 ComputationalModelsofNeuralSystems 21 Stucture of the Dentate Gyrus Granule cell layer holds principal cell bodies their axons for
6、m the mossy fiber pathway Molecular layer: gc dendritic tree; afferent connections Polymorphic cell layer (hilus): interneurons, mf collaterals 09/25/13 ComputationalModelsofNeuralSystems 22 Mossy Fiber Synapse Onto CA3 Cells The dentate gyrus projection to CA3 terminates in large mossy fiber synaps
7、es. CA3 dendrites have “thorny excresences” with complex spine shapes. A mossy fiber can make 30-40 synapses within one excresence. Each granule cells contacts only about 15 CA3 pyramidal cells. Each pyramidal cell receives input from only about 72 granule cells. 09/25/13 ComputationalModelsofNeural
8、Systems 23 Structure of CA3 stratum radiatum: entorhinal afferents; mossy fibers enter from DG, make synapses in s. lucidum stratum lucidum stratum pyramidale stratum oriens: recurrent collaterals thornyexcresences 09/25/13 ComputationalModelsofNeuralSystems 24 Structure of CA1 stratum lacunosum- mo
9、leculare: entorhinal afferents stratum radiatum: Schaeffer collaterals, commissural fibers stratum pyramidale stratum oriens 09/25/13 ComputationalModelsofNeuralSystems 25 Interneurons in CA3/CA1 09/25/13 ComputationalModelsofNeuralSystems 26 Structured Projections: EC Layer II vs. III EClayerIII EC
10、layerII 09/25/13 ComputationalModelsofNeuralSystems 27 Layer II Projections MPP/LPP= medial/lateral perforantpath 09/25/13 ComputationalModelsofNeuralSystems 28 Layer III Projections 09/25/13 ComputationalModelsofNeuralSystems 29 Temporal-L 09/25/13 ComputationalModelsofNeuralSystems 30 09/25/13 Com
11、putationalModelsofNeuralSystems 31 Some Numbers for the Rat Dentate Gyrus 1.2 million granule cells 4K basket cells 32K hilar interneurons (20K mossy cells) CA3/CA1 330K /420K pyramidal cells various interneurons Entorhinal cortex layer II Around 200K cells (20% interneurons?) Subiculum Around 180K
12、cells 09/25/13 ComputationalModelsofNeuralSystems 32 Rat Connectivity Perforant path projection to DG Around 4500 spines per granule cell (75% from EC) One EC cells makes about 18,000 synapses with granule cells CA3: three distinct inputs 50-80 mossy fibers from DG 3,500 perforant path synapses from
13、 EC II 12,000 recurrent collaterals from other CA3 cells 8,000 to basilar dendrites (stratum oriens) 4,000 to apical dendrites (stratum radiatum) CA1: inputs from CA3 and EC From CA3 Schaffer collaterals: 4,500 basilar, 6500 apical synapses From EC layer III: 2,500 synapses 09/25/13 ComputationalMod
14、elsofNeuralSystems 33 Why Does the Circuitry Look Like This? Why so many kinds of interneurons? Why have recurrent connections in some regions and not others? What do these regions compute? CA3 09/25/13 ComputationalModelsofNeuralSystems 34 The Hippocampus Is Very Well Connected to Other Brain Areas
15、 Connected via EC and fimbria-fornix pathway to: Prefrontal / orbitorfrontal cortices Cingulate cortex Piriform cortex Perirhinal and Postrhinal cortices (sensory) Striatum Amygdala Septum Mammillary bodies Thalamus Hypothalamus 09/25/13 ComputationalModelsofNeuralSystems 35 LEA/MEA=lateral/medial e
16、ntorhinalarea PER 09/25/13 ComputationalModelsofNeuralSystems 36 Neuromodulatory Projections to HC locuscoeruleus raphenuclei substantianigra acetylcholine medialseptum NA:Attention 5HT:Mood DA:Reward ACh:Novelty 09/25/13 ComputationalModelsofNeuralSystems 37 Hippocampal EEG Awake Active exploration
17、: theta (8-12 Hz) plus gamma (40 Hz) Resting: LIA (Large-amplitude Irregular Activity) w/transient sharp waves Asleep REM sleep: theta Slow wave sleep: LIA S-SIA: small-amplitude irregular activity (Jarosiewicz spatial attention cells in monkeys Configural association theory? Lesioned rats are impaired on tasks requiring them to recognize cue configurations