1 12. Anatomical, physiological, and pharmacological properties underlying hippocampal sensorimotor integration BRAIN H. BLAND PT : Kim, Hoon-Hee (SNU-BI)

(C) 2007 SNU CSE Biointelligence Lab Contents The Cellular basis of theta-band oscillation and synchrony The ascending brainstem hippocampal synchronizing pathways The ascending brainstem hippocampal desynchronizing pathways Data supporting the sensorimotor integration model of hippocampal function 2

(C) 2007 SNU CSE Biointelligence Lab 3 The Cellular basis of theta-band oscillation and synchrony (1) Limbic cortex, Limbic structure Hippocampal formation (HPC) Theta oscillation and synchrony. The asynchrony activity : large amplitude irregular activity(LIA) Type 1 theta  Atropine-resistant  movement Type 2 theta  Atropine-sensitive  Immobility  Sensory processing

(C) 2007 SNU CSE Biointelligence Lab The Cellular basis of theta-band oscillation and synchrony (2) Theta-ON cells Hippocampal CA1, CA3 pyramidal cell MPOs occurred only during theta field activity Oscillation : voltage-dependent Frequency : voltage-independent No phase changes observed during current injection 4

(C) 2007 SNU CSE Biointelligence Lab The Cellular basis of theta-band oscillation and synchrony (2) Theta-OFF cells Hippocampal CA1 basket cells MPOs occurred only during theta field activity Amplitude : voltage-dependent Frequency : voltage-independent 5

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways The rostral pontine region  The nucleous reticularis pontis oralis (RPO)  The pedunculopontine tegmental nucleus (PPT) Cellular activity in the RPO and PPT in relation to hippocampal theta generation have revealed only irregular (tonic) discharge patterns. 6

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways The caudal diencephalic region  Primarily the posterior hypothalamic (PH)  The supramammillary (SUM) nucleus PH and SUM nuclei A critical part of the ascending synchronizing pathway 7

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways Phasic theta-ON cells in the HPC translated the level of activation of the ascending synchronizing pathways through their discharge rates 8

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways A phasic theta-OFF cell during the transition from higher- frequency theta to lower- frequency theta to LIA 9

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways Phasic theta-OFF cells were inhibited by PH stimulation and the inhibition was not abolished by the administration of atropine sulfate 10

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways Rhythmic and non-rhythmic patterns Tonic theta-ON cells in the PH discharged at significantly higher rates during theta Tonic theta-ON Cells Thalamic centromedial (CM) 11

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways Tonic theta-off cells discharging at significantly higher rates during LIA 12

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways From SUM Phasic theta-on cells Not significantly increase their discharge rate during the transition from LIA to theta field activity. 13

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways The medial septal region (MS/vDBB)  “pacemaker” function NMDA effect Lon-lasting (20-30mins) induction of hippocampal synchrony at the field and cellular level ATSO4 (atropine) 14

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal synchronizing pathways The combination of carbachol and bicuculline microinfusions into the HPC of septally deafferented rats produced theta-like field oscillations Rhythmic discharges of phasic theta-ON cells 15

(C) 2007 SNU CSE Biointelligence Lab The ascending brainstem hippocampal desynchronizing pathways The median raphe (MR) Electrial stimulation of the MR in anesthetized rats also has a disruptive effect on rhythmically discharging medial septal neurons while in freely moving rabbits such stimulation also disrupted the rhythmic discharges of both medial septal cells and hippocampal theta. The sensorimotor integration model would predict that MR stimulation in the freely moving rat should result in the inhibition of Type 1 theta-related behaviors. 16

(C) 2007 SNU CSE Biointelligence Lab Data supporting the sensorimotor integration model of hippocampal function Two separate theta inputs to the HPC  Type 1 movement related theta  Type 2 sensory processing theta The number of discharges per rhythmic bust was always lower during type 2 theta compared to type 1 theta. 17

(C) 2007 SNU CSE Biointelligence Lab Data supporting the sensorimotor integration model of hippocampal function The immobility period prior to the execution of the jump could be divided into two components:  a sensory processing period  a movement preparation period 18

(C) 2007 SNU CSE Biointelligence Lab Data supporting the sensorimotor integration model of hippocampal function An updated diagrammatic representation of the sensorimotor model for the hippocampal formation theta subsystems. 19