scholarly journals Excitatory and inhibitory modulation of septal and striatal neurons during hippocampal sharp-wave ripple events

2020 ◽  
Author(s):  
Andrew G. Howe ◽  
Hugh T. Blair
Keyword(s):  
Striatal Neurons ◽  
Maze Task ◽  
Running Speed ◽  
State Action ◽  
Firing Rates ◽  
Freely Behaving ◽  
Excitatory Responses ◽  
Motor Actions ◽  
Hippocampal Theta ◽  
Septal Neurons

ABSTRACTSingle-units were recorded in hippocampus, septum, and striatum while freely behaving rats (n=3) ran trials in a T-maze task, and rested in a holding bucket between trials. During periods of motor inactivity, SWRs triggered excitatory responses from 28% (64/226) and inhibitory responses from 14% (31/226) of septal neurons. By contrast, only 4% (14/378) of striatal neurons were excited and 6% (24/378) were inhibited during SWRs. In both structures, SWR-responsive neurons exhibited greater spike coherence with hippocampal theta rhythm than neurons that did not respond to SWRs. In septum, neurons that were excited by SWRs fired at late phases of the theta cycle, whereas neurons that were inhibited by SWRs fired at early phases of the theta cycle. By contrast, SWR-responsive striatal neurons did not show consistent phase preferences during the theta cycle. A subset of SWR-responsive neurons in septum (55/95) and striatum (26/38) behaved as speed cells, with firing rates that were positively or negatively modulated by the rat’s running speed. In both structures, firing rates of most SWR-excited speed cells were positively modulated by running speed, whereas firing rates of most SWR-inhibited speed cells were negatively modulated by running speed. These findings are consistent with a growing body of evidence that SWRs can activate subcortical representations of motor actions in conjunction with hippocampal representations of places and states, which may be important for storing and retrieving values of state-action pairs during reinforcement learning and memory consolidation.

scholarly journals A selective projection from the subthalamic nucleus to parvalbumin-expressing interneurons of the striatum

2020 ◽  
Author(s):  
Krishnakanth Kondabolu ◽  
Natalie M. Doig ◽  
Olaoluwa Ayeko ◽  
Bakhtawer Khan ◽  
Alexandra Torres ◽  
...  
Keyword(s):  
Basal Ganglia ◽  
Subthalamic Nucleus ◽  
Ex Vivo ◽  
Cell Types ◽  
Projection Neurons ◽  
Striatal Neurons ◽  
Primary Input ◽  
Cholinergic Interneurons ◽  
Axonal Connections ◽  
Excitatory Responses

AbstractThe striatum and subthalamic nucleus (STN) are considered to be the primary input nuclei of the basal ganglia. Projection neurons of both striatum and STN can extensively interact with other basal ganglia nuclei, and there is growing anatomical evidence of direct axonal connections from the STN to striatum. There remains, however, a pressing need to elucidate the organization and impact of these subthalamostriatal projections in the context of the diverse cell types constituting the striatum. To address this, we carried out monosynaptic retrograde tracing from genetically-defined populations of dorsal striatal neurons in adult male and female mice, quantifying the connectivity from STN neurons to spiny projection neurons, GABAergic interneurons, and cholinergic interneurons. In parallel, we used a combination of ex vivo electrophysiology and optogenetics to characterize the responses of a complementary range of dorsal striatal neuron types to activation of STN axons. Our tracing studies showed that the connectivity from STN neurons to striatal parvalbumin-expressing interneurons is significantly higher (~ four-to eight-fold) than that from STN to any of the four other striatal cell types examined. In agreement, our recording experiments showed that parvalbumin-expressing interneurons, but not the other cell types tested, commonly exhibited robust monosynaptic excitatory responses to subthalamostriatal inputs. Taken together, our data collectively demonstrate that the subthalamostriatal projection is highly selective for target cell type. We conclude that glutamatergic STN neurons are positioned to directly and powerfully influence striatal activity dynamics by virtue of their enriched innervation of GABAergic parvalbumin-expressing interneurons.

Septo-Hippocampal Networks in Chronically Epileptic Rats: Potential Antiepileptic Effects of Theta Rhythm Generation

2006 ◽  
Vol 95 (6) ◽  
pp. 3645-3653 ◽  
Author(s):  
Luis V. Colom ◽  
Antonio García-Hernández ◽  
Maria T. Castañeda ◽  
Miriam G. Perez-Cordova ◽  
Emilio R. Garrido-Sanabria
Keyword(s):  
Theta Rhythm ◽  
Cellular Level ◽  
Rhythm Generation ◽  
Firing Rates ◽  
Sharp Waves ◽  
Lower Amplitude ◽  
Epileptic Discharges ◽  
Pilocarpine Model ◽  
Hippocampal Networks ◽  
Septal Neurons

A series of experiments was carried out testing the hypothesis that the septal region decreases the hippocampal susceptibility to hyperexcitability states through theta rhythm generation. Medial septal neurons were simultaneously recorded with hippocampal field potentials to investigate the septo-hippocampal function in the pilocarpine model of chronic epilepsy. The theta rhythm from chronically epileptic rats had lower amplitude (20% less) and higher frequency than controls (from 3.38 to 4.25 Hz), suggesting that both generator and pacemaker structures are affected during the epileptic process. At the cellular level, the group of rhythmically bursting firing medial septal neurons, in the epileptic animals, significantly and chronically increased their firing rates in relation to controls (from 13.86 to 29.14 spikes/s). Peristimulus histograms performed around hippocampal sharp waves showed that all high-frequency firing neurons, including rhythmically bursting neurons and most slow firing neurons, decreased firing rates immediately after hippocampal epileptic discharges. Thus inhibitory hippocampo-septal influences prevail during hippocampal epileptic discharges. The occurrence of epileptic discharges was reduced 86–97% of the number observed during spontaneous theta and theta induced by sensory (tail pinch) or chemical stimulation (carbachol), suggesting that the presence of the theta state regardless of how it was produced was responsible for the reduction in epileptic discharge frequency. The understanding of the theta rhythm “anti-epileptic” effect at the cellular and molecular levels may result in novel therapeutic approaches dedicated to protect the brain against abnormal excitability states.

Relationship between hippocampal theta activity and running speed in the rat.

1975 ◽  
Vol 88 (1) ◽  
pp. 324-328 ◽  
Author(s):  
Willard L. McFarland ◽  
Herman Teitelbaum ◽  
Elizabeth K. Hedges
Keyword(s):  
Theta Activity ◽  
Running Speed ◽  
Hippocampal Theta Activity ◽  
Hippocampal Theta

scholarly journals Learning shapes the aversion and reward responses of lateral habenula neurons

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Daqing Wang ◽  
Yi Li ◽  
Qiru Feng ◽  
Qingchun Guo ◽  
Jingfeng Zhou ◽  
...  
Keyword(s):  
Behavioral Responses ◽  
Social Stimuli ◽  
Sucrose Reward ◽  
Lateral Habenula ◽  
High Reward ◽  
Freely Behaving ◽  
Single Unit Recordings ◽  
Motivational Values ◽  
Excitatory Responses ◽  
Selection Of

The lateral habenula (LHb) is believed to encode negative motivational values. It remains unknown how LHb neurons respond to various stressors and how learning shapes their responses. Here, we used fiber-photometry and electrophysiology to track LHb neuronal activity in freely-behaving mice. Bitterness, pain, and social attack by aggressors intensively excite LHb neurons. Aversive Pavlovian conditioning induced activation by the aversion-predicting cue in a few trials. The experience of social defeat also conditioned excitatory responses to previously neutral social stimuli. In contrast, fiber photometry and single-unit recordings revealed that sucrose reward inhibited LHb neurons and often produced excitatory rebound. It required prolonged conditioning and high reward probability to induce inhibition by reward-predicting cues. Therefore, LHb neurons can bidirectionally process a diverse array of aversive and reward signals. Importantly, their responses are dynamically shaped by learning, suggesting that the LHb participates in experience-dependent selection of behavioral responses to stressors and rewards.

Loss of Rhythmically Bursting Neurons in Rat Medial Septum Following Selective Lesion of Septohippocampal Cholinergic System

1998 ◽  
Vol 79 (4) ◽  
pp. 1633-1642 ◽  
Author(s):  
Emmanuelle Apartis ◽  
Frederique R. Poindessous-Jazat ◽  
Yvon A. Lamour ◽  
Marie H. Bassant
Keyword(s):  
Cholinergic System ◽  
Hippocampal Formation ◽  
Paradoxical Sleep ◽  
Significant Proportion ◽  
Medial Septum ◽  
Gabaergic Neurons ◽  
Bursting Neurons ◽  
Selective Lesion ◽  
Hippocampal Theta ◽  
Septal Neurons

Apartis, Emmanuelle, Frederique R. Poindessous-Jazat, Yvon A. Lamour, and Marie H. Bassant. Loss of rhythmically bursting neurons in rat medial septum following selective lesion of septohippocampal cholinergic system. J. Neurophysiol. 79: 1633–1642, 1998. The medial septum contains cholinergic and GABAergic neurons that project to the hippocampal formation. A significant proportion of the septohippocampal neurons (SHN) exhibit a rhythmically bursting (RB) activity that is involved in the generation of the hippocampal theta rhythm. The neurochemical nature of septal RB neurons is not firmly established. To address this question, the septal unit activity has been recorded in rats after selective destruction of the cholinergic septal neurons by the immunotoxin 192 IgG-saporin. Experiments have been performed in urethan-anesthetized and unanesthetized rats, 14–21 days after lesion. Acetylcholinesterase (AChE) histochemistry revealed a near-complete loss of cholinergic septal neurons and of cholinergic fibers in the hippocampus. The recorded neurons were located in the medial septum-diagonal band of Broca area. A number of these neurons were identified as projecting to the hippocampus (SHN) by their antidromic response to the electrical stimulation of the fimbria-fornix. In urethan-anesthetized lesioned rats, the percentage of RB neurons decreased significantly as compared with controls (17 vs. 41% for SHNs and 5 vs. 19% for unidentified septal neurons). The axonal conduction velocity and the burst frequency of the SHNs that retained a RB activity were higher in lesioned as compared with control rats. The number of spikes per burst was lower and the burst duration was shorter in lesioned rats as compared with controls. The urethan-resistant hippocampal theta was altered both in terms of frequency and amplitude. In unanesthetized lesioned rats, no RB septal neurons were found during arousal, as compared with 25% in controls. Their number was also markedly reduced during paradoxical sleep (9.7 vs. 38.5%). Histochemistry in 192 IgG-saporin–treated rats showed that RB neurons were found in areas devoid of AChE-positive neurons but containing parvalbumine-positive (presumably GABAergic) neurons. These data show that RB activity is considerably reduced after selective lesion of the cholinergic medial septal neurons. They suggested that the large majority of the RB septal neurons are cholinergic and that the few neurons that display RB activity in lesioned rats are GABAergic.

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