scholarly journals Spatial maps in olfactory cortex during olfactory navigation

2020 ◽  
Author(s):  
Cindy Poo ◽  
Gautam Agarwal ◽  
Niccolò Bonacchi ◽  
Zachary Mainen
Keyword(s):  
Theta Rhythm ◽  
Spatial Navigation ◽  
Piriform Cortex ◽  
Spatial Location ◽  
Functional Coupling ◽  
Odor Cues ◽  
Olfactory Information ◽  
Strong Candidate ◽  
Hippocampal Theta ◽  
The Brain

AbstractAnimals rely on chemical signals to forage for food, shelter, and mates. Such behaviors call for odor cues to be linked to locations within their environment. Nonetheless, where and how this happens in the brain is not known. Here, we show that spatial and olfactory information converge in posterior piriform cortex (pPCx), an olfactory region with strong associative circuity. Ensembles of pPCx neurons recorded in rats performing an odor-cued spatial navigation task were robustly selective for both odor identity and spatial location, forming an “odor-place map”. Spatially-selective pPCx neurons displayed joint selectivity for odors, stability across behavioral contexts and functional coupling to the hippocampal theta rhythm. These results implicate the pPCx as a strong candidate region to associate spatial and olfactory information in support of navigational behavior.

scholarly journals Hippocampal Stimulation of Fornical-lesioned Rats Improves Working Memory

1994 ◽  
Vol 21 (2) ◽  
pp. 100-103 ◽  
Author(s):  
J. Turnbull ◽  
F. Jiang ◽  
R. Racine
Keyword(s):  
Working Memory ◽  
Memory Impairment ◽  
Theta Rhythm ◽  
Rhythmic Activity ◽  
Hippocampal Theta Rhythm ◽  
Disease States ◽  
Hippocampal Stimulation ◽  
Hippocampal Theta ◽  
The Brain ◽  
Normal Cognition

Abstract:Intrinsic rhythmic electrical activity in the brain, such as the hippocampal theta rhythm, might serve important roles in normal cognition. Lesions to the medial septal nuclei, or to the fimbria/fornix, disrupt the hippocampal theta rhythm and lead to memory impairment. We have superimposed an artifical stimulating rhythm to the hippocampus of rats with prior lesion of the fornix, during testing in the Morris water maze. This intervention improves performance in a test of working memory, and lends support to the view that intrinsic rhythmic activity may play an important role in normal physiology, and in certain disease states.

Carotid and cardiopulmonary chemoreceptor activity increases hippocampal theta rhythm in conscious rabbits

2000 ◽  
Vol 278 (4) ◽  
pp. R973-R979 ◽  
Author(s):  
Ying-Hui Yu ◽  
W. W. Blessing
Keyword(s):  
Carotid Artery ◽  
Common Carotid Artery ◽  
Theta Rhythm ◽  
Ringer Solution ◽  
The Common ◽  
Conscious Rabbits ◽  
Hippocampal Theta ◽  
Electroencephalogram Eeg ◽  
Hippocampal Eeg ◽  
The Brain

We have examined whether activation of carotid artery chemoreceptors causes alerting in conscious rabbits. Injection of phenylbiguanide (a 5-hydroxytryptamine3-receptor agonist) into the common carotid artery of conscious rabbits increased the proportion of theta rhythm in the hippocampal EEG, commencing in the first 5-s epoch after the injection. Intravenous injection of phenylbiguanide also increased the proportion of theta rhythm in the hippocampal electroencephalogram (EEG), but the onset of the change was not until the second 5-s epoch following injection. Injection of Ringer solution, either into the common carotid artery or into the marginal ear vein, did not affect the hippocampal EEG. Results suggest that phenylbiguanide-mediated activation of carotid and cardiopulmonary chemoreceptor afferents alerts the animal, as assessed by induction of theta rhythm in the hippocampal EEG. This alerting response presumably reflects the action of neural inputs that enter the brain with the carotid sinus nerve at the level of the medulla oblongata.

scholarly journals Hippocampal-Prefrontal Interactions during Spatial Decision-Making

2020 ◽  
Author(s):  
Lucas CS Tavares ◽  
Adriano BL Tort
Keyword(s):  
Decision Making ◽  
Prefrontal Cortex ◽  
Local Field ◽  
Theta Rhythm ◽  
Spatial Navigation ◽  
Choice Point ◽  
Reverse Direction ◽  
Spatial Alternation ◽  
Hippocampal Theta ◽  
Alternation Task

AbstractThe hippocampus has been linked to memory encoding and spatial navigation, while the prefrontal cortex is associated with cognitive functions such as decision-making. These regions are hypothesized to communicate in tasks that demand both spatial navigation and decision-making processes. However, the electrophysiological signatures underlying this communication remain to be better elucidated. To investigate the dynamics of the hippocampal-prefrontal interactions, we have analyzed their local field potentials and spiking activity recorded from rats performing an odor-cued spatial alternation task in an 8-shaped maze. We found that the phase coherence of theta peaked around the choice point area of the maze. Moreover, Granger causality revealed a hippocampus->prefrontal cortex directionality of information flow at theta frequency, peaking at starting areas of the maze, and on the reverse direction at delta frequency, peaking near the turn onset. Additionally, the patterns of phase-amplitude cross-frequency coupling within and between the regions also showed spatial selectivity, and a new method revealed that hippocampal theta and prefrontal delta modulated not only gamma amplitude but also inter-regional gamma synchrony. Lastly, we found that the theta rhythm dynamically modulated neurons in both regions, with the highest modulation at the choice area; interestingly, prefrontal cortex neurons were more strongly modulated by the hippocampal theta rhythm than by their local field rhythm. In all, our results reveal maximum electrophysiological interactions between the hippocampus and the prefrontal cortex near the decision-making period of the spatial alternation task. These results corroborate the hypothesis that a dynamic interplay between these regions takes place during spatial decisions.

scholarly journals Hippocampal theta oscillations are slower in humans than in rodents: implications for models of spatial navigation and memory

2014 ◽  
Vol 369 (1635) ◽  
pp. 20130304 ◽  
Author(s):  
Joshua Jacobs
Keyword(s):  
Electrical Activity ◽  
Large Amplitude ◽  
Theta Rhythm ◽  
Spatial Navigation ◽  
Theta Oscillations ◽  
Mammalian Brain ◽  
Neural Basis ◽  
Human Hippocampus ◽  
Neurosurgical Patients ◽  
Hippocampal Theta

The theta oscillation is a neuroscience enigma. When a rat runs through an environment, large-amplitude theta oscillations (4–10 Hz) reliably appear in the hippocampus's electrical activity. The consistency of this pattern led to theta playing a central role in theories on the neural basis of mammalian spatial navigation and memory. However, in fact, hippocampal oscillations at 4–10 Hz are rare in humans and in some other species. This presents a challenge for theories proposing theta as an essential component of the mammalian brain, including models of place and grid cells. Here, I examine this issue by reviewing recent research on human hippocampal oscillations using direct brain recordings from neurosurgical patients. This work indicates that the human hippocampus does indeed exhibit rhythms that are functionally similar to theta oscillations found in rodents, but that these signals have a slower frequency of approximately 1–4 Hz. I argue that oscillatory models of navigation and memory derived from rodent data are relevant for humans, but that they should be modified to account for the slower frequency of the human theta rhythm.

Eyeblink conditioning contingent on hippocampal theta enhances hippocampal and medial prefrontal responses

2011 ◽  
Vol 105 (5) ◽  
pp. 2213-2224 ◽  
Author(s):  
Ryan D. Darling ◽  
Kanako Takatsuki ◽  
Amy L. Griffin ◽  
Stephen D. Berry
Keyword(s):  
Neural Activity ◽  
Theta Rhythm ◽  
Eyeblink Conditioning ◽  
Trace Conditioning ◽  
Distributed Network ◽  
Field Potentials ◽  
Trace Interval ◽  
Behavioral Learning ◽  
Paired Group ◽  
Hippocampal Theta

Trace eyeblink classical conditioning (tEBCC) can be accelerated by making training trials contingent on the naturally generated hippocampal 3- to 7-Hz theta rhythm. However, it is not well-understood how the presence (or absence) of theta affects stimulus-driven changes within the hippocampus and how it correlates with patterns of neural activity in other essential trace conditioning structures, such as the medial prefrontal cortex (mPFC). In the present study, a brain-computer interface delivered paired or unpaired conditioning trials to rabbits during the explicit presence (T+) or absence (T−) of theta, yielding significantly faster behavioral learning in the T+-paired group. The stimulus-elicited hippocampal unit responses were larger and more rhythmic in the T+-paired group. This facilitation of unit responses was complemented by differences in the hippocampal local field potentials (LFP), with the T+-paired group demonstrating more coherent stimulus-evoked theta than T−-paired animals and both unpaired groups. mPFC unit responses in the rapid learning T+-paired group displayed a clear inhibitory/excitatory sequential pattern of response to the tone that was not seen in any other group. Furthermore, sustained mPFC unit excitation continued through the trace interval in T+animals but not in T−animals. Thus theta-contingent training is accompanied by 1) acceleration in behavioral learning, 2) enhancement of the hippocampal unit and LFP responses, and 3) enhancement of mPFC unit responses. Together, these data provide evidence that pretrial hippocampal state is related to enhanced neural activity in critical structures of the distributed network supporting the acquisition of tEBCC.

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