Theta-modulation drives the emergence of connectivity patterns underlying replay in a network model of place cells

Place cells of the rodent hippocampus fire action potentials when the animal traverses a particular spatial location in any environment. Therefore for any given trajectory one observes a repeatable sequence of place cell activations. When the animal is quiescent or sleeping, one can observe similar sequences of activation known as replay, which underlie the process of memory consolidation. However, it remains unclear how replay is generated. Here we show how a temporally asymmetric plasticity rule during spatial exploration gives rise to spontaneous replay in a model network by shaping the recurrent connectivity to reflect the topology of the learned environment. Crucially, the rate of this encoding is strongly modulated by ongoing rhythms. Oscillations in the theta range optimize learning by generating repeated pre-post pairings on a time-scale commensurate with the window for plasticity, while lower and higher frequencies generate learning rates which are lower by orders of magnitude

Theta-modulation drives the emergence of connectivity patterns underlying replay in a network model of place cells

Place cells of the rodent hippocampus fire action potentials when the animal traverses a particular spatial location in any environment. Therefore for any given trajectory one observes a repeatable sequence of place cell activations. When the animal is quiescent or sleeping, one can observe similar sequences of activation known as replay, which underlie the process of memory consolidation. However, it remains unclear how replay is generated. Here we show how a temporally asymmetric plasticity rule during spatial exploration gives rise to spontaneous replay in a model network by shaping the recurrent connectivity to reflect the topology of the learned environment. Crucially, the rate of this encoding is strongly modulated by ongoing rhythms. Oscillations in the theta range optimize learning by generating repeated pre-post pairings on a time-scale commensurate with the window for plasticity, while lower and higher frequencies generate learning rates which are lower by orders of magnitude

Fluctuations in perceptual decisions : cortical microcircuit dynamics mediating alternations in conscious visual perception

Fluctuations in perceptual decisions emerge when our brain confronts with ambiguous sensory stimuli. For instance, our perception alternates between two conflicting images when presented dichoptically to our eyes, allowing a dissociation of the sensory stimulation from the conscious visual perception, and therefore providing a gateway to consciousness. How does the brain work when it deals with such ambiguous sensory stimuli? We addressed this question theoretically by employing a biophysically realistic attractor network, by consistently reducing it to a four- variable rate- based model, and by extracting analytical expressions for second- order statistics. We considered human behavioral and macaque neurophysiological data collected when subjects were confronting with such ambiguities. Our results show the relevance of neuronal adaptation in perceptual decision making, as well as that it contributes to the speed- accuracy trade- off. Furthermore, our findings affirm that both noise and neural adaptation operate in balance during the fluctuating states of visual awareness and suggest that while adaptation in inhibition is not relevant for the perceptual alternations, it contributes to the brain dynamics at rest. Finally, we explain the observed neuronal noise- decorrelation during visual consciousness and provide insights on the long- standing question: where in the brain rivalry is resolved.Les fluctuacions en les decisions perceptives sorgeixen quan el nostre cervell s'enfronta a estímuls sensorials ambigus. Per exemple, la nostra percepció alterna entre dues imatges contradictòries quan es presenten de forma dicòptica als nostres ulls, cosa que permet una dissociació de l'estimulació sensorial de la percepció visual conscient, i per tant proporciona una porta d'entrada a la consciència. Com funciona el cervell quan es tracta d'aquest tipus d'estímuls sensorials ambigus? Hem tractat aquesta qüestió de forma teòrica mitjançant l'ús d'una xarxa d'atractors biofísicament realista, reduint-la de forma consistent a un model de quatre variables basat en la freqüència, i extraient expressions analítiques pels estadístics de segon ordre. Hem emprat dades neurofisiològiques de comportament d'humans i macacos recollides quan els subjectes s'enfrontaven a aquest tipus d'ambigüitats. Els nostres resultats mostren la importància de l'adaptació neuronal en la presa de decisions perceptives i mostren la seva contribució a l'equilibri velocitat-precisió. D'altra banda, els nostres resultats confirmen que tant el soroll com l'adaptació neural operen en equilibri durant els estats fluctuants de consciència visual i suggereixen que, si bé l'adaptació en la inhibició no és rellevant per a les alternances de percepció, contribueix a la dinàmica del cervell en repòs. Finalment, expliquem la decorrelació del soroll neuronal observada durant la consciència visual i proporcionem noves idees en relació a l’antiga qüestió de en quin lloc del cervell es resol la rivalitat visual

Διακυμάνσεις στις αντιληπτικές αποφάσεις: δυναμική μικροκυκλώματος φλοιού που μεσολαβεί εναλλαγές στη συνειδητή οπτική αντίληψη

Fluctuations in perceptual decisions emerge when our brain confronts with ambiguous sensory stimuli. For instance, our perception alternates between two conflicting images when presented dichoptically to our eyes, allowing a dissociation of the sensory stimulation from the conscious visual perception, and therefore providing a gateway to consciousness. How does the brain work when it deals with such ambiguous sensory stimuli?We addressed this question theoretically by employing a biophysically realistic attractor network, by consistently reducing it to a four- variable rate- based model, and by extracting analytical expressions for second- order statistics. We considered human behavioral and macaque neurophysiological data collected when subjects were confronting with such ambiguities. Our results show the relevance of neuronal adaptation in perceptual decision making, as well as that it contributes to the speed- accuracy trade- off. Furthermore, our findings affirm that both noise and neural adaptation operate in balance during the fluctuating states of visual awareness and suggest that while adaptation in inhibition is not relevant for the perceptual alternations, it contributes to the brain dynamics at rest. Finally, we explain the observed neuronal noise- decorrelation during visual consciousness and provide insights on the long- standing question: where in the brain rivalry is resolved.Οι διακυμάνσεις στις αντιληπτικές αποφάσεις εμφανίζονται όταν ο εγκέφαλός μας έρχεται αντιμέτωπος με διφορούμενα αισθητηριακά ερεθίσματα. Για παράδειγμα, η αντίληψή μας εναλλάσσεται μεταξύ δύο αντικρουόμενων εικόνων όταν παρουσιάζονται διχοπτικά στα μάτια μας, επιτρέποντας μια διάσπαση της αισθητηριακής διέγερσης από τη συνειδητή οπτική αντίληψη και επομένως παρέχοντας μια πύλη στη συνείδηση. Πώς λειτουργεί ο εγκέφαλος όταν αντιμετωπίζει τόσο διφορούμενα αισθητηριακά ερεθίσματα; Αντιμετωπίσαμε αυτό το ερώτημα θεωρητικά χρησιμοποιώντας ένα βιοφυσικά ρεαλιστικό δίκτυο ελκυστικών, που με συνέπεια το ανάγαμε σε ένα μοντέλο τεσσάρων μεταβλητών, βασισμένο στη ρυθμική νευρωνική δραστηριότητα, και εξάγοντας αναλυτικές εκφράσεις για στατιστική δεύτερης τάξης. Θεωρήσαμε νευροφυσιολογικά δεδομένα ανθρώπινης συμπεριφοράς και μακάκου που συλλέχθηκαν όταν τα υποκείμενα αντιμετώπιζαν τέτοιες ασάφειες. Τα αποτελέσματά μας δείχνουν τη συνάφεια της προσαρμογής των νευρώνων στη λήψη αντιληπτικών αποφάσεων, καθώς και ότι συμβάλλει στην αντιστάθμιση ταχύτητας-ακρίβειας. Επιπλέον, τα ευρήματά μας επιβεβαιώνουν ότι τόσο ο θόρυβος όσο και η νευρική προσαρμογή λειτουργούν σε ισορροπία κατά τη διάρκεια των κυμαινόμενων καταστάσεων της οπτικής επίγνωσης και υποδηλώνουν ότι ενώ η προσαρμογή στην αναστολή δεν σχετίζεται με τις αντιληπτικές εναλλαγές, συμβάλλει στη δυναμική του εγκεφάλου σε ηρεμία. Τέλος, εξηγούμε την παρατηρούμενη νευρωνική αποσυσχέτιση θορύβου κατά τη διάρκεια της οπτικής συνείδησης και παρέχουμε προτάσεις για το μακροχρόνιο ερώτημα: πού επιλύεται ο ανταγωνισμός στον εγκέφαλο

Rat A992 on novel square track w muscimol

Matlab file with multi-unit, lfp and animal position. 35 min exploration of novel square track, medial septum inactivated by muscimol. From Pastalkova lab at Janelia Research Campus, data collected by Yingxue Wang

Rat A992 on novel hexagonal track

Matlab file with multi-unit, lfp and animal position. 35 min exploration of novel hexagonal track: session 1. From Pastalkova lab at Janelia Research Campus, data collected by Yingxue Wang

Rat A991 on novel hexagonal track

Matlab file with multi-unit, lfp and animal position. 35 min exploration of novel hexagonal track: session 1. From Pastalkova lab at Janelia Research Campus, data collected by Yingxue Wang

Rat A992 on novel hexagonal track (3rd session)

Matlab file with multi-unit, lfp and animal position. 35 min exploration of novel hexagonal track: session 3. From Pastalkova lab at Janelia Research Campus, data collected by Yingxue Wang

Rat A991 on novel hexagonal track (2nd session)

Matlab file with multi-unit, lfp and animal position. 35 min exploration of novel hexagonal track: session 2. From Pastalkova lab at Janelia Research Campus, data collected by Yingxue Wang