{"id":{"repo_id":"freiburg-diss","oai_identifier":"oai:freidok.uni-freiburg.de:1262"},"canonical_url":"https://search.dev.ndltd.org/etd/freiburg-diss/oai:freidok.uni-freiburg.de:1262","repository":{"repo_id":"freiburg-diss","name":"University of Freiburg","base_url":"https://freidok.uni-freiburg.de/oai/oai2.php"},"display":{"title":"Spatio-temporal structure of thalamically evoked activity in the barrel cortex","abstract":"The barrel cortex integrates incoming information conveyed via thalamocortical pathways and ongoing activity thereby extracting the relevant details from spatio-temporal dynamic stimuli that carry information about the environment. In the course of this, the cortical response to the incoming information depends on the actual state of activity of the network and the state of activity is influenced by the incoming information. <br>In this project, I investigated how the pattern of activity in the barrel cortex is shaped by incoming sensory information, and how successive stimuli interact with each other. I used rat thalamocortical slices preserving the functional coupling between the ventrobasal thalamic nucleus and the ‘barrel’ cortex. Local field potentials (LFP) and spike activity were recorded in the ‘barrel’ cortex with multi-electrode arrays, while electrical stimulation of the thalamocortical pathway simulated incoming sensory information. <br>Glutamatergic responses to thalamocortical stimulation spanned multiple barrels starting 1–2 ms after the first fibre volley in the input layers IV and Vb and afterwards spread to supra- and infragranular layers. Glutamatergic responses were immediately followed by feed-forward inhibition. A model based on common biophysical assumptions reproduced the LFP waveform showing that monosynaptic glutamatergic activation was followed by disynaptic inhibition. This inhibition often led to rebound activity manifested as population EPSPs (pEPSP) and stimulus locked spike activity (mostly in IV). Spike activity was also found locked to the first pEPSP. <br>Besides paired-pulse depression on the short time scale, the first stimulus was also able to change the network state on a longer time scale, resulting in a different type of response to the second stimulus: long lasting and highly variable LFP fluctuations or ensemble activity starting ~10–100 ms poststimulus time and lasting for several hundred milliseconds. Ensemble activity was best induced with an intra-pair interval of 20 ms and an inter-pair interval of 20 s. The observation that the ensemble activity was induced less effectively by using a shorter inter-pair interval of 5 s is a very interesting finding as it indicates that network properties are changed on the time scale of several seconds by such stimuli. During application of bicuculline, ensemble activity was blocked, instead epileptiform activity appeared with ten-fold higher amplitudes in the LFP. The observations that ensemble activity had a much smaller amplitude than epileptiform activity, that the on- and offsets of ensemble activity were variable and that ensemble activity showed highly variable fluctuations of the waveform over trials, led to the hypothesis that ensemble activity locally and dynamically recruits neurones into changing ensembles of synchronous activity. It might use the same mechanisms as ongoing or background activity in vivo.","abstract_html":"The barrel cortex integrates incoming information conveyed via thalamocortical pathways and ongoing activity thereby extracting the relevant details from spatio-temporal dynamic stimuli that carry information about the environment. In the course of this, the cortical response to the incoming information depends on the actual state of activity of the network and the state of activity is influenced by the incoming information. &lt;br&gt;In this project, I investigated how the pattern of activity in the barrel cortex is shaped by incoming sensory information, and how successive stimuli interact with each other. I used rat thalamocortical slices preserving the functional coupling between the ventrobasal thalamic nucleus and the ‘barrel’ cortex. Local field potentials (LFP) and spike activity were recorded in the ‘barrel’ cortex with multi-electrode arrays, while electrical stimulation of the thalamocortical pathway simulated incoming sensory information. &lt;br&gt;Glutamatergic responses to thalamocortical stimulation spanned multiple barrels starting 1–2 ms after the first fibre volley in the input layers IV and Vb and afterwards spread to supra- and infragranular layers. Glutamatergic responses were immediately followed by feed-forward inhibition. A model based on common biophysical assumptions reproduced the LFP waveform showing that monosynaptic glutamatergic activation was followed by disynaptic inhibition. This inhibition often led to rebound activity manifested as population EPSPs (pEPSP) and stimulus locked spike activity (mostly in IV). Spike activity was also found locked to the first pEPSP. &lt;br&gt;Besides paired-pulse depression on the short time scale, the first stimulus was also able to change the network state on a longer time scale, resulting in a different type of response to the second stimulus: long lasting and highly variable LFP fluctuations or ensemble activity starting ~10–100 ms poststimulus time and lasting for several hundred milliseconds. Ensemble activity was best induced with an intra-pair interval of 20 ms and an inter-pair interval of 20 s. The observation that the ensemble activity was induced less effectively by using a shorter inter-pair interval of 5 s is a very interesting finding as it indicates that network properties are changed on the time scale of several seconds by such stimuli. During application of bicuculline, ensemble activity was blocked, instead epileptiform activity appeared with ten-fold higher amplitudes in the LFP. The observations that ensemble activity had a much smaller amplitude than epileptiform activity, that the on- and offsets of ensemble activity were variable and that ensemble activity showed highly variable fluctuations of the waveform over trials, led to the hypothesis that ensemble activity locally and dynamically recruits neurones into changing ensembles of synchronous activity. It might use the same mechanisms as ongoing or background activity in vivo.","abstract_has_math":false,"creators":["Schlabrendorff, Carl-Ludwig von"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":["Aertsen, Ad"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":null,"date_issued":"","date_published":null,"updated_at":"2026-07-24T02:22:10Z","subjects":["barrel cortex","thalamus","in vitro","micro-electrode arrays","rat"],"languages":[],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://freidok.uni-freiburg.de/data/1262","outbound_label":"Repository record","outbound_source":"source_url"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Aertsen, Ad"]},{"key":"dc:creator","label":"Author","values":["Schlabrendorff, Carl-Ludwig von"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:type","label":"Dc Type","values":["DoctoralThesis"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["barrel cortex","thalamus","in vitro","micro-electrode arrays","rat"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description.abstract","label":"Abstract","values":["The barrel cortex integrates incoming information conveyed via thalamocortical pathways and ongoing activity thereby extracting the relevant details from spatio-temporal dynamic stimuli that carry information about the environment. In the course of this, the cortical response to the incoming information depends on the actual state of activity of the network and the state of activity is influenced by the incoming information. <br>In this project, I investigated how the pattern of activity in the barrel cortex is shaped by incoming sensory information, and how successive stimuli interact with each other. I used rat thalamocortical slices preserving the functional coupling between the ventrobasal thalamic nucleus and the ‘barrel’ cortex. Local field potentials (LFP) and spike activity were recorded in the ‘barrel’ cortex with multi-electrode arrays, while electrical stimulation of the thalamocortical pathway simulated incoming sensory information. <br>Glutamatergic responses to thalamocortical stimulation spanned multiple barrels starting 1–2 ms after the first fibre volley in the input layers IV and Vb and afterwards spread to supra- and infragranular layers. Glutamatergic responses were immediately followed by feed-forward inhibition. A model based on common biophysical assumptions reproduced the LFP waveform showing that monosynaptic glutamatergic activation was followed by disynaptic inhibition. This inhibition often led to rebound activity manifested as population EPSPs (pEPSP) and stimulus locked spike activity (mostly in IV). Spike activity was also found locked to the first pEPSP. <br>Besides paired-pulse depression on the short time scale, the first stimulus was also able to change the network state on a longer time scale, resulting in a different type of response to the second stimulus: long lasting and highly variable LFP fluctuations or ensemble activity starting ~10–100 ms poststimulus time and lasting for several hundred milliseconds. Ensemble activity was best induced with an intra-pair interval of 20 ms and an inter-pair interval of 20 s. The observation that the ensemble activity was induced less effectively by using a shorter inter-pair interval of 5 s is a very interesting finding as it indicates that network properties are changed on the time scale of several seconds by such stimuli. During application of bicuculline, ensemble activity was blocked, instead epileptiform activity appeared with ten-fold higher amplitudes in the LFP. The observations that ensemble activity had a much smaller amplitude than epileptiform activity, that the on- and offsets of ensemble activity were variable and that ensemble activity showed highly variable fluctuations of the waveform over trials, led to the hypothesis that ensemble activity locally and dynamically recruits neurones into changing ensembles of synchronous activity. It might use the same mechanisms as ongoing or background activity in vivo.","Der Barrel-Kortex integriert eingehende Information von den thalamokortikalen Bahnen und Hintergrundaktivität um die relevanten Details aus den raumzeitlich dynamischen Stimuli zu extrahieren. Dabei hängt die kortikale Antwort vom Aktivitätszustand des Netzwerks ab und der Aktivitätszustand wird von der eingehenden Information beeinflußt. <br>In dieser Arbeit habe ich untersucht, wie raum-zeitliche Aktivitätsmuster im Barrel-Kortex durch eingehende sensorische Information verändert werden und wie aufeinanderfolgende Stimuli miteinander wechselwirken. Dazu wurden thalamokortikale Hirnschnitte von Ratten benutzt, in denen Teile des ventrobasalen Nukleus des Thalamus und des Barrel-Kortex sowie eine intakte Verbindung zwischen ihnen erhalten bleiben. Lokale Feldpotentiale (LFP) und Einzelzellaktivität wurden mit Multielektrodenarrays im Barrel-Kortex gemessen, während eingehende sensorische Information durch elektrische Stimulation der thalamokortikalen Bahnen simuliert wurde. <br>Glutamaterge Antworten auf thalamokortikale Stimulation erschienen 1–2 ms nach dem Fibre Volley in den Schichten IV und Vb von mehreren Barrels. Danach breitete sich die Aktivität auf supra- und infragranuläre Schichten aus. Auf die glutamaterge Antwort folgte umgehend vorwärtsgekoppelte („feed-forward“) Inhibition. Ein Modell, welches auf allgemeinen biophysikalischen Annahmen basierte, konnte die LFP Wellenform reproduzieren und zeigte, daß auf die glutamaterge Aktivität disynaptische Inhibition folgte. Das Abklingen der Inhibition führte oft zu einem Überschießen („Rebound“) an Populations-EPSPs (pEPSP) und Stimulus gekoppelter Einzelzellaktivität. Darüber hinaus gab es auch Einzelzellaktivität, die an das erste pEPSP gekoppelt war. <br>Neben Doppelpuls-Depression, die auf kurzen Zeitskalen auftrat, führte der erste Stimulus auch zu einer Änderung des Netzwerkzustands auf einer längeren Zeitskala, die zu einer anderen Art von Antwort auf den zweiten Stimulus führte: lang anhaltende und hoch variable LFP Fluktuationen bzw. Ensembleaktivität, die ~10–100 ms nach dem Stimulus begannen und mehrere hundert Millisekunden dauerten. Ensembleaktivität wurde am besten mit 20 ms Intra-Paarintervallen und 20 s Inter-Paarintervallen induziert. Die Beobachtung, daß Ensembleaktivität mit 5 s Inter-Paarintervallen weniger effizient induziert wurde, ist eine wichtige Entdeckung, da sie auf Veränderungen von Netzwerkeigenschaften auf einer Zeitskala von mehreren Sekunden hinweist. Bicuculline verhinderte diese Ensembleaktivität und rief statt dessen epileptiforme Aktivität hervor, die eine zehnfach höhere Amplitude besaß. Die Beobachtungen, daß Ensembleaktivität eine sehr viel kleinere Amplitude als epileptiforme Aktivität besaß, daß Beginn und Ende der Ensembleaktivität fluktuierten, und daß Ensembleaktivität durch hoch variable Fluktuationen der Wellenform verglichen über verschiedene Versuchsdurchläufe charakterisiert war, führten zu der Hypothese, daß Ensembleaktivität Neuronen dynamisch auf lokaler Ebene rekrutiert und sie in andauernd wechselnde Ensembles synchroner Aktivität einbindet. Ensembleaktivität könnte dieselben Mechanismen wie Hintergrundaktivität in vivo benutzen."]},{"key":"dc:format.medium","label":"Dc Format Medium","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Spatio-temporal structure of thalamically evoked activity in the barrel cortex","Raum-zeitliche Strukuren thalamisch induzierter Aktivität im Barrel-Kortex"]}]}],"canonical_facts":{"dc:contributor":["Aertsen, Ad"],"dc:creator":["Schlabrendorff, Carl-Ludwig von"],"dc:description.abstract":["The barrel cortex integrates incoming information conveyed via thalamocortical pathways and ongoing activity thereby extracting the relevant details from spatio-temporal dynamic stimuli that carry information about the environment. In the course of this, the cortical response to the incoming information depends on the actual state of activity of the network and the state of activity is influenced by the incoming information. <br>In this project, I investigated how the pattern of activity in the barrel cortex is shaped by incoming sensory information, and how successive stimuli interact with each other. I used rat thalamocortical slices preserving the functional coupling between the ventrobasal thalamic nucleus and the ‘barrel’ cortex. Local field potentials (LFP) and spike activity were recorded in the ‘barrel’ cortex with multi-electrode arrays, while electrical stimulation of the thalamocortical pathway simulated incoming sensory information. <br>Glutamatergic responses to thalamocortical stimulation spanned multiple barrels starting 1–2 ms after the first fibre volley in the input layers IV and Vb and afterwards spread to supra- and infragranular layers. Glutamatergic responses were immediately followed by feed-forward inhibition. A model based on common biophysical assumptions reproduced the LFP waveform showing that monosynaptic glutamatergic activation was followed by disynaptic inhibition. This inhibition often led to rebound activity manifested as population EPSPs (pEPSP) and stimulus locked spike activity (mostly in IV). Spike activity was also found locked to the first pEPSP. <br>Besides paired-pulse depression on the short time scale, the first stimulus was also able to change the network state on a longer time scale, resulting in a different type of response to the second stimulus: long lasting and highly variable LFP fluctuations or ensemble activity starting ~10–100 ms poststimulus time and lasting for several hundred milliseconds. Ensemble activity was best induced with an intra-pair interval of 20 ms and an inter-pair interval of 20 s. The observation that the ensemble activity was induced less effectively by using a shorter inter-pair interval of 5 s is a very interesting finding as it indicates that network properties are changed on the time scale of several seconds by such stimuli. During application of bicuculline, ensemble activity was blocked, instead epileptiform activity appeared with ten-fold higher amplitudes in the LFP. The observations that ensemble activity had a much smaller amplitude than epileptiform activity, that the on- and offsets of ensemble activity were variable and that ensemble activity showed highly variable fluctuations of the waveform over trials, led to the hypothesis that ensemble activity locally and dynamically recruits neurones into changing ensembles of synchronous activity. It might use the same mechanisms as ongoing or background activity in vivo.","Der Barrel-Kortex integriert eingehende Information von den thalamokortikalen Bahnen und Hintergrundaktivität um die relevanten Details aus den raumzeitlich dynamischen Stimuli zu extrahieren. Dabei hängt die kortikale Antwort vom Aktivitätszustand des Netzwerks ab und der Aktivitätszustand wird von der eingehenden Information beeinflußt. <br>In dieser Arbeit habe ich untersucht, wie raum-zeitliche Aktivitätsmuster im Barrel-Kortex durch eingehende sensorische Information verändert werden und wie aufeinanderfolgende Stimuli miteinander wechselwirken. Dazu wurden thalamokortikale Hirnschnitte von Ratten benutzt, in denen Teile des ventrobasalen Nukleus des Thalamus und des Barrel-Kortex sowie eine intakte Verbindung zwischen ihnen erhalten bleiben. Lokale Feldpotentiale (LFP) und Einzelzellaktivität wurden mit Multielektrodenarrays im Barrel-Kortex gemessen, während eingehende sensorische Information durch elektrische Stimulation der thalamokortikalen Bahnen simuliert wurde. <br>Glutamaterge Antworten auf thalamokortikale Stimulation erschienen 1–2 ms nach dem Fibre Volley in den Schichten IV und Vb von mehreren Barrels. Danach breitete sich die Aktivität auf supra- und infragranuläre Schichten aus. Auf die glutamaterge Antwort folgte umgehend vorwärtsgekoppelte („feed-forward“) Inhibition. Ein Modell, welches auf allgemeinen biophysikalischen Annahmen basierte, konnte die LFP Wellenform reproduzieren und zeigte, daß auf die glutamaterge Aktivität disynaptische Inhibition folgte. Das Abklingen der Inhibition führte oft zu einem Überschießen („Rebound“) an Populations-EPSPs (pEPSP) und Stimulus gekoppelter Einzelzellaktivität. Darüber hinaus gab es auch Einzelzellaktivität, die an das erste pEPSP gekoppelt war. <br>Neben Doppelpuls-Depression, die auf kurzen Zeitskalen auftrat, führte der erste Stimulus auch zu einer Änderung des Netzwerkzustands auf einer längeren Zeitskala, die zu einer anderen Art von Antwort auf den zweiten Stimulus führte: lang anhaltende und hoch variable LFP Fluktuationen bzw. Ensembleaktivität, die ~10–100 ms nach dem Stimulus begannen und mehrere hundert Millisekunden dauerten. Ensembleaktivität wurde am besten mit 20 ms Intra-Paarintervallen und 20 s Inter-Paarintervallen induziert. Die Beobachtung, daß Ensembleaktivität mit 5 s Inter-Paarintervallen weniger effizient induziert wurde, ist eine wichtige Entdeckung, da sie auf Veränderungen von Netzwerkeigenschaften auf einer Zeitskala von mehreren Sekunden hinweist. Bicuculline verhinderte diese Ensembleaktivität und rief statt dessen epileptiforme Aktivität hervor, die eine zehnfach höhere Amplitude besaß. Die Beobachtungen, daß Ensembleaktivität eine sehr viel kleinere Amplitude als epileptiforme Aktivität besaß, daß Beginn und Ende der Ensembleaktivität fluktuierten, und daß Ensembleaktivität durch hoch variable Fluktuationen der Wellenform verglichen über verschiedene Versuchsdurchläufe charakterisiert war, führten zu der Hypothese, daß Ensembleaktivität Neuronen dynamisch auf lokaler Ebene rekrutiert und sie in andauernd wechselnde Ensembles synchroner Aktivität einbindet. Ensembleaktivität könnte dieselben Mechanismen wie Hintergrundaktivität in vivo benutzen."],"dc:format.medium":["application/pdf"],"dc:subject":["barrel cortex","thalamus","in vitro","micro-electrode arrays","rat"],"dc:title":["Spatio-temporal structure of thalamically evoked activity in the barrel cortex","Raum-zeitliche Strukuren thalamisch induzierter Aktivität im Barrel-Kortex"],"dc:type":["DoctoralThesis"]},"updated_at":"2026-07-24T02:22:10Z"}