A la fin des années 50, les premières descriptions d'amnésie antérograde chez le patient H.M. ont mis en évidence le rôle crucial de l'hippocampe dans la mémoire. Ces travaux fondateurs ont été étendus grâce à l'enregistrement de l'activité cérébrale chez le rat libre de ses mouvements, avec l'étonnante découverte que les neurones hippocampiques codent la position de l'animal dans l'environnement (« cellules de lieu »). Lorsqu'un rat parcourt une trajectoire, il traverse successivement différents « champs de lieu », et les cellules de lieu correspondantes déchargent les unes après les autres en séquences. De façon surprenante, lorsque la décharge d'une cellule de lieu est observée par rapport au rythme thêta (~8 Hz) présent dans l'hippocampe lorsque le rat explore son environnement, l'ordre dans lequel les cellules déchargent est maintenu à une échelle de temps très rapide (~150 ms), au sein de chaque cycle de l'oscillation thêta. Ces « séquences thêta » reflètent ainsi les positions passée, présente et future de l'animal, ancrant les lieux visités par l'animal dans leur contexte temporel. Pendant le sommeil, les séquences d'activité des cellules hippocampiques sont spontanément réactivées, reproduisant virtuellement la trajectoire du rat lors de son exploration. Ces réactivations ont lieu lors de patterns d'activité transitoires appelés sharp wave-ripples (SPW-Rs). La réintégration répétitive de l'activité séquentielle liée à l'expérience pourrait renforcer les connexions synaptiques entre les cellules. De plus, il a été montré que les SWR-Rs et leurs réactivations associées jouent un rôle causal dans la consolidation de la mémoire. Comment ces réactivations peuvent-elles avoir lieu ? De façon intéressante, pendant l'exploration, les séquences thêta permettent la compression des trajectoires de l'animal à une échelle de temps compatible avec des processus de plasticité. Par conséquent, ces séquences thêta pourraient soutenir l'apprentissage séquentiel pendant l'exploration, et pourraient sous-tendre le codage initial des traces mnésiques. Toutefois, des preuves directes en faveur de ce scénario n'ont pas été fournies... / In the late 50's, the first descriptions of anterograde amnesia in patient H.M. have highlighted the crucial role of the hippocampus in memory. These seminal works have been extended with brain electrophysiological recordings in freely moving rats, with the striking discovery that hippocampal neurons code for the location of the animal in the environment (‘place cells'). When a rat runs through a trajectory, it successively crosses multiple ‘place fields', and the corresponding place cells fire one after the other in sequence, in an order corresponding to the trajectory of the rat. Strikingly, when the place cell firing is observed relative to the ongoing theta rhythm (~8 Hz) recorded in the hippocampus when the rats is exploring its environment, the order in which the cells fire is maintained at a much shorter time scale (~150 ms), in each cycle of the theta oscillations. These ‘theta sequences' thus reflects the past, present and future locations of the animal, anchoring locations in their temporal context. During subsequent sleep, the sequences of hippocampal cell activity are spontaneously reactivated, virtually reproducing the trajectory of the rat during its previous exploration. This replay occurs during transient hippocampal activity patterns called sharp wave-ripples (SPW-Rs). Repetitive reinstatement of experience-related sequential activity may strengthen synaptic connections between cells. Moreover, SPW-Rs and their associated replay have been causally linked to memory consolidation. How does such replay occur during sleep? Interestingly, during exploration, theta sequences allowed the temporal compression of the animal’s trajectory at a time-scale compatible with synaptic plasticity processes. Therefore, these theta sequences have been hypothetized to support sequential structure learning during exploration, and might underlie the initial encoding of memory traces. However, direct evidence supporting this scenario remains elusive...

Orientador: Fernando Cendes / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-23T22:00:31Z (GMT). No. of bitstreams: 1 Ghizoni_Enrico_D.pdf: 2667786 bytes, checksum: 25592a6b5141d281fe4e92c2e525d68d (MD5) Previous issue date: 2013 / Resumo: Introdução: Os acessos cirúrgicos seletivos no tratamento da epilepsia de lobo temporal (ELT) tem como principal objetivo a ressecção da amígdala e do hipocampo com mínima agressão ao néocortex, ao tronco temporal (TT) e às radiações ópticas. Entre os acessos seletivos, o acesso transuncus (TU) foi recentemente proposto em estudos anatômicos, embora não tenha sido validado clinicamente. O objetivo deste estudo é avaliar a eficiência e segurança do acesso TU no tratamento cirúrgico da ELT. Métodos: Realizou-se estudo prospectivo de pacientes submetidos ao acesso TU. Foram avaliados dados clínicos e radiológicos, sendo os resultados comparados com banco de dados de série histórica de pacientes submetidos a outros dois acessos em nossa instituição, a lobectomia anterior (LA) e a amígdalo- hipocampectomia seletiva através do sulco circular inferior da ínsula (TI). Resultados: Em 25 pacientes submetidos ao acesso TU, a idade média foi de 40±8,21 anos. O seguimento médio foi de 26,44+12,58 meses, com 21 (84%) pacientes classificados como Engel I (bom controle de crises). Não houve diferença significativa quanto ao controle de crises em relação aos grupos submetidos à cirurgia de LA e TI (78,9% e 84,6% respectivamente). Os pacientes submetidos ao acesso TU tiveram, significativamente, menos danos ao TT e às radiações ópticas (p<0,001 e p=0,004 respectivamente) quando comparados aos acessos LA e TI. Entre as complicações do acesso TU, não houve nenhum óbito e apenas um paciente apresentou hemiparesia pós-operatória persistente. Conclusões: Os resultados demonstraram que a amígdalo-hipocampectomia seletiva transuncus é um acesso eficiente e seguro no tratamento cirúrgico da epilepsia do lobo temporal. O acesso TU se mostrou mais seletivo do que os acessos LA e TI com maior preservação do TT e radiações ópticas / Abstract: Introduction: The main objective of the selective approaches on the surgical treatment of the temporal lobe epilepsy (TLE) is to resect the amygdala and hyppocampus with minimal agression to the neocortex, temporal stem (TS) and optic radiations. Anatomic reports have described and proposed the transuncus (TU) approach as a very selective one, but this approach has not been validated in the clinical setting yet. The objective of this study is to evaluate the efficiency and safety of the TU approach in the surgical treatment of the TLE. Methods: A prospective study of patients submitted to the TU approach was performed. Clinical and radiological data were evaluated, and the results were compared with those in our data base about the surgical series of patients operated earlier through two other approaches in our institution, anterior temporal lobectomy (ATL) and selective amygdalohyppocampectomy through inferior circular sulcus of insula (TI). Results: In 25 patients operated through the TU approach the mean age was 40±8,21 years-old. The mean follow-up was 26,44+12,58 months and 21 (84%) patients were classified as Engel I (good seizure control). About the seizure control, there were no significant differences with that of the patients operated through the ATL and TI approaches (78,9% e 84,6% respectively of Enegel I). The patients submitted to the TU approach had, significantly, less injuries to the TS and to the optic radiations (p<0,001 e p=0,004 respectively) when compared to the patients submitted to the ATL and TI approaches. There were no mortality and only one patient had permanent morbidity (residual hemiparesis) in this series. Conclusion: The results showed that the transuncus selective amygdalo-hippocampectomy is an efficient and safe approach in the surgical treatment of the temporal lobe epilepsy. The TU approach showed to be more selective then the ATL and TI approaches with better preservation of the TS and optic radiations / Doutorado / Neurociencias / Doutor em Fisiopatologia Medica