The role of pulvinar-parietal circuitryin goal-directed saccades
von Mathieu Pachoud
Datum der mündl. Prüfung:2022-11-29
Erschienen:2023-11-28
Betreuer:Dr. Igor Kagan
Gutachter:Prof. Dr. Melanie Wilke
Gutachter:Prof. Dr. Hansjörg Scherberger
Dateien
Name:Thesis_manuscript_Pachoud.pdf
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Description:Thesis manuscript
Zusammenfassung
Englisch
The pulvinar, an important higher-order thalamic nucleus supporting many functions, is reciprocally connected with frontoparietal areas involved in sensorimotor transformations. Priorperturbation studies also revealed its role in spatial decision-making. In this thesis, we tried to geta better understanding on the role of pulvinar-parietal circuitry in visually-guided saccades andspatial decision-making, within one hemisphere and also in the context of inter-hemisphericinteractions. To do so, in the first study we characterized neuronal activity and functionalconnectivity using local field potential (LFP) and spike-LFP synchronization within and between the dorsal pulvinar and area LIP. In the second study, we investigated the effect of reversibleunilateral dorsal pulvinar inactivation on neuronal activity in area LIP in the inactivated and the opposite hemisphere. We showed the flexibility of functional interactions between the dorsalpulvinar and LIP with ongoing oscillations during the maintained fixation and movementpreparation, and also in transient shifts upon visual processing and around saccade events. Inaddition, we reported that a stronger connectivity during free-choice trials led to a higherprobability of selecting contralateral targets. We also showed that unilateral dorsal pulvinarinactivation led to an ipsilesional choice bias, a decreased cortical ‘alert state’ that might explain more general inactivation effects such as slight drowsiness, and an altered contralesionalrepresentation of visual goals as well as neuronal synchronization in area LIP in the samehemisphere. On the contrary, there was an upregulated neuronal activity in the oppositehemisphere. Finally, we found a decreased inter-hemispheric functional connectivity after theinactivation. Altogether, these studies shed light on a crucial role for pulvinar-parietal interactionsin maintaining cortical alertness, the representation of contralateral visual goals and subsequentmovement selection and planning. In a more general perspective, this work highlights theimportance of thalamo-cortical loops in shaping the neuronal activity locally and inter-hemispherically across homotopic regions, as opposed to only relaying information across cortical regionswithin the same hemisphere. Finally, our results suggest push-pull interactions between the twohemispheres during spatial selection and oculomotor preparation.
Keywords: Pulvinar; Cognitive Neuroscience; Visually-guided movements; Parietal cortex