1,721,051 research outputs found
A journey through neural space: Neuronal population correlates of visual processing and perception
Full text linkSingle neurons can often show strong correlations with an animal’s behavioral output, but it is currently unclear what role population-level interactions play in visual processing and perception. To address these questions, I performed several two-photon calcium imaging experiments in layers 2/3 of mouse primary visual cortex (V1). In Chapter two, I present evidence that signals related to the sensory input may be anatomically differentiated from fluctuations in population activity, and highlight the importance of correlations for the information content of neural codes. Chapters three and four describe the results from an experiment in which mice were trained to perform a visual detection task, while the concurrent activity of ~100 neurons was recorded. Two main conclusions could be drawn from these data: 1) rather than the hitherto assumed importance of mean neuronal activity, it appeared more pivotal for the behavioral detection of visual stimuli that neurons in V1 responded heterogeneously; and 2) specific sequential patterns in neuronal activity were consistently correlated with stimulus detection. This suggests that temporal properties of neuronal activity may play a larger role in sensory processing than is often thought. Finally, chapter five describes how multidimensional population codes may present a more parsimonious explanation for many experimentally observed phenomena in neuronal activation patterns. From a multidimensional perspective, neural codes are more temporally stable, more information efficient, and more robust to trial-by-trial fluctuations in activity. Conceptually integrating these results in chapter 6, I conclude that some seemingly disparate experimental observations may be reconciled by adopting a population-level perspective
The pairwise phase consistency: A bias-free measure of rhythmic neuronal synchronization
No full textThe ventral striatum in goal-directed behavior and sleep: intrinsic network dynamics, motivational information and relation with the hippocampus
Full text linkNMDA receptor dependent functions of hippocampal networks in spatial navigation and memory formation
Full text linkIn this work, we studied neural patterns of activity in the CA 1 region of the hippocampus of the mouse, when different strategies are used. Different input areas support CA 1, depending on the type of navigation: when the animal uses sensory (such as environmental cues) and non-sensory (self-motion) information to guide behavior (place navigation), the entorhinal cortex plays a crucial role, while if the animal executes a sequence of body movements (sequence navigation), CA3 area supports CA1 activity. Our findings show that network oscillations in the gamma range allow CA 1 to tune to one or the other input area, according to the strategy being employed: low gamma oscillations (20-45 Hz) are predominant during the use of a sequence-navigation strategy, while high gamma oscillations (55-90 Hz) prevail during place-navigation. We further show that the NMDA receptors in region CA 1 shape network oscillations: by monitoring knock-out mice lacking this receptor in CA 1, we report that its role is particularly important during sequence navigation, as shown by the impaired behavior and affected neural activity during this type of navigation. KO mice show a lower resolution of spatial representation and our research indicates that this is a consequence of variability across trials and that single-trial properties of CA 1 neuronal activity is largely intact. This work offers new insight into how CA 1, assisted by NMDA receptors, integrates different sources of information and how it uses different frequency channels to communicate with different brain areas
Good vibrations: Rhythms and plasticity in neural correlates of value in rat orbitofrontal cortex
Full text linkHet verstoren van een bepaalde receptor heeft invloed op de manier waarop het rattenbrein informatie verwerkt die van belang is voor het nemen van beslissingen. In de orbitofrontale schors in de hersenen van ratten zijn neuronen actief waarvan de activiteit samenhangt met de waarde die bepaalde stimuli in de omgeving voorspellen. Marijn van Wingerden toont aan dat deze waardecodering bij ratten verandert gedurende het aanleren van associaties tussen geurstimuli en beloningen. Bovendien blijkt uit Van Wingerdens onderzoek dat de neuronen ritmisch actief zijn ten opzichte van langzame (thèta-) en snelle (gamma-) golfbewegingen in een EEG (Electro-Encephalogram), gemeten in de orbitofrontale schors van ratten. Onderling hangen de thèta- en gammaritmes ook samen. Hoe beter die samenhang, hoe succesvoller de beslissingen van de ratten, laat Van Wingerden zien. Het nemen van slechte beslissingen is een belangrijk kenmerk van verschillende psychische aandoeningen, zoals verslaving, obsessief-compulsieve stoornis (OCD) en schizofrenie. Het beter begrijpen van de neurale basis van slechte en goede beslissingen kan bijdragen aan een beter begrip van deze ziektebeelden
Neural representation of reward information : coding by single cells and populations in rat orbitofrontal cortex
Full text linkLost in place: Impaired hippocampal information processing in a mouse model of intellectual disability
No full textCertain forms of learning and long-term memory are mediated by neuronal activity in the hippocampus. For example, electrophysiological activity of hippocampal neurons recorded from rodents during exploration of an environment can reflect mapping of spatial information. These recordings can provide valuable information on impaired cognitive functioning, such as in psychiatric disease. Fragile X syndrome (FXS) is the most common inherited cause of intellectual disability and autism, yet it has no effective treatment, in part because it has proven difficult to establish reliable animal models of its cognitive manifestations. Several neurophysiological and developmental hallmarks of the disease have been identified in the Fmr1-KO mouse model of FXS, which was developed to carry a mutation in same gene as the human patients. In this thesis, we describe electrophysiological characteristics of impaired hippocampal spatial information processing in Fmr1-KO, characterizing how its neurodevelopmental phenotype affects learning and memory formation. We recorded activity from individual neurons as well as the simultaneously occurring neuronal network activity in the CA1 area of the hippocampus, while Fmr1-KO mice freely explored an environment. By contrasting these data to recordings done in healthy wild type control mice (WT), we characterize deficits in hippocampal synaptic plasticity as a result of the FXS mutation, linking its effects to an electrophysiological phenotype. Our results illustrate how affected neural coding and neuronal communication in area CA1 may contribute to the devastating cognitive symptoms of FXS, and may lead to novel approaches for potential treatment
Exploring the triad of behaviour, genes and neuronal networks: Heritability of instrumental conditioning and the Arc/Arg3.1 gene in hippocampal coding
Full text linkIn this thesis, we set out to study the genetic background of neuronal function that enables adaptive behaviours that are essential for survival, such as understanding the relations between actions and outcomes and forming accurate representations of the environment. In the experimental protocols we used, exploratory and cue-response behaviour were motivated by sweet rewards, mimicking real-life situations in which we form memories of environments and action-outcome series associated with rewards. We demonstrated that operant learning and extinction consist of multiple stages that are dissociable, heritable and regulated by different chromosomal areas, characterized the performance of common laboratory mouse lines in acquisition and extinction tasks and suggested mouse models for perseverative disorders. We dissected the role of Arc/Arg3.1 in neuronal processes that take place during active exploration of environment and subsequent sleep. We found that Arc/Arg3.1 knockout (KO) mice exhibited attenuated hippocampal oscillatory activity in the high frequency range and disrupted synchronized firing during track running. Furthermore, we showed that Arc/Arg3.1 KO mice had decreased hippocampal sharp wave-ripple activity and that correlated firing activity during sleep was diminished. These alterations may explain why Arc/Arg3.1 mice are impaired spatial learning and lack memory consolidation. Together, these findings paint an intriguing picture of the genetic background and neuronal processes involved in complex behaviours that are crucial for survival. In order to further understand and unravel this intricate linkage, we will need to continue to study the triad of genes, neuronal networks and behaviour from all its corners
Neural coding of attention and attentional set shifting in the rat medial prefrontal cortex
Full text linkWe investigated cognitive control in the rat medial prefrontal cortex (mPFC) and specifically asked how neural activity changes when the animal directs attention to relevant information while ignoring irrelevant inputs. With the multi-tetrode recording technique, we aimed to find out what happens in this brain structure when previously irrelevant information becomes relevant. The new insights we obtained in these mechanisms will aid us in extending our knowledge on the neural basis of neurological disorders involving the frontal lobes including schizophrenia, ADHD and Parkinson's disease
Contextual signals in visual cortex: How sounds, state, and task setting shape how we see
Full text linkWhat we see is not always what we get. Even though the light that hits the retina might convey the same images, how visual information is processed and what we eventually do with it depend on many contextual factors. In this thesis, we show in a series of experiments how the sensory processing of the same visual input in the visual cortex of mice is affected by our internal state, movements, other senses and any task we are performing. We found that recurrent activity originating within higher visual areas modulates activity in the primary visual cortex (V1) and selectivity amplifies weak compared to strong sensory-evoked responses. Second, visual stimuli evoked similar early activity in V1, but later activity strongly depended on whether mice were trained to report the visual stimuli, and on the specific task. Specifically, adding a second modality to the task demands extended the temporal window during which V1 was causally involved in visual perception. Third, we report that not only visual stimuli but also sounds led to strong responses in V1, composed of distinct auditory-related and motor-related activity. Finally, we studied the role of Posterior Parietal Cortex in an audiovisual change detection task. Despite extensive single-neuron and population-level encoding of task-relevant visual and auditory stimuli, as well as upcoming behavioral responses, optogenetic inactivation did not affect task performance. Whereas these contextual factors have previously been studied in isolation, we obtain a more integrated understanding of how factors beyond visual information determine what we actually see
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