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Published: 29 September 2023, Social and nonsocial directional stimuli (such as gaze and arrows, respectively) share their ability to trigger attentional processes, although the issue of whether social stimuli generate other additional (and unique) attentional effects is still under debate. In this study, we used the spatial interference paradigm to explore, using functional magnetic resonance imaging, shared and dissociable brain activations produced by gaze and arrows. Results showed a common set of regions (right parieto-temporo-occipital) similarly involved in conflict resolution for gaze and arrows stimuli, which showed stronger co-activation for incongruent than congruent trials. The frontal eye field showed stronger functional connectivity with occipital regions for congruent as compared with incongruent trials, and this effect was enhanced for gaze as compared with arrow stimuli in the right hemisphere. Moreover, spatial interference produced by incongruent (as compared with congruent) arrows was associated with increased functional coupling between the right frontal eye field and a set of regions in the left hemisphere. This result was not observed for incongruent (as compared with congruent) gaze stimuli. The right frontal eye field also showed greater coupling with left temporo-occipital regions for those conditions in which larger conflict was observed (arrow incongruent vs. gaze incongruent trials, and gaze congruent vs. arrow congruent trials). These findings support the view that social and nonsocial stimuli share some attentional mechanisms, while at the same time highlighting other differential effects.

183 p., The magnocellular and parvocellular systems are major visual recognition pathways, with distinct histological and physiological properties. Despite their critical role, there is limited evidence on the specific contributions of these visual pathways to visual recognition in general, word reading in particular, as well as in regard to their developmental trajectories. This doctoral dissertation is aimed at examining the involvement of the magnocellular and parvocellular pathways in reading over development (Empirical Part I), in visual cortex regions during reading and visual recognition (Empirical Part II) and in the two main reading ventral and dorsal networks (Empirical Part III). Our results revealed i) a more protracted maturation of the magnocellular visual pathway compared to the magnocellular pathway from middle childhood to adulthood, ii) a functional division of labor in the visual cortex as a function of the parvocellular and magnocellular properties of the stimuli, and iii) that both the magnocellular and parvocellular pathways are involved in reading processes, with the parvocellular pathway mainly contributing to the ventral reading network and the magnocellular pathway mainly contributing to the dorsal reading network.

Published: November 15, 2023, Animal studies have established that the mediodorsal nucleus (MD) of the thalamus is heavily and reciprocally connected with all areas of the prefrontal cortex (PFC). In humans, however, these connections are difficult to investigate. High-resolution imaging protocols capable of reliably tracing the axonal tracts linking the human MD with each of the PFC areas may thus be key to advance our understanding of the variation, development, and plastic changes of these important circuits, in health and disease. Here, we tested in adult female and male humans the reliability of a new reconstruction protocol based on in vivo diffusion MRI to trace, measure, and characterize the fiber tracts interconnecting the MD with 39 human PFC areas per hemisphere. Our protocol comprised the following three components: (1) defining regions of interest; (2) preprocessing diffusion data; and, (3) modeling white matter tracts and tractometry. This analysis revealed largely separate PFC territories of reciprocal MD–PFC tracts bearing striking resemblance with the topographic layout observed in macaque connection-tracing studies. We then examined whether our protocol could reliably reconstruct each of these MD–PFC tracts and their profiles across test and retest sessions. Results revealed that this protocol was able to trace and measure, in both left and right hemispheres, the trajectories of these 39 area-specific axon bundles with good-to-excellent test-retest reproducibility. This protocol, which has been made publicly available, may be relevant for cognitive neuroscience and clinical studies of normal and abnormal PFC function, development, and plasticity.

Published: 2023 Apr 12, Diffusion MRI is a complex technique, where new discoveries and implementations occur at a fast pace. The expertise needed for data analyses and accurate and reproducible results is increasingly demanding and requires multidisciplinary collaborations. In the present work we introduce Reproducible Tract Profiles 2 (RTP2), a set of flexible and automated methods to analyze anatomical MRI and diffusion weighted imaging (DWI) data for reproducible tractography. RTP2 reads structural MRI data and processes them through a succession of serialized containerized analyses. We describe the DWI algorithms used to identify white-matter tracts and their summary metrics, the flexible architecture of the platform, and the tools to programmatically access and control the computations. The combination of these three components provides an easy-to-use automatized tool developed and tested over 20 years, to obtain usable and reliable state-of-the-art diffusion metrics at the individual and group levels for basic research and clinical practice.

Advance access publication date 30 April 2022, Our sensory system constantly receives information from the environment and our own body. Despite our impression to the contrary, we remain largely unaware of this information and often cannot report it correctly. Although perceptual processing does not require conscious effort on the part of the observer, it is often complex, giving rise to errors such as incorrect integration of features (illusory conjunctions). In the present study, we use functional magnetic resonance imaging to study the neural bases of feature integration in a dual task that produced ~30% illusions. A distributed set of regions demonstrated increased activity for correct compared to incorrect (illusory) feature integration, with increased functional coupling between occipital and parietal regions. In contrast, incorrect feature integration (illusions) was associated with increased occipital (V1–V2) responses at early stages, reduced functional connectivity between right occipital regions and the frontal eye field at later stages, and an overall decrease in coactivation between occipital and parietal regions. These results underscore the role of parietal regions in feature integration and highlight the relevance of functional occipito-frontal interactions in perceptual processing.

205 p., La comunicación humana y comprensión del mundo dependen en gran medida de las palabras y conceptos que empleamos. En el marco de esta tesis, mi investigación se enfoca en comprender la naturaleza dinámica de las representaciones conceptuales en el cerebro humano. Mi objetivo es investigar cómo procesos naturales, como el envejecimiento, impactan en las representaciones conceptuales a nivel neural. Además, busco explorar las posibilidades de la neuromodulación artificial a través del neurofeedback decodificado -fMRI-DecNef-, utilizando técnicas de aprendizaje automático (machine learning) y resonancia magnética funcional. En mi primer estudio, examiné cómo el envejecimiento afecta a las representaciones neurales de categorías semánticas, específicamente en la distinción entre seres vivos y objetos inanimados. Para ello, hice uso de métodos avanzados de análisis multivariado y computacionales. Los resultados revelaron que, con el envejecimiento, las representaciones de estas categorías muestran una disminución en su distintividad y especificidad en ciertas regiones cerebrales. En mi segundo estudio, desarrollé y puse a prueba un innovador protocolo de fMRI-DecNef, con la intención de investigar su potencial para manipular las representaciones conceptuales a nivel neural y explorar su viabilidad en el abordaje de ciertos trastornos o deterioros cognitivos asociados a la edad. El objetivo principal fue investigar la capacidad de este enfoque para dotar de forma inconsciente de nuevos significados a estímulos previamente neutrales, por medio de aprendizaje asociativo. Los resultados sugieren que el fMRI-DecNef puede reconfigurar las representaciones conceptuales de manera inconsciente. Ambos hallazgos amplían nuestro entendimiento sobre la formación y modificación de las representaciones conceptuales a lo largo del tiempo, y presentan oportunidades prometedoras para el desarrollo de terapias que utilicen técnicas de neuromodulación y neurofeedback decodificado.

Published online 11 March 2022, Bilingual language production requires both language knowledge and language control in order to communicate in a target language. Learning or improving a language in adulthood is an increasingly common undertaking, and this has complex effects on the cognitive and neural processes underlying language production. The current functional magnetic resonance imaging (fMRI) experiment investigated the functional plasticity of verbal production in adult language learners, and examined the dynamics of word retrieval in order to dissociate the contributions of language knowledge and executive control. Thirty four adults who were either intermediate or advanced language learners, underwent MRI scanning while performing verbal fluency tasks in their native and new languages. A multipronged analytical approach revealed (i) time-varying contributions of language knowledge and executive control to verbal fluency performance, (ii) learning-related changes in the functional correlates of verbal fluency in both the native and new languages, (iii) no effect of learning on lateralization, and (iv) greater functional coupling between language and language control regions with greater second language experience. Collectively, our results point to significant functional plasticity in adult language learners that impacts the neural correlates of production in both the native and new languages, and provide new insight into the widely used verbal fluency task.

Published on 28 December 2022, The testing effect describes the finding that retrieval practice enhances memory performance compared to restudy practice. Prior evidence demonstrates that this effect can be boosted by providing feedback after retrieval attempts (i.e. test-potentiated encoding [TPE]). The present fMRI study investigated the neural processes during successful memory retrieval underlying this beneficial effect of correct answer feedback compared with restudy and whether additional performance feedback leads to further benefits. Twenty-seven participants learned cue-target pairs by (i) restudying, (ii) standard TPE including a restudy opportunity, or (iii) TPE including a restudy opportunity immediately after a positive or negative performance feedback. One day later, a cued retrieval recognition test was performed inside the MRI scanner. Behavioral results confirmed the testing effect and that adding explicit performance feedback-enhanced memory relative to restudy and standard TPE. Stronger functional engagement while retrieving items previously restudied was found in lateral prefrontal cortex and superior parietal lobe. By contrast, lateral temporo-parietal areas were more strongly recruited while retrieving items previously tested. Performance feedback increased the hippocampal activation and resulted in stronger functional coupling between hippocampus, supramarginal gyrus, and ventral striatum with lateral temporo-parietal cortex. Our results unveil the main functional dynamics and connectivity nodes underlying memory benefits from additional performance feedback.

20 April 2023, Introduction: Long-term memory retention is enhanced after testing compared to restudying (testing effect). Notably, memory retrieval further improves when correct-answer feedback is provided after the retrieval attempt (test-potentiated encoding–TPE). Methods: To evaluate whether explicit positive or negative feedback further enhances memory performance beyond the effect of TPE, in two experiments additional explicit positive or negative performance-contingent feedback was presented before providing correct-answer feedback. After an initial exposure to the full material, 40 participants learned 210 weakly associated cue-target word pairs by either restudying or testing (Experiment 1). Depending on the accuracy of the retrieval attempt, the tested word pairs were followed by positive or negative performance feedback (50%) or no feedback (50%). Irrespective of the type of repetition, trials were followed by a restudy opportunity. Participants returned to perform a final cued-recall test (Day 2). Results: Final test results replicated the testing effect (better memory performance for tested compared to restudied items). Explicit performance feedback in addition to correct-answer feedback increased retrieval performance, but only on Day 2. This pattern of results was replicated in Experiment 2 in an independent sample of 25 participants. To assess the specific effects of learning history, we also examined retrieval accuracy and reaction times during repetition cycles: Explicit feedback improved retrieval for material successfully encoded in the initial study phase (consistent positive feedback) as well as for material learned during the repetition phase (mixed positive and negative feedback). Discussion: Performance feedback improves learning beyond the effects of retrieval practice and correct-answer feedback, suggesting that it strengthens memory representations and promotes re-encoding of the material.

183 p., The magnocellular and parvocellular systems are major visual recognition pathways, with distinct histological and physiological properties. Despite their critical role, there is limited evidence on the specific contributions of these visual pathways to visual recognition in general, word reading in particular, as well as in regard to their developmental trajectories. This doctoral dissertation is aimed at examining the involvement of the magnocellular and parvocellular pathways in reading over development (Empirical Part I), in visual cortex regions during reading and visual recognition (Empirical Part II) and in the two main reading ventral and dorsal networks (Empirical Part III). Our results revealed i) a more protracted maturation of the magnocellular visual pathway compared to the magnocellular pathway from middle childhood to adulthood, ii) a functional division of labor in the visual cortex as a function of the parvocellular and magnocellular properties of the stimuli, and iii) that both the magnocellular and parvocellular pathways are involved in reading processes, with the parvocellular pathway mainly contributing to the ventral reading network and the magnocellular pathway mainly contributing to the dorsal reading network.

222 p., Parkinson's disease (PD) is the second most common neurodegenerative disorder associated with aging. Approximately 40% of the PD patients treated with dopaminergic medication will develop Impulse Control Disorder (ICD). PD patients with ICD engage in pathological behaviors akin to behavioral addictions, as a result of a malfunction of their reward system due to chronic exposure to dopaminergic medication. Cognitive neuroscience research has investigated cognitive impulsivity and reward mechanisms in PD patients with ICD. However, functional and molecular imaging evidence indicates abnormalities in regions and networks that are not associated with cognitive impulsivity, but with domains such as movement, inhibitory control, and semantic processing. These domains have either not been previously investigated in this population, or previous literature shows mixed results. This doctoral dissertation aims at examining the neural correlates of three different domains in a group of patients with PD and ICD, a group of patients with PD and no ICD, and a group of healthy control participants using functional magnetic resonance imaging (fMRI). The three domains examined in each Experiment are motor function through a sequential finger-tapping task (Experiment I), inhibitory control through measures of response inhibition (Experiment II), and semantic processing via an auditory processing task (Experiment III). We were particularly interested in group differences in the functional networks and regions implicated in these tasks. Our results revealed that, across the three examined domains (i.e., motor, response inhibition, semantic processing), PD patients with ICD showed differential functional coupling among regions relative to their control counterparts, which remarks the importance of neural networks in cognitive neuroscience. Although the domains examined here had not received special attention in PD patients with ICD, we show that these patients exhibit functional differen

139 p., During evolution the expansion of the neocortex has been linked with the emergence of higher level cognitive functions, such as reasoning, abstract thinking, or language in human beings. Current research on cognitive neuroscience is mainly focused on the cerebral cortex. Whereas the thalamus is a structure that has extensive white-matter connections with the cerebral cortex, its expansion during evolution is parallel to the expansion of the neocortex. The thalamocortical connections are involved in communication between cortical areas. Thus, to fully understand the neural basis of cognition, a better understanding of the role of the thalamus in cortical function is necessary. The present doctoral dissertation is focused on the structure and function of the thalamus: the first study proposes a reproducible protocol to reconstruct the first-order thalamic white-matter tracts from diffusion-weighted imaging data; the second study investigates the higher-order thalamic white-matter tracts and a similar protocol is proposed to reconstruction those tracts; the third study uses task-based fMRI to examine the involvement of first-order thalamic nuclei in the main language systems.the current dissertation successfully reconstructed first-order and higher-order thalamic white-matter tracts from DWI data, and has proved high reproducibility of the reconstruction protocol. This protocol could benefit the tractography community to better understand the structural connectivity of the thalamus with cortical and subcortical structures and facilitate the research on thalamocortical pathways in humans. We also found evidence for differences in the processing of linguistic and nonlinguistic stimuli in first-order thalamic nuclei through a task-based fMRI study. These results suggest that the first-order thalamic nuclei play roles in human language that are beyond relaying sensory information from periphery to cerebral cortex. These findings are important to push forward our understand

Published:17 December 2021, The left ventral occipito-temporal cortex (vOTC) supports extraction and processing of visual features. However, it has remained unclear whether left vOTC-based functional connectivity (FC) differs according to task-relevant representations (e.g., lexical, visual) and control demands imposed by the task, even when similar visual-semantic processing is required for object identification. Here, neural responses to the same set of pictures of meaningful objects were measured, while the type of task that participants had to perform (picture naming versus size-judgment task), and the level of cognitive control required by the picture naming task (high versus low interference contexts) were manipulated. Explicit retrieval of lexical representations in the picture naming task facilitated activation of lexical/phonological representations, modulating FC between left vOTC and dorsal anterior-cingulate-cortex/pre-supplementary-motor-area. This effect was not observed in the size-judgment task, which did not require explicit word-retrieval of object names. Furthermore, retrieving the very same lexical/phonological representation in the high versus low interference contexts during picture naming increased FC between left vOTC and left caudate. These findings support the proposal that vOTC functional specialization emerges from interactions with task-relevant brain regions.

Published: 12 March 2022, We often use inner narration when thinking about past and future events. The present paradigm explicitly addresses the influence of the language used in inner narration on the hippocampus-dependent event construction process. We assessed the language context effect during the inner narration of different event types: past, future, daydream, and self-unrelated fictitious events. The language context was assessed via a fluent bilingual population who used inner narration, either in their first language (L1) or second language (L2). Not all inner narration of events elicited hippocampo-cortical activity. In fact, only the angular gyrus and precuneus-retrosplenial cortex were activated by inner narration across all event types. More precisely, only inner narration of events which entailed the simulation of bodily self-location in space (whether or not they were time-marked: past, future, daydream) depended on the hippocampo-cortical system, while inner narration of events that did not entail bodily self-location (self-unrelated fictitious) did not. The language context of the narration influenced the bilinguals’ hippocampo-cortical system by enhancing the co-activation of semantic areas with the hippocampus for inner narration of events in the L2. Overall, this study highlights 2 important characteristics of hippocampo-cortical-dependent inner narration of events: The core episodic hippocampal system is activated for inner narration of events simulating self-location in space (regardless of time-marking), and the inner language used for narration (L1 or L2) mediates hippocampal functional connectivity.