Biology subjects

Paz-Alonso, P. M.

Publications and source records attributed to Paz-Alonso, P. M..

9 recordsLinked to original sources

bioRxiv2026

Low-frequency neural responses synchronize to distinct structural rather than lexical features during sentence comprehension

Language comprehension involves the integration of single words (lexical units) into phrases and sentences (multi-word structures). Previous frequency-tagging studies have found that low-frequency neural responses synchronize to the frequency of multi-word structures. However, it is currently unclear how exactly structural and lexical processes jointly impact these synchronization findings. The present magnetoencephalography experiment implemented the frequency-tagging paradigm in the visual modality with written words to investigate neural synchronization to multi-word sentences varying in internal structure (reversed word orders between verb-initial Spanish and verb-final Basque sentences) and in lexical content (real words and pseudo words). We find converging evidence that neural responses largely synchronize to structural rather than lexical features. This was observed as robust phase synchronization strength to the frequency of sentences containing reversed structures, with certain lexical modulations depending on language-specific structural features. Crucially, we also found shifted phase angle dynamics between the reversed structures of Spanish and Basque sentences independently of word-level lexical characteristics. Together, these findings suggest that neural synchronization to multi-word structures is largely driven by distinct structural features operating via two segregated neural dimensions: frequency coding for the coarser aspects (i.e., timescale/duration) and phase representing the finer-grained aspects (i.e., internal structure) of multi-word structures. Our findings thus advance key insights into the core components of the neural mechanisms supporting language comprehension. HighlightsO_LINeural synchronization to sentences is driven by structural (not lexical) features. C_LIO_LIRobust sentence-frequency synchronization across languages varying in structure. C_LIO_LIPhase angle is selectively sensitive to cross-linguistic structural differences. C_LIO_LILexical modulations depend on language-specific structure. C_LIO_LIStructure synchronization segregates into two dimensions: frequency and phase. C_LI

neuroscience↗

bioRxiv2026

Dual thalamic drive defines the intra-amygdala wiring complexity

The amygdala plays a key role in affective behaviors by integrating incoming signals and conveying them towards subcortical output regions. Current models suggest a serial information flow within the amygdala from the lateral and basolateral towards the central subnuclei driven by incoming thalamic and cortical excitation. However, due to the lack of universally accepted parcellation principles, the precise connectivity and thus, the signal propagation within the circuit remain debated. Using a molecular-based parcellation, our subnucleus-specific anatomical and electrophysiological mapping revealed a previously overlooked complexity in the intra-amygdala wiring pattern in mice. Specifically, the intra-amygdala signal transfer relies on separate lateral thalamus-driven routes via the lateral subnucleus mostly bypassing the anterior basolateral and centrolateral subnuclei. In contrast, the anterior basolateral nucleus, innervated by the dorsal midline thalamus, supplies mostly extra-, but not intra-amygdala routes. We also demonstrated that a similar dual thalamo-cortico-amygdala organization exists in the human brain. Collectively, our findings identified unconventional amygdala wiring principles challenging the traditional serial lateral-basolateral-central stream model which can redefine our understanding of behaviorally relevant intra-amygdala computations.

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bioRxiv2026

Mapping subcortical fear pathways in the human brain: thalamo-amygdala connections revealed by high-resolution tractography

Influential models of emotion have postulated the existence of several direct subcortical pathways, or low roads, that convey fast sensory thalamic inputs to the amygdala for affective processing. In rodents and non-human primates, specific thalamo-amygdala connections have been identified and linked to fear responses. These connections mainly originate in three thalamic nuclear groups (posterior, intralaminar, and medial) and project to the basolateral amygdala (BLA). However, the existence of similar thalamo-amygdala pathways in humans remains uncertain. Here, aiming to reproduce subcortical amygdala connections previously described in the non-human animal literature, we mapped those tracts in 113 human participants of either sex. We implemented an advanced high-resolution tractography protocol optimized for reliably tracing axonal pathways through regions with complex white-matter architecture. We reconstructed white matter tracts connecting thalamic nuclei to the BLA, and assessed their test-retest reproducibility to evaluate their anatomical plausibility. Among posterior thalamic nuclei, projections from the medial geniculate nucleus and the medial and inferior pulvinar to the BLA emerged as the strongest and most robust thalamo-amygdala pathways. In turn, the mediodorsal nucleus within the medial group exhibited a prominent connection to the BLA, with a high number of streamlines and moderate-to-high reliability across sessions. Finally, intralaminar thalamic nuclei (parafascicular, central medial, and centromedian) showed consistent connections to the BLA, albeit with higher intrasubject variability and moderate-to-low reproducibility. Together, these findings provide a unifying anatomical framework for multiple direct thalamo-amygdala pathways in the human brain, and suggest the existence of distinct evolutionarily conserved routes for subcortical affective processing. Significance statementAnimal studies have identified several subcortical "low road" pathways that may convey direct sensory inputs from the thalamus to the amygdala. Here, we analyzed human diffusion magnetic resonance imaging data to reconstruct thalamo-amygdala pathways previously reported in non-human species and assessed their test-retest reproducibility. White matter tracts linking the medial geniculate nucleus, as well as the medial and inferior pulvinar, to the basolateral amygdala appeared to be the most robust and reliable. Additional connections were found between the mediodorsal and intralaminar nuclei of the thalamus and the basolateral amygdala. These findings reveal the presence of multiple conserved direct pathways to the amygdala in humans, likely supporting rapid affective processing across modalities.

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bioRxiv2024

Biases in volumetric versus surface analyses in population receptive field mapping

Population receptive field (pRF) mapping is a quantitative fMRI analysis method that links visual field positions with specific locations in the visual cortex. A common preprocessing step in pRF analyses involves projecting volumetric fMRI data onto the cortical surface, often leading to upsampling of the data. This process may introduce biases in the resulting pRF parameters. To investigate this, we present CON-pRF, a fully containerized pipeline for pRF mapping analysis that is designed to maximize reproducibility in pRF mapping studies. Using this pipeline, we compared pRF maps generated from original volumetric with those from upsampled surface data. Our results show substantial increases in pRF coverage in the central visual field of upsampled data sets. These effects were consistent across early visual cortex areas V1-3. Further analysis indicates that this bias is primarily driven by the non-linear relationship between cortical distance and visual field eccentricity, known as cortical magnification. Our results demonstrate that reproducible analysis pipelines enable the detection of potential biases introduced by varying processing steps, particularly when comparing across differently processed datasets. Key PointsO_LISpatial upsampling increases pRF coverage in the fovea due to enhanced CNR and cortical magnification. C_LIO_LIThe study highlights the need for careful consideration of data processing steps. C_LIO_LICON-pRF is a containerized pipeline for enhanced reproducibility in pRF analysis. C_LI

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bioRxiv2022

Reproducible Tract Profiles (RTP2): from diffusion MRI acquisition to clinical practice and research

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 (RTP2): a set of flexible and automated methods to analyze anatomical MRI and diffusion weighted imaging (DWI) data for reproducible tractography. The tools read structural MRI data and process 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. HighlightsO_LIAutomated, flexible and reproducible protocol for white-matter tractography and tractometry. C_LIO_LIHigh computational (same data, different computations) and test-retest reproducibility (data from different sessions, different computations). C_LIO_LIOpen-source code and publicly available containers. C_LI

neuroscience↗

bioRxiv2022

Brain structure, phenotypic and genetic correlates of reading abilities

Reading is an evolutionary new development that recruits and tunes brain circuitry connecting visual- and language-processing regions. We investigated the structural correlates of reading and whether genetics influence brain-reading associations. First, we identified left hemisphere cortical surface area (CSA) and cortical thickness (CT) correlates of reading in the large ABCD dataset (N=9,013) of 9-to-10-year-olds. Next, the heritability of cognitive and brain measures of interest was examined through complementary approaches. Last, shared genetic effects between reading, reading-related cognitive traits and reading-associated brain measures were examined by computing genetic correlations and polygenic score analyses, and through mediation analyses. Our results support that morphometric brain measures are related to reading abilities, and that the total left CSA in general, and left superior temporal gyrus CSA in particular, contribute to reading partially through genetic factors.

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bioRxiv2022

A parvocellular-magnocellular functional gradient in human visual cortex

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 these visual pathways make to visual recognition in general and to word reading in particular. Using a multimodal functional MRI approach and individual-subject analyses, here we investigate the involvement of visual cortex regions in the recognition of magnocellular- and parvocellular-biased words and images. Our results reveal a functional gradient in the activation profile of both left and right visual cortex: posterior regions are more strongly recruited for processing parvocellular-biased, while anterior regions are more involved in processing magnocellular-biased stimuli. Furthermore, functional connectivity analyses show clustering in the strength of functional coupling among visual cortex regions as a function of the distance between regions, with greater coupling within and less coupling across posterior and anterior regions. Finally, we found minimal differences in lateralization for word and image recognition in these visual cortical regions. These results were replicated in a retest session with a subset of participants. Our findings underscore a functional division of labor in the visual cortex as a function determined by a parvocellular or magnocellular bias in properties of the stimuli and further reveal that in this context the visual cortex is not particularly biased towards words or images.

neuroscience↗

bioRxiv2018

Functional connectivity reveals dissociable ventrolateral prefrontal mechanisms for the control of multilingual word retrieval

A fundamental cognitive operation involved in speech production is word retrieval from the mental lexicon, which in monolinguals is supported by dissociable ventro-lateral prefrontal cortex (vlPFC) mechanisms associated with proactive and reactive control. This functional magnetic resonance imaging (fMRI) study established whether in multilinguals word retrieval is supported by the same prefrontal mechanisms, and whether proactive modulation consists in suppression of the non-target lexicon. Healthy multilingual volunteers participated in a task that required them to name pictures alternatively in their dominant and less-dominant language. Two crucial variables were manipulated: the cue-target interval (CTI) to either engage (long CTI) or prevent proactive control processes (short CTI), and the cognate status of the pictures to-be-named (non-cognates versus cognates) to capture the presence of selective pre-activation of the target language. Results support the two-process account of vlPFC and indicate that multilinguals engage in proactive control to prepare the target language. This proactive modulation, enacted by anterior vlPFC, is achieved by boosting the activation of lexical representations of the target language. Control processes supported by mid-vlPFC and left inferior parietal lobe together, are similarly engaged in pre-and post-word retrieval, possibly exerted on phonological representations to reduce cross-language interference.\n\nSignificance Statement\n\nWord retrieval in monolingual speech production is enacted by left ventro-lateral prefrontal cortex (vlPFC) supporting controlled access to conceptual representations (proactive control), and left mid-vlPFC supporting post-retrieval lexical selection (reactive control). In this functional magnetic resonance imaging (fMRI) study we demonstrate that multilingual word retrieval is supported by similar prefrontal mechanisms. However, differently from monolinguals, multilingual speakers retrieve words by applying proactive control on lexical representations to reduce cross-language interference. Alternatively to what it has been proposed by one of the most influential models, here we show that this proactive modulation is achieved by boosting the activation of lexical representations of the target language.

neuroscience↗

bioRxiv2017

How the human brain introspects about one’s own episodes of cognitive control

Metacognition refers to our capacity to reflect upon our experiences, thoughts and actions. Metacognition processes are linked to cognitive control functions that allow keeping our actions on-task. But it is unclear how the human brain builds an internal model of ones cognition and behaviour. We conducted 2 fMRI experiments in which brain activity was recorded online as participants engaged in a memory-guided search task and then later offline when participants introspected about their prior experience and cognitive states during performance. In Experiment 1 the memory cues were task-relevant while in Experiment 2 they were irrelevant. Across Experiments, the patterns of brain activity, including frontoparietal regions, were similar during on-task and introspection states. However the connectivity profile amongst frontoparietal areas was distint during introspection and modulated by the relevance of the memory cues. Introspection was also characterized by increased temporal correlation between the default-mode network (DMN), frontoparietal and dorsal attention networks and visual cortex. We suggest that memories of ones own experience during task performance are encoded in large-scale patterns of brain activity and that coupling between DMN and frontoparietal control networks may be crucial to build an internal model of ones behavioural performance.

neuroscience↗