francisco martini - Academia.edu (original) (raw)
Papers by francisco martini
Science
Whereas sensory perception relies on specialized sensory pathways, it is unclear whether these pa... more Whereas sensory perception relies on specialized sensory pathways, it is unclear whether these pathways originate as modality-specific circuits. We demonstrated that somatosensory and visual circuits are not by default segregated but require the earliest retinal activity to do so. In the embryo, somatosensory and visual circuits are intermingled in the superior colliculus, leading to cortical multimodal responses to whisker pad stimulation. At birth, these circuits segregate, and responses switch to unimodal. Blocking stage I retinal waves prolongs the multimodal configuration into postnatal life, with the superior colliculus retaining a mixed somato-visual molecular identity and defects arising in the spatial organization of the visual system. Hence, the superior colliculus mediates the timely segregation of sensory modalities in an input-dependent manner, channeling specific sensory cues to their appropriate sensory pathway.
Neuroscience
Sensory processing relies on the correct development of thalamocortical loops. Visual corticothal... more Sensory processing relies on the correct development of thalamocortical loops. Visual corticothalamic axons (CTAs) invade the dorsolateral geniculate nucleus (dLGN) of the thalamus in early postnatal mice according to a regulated program that includes activity-dependent mechanisms. Spontaneous retinal activity influences the thalamic incursion of CTAs, yet the perinatal thalamus also generates intrinsic patterns of spontaneous activity whose role in modulating afferent connectivity remains unknown. Here, we found that patterned spontaneous activity in the dLGN contributes to proper spatial and temporal innervation of CTAs. Disrupting patterned spontaneous activity in the dLGN delays corticogeniculate innervation under normal conditions and upon eye enucleation. The delayed innervation was evident throughout the first two postnatal weeks but resumes after eye-opening, suggesting that visual experience is necessary for the homeostatic recovery of corticogeniculate innervation.
Annual Review of Neuroscience
Unimodal sensory loss leads to structural and functional changes in both deprived and nondeprived... more Unimodal sensory loss leads to structural and functional changes in both deprived and nondeprived brain circuits. This process is broadly known as cross-modal plasticity. The evidence available indicates that cross-modal changes underlie the enhanced performances of the spared sensory modalities in deprived subjects. Sensory experience is a fundamental driver of cross-modal plasticity, yet there is evidence from early–visually deprived models supporting an additional role for experience-independent factors. These experience-independent factors are expected to act early in development and constrain neuronal plasticity at later stages. Here we review the cross-modal adaptations elicited by congenital or induced visual deprivation prior to vision. In most of these studies, cross-modal adaptations have been addressed at the structural and functional levels. Here, we also appraise recent data regarding behavioral performance in early–visually deprived models. However, further research is...
Innovación Docente e Investigación en Salud: Nuevos Enfoques en la Metodología Docente.
SummarySensory processing relies on the correct development of circuits connecting thalamus and c... more SummarySensory processing relies on the correct development of circuits connecting thalamus and cortex. Visual corticothalamic axons (CTAs) invade the thalamic dorsolateral geniculate nucleus (dLGN) of the thalamus following an early postnatal time-regulated programme in mice. Retinal spontaneous activity influences the thalamic incursion of CTAs, however, the perinatal thalamus also generates intrinsic patterns of spontaneous activity whose role in modulating afferent connectivity remains unknown. Here, we found that patterned spontaneous activity in the dLGN is critical for the proper spatial and temporal innervation of CTAs. When the spontaneous dLGN activity is disrupted in vivo, CTA innervation is severely delayed until eye-opening. Indeed, visual input influenced the temporal development of CTAs by modulating thalamic activity, as embryonic enucleation enhanced thalamic calcium waves and accelerated the entrance of CTAs into the dLGN. Our results show that patterned spontaneou...
El tema de estudio en esta tesis es la migracion tangencial de las interneuronas corticales duran... more El tema de estudio en esta tesis es la migracion tangencial de las interneuronas corticales durante el desarrollo embrionario. Las interneuronas corticales se originan en el telencefalo ventral y migran tangencialmente hasta el telencefalo dorsal donde formaran la corteza cerebral junto con las neuronas piramidales o excitatorias. Los resultadospresentados en esta tesis aportan nuevos elementos sobre dos aspectos fundamentales de la migracion neuronal: la guia direccional y los mecanismos propulsores del movimiento. En el primer caso, nuestros datos indican que las interneuronas corticales delinean su trayectoria de migracion utilizando una estrategia celular basada en la generacion de un proceso guia bifurcado y la posterior seleccion de la rama mejor orientada con el gradiente quimiotactico. En segundo lugar, proporcionamos una explicacion dinamica sobre el mecanismo molecular responsable del movimiento del nucleo en las interneuronas corticales. El nucleo es impulsado hacia adela...
Neuron, 2021
Developing sensory circuits exhibit different patterns of spontaneous activity, patterns that are... more Developing sensory circuits exhibit different patterns of spontaneous activity, patterns that are related to the construction and refinement of functional networks. During the development of different sensory modalities, spontaneous activity originates in the immature peripheral sensory structures and in the higher-order central structures, such as the thalamus and cortex. Certainly, the perinatal thalamus exhibits spontaneous calcium waves, a pattern of activity that is fundamental for the formation of sensory maps and for circuit plasticity. Here we will review our current understanding of the maturation of early (including embryonic) patterns of spontaneous activity, and their influence on the assembly of thalamic and cortical sensory networks. Overall, the data currently available suggests similarities between the developmental trajectory of brain activity in experimental models and humans, which in the future may help to improve the early diagnosis of developmental disorders.
The thalamus is the largest structure of the diencephalon, the central region of the brain betwee... more The thalamus is the largest structure of the diencephalon, the central region of the brain between the midbrain and telencephalon. In the mature thalamus, neurons sharing similar structural and functional properties are spatially aggregated in cellular clusters called nuclei, unlike cortical areas where neurons are organized in horizontal layers. While neurons within nuclei share many properties, a varied collection of features arises when comparing neurons among nuclei, including different patterns of connectivity, molecular signatures, cell morphology, electrophysiological profile, and many other properties. Even more functional and cellular diversity is found if other diencephalic territories are taken in account. Remarkably, this congregation of heterogeneous cell types and connectivity patterns emerges from a rather homogeneous territory early in development. A progressive sequence of specification and differentiation programs patterns the initial diencephalon to craft dozens o...
Science
The mammalian brain’s somatosensory cortex is a topographic map of the body’s sensory experience.... more The mammalian brain’s somatosensory cortex is a topographic map of the body’s sensory experience. In mice, cortical barrels reflect whisker input. We asked whether these cortical structures require sensory input to develop or are driven by intrinsic activity. Thalamocortical columns, connecting the thalamus to the cortex, emerge before sensory input and concur with calcium waves in the embryonic thalamus. We show that the columnar organization of the thalamocortical somatotopic map exists in the mouse embryo before sensory input, thus linking spontaneous embryonic thalamic activity to somatosensory map formation. Without thalamic calcium waves, cortical circuits become hyperexcitable, columnar and barrel organization does not emerge, and the somatosensory map lacks anatomical and functional structure. Thus, a self-organized protomap in the embryonic thalamus drives the functional assembly of murine thalamocortical sensory circuits.
Neuroscience, 2017
The development of cortical maps requires the balanced interaction between genetically determined... more The development of cortical maps requires the balanced interaction between genetically determined programs and input/activity-dependent signals generated spontaneously or triggered from the environment. The somatosensory pathway of mice provides an excellent scenario to study cortical map development because of its highly organized cytoarchitecture, known as the barrel field. This precise organization makes evident even small alterations in the cortical map layout. In this review, we will specially focus on the thalamic factors that control barrel field development. We will summarize the role of thalamic input integration and identity, neurotransmission and spontaneous activity in cortical map formation and early cross-modal plasticity.
Cerebral Cortex, 2017
Interspersed distribution of selectivity to kinematic stimulus features in supragranular layers o... more Interspersed distribution of selectivity to kinematic stimulus features in supragranular layers of mouse barrel cortex. Cerebral Cortex, 27 (7). pp. 3782-2789.
Nature Neuroscience, 2015
Sensory perception depends on the context within which a stimulus occurs. Prevailing models empha... more Sensory perception depends on the context within which a stimulus occurs. Prevailing models emphasize cortical feedback as the source of contextual modulation. However, higher-order thalamic nuclei, such as the pulvinar, interconnect with many cortical and subcortical areas, suggesting a role for the thalamus in providing sensory and behavioral context-yet the nature of the signals conveyed to cortex by higher-order thalamus remains poorly understood. Here we use axonal calcium imaging to measure information provided to visual cortex by the pulvinar equivalent in mice, the lateral posterior nucleus (LP), as well as the dorsolateral geniculate nucleus (dLGN). We found that dLGN conveys retinotopically precise visual signals, while LP provides distributed information from the visual scene. Both LP and dLGN projections carry locomotion signals. However, while dLGN inputs often respond to positive combinations of running and visual flow speed, LP signals discrepancies between self-generated and external visual motion. This higher-order thalamic nucleus therefore conveys diverse contextual signals that inform visual cortex about visual scene changes not predicted by the animal's own actions. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Frontiers in neural circuits, 2016
Short-term synaptic plasticity (STP) sets the sensitivity of a synapse to incoming activity and d... more Short-term synaptic plasticity (STP) sets the sensitivity of a synapse to incoming activity and determines the temporal patterns that it best transmits. In "driver" thalamocortical (TC) synaptic populations, STP is dominated by depression during stimulation from rest. However, during ongoing stimulation, lemniscal TC connections onto layer 4 neurons in mouse barrel cortex express variable STP. Each synapse responds to input trains with a distinct pattern of depression or facilitation around its mean steady-state response. As a result, in common with other synaptic populations, lemniscal TC synapses express diverse rather than uniform dynamics, allowing for a rich representation of temporally varying stimuli. Here, we show that this STP diversity is regulated presynaptically. Presynaptic adenosine receptors of the A1R type, but not kainate receptors (KARs), modulate STP behavior. Blocking the receptors does not eliminate diversity, indicating that diversity is related to he...
Science
Whereas sensory perception relies on specialized sensory pathways, it is unclear whether these pa... more Whereas sensory perception relies on specialized sensory pathways, it is unclear whether these pathways originate as modality-specific circuits. We demonstrated that somatosensory and visual circuits are not by default segregated but require the earliest retinal activity to do so. In the embryo, somatosensory and visual circuits are intermingled in the superior colliculus, leading to cortical multimodal responses to whisker pad stimulation. At birth, these circuits segregate, and responses switch to unimodal. Blocking stage I retinal waves prolongs the multimodal configuration into postnatal life, with the superior colliculus retaining a mixed somato-visual molecular identity and defects arising in the spatial organization of the visual system. Hence, the superior colliculus mediates the timely segregation of sensory modalities in an input-dependent manner, channeling specific sensory cues to their appropriate sensory pathway.
Neuroscience
Sensory processing relies on the correct development of thalamocortical loops. Visual corticothal... more Sensory processing relies on the correct development of thalamocortical loops. Visual corticothalamic axons (CTAs) invade the dorsolateral geniculate nucleus (dLGN) of the thalamus in early postnatal mice according to a regulated program that includes activity-dependent mechanisms. Spontaneous retinal activity influences the thalamic incursion of CTAs, yet the perinatal thalamus also generates intrinsic patterns of spontaneous activity whose role in modulating afferent connectivity remains unknown. Here, we found that patterned spontaneous activity in the dLGN contributes to proper spatial and temporal innervation of CTAs. Disrupting patterned spontaneous activity in the dLGN delays corticogeniculate innervation under normal conditions and upon eye enucleation. The delayed innervation was evident throughout the first two postnatal weeks but resumes after eye-opening, suggesting that visual experience is necessary for the homeostatic recovery of corticogeniculate innervation.
Annual Review of Neuroscience
Unimodal sensory loss leads to structural and functional changes in both deprived and nondeprived... more Unimodal sensory loss leads to structural and functional changes in both deprived and nondeprived brain circuits. This process is broadly known as cross-modal plasticity. The evidence available indicates that cross-modal changes underlie the enhanced performances of the spared sensory modalities in deprived subjects. Sensory experience is a fundamental driver of cross-modal plasticity, yet there is evidence from early–visually deprived models supporting an additional role for experience-independent factors. These experience-independent factors are expected to act early in development and constrain neuronal plasticity at later stages. Here we review the cross-modal adaptations elicited by congenital or induced visual deprivation prior to vision. In most of these studies, cross-modal adaptations have been addressed at the structural and functional levels. Here, we also appraise recent data regarding behavioral performance in early–visually deprived models. However, further research is...
Innovación Docente e Investigación en Salud: Nuevos Enfoques en la Metodología Docente.
SummarySensory processing relies on the correct development of circuits connecting thalamus and c... more SummarySensory processing relies on the correct development of circuits connecting thalamus and cortex. Visual corticothalamic axons (CTAs) invade the thalamic dorsolateral geniculate nucleus (dLGN) of the thalamus following an early postnatal time-regulated programme in mice. Retinal spontaneous activity influences the thalamic incursion of CTAs, however, the perinatal thalamus also generates intrinsic patterns of spontaneous activity whose role in modulating afferent connectivity remains unknown. Here, we found that patterned spontaneous activity in the dLGN is critical for the proper spatial and temporal innervation of CTAs. When the spontaneous dLGN activity is disrupted in vivo, CTA innervation is severely delayed until eye-opening. Indeed, visual input influenced the temporal development of CTAs by modulating thalamic activity, as embryonic enucleation enhanced thalamic calcium waves and accelerated the entrance of CTAs into the dLGN. Our results show that patterned spontaneou...
El tema de estudio en esta tesis es la migracion tangencial de las interneuronas corticales duran... more El tema de estudio en esta tesis es la migracion tangencial de las interneuronas corticales durante el desarrollo embrionario. Las interneuronas corticales se originan en el telencefalo ventral y migran tangencialmente hasta el telencefalo dorsal donde formaran la corteza cerebral junto con las neuronas piramidales o excitatorias. Los resultadospresentados en esta tesis aportan nuevos elementos sobre dos aspectos fundamentales de la migracion neuronal: la guia direccional y los mecanismos propulsores del movimiento. En el primer caso, nuestros datos indican que las interneuronas corticales delinean su trayectoria de migracion utilizando una estrategia celular basada en la generacion de un proceso guia bifurcado y la posterior seleccion de la rama mejor orientada con el gradiente quimiotactico. En segundo lugar, proporcionamos una explicacion dinamica sobre el mecanismo molecular responsable del movimiento del nucleo en las interneuronas corticales. El nucleo es impulsado hacia adela...
Neuron, 2021
Developing sensory circuits exhibit different patterns of spontaneous activity, patterns that are... more Developing sensory circuits exhibit different patterns of spontaneous activity, patterns that are related to the construction and refinement of functional networks. During the development of different sensory modalities, spontaneous activity originates in the immature peripheral sensory structures and in the higher-order central structures, such as the thalamus and cortex. Certainly, the perinatal thalamus exhibits spontaneous calcium waves, a pattern of activity that is fundamental for the formation of sensory maps and for circuit plasticity. Here we will review our current understanding of the maturation of early (including embryonic) patterns of spontaneous activity, and their influence on the assembly of thalamic and cortical sensory networks. Overall, the data currently available suggests similarities between the developmental trajectory of brain activity in experimental models and humans, which in the future may help to improve the early diagnosis of developmental disorders.
The thalamus is the largest structure of the diencephalon, the central region of the brain betwee... more The thalamus is the largest structure of the diencephalon, the central region of the brain between the midbrain and telencephalon. In the mature thalamus, neurons sharing similar structural and functional properties are spatially aggregated in cellular clusters called nuclei, unlike cortical areas where neurons are organized in horizontal layers. While neurons within nuclei share many properties, a varied collection of features arises when comparing neurons among nuclei, including different patterns of connectivity, molecular signatures, cell morphology, electrophysiological profile, and many other properties. Even more functional and cellular diversity is found if other diencephalic territories are taken in account. Remarkably, this congregation of heterogeneous cell types and connectivity patterns emerges from a rather homogeneous territory early in development. A progressive sequence of specification and differentiation programs patterns the initial diencephalon to craft dozens o...
Science
The mammalian brain’s somatosensory cortex is a topographic map of the body’s sensory experience.... more The mammalian brain’s somatosensory cortex is a topographic map of the body’s sensory experience. In mice, cortical barrels reflect whisker input. We asked whether these cortical structures require sensory input to develop or are driven by intrinsic activity. Thalamocortical columns, connecting the thalamus to the cortex, emerge before sensory input and concur with calcium waves in the embryonic thalamus. We show that the columnar organization of the thalamocortical somatotopic map exists in the mouse embryo before sensory input, thus linking spontaneous embryonic thalamic activity to somatosensory map formation. Without thalamic calcium waves, cortical circuits become hyperexcitable, columnar and barrel organization does not emerge, and the somatosensory map lacks anatomical and functional structure. Thus, a self-organized protomap in the embryonic thalamus drives the functional assembly of murine thalamocortical sensory circuits.
Neuroscience, 2017
The development of cortical maps requires the balanced interaction between genetically determined... more The development of cortical maps requires the balanced interaction between genetically determined programs and input/activity-dependent signals generated spontaneously or triggered from the environment. The somatosensory pathway of mice provides an excellent scenario to study cortical map development because of its highly organized cytoarchitecture, known as the barrel field. This precise organization makes evident even small alterations in the cortical map layout. In this review, we will specially focus on the thalamic factors that control barrel field development. We will summarize the role of thalamic input integration and identity, neurotransmission and spontaneous activity in cortical map formation and early cross-modal plasticity.
Cerebral Cortex, 2017
Interspersed distribution of selectivity to kinematic stimulus features in supragranular layers o... more Interspersed distribution of selectivity to kinematic stimulus features in supragranular layers of mouse barrel cortex. Cerebral Cortex, 27 (7). pp. 3782-2789.
Nature Neuroscience, 2015
Sensory perception depends on the context within which a stimulus occurs. Prevailing models empha... more Sensory perception depends on the context within which a stimulus occurs. Prevailing models emphasize cortical feedback as the source of contextual modulation. However, higher-order thalamic nuclei, such as the pulvinar, interconnect with many cortical and subcortical areas, suggesting a role for the thalamus in providing sensory and behavioral context-yet the nature of the signals conveyed to cortex by higher-order thalamus remains poorly understood. Here we use axonal calcium imaging to measure information provided to visual cortex by the pulvinar equivalent in mice, the lateral posterior nucleus (LP), as well as the dorsolateral geniculate nucleus (dLGN). We found that dLGN conveys retinotopically precise visual signals, while LP provides distributed information from the visual scene. Both LP and dLGN projections carry locomotion signals. However, while dLGN inputs often respond to positive combinations of running and visual flow speed, LP signals discrepancies between self-generated and external visual motion. This higher-order thalamic nucleus therefore conveys diverse contextual signals that inform visual cortex about visual scene changes not predicted by the animal's own actions. Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
Frontiers in neural circuits, 2016
Short-term synaptic plasticity (STP) sets the sensitivity of a synapse to incoming activity and d... more Short-term synaptic plasticity (STP) sets the sensitivity of a synapse to incoming activity and determines the temporal patterns that it best transmits. In "driver" thalamocortical (TC) synaptic populations, STP is dominated by depression during stimulation from rest. However, during ongoing stimulation, lemniscal TC connections onto layer 4 neurons in mouse barrel cortex express variable STP. Each synapse responds to input trains with a distinct pattern of depression or facilitation around its mean steady-state response. As a result, in common with other synaptic populations, lemniscal TC synapses express diverse rather than uniform dynamics, allowing for a rich representation of temporally varying stimuli. Here, we show that this STP diversity is regulated presynaptically. Presynaptic adenosine receptors of the A1R type, but not kainate receptors (KARs), modulate STP behavior. Blocking the receptors does not eliminate diversity, indicating that diversity is related to he...