Frontiers in Neuroanatomy

Neuroanatomical organization: the palato-pharyngeal complex as a sensory-motor hub

2026-03-30

Yong-Shin Hong, Young-Seok Park

The pharynx has traditionally been described as a musculo-membranous conduit involved in respiration and deglutition. From a neuroanatomical perspective, however, this region also represents a multi-nerve interface where somatic afferents of the trigeminal nerve (V) and visceral afferents of the glossopharyngeal (IX) and vagus (X) nerves converge. In this review, we use the term Palato-Pharyngeal Complex (PPC) to describe this anatomically integrated region and discuss its potential role as a sensory–motor interface associated with brainstem circuits involving the nucleus tractus solitarius (NTS) and nucleus ambiguus (NA). We highlight the coordinated activity of the tensor veli palatini (innervated by V3) and the levator veli palatini (innervated by X) as an example of somatic–visceral motor integration within this region. Building on existing models of brainstem central pattern generators, we discuss a hierarchical control framework in which brainstem circuits may be modulated by supranuclear influences from cortical and limbic systems. Within this context, we introduce the concept of a Reflex–Volition Coupling (RVC) zone as a possible functional interface between reflexive brainstem rhythms and volitional or affective control. By integrating comparative and connectomic perspectives, this review outlines how branchial motor circuitry may support a range of behaviors including airway protection, vocalization, and speech. Together, these observations suggest that the PPC may represent an anatomically strategic interface linking peripheral cranial nerve afferents with brainstem integrative networks involved in arousal and behavioral coordination. This framework provides a basis for future studies exploring how oropharyngeal sensory pathways interact with central neural circuits.

A semi-automated pipeline integrating ImageJ/Fiji and StarDist for the reproducible quantification of cellular and optical density metrics in immunofluorescence images of brain tissue

2026-03-27

Sandra Isabel Marques, Helena Carmo, Félix Carvalho, João Pedro Silva, Susana Isabel Sá

Quantitative immunofluorescence is widely used to assess molecular expression and cellular distribution across biological tissues, yet the analysis of large image datasets remains time-consuming and prone to user-dependent variability. To address these limitations, we herein developed a semi-automated workflow that integrates ImageJ/Fiji for image processing, StarDist for nuclear segmentation, and spreadsheet- or Python-based routines for data curation. The pipeline standardizes critical analytical steps, including scale calibration, region-of-interest (ROI) definition, channel selection, and z-stack handling, while preserving essential metadata through a structured file-naming system. Optical density and cell-number metrics are exported automatically in a consistent format, enabling efficient consolidation into a unified dataset. Subsequent curation can be performed either manually in a spreadsheet software or fully automatically through custom Python scripts, allowing extraction of sample identifiers, regions, and markers, as well as calculation of normalized intensity values. Comparison with existing protocols proved that this workflow adheres to widely accepted quantification principles while markedly improving reproducibility, consistency, and analytical throughput. This method offers a straightforward, transparent, and scalable solution for fluorescence-based quantification suitable for laboratories with varying levels of computational expertise.

Correction: Unveiling the mechanisms of neuropathic pain suppression: perineural resiniferatoxin targets Trpv1 and beyond

2026-03-27

Safa Shehab, Hayate Javed, Aishwarya Mary Johnson, Saeed Tariq, Challagandla Anil Kumar, Bright Starling Emerald

Postnatal expression of the transcription factor Ebf2 in motivation, reward, and pain-related circuits of the mouse brain

2026-03-04

Moisés Martínez-Estrada, M. Blanca D. Cepeda-Varela, A. Damaris Salinas-Villarreal, Mara C. Obregón-Fuentes, Danna A. Real-Marín, Melani A. Balderas-Díaz, Viviana Zomosa-Signoret, Jesús Santana-Solano, Moisés Santillán-Zerón, Román Vidaltamayo

IntroductionEarly B-cell factor 2 (Ebf2) is a transcription factor required for neuronal differentiation. However, its postnatal expression pattern and functional roles in the brain are not well characterized. This study examined the spatial distribution of Ebf2 in postnatal day 10 (P10) mouse brains and investigated its association with neural circuits mediating motivation, reward, and nociception.Materials and methodsEbf2-TGFP transgenic mice, which express green fluorescent protein (GFP) as a reporter for Ebf2, were utilized. Immunofluorescence labeling and high-resolution microscopy were employed to visualize Ebf2 expression. Image data were analyzed using a deep learning–based segmentation pipeline for soma and axon identification. Three-dimensional reconstructions were registered to the Allen Brain Atlas. Quantitative comparisons between hemizygous and Ebf2-null mutant genotypes were conducted using linear mixed-effects models with Bonferroni and false discovery rate (FDR) corrections.ResultsEbf2 expression was prominent in the dorsal diencephalic conduction system, including the septum, habenula, and interpeduncular nucleus. Ebf2 expression can also be detected in the lateral hypothalamic area, zona incerta, ventral tegmental area, and parabrachial nucleus. Expression was also detected in nociceptive and sensory-motor regions such as the periaqueductal gray, anterior pretectal nucleus, principal sensory nucleus of the trigeminal nerve, and superior colliculus. Ebf2-null mutant mice showed a significant reduction in Ebf2-TGFP cells across most of these regions.DiscussionThe results demonstrate that Ebf2 expression persists beyond embryonic development and is selectively enriched in neural circuits associated with motivation, reward processing, and nociceptive modulation. The marked reduction of Ebf2-TGFP expressing neurons in null mutants provides evidence for a postnatal requirement of Ebf2 in neuronal maintenance, rather than solely in early differentiation. Collectively, these findings broaden the functional scope of Ebf2 to include postnatal circuit stabilization and support its sustained regulatory role in brain systems that govern affective and pain-related behaviors.

Differential morphology and distribution of GFAP astrocytes in vocal brain circuit in a songbird Southern house wren and humans

2026-02-06

Santiago Hinestroza-Morales, Carolina López-Murillo, Hernán Hoyos-Maya, Geysson J. Fernandez, Andrés Villegas-Lanau, Hector Fabio Rivera-Gutierrez, Rafael Posada-Duque

Speech and song exhibit notable parallels between humans and birds. In humans, speech involves the Laryngeal Motor Cortex (LMC), Sensorimotor cortex (SMC), Broca’s and Wernicke’s areas, and the basal ganglia (striatum), which show convergent gene expression with avian song-control regions (RA, LMAN, HVC) and basal ganglia (Area X and medial striatum). While astrocyte morphology has been implicated in human speech, its role in song remains unknown. To compare astrocytes involved in speech and song, we evaluated cell density, astrocyte types, and their distribution in healthy humans and Southern house wrens using Nissl staining, GFAP and GS immunostaining, and 3D confocal imaging. The basal ganglia, human striatum and avian medial striatum, showed the highest cell density in both species. Human astrocyte distribution followed established cortical patterns, with enrichment in layers I–III and white matter (WM). In contrast, Southern house wrens exhibited restricted GFAP-positive astrocytes in vocal nuclei, with expression instead concentrated in telencephalic borders, vascular regions, and basal ganglia WM. Astrocyte morphology varied regionally in both species; basal ganglia astrocytes were especially complex, yet Southern house wrens exhibited reduced branching even after normalizing for brain volume/body weight ratio, indicating species-specific differences in complexity. GS-positive astrocytes were abundant and homogeneous throughout the pallium, including all vocal nuclei, unlike the more restricted GFAP-positive subset. Cross-species analysis of public songbird datasets confirmed minimal GFAP and strong GLUL (GS gene) expression in telencephalic astrocytes, opposite to humans, who show robust expression of both markers. Overall, GS astrocytes displayed a broadly uniform organization in both species, whereas GFAP astrocytes exhibited more restricted and enriched distributions, particularly in human speech-related basal ganglia, revealing species-specific differences in astrocyte architecture within vocal circuits.

Functional neuroanatomy of dopaminergic arousal systems: implications for the wake-promoting effect of psychostimulants, with particular reference to modafinil

2025-12-09

Elemer Szabadi

Arousal involves activation of the cerebral cortex by inputs from subcortical (hypothalamic, brainstem) wake-promoting nuclei, utilizing monoamine (noradrenaline, dopamine, serotonin, histamine) and neuropeptide (orexin) neurotransmitters. Dopaminergic neurones of the midbrain, originating from distinct nuclei [pars compacta of substantia nigra (SNc), ventral tegmental area (VTA), and other clusters of dopaminergic neurones in the ventral periaqueductal gray (vPAG)] and the pontine dorsal raphe nucleus (DRN), constitute a powerful wake-promoting system. Cortical activation by dopaminergic neurones can be due to either direct projections from the VTA and vPAG/DRN, to the cerebral cortex, or indirect projections from the VTA via the nucleus accumbens (NAc)/ventral pallidum (VP) and from the SNc via the thalamus. Stimulation of the VP, by inputs from the VTA via the NAc, can activate wake-promoting noradrenergic and orexinergic neurones, and stimulation of the thalamus, by inputs from the SNc, can activate wake-promoting glutamatergic thalamocortical neurones. There is also a two-way mutually reinforcing connection between the VTA/NAc/VP and SNc/thalamus systems, indicating the key role of the NAc in dopaminergic arousal regulation. Dopaminergic psychostimulants (e.g., amphetamine, cocaine) are highly addictive drugs of abuse, that activate both reinforcement mechanisms and promote wakefulness, by enhancing dopaminergic neurotransmission. The addictive potential of psychostimulants is related to the stimulation of reinforcement processes. Modafinil, an atypical psychostimulant, enhances wakefulness without affecting reinforcement, and thus is devoid of addictive potential. Unraveling the mode of action of modafinil may give insight into the neural mechanisms controlling reinforcement and arousal. Recent evidence indicates that the powerful arousal-enhancing effect of psychostimulants may mainly be due to indirect cortical activation via the NAc and thalamus.