• brain development
• interstitial white matter neurons
• neurodegenerative diseases
• neurons
• oligodendrocytes
• psychiatric diseases
• synaptic circuits
• white matter

• GluRs
• GlutTs
• NADPHd
• NK1
• aspartate
• glutamate
• nNOS
• vGLUTs

• NADPH-d
• subcortical
• subplate
• white matter neurons

• Animals
• Humans
• White Matter/metabolism
• Acetylcholinesterase/metabolism
• NADP/metabolism
• Calbindins/metabolism
• Neurons/metabolism
• Calbindin 2/metabolism
• NADPH Dehydrogenase/metabolism
• Alzheimer Disease/pathology
• S100 Calcium Binding Protein G/metabolism

• R01AG062566 NIA NIH HHS
• F31AG07631 NIA NIH HHS
• R01 AG007631 NIA NIH HHS
• U01 AG016976 NIA NIH HHS
• T32NS047987 NINDS NIH HHS
• P30AG072977 NIA NIH HHS
• T32 NS047987 NINDS NIH HHS
• P30 AG072977 NIA NIH HHS
• R01 AG062566 NIA NIH HHS
• F31 AG076318 NIA NIH HHS
• U24 AG072122 NIA NIH HHS

• BOLD effect
• Cerebral blood flow
• Corpus callosum
• Immunofluorescence
• Immunohistochemistry
• Neuro-vascular unit

The stria terminalis (ST) is a major bidirectional fiber tract anchored in the amygdala and bed nucleus (BNST). Extensive investigations in rodents report a complex arrangement of neurochemically diverse neurons within the ST, but fewer data are available for non-human primates. Given the functional importance of the ST, we investigated its microarchitecture in one newborn, four infant, and two adult macaque brains, by parallel immunocytochemical series for cells or fibers. Main results are as follows: (1) The pan-neuronal marker NeuN shows scattered neurons and small neuronal clusters in both the dorsal and ventral ST, but more numerous dorsally; (2) smaller neuronal subpopulations are labeled by calretinin (CR), neuropeptide Y (NPY), calbindin (CB), and somatostatin (SOM), of which the CR + neurons are the most numerous; (3) the infant brains on average have more neurons in the ST than the adult brains, but across our sample, there is notable individual variability; and (4) fiber architectonics have a complex organization, which can be referenced to myelin-poor or myelin-dense zones. Myelin-poor zones coincide with concentrations of fibers positive for CB, CR, or tyrosine hydroxylase (TH). Neurons have been reported in other white matter domains (e.g., anterior commissure, corpus callosum, cingulum bundle, and subcortical white matter). Like these, at least some neurons within the ST may give rise to long-distance connections, and/or participate in more local functions, such as vascular regulation or axon guidance/maintenance.

• R01 MH113257 NIMH NIH HHS
• National Institute of Mental Health

• Astrocytes
• Hypoxia
• Immunofluorescence
• Immunohistochemistry
• Neuronal nitric oxide synthase
• Post-mortem human brain

• MRI
• axon morphology
• brain
• conduction velocity
• myelination

• Animals
• Axons/physiology
• Female
• Haplorhini
• Imaging, Three-Dimensional
• Magnetic Resonance Imaging
• Myelin Sheath/metabolism
• Structure-Activity Relationship
• Vacuoles/metabolism
• White Matter/anatomy & histology

• GABAergic projection neurons
• RRID: AB_221544
• RRID: AB_2630395
• RRID: AB_477019
• interstitial neurons
• nonhuman primate
• striatum

• NADPH-d
• cell types
• extracellular matrix
• inhibition
• parvalbumin

• NeuN
• cerebral cortex
• interstial neurons
• nonhuman primate
• subplate

• R01 AG043640 NIA NIH HHS
• R21 MH107456 NIMH NIH HHS
• RF1 AG043640 NIA NIH HHS

• Anterograde
• Distributed
• Feedback
• Feedforward
• Inputs
• Interneurons
• Projections

• corpus callosum
• immunocytochemistry
• intracallosal neurons
• neurokinin
• tachykinin

In humans and non-human primates (NHP), white matter neurons (WMNs) persist beyond early development. Their functional importance is largely unknown, but they have both corticothalamic and corticocortical connectivity and at least one subpopulation has been implicated in vascular regulation and sleep. Several other studies have reported that the density of WMNs in humans is altered in neuropathological or psychiatric conditions. The present investigation evaluates and compares the density of superficial and deep WMNs in frontal (FR), temporal (TE), and parietal (Par) association regions of four young adult and four aged male rhesus monkeys. A major aim was to determine whether there was age-related neuronal loss, as might be expected given the substantial age-related changes known to occur in the surrounding white matter environment. Neurons were visualized by immunocytochemistry for Neu-N in coronal tissue sections (30 μm thickness), and neuronal density was assessed by systematic random sampling. Per 0.16 mm² sampling box, this yielded about 40 neurons in the superficial WM and 10 in the deep WM. Consistent with multiple studies of cell density in the cortical gray matter of normal brains, neither the superficial nor deep WM populations showed statistically significant age-related neuronal loss, although we observed a moderate decrease with age for the deep WMNs in the frontal region. Morphometric analyses, in contrast, showed significant age effects in soma size and circularity. In specific, superficial WMNs were larger in FR and Par WM regions of the young monkeys; but in the TE, these were larger in the older monkeys. An age effect was also observed for soma circularity: superficial WMNs were more circular in FR and Par of the older monkeys. This second, morphometric result raises the question of whether other age-related morphological, connectivity, or molecular changes occur in the WMNs. These could have multiple impacts, given the wide range of putative WMN functions and their involvement in both corticothalamic and corticocortical circuitry.

• Neu-N
• aging
• interstitial
• morphometrics
• non-human primate

This short review examines the most recent functional studies of the topographic organization of the human corpus callosum, the main interhemispheric commissure. After a brief description of its anatomy, development, microstructure, and function, it examines and discusses the latest findings obtained using diffusion tensor imaging (DTI) and tractography (DTT) and functional magnetic resonance imaging (fMRI), three recently developed imaging techniques that have significantly expanded and refined our knowledge of the commissure. While DTI and DTT have been providing insights into its microstructure, integrity and level of myelination, fMRI has been the key technique in documenting the activation of white matter fibers, particularly in the corpus callosum. By combining DTT and fMRI it has been possible to describe the trajectory of the callosal fibers interconnecting the primary olfactory, gustatory, motor, somatic sensory, auditory and visual cortices at sites where the activation elicited by peripheral stimulation was detected by fMRI. These studies have demonstrated the presence of callosal fiber tracts that cross the commissure at the level of the genu, body, and splenium, at sites showing fMRI activation. Altogether such findings lend further support to the notion that the corpus callosum displays a functional topographic organization that can be explored with fMRI.

• Corpus callosum
• Interhemispheric transfer
• Functional magnetic resonance imaging and diffusion tensor imaging
• Brain imaging
• Topographic organization

• NK1
• colocalization
• corpus callosum
• immunocytochemistry
• immunofluorescence
• nitric oxide

In the central nervous system, nitric oxide (NO) transmits signals from one neurone to another, or from neurones to astrocytes or blood vessels, but the possibility of oligodendrocytes being physiological NO targets has been largely ignored. By exploiting immunocytochemistry for cGMP, the second messenger generated on activation of NO receptors, oligodendrocytes were found to respond to both exogenous and endogenous NO in cerebellar slices from rats aged 8 days to adulthood. Atrial natriuretic peptide, which acts on membrane-associated guanylyl cyclase-coupled receptors, also raised oligodendrocyte cGMP in cerebellar slices. The main endogenous source of NO accessing oligodendrocytes appeared to be the neuronal NO synthase isoform, which was active even under basal conditions and in a manner that was independent of glutamate receptors. Oligodendrocytes in brainstem slices were also shown to be potential NO targets. In contrast, in the optic nerve, oligodendrocyte cGMP was raised by natriuretic peptides but not NO. When cultures of cerebral cortex were continuously exposed to low NO concentrations (estimated as 40–90 pM), oligodendrocytes responded with a striking increase in arborization. This stimulation of oligodendrocyte growth could be replicated by low concentrations of 8-bromo-cGMP (maximum effect at 1 µM). It is concluded that oligodendrocytes are probably widespread targets for physiological NO (or natriuretic peptide) signals, with the resulting rise in cGMP serving to enhance their growth and maturation. NO might help coordinate the myelination of axons to the ongoing level of neuronal activity during development and could potentially contribute to adaptive changes in myelination in the adult.

• brainstem
• cGMP
• cerebellum
• myelination
• natriuretic peptide
• optic nerve

• Colocalization
• GFAP
• NADPH-d
• immunocytochemistry
• nNOS
• nitric oxide

• atypical cells
• barrel cortex
• fuzzy sets
• interneuron diversity
• neuronal diversity
• petilla terminology
• unsupervised clustering

• birthdating
• development
• interneurons
• mouse
• nNOS

Following the discovery of the vasorelaxant properties of nitric oxide (NO) by Furchgott and Ignarro, the finding by Bredt and coll. of a constitutively expressed NO synthase in neurons (nNOS) led to the presumption that neuronal NO may control cerebrovascular functions. Consequently, numerous studies have sought to determine whether neuraly-derived NO is involved in the regulation of cerebral blood flow (CBF). Anatomically, axons, dendrites, or somata of NO neurons have been found to contact the basement membrane of blood vessels or perivascular astrocytes in all segments of the cortical microcirculation. Functionally, various experimental approaches support a role of neuronal NO in the maintenance of resting CBF as well as in the vascular response to neuronal activity. Since decades, it has been assumed that neuronal NO simply diffuses to the local blood vessels and produce vasodilation through a cGMP-PKG dependent mechanism. However, NO is not the sole mediator of vasodilation in the cerebral microcirculation and is known to interact with a myriad of signaling pathways also involved in vascular control. In addition, cerebrovascular regulation is the result of a complex orchestration between all components of the neurovascular unit (i.e., neuronal, glial, and vascular cells) also known to produce NO. In this review article, the role of NO interneuron in the regulation of cortical microcirculation will be discussed in the context of the neurovascular unit.

• GABA
• astrocyte
• autoregulation
• cerebral blood flow
• interneuron
• magnetic resonance imaging
• neurovascular coupling
• nitric oxide