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Andrade López JM, Pani AM, Wu M, Gerhart J, Lowe CJ. Molecular characterization of nervous system organization in the hemichordate acorn worm Saccoglossus kowalevskii. PLoS Biol 2023; 21:e3002242. [PMID: 37725784 PMCID: PMC10508912 DOI: 10.1371/journal.pbio.3002242] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2023] [Accepted: 07/11/2023] [Indexed: 09/21/2023] Open
Abstract
Hemichordates are an important group for investigating the evolution of bilaterian nervous systems. As the closest chordate outgroup with a bilaterally symmetric adult body plan, hemichordates are particularly informative for exploring the origins of chordates. Despite the importance of hemichordate neuroanatomy for testing hypotheses on deuterostome and chordate evolution, adult hemichordate nervous systems have not been comprehensively described using molecular techniques, and classic histological descriptions disagree on basic aspects of nervous system organization. A molecular description of hemichordate nervous system organization is important for both anatomical comparisons across phyla and for attempts to understand how conserved gene regulatory programs for ectodermal patterning relate to morphological evolution in deep time. Here, we describe the basic organization of the adult hemichordate Saccoglossus kowalevskii nervous system using immunofluorescence, in situ hybridization, and transgenic reporters to visualize neurons, neuropil, and key neuronal cell types. Consistent with previous descriptions, we found the S. kowalevskii nervous system consists of a pervasive nerve plexus concentrated in the anterior, along with nerve cords on both the dorsal and ventral side. Neuronal cell types exhibited clear anteroposterior and dorsoventral regionalization in multiple areas of the body. We observed spatially demarcated expression patterns for many genes involved in synthesis or transport of neurotransmitters and neuropeptides but did not observe clear distinctions between putatively centralized and decentralized portions of the nervous system. The plexus shows regionalized structure and is consistent with the proboscis base as a major site for information processing rather than the dorsal nerve cord. In the trunk, there is a clear division of cell types between the dorsal and ventral cords, suggesting differences in function. The absence of neural processes crossing the basement membrane into muscle and extensive axonal varicosities suggest that volume transmission may play an important role in neural function. These data now facilitate more informed neural comparisons between hemichordates and other groups, contributing to broader debates on the origins and evolution of bilaterian nervous systems.
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Affiliation(s)
- José M. Andrade López
- Department of Biology, Stanford University, Stanford, California, United States of America
| | - Ariel M. Pani
- Departments of Biology and Cell Biology, University of Virginia, Charlottesville, Virginia, Unites States of America
| | - Mike Wu
- Department of Molecular and Cell Biology, University of California, Berkeley, California, Unites States of America
| | - John Gerhart
- Department of Molecular and Cell Biology, University of California, Berkeley, California, Unites States of America
| | - Christopher J. Lowe
- Department of Biology, Stanford University, Stanford, California, United States of America
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Moroz LL. Multiple Origins of Neurons From Secretory Cells. Front Cell Dev Biol 2021; 9:669087. [PMID: 34307354 PMCID: PMC8293673 DOI: 10.3389/fcell.2021.669087] [Citation(s) in RCA: 30] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2021] [Accepted: 05/26/2021] [Indexed: 12/12/2022] Open
Affiliation(s)
- Leonid L. Moroz
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL, United States
- Whitney Laboratory for Marine Biosciences, University of Florida, St. Augustine, FL, United States
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Moroz LL, Romanova DY, Kohn AB. Neural versus alternative integrative systems: molecular insights into origins of neurotransmitters. Philos Trans R Soc Lond B Biol Sci 2021; 376:20190762. [PMID: 33550949 PMCID: PMC7935107 DOI: 10.1098/rstb.2019.0762] [Citation(s) in RCA: 46] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 11/23/2020] [Indexed: 12/18/2022] Open
Abstract
Transmitter signalling is the universal chemical language of any nervous system, but little is known about its early evolution. Here, we summarize data about the distribution and functions of neurotransmitter systems in basal metazoans as well as outline hypotheses of their origins. We explore the scenario that neurons arose from genetically different populations of secretory cells capable of volume chemical transmission and integration of behaviours without canonical synapses. The closest representation of this primordial organization is currently found in Placozoa, disk-like animals with the simplest known cell composition but complex behaviours. We propose that injury-related signalling was the evolutionary predecessor for integrative functions of early transmitters such as nitric oxide, ATP, protons, glutamate and small peptides. By contrast, acetylcholine, dopamine, noradrenaline, octopamine, serotonin and histamine were recruited as canonical neurotransmitters relatively later in animal evolution, only in bilaterians. Ligand-gated ion channels often preceded the establishment of novel neurotransmitter systems. Moreover, lineage-specific diversification of neurotransmitter receptors occurred in parallel within Cnidaria and several bilaterian lineages, including acoels. In summary, ancestral diversification of secretory signal molecules provides unique chemical microenvironments for behaviour-driven innovations that pave the way to complex brain functions and elementary cognition. This article is part of the theme issue 'Basal cognition: multicellularity, neurons and the cognitive lens'.
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Affiliation(s)
- Leonid L. Moroz
- Department of Neuroscience, McKnight Brain Institute and Whitney laboratory, University of Florida, 9505 Ocean shore Blvd, St Augustine, FL 32080, USA
| | - Daria Y. Romanova
- Laboratory of Cellular Neurobiology of Learning, Institute of Higher Nervous Activity and Neurophysiology of RAS, 5A Butlerova Street, Moscow 117485, Russia
| | - Andrea B. Kohn
- Department of Neuroscience, McKnight Brain Institute and Whitney laboratory, University of Florida, 9505 Ocean shore Blvd, St Augustine, FL 32080, USA
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Carvalho GB, Damasio A. Interoception and the origin of feelings: A new synthesis. Bioessays 2021; 43:e2000261. [PMID: 33763881 DOI: 10.1002/bies.202000261] [Citation(s) in RCA: 39] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 02/26/2021] [Accepted: 03/02/2021] [Indexed: 02/06/2023]
Abstract
Feelings are conscious mental events that represent body states as they undergo homeostatic regulation. Feelings depend on the interoceptive nervous system (INS), a collection of peripheral and central pathways, nuclei and cortical regions which continuously sense chemical and anatomical changes in the organism. How such humoral and neural signals come to generate conscious mental states has been a major scientific question. The answer proposed here invokes (1) several distinctive and poorly known physiological features of the INS; and (2) a unique interaction between the body (the 'object' of interoception) and the central nervous system (which generates the 'subject' of interoception). The atypical traits of the INS and the direct interactions between neural and non-neural physiological compartments of the organism, neither of which is present in exteroceptive systems, plausibly explain the qualitative and subjective aspects of feelings, thus accounting for their conscious nature.
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Affiliation(s)
- Gil B Carvalho
- Brain and Creativity Institute, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California, USA
| | - Antonio Damasio
- Brain and Creativity Institute, Dornsife College of Letters, Arts, and Sciences, University of Southern California, Los Angeles, California, USA
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Braak H, Del Tredici K. Top-Down Projections Direct the Gradual Progression of Alzheimer-Related Tau Pathology Throughout the Neocortex. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1184:291-303. [PMID: 32096045 DOI: 10.1007/978-981-32-9358-8_22] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
In sporadic Alzheimer's disease (sAD), tau pathology gradually but relentlessly progresses from the transentorhinal region of the temporal lobe into both the allocortex and temporal high order association areas of the neocortex. From there, it ultimately reaches the primary sensory and motor fields of the neocortex. The brunt of the changes seen during neurofibrillary stages (NFT) I-VI is borne by top-down projection neurons that contribute to cortico-cortical connectivities between different neocortical fields. Very early changes develop in isolated pyramidal cells in layers III and V, and these cells are targets of top-down projections terminating in association areas of the first temporal gyrus or in peristriate regions of the occipital lobe. Neurofibrillary pathology in these regions is routinely associated with late NFT stages. Sequential changes occur in different cell compartments (dendritic, somatic, axonal) of these early-involved neurons. Tau pathology first develops in distal segments of basal dendrites, then in proximal dendrites, the soma, and, finally, in the axon of affected pyramidal neurons. This sequence of abnormal changes supports the concept that axons of cortico-cortical top-down neurons may carry and spread abnormal tau seeds in a focused manner (transsynaptically) into the distal dendritic segments of nerve cells directly following in the neuronal chain, thereby sustaining tau-seeded templating in sAD.
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Affiliation(s)
- Heiko Braak
- Clinical Neuroanatomy Section/Department of Neurology, Center for Biomedical Research, University of Ulm, Ulm, Germany
| | - Kelly Del Tredici
- Clinical Neuroanatomy Section/Department of Neurology, Center for Biomedical Research, University of Ulm, Ulm, Germany.
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Braak H, Del Tredici K. Spreading of Tau Pathology in Sporadic Alzheimer's Disease Along Cortico-cortical Top-Down Connections. Cereb Cortex 2018; 28:3372-3384. [PMID: 29982389 PMCID: PMC6095209 DOI: 10.1093/cercor/bhy152] [Citation(s) in RCA: 96] [Impact Index Per Article: 16.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2018] [Revised: 05/11/2018] [Accepted: 06/06/2018] [Indexed: 02/02/2023] Open
Abstract
By using AT8-immunocytochemistry that visualizes hyperphosphorylated tau protein, we examined neurofibrillary changes related to sporadic Alzheimer's disease (AD) in N = 40 individuals at neurofibrillary tangle (NFT) stages I-IV. We report the presence of abnormal tau changes within solitary pyramidal neurons in layers III and V of the neocortex. These pyramidal cells showed pathology in different cell compartments (dendritic, somatic, axonal) that appeared to occur sequentially: Tau pathology was seen in distal segments of the basal dendrites, then in proximal dendrites, the soma, and, finally, in the axon of affected neurons. These findings are remarkable in that they point to the existence of neurofibrillary changes in regions routinely associated with later NFT stages. In addition, they lend support to the idea that it may be the axons of cortico-cortical top-down neurons in neocortical fields involved in AD that carry and spread abnormal tau seeds in a focused manner (transsynaptically) into the distal dendritic segments of nerve cells following directly in the neuronal chain, thereby sustaining further tau-seeded templating.
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Affiliation(s)
- Heiko Braak
- Clinical Neuroanatomy Section/Department of Neurology, Center for Biomedical Research, University of Ulm, Helmholtzstrasse 8/1, Ulm, Germany
| | - Kelly Del Tredici
- Clinical Neuroanatomy Section/Department of Neurology, Center for Biomedical Research, University of Ulm, Helmholtzstrasse 8/1, Ulm, Germany
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Braak H, Del Tredici K. The preclinical phase of the pathological process underlying sporadic Alzheimer’s disease. Brain 2015; 138:2814-33. [DOI: 10.1093/brain/awv236] [Citation(s) in RCA: 293] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2015] [Accepted: 07/21/2015] [Indexed: 12/13/2022] Open
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Spreading of pathology in neurodegenerative diseases: a focus on human studies. Nat Rev Neurosci 2015; 16:109-20. [PMID: 25588378 DOI: 10.1038/nrn3887] [Citation(s) in RCA: 547] [Impact Index Per Article: 60.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The progression of many neurodegenerative diseases is thought to be driven by the template-directed misfolding, seeded aggregation and cell-cell transmission of characteristic disease-related proteins, leading to the sequential dissemination of pathological protein aggregates. Recent evidence strongly suggests that the anatomical connections made by neurons - in addition to the intrinsic characteristics of neurons, such as morphology and gene expression profile - determine whether they are vulnerable to degeneration in these disorders. Notably, this common pathogenic principle opens up opportunities for pursuing novel targets for therapeutic interventions for these neurodegenerative disorders. We review recent evidence that supports the notion of neuron-neuron protein propagation, with a focus on neuropathological and positron emission tomography imaging studies in humans.
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Lacalli T. The Middle Cambrian fossil Pikaia and the evolution of chordate swimming. EvoDevo 2012; 3:12. [PMID: 22695332 PMCID: PMC3390900 DOI: 10.1186/2041-9139-3-12] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 06/13/2012] [Indexed: 12/02/2022] Open
Abstract
Conway Morris and Caron (2012) have recently published an account of virtually all the available information on Pikaia gracilens, a well-known Cambrian fossil and supposed basal chordate, and propose on this basis some new ideas about Pikaia’s anatomy and evolutionary significance. Chief among its chordate-like features are the putative myomeres, a regular series of vertical bands that extends the length of the body. These differ from the myomeres of living chordates in that boundaries between them (the myosepta) are gently curved, with minimal overlap, whereas amphioxus and vertebrates have strongly overlapping V- and W-shaped myomeres. The implication, on biomechanical grounds, is that myomeres in Pikaia exerted much less tension on the myosepta, so the animal would have been incapable of swimming as rapidly as living chordates operating in the fast-twitch mode used for escape and attack. Pikaia either lacked the fast-twitch fibers necessary for such speeds, having instead only slow-twitch fibers, or it had an ancestral fiber type with functional capabilities more like modern slow fibers than fast ones. The first option is supported by the sequence of development in zebrafish, where both myoseptum formation and fast fiber deployment show a dependence on slow fibers, which develop first. For Pikaia, the absence of fast fibers has both behavioral and anatomical implications, which are discussed. Among the latter is the possibility that a notochord may not have been needed as a primary stiffening device if other structures (for example, the dorsal organ) could perform that role.
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Affiliation(s)
- Thurston Lacalli
- Biology Department, University of Victoria, Cunningham Building, Victoria, BC, V8W-3N5, Canada.
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Feng CY, Wiggins LM, von Bartheld CS. The locus ceruleus responds to signaling molecules obtained from the CSF by transfer through tanycytes. J Neurosci 2011; 31:9147-58. [PMID: 21697366 PMCID: PMC4050199 DOI: 10.1523/jneurosci.5018-10.2011] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2010] [Revised: 05/02/2011] [Accepted: 05/04/2011] [Indexed: 12/15/2022] Open
Abstract
Neurons can access signaling molecules through two principal pathways: synaptic transmission ("wiring transmission") and nonsynaptic transmission ("volume transmission"). Wiring transmission is usually considered the far more important mode of neuronal signaling. Using embryonic chick locus ceruleus (LoC) as a model, we quantified and compared routes of delivery of the neurotrophin nerve growth factor (NGF), either through a multisynaptic axonal pathway or via the CSF. We now show that the axonal pathway from the eye to the LoC involves axo-axonic transfer of NGF with receptor switching (p75 to trkA) in the optic tectum. In addition to the axonal pathway, the LoC of chick embryos has privileged access to the CSF through a specialized glial/ependymal cell type, the tanycyte. The avian LoC internalizes from the CSF in a highly specific fashion both NGF and the hormone urotensin (corticotropin-releasing factor family ligand). Quantitative autoradiography at the ultrastructural level shows that tanycytes transcytose and deliver NGF to LoC neurons via synaptoid contacts. The LoC-associated tanycytes express both p75 and trkA receptors. The NGF extracted by tanycytes from the CSF has physiological effects on LoC neurons, as evidenced by significantly altered nuclear diameters in both gain-of-function and loss-of-function experiments. Quantification of NGF extraction shows that, compared with multisynaptic axonal routes of NGF trafficking to LoC, the tanycyte route is significantly more effective. We conclude that some clinically important neuronal populations such as the LoC can use a highly efficient "back door" interface to the CSF and can receive signals via this tanycyte-controlled pathway.
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Affiliation(s)
- Cheng-Yuan Feng
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557
| | - Larisa M. Wiggins
- Department of Physiology and Cell Biology, University of Nevada School of Medicine, Reno, Nevada 89557
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11
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Veening JG, de Jong T, Barendregt HP. Oxytocin-messages via the cerebrospinal fluid: behavioral effects; a review. Physiol Behav 2010; 101:193-210. [PMID: 20493198 DOI: 10.1016/j.physbeh.2010.05.004] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Revised: 04/21/2010] [Accepted: 05/04/2010] [Indexed: 12/16/2022]
Abstract
The cerebrospinal fluid (CSF) usually is considered as a protective 'nutrient and waste control' system for the brain. Recent findings suggest, however, that the composition of CSF is actively controlled and may play an influential role in the changes in brain activity, underlying different behavioral states. In the present review, we present an overview of available data concerning the release of oxytocin into the CSF, the location of the oxytocin-receptive brain areas and the behavioral effects of intracerebroventricular oxytocin. About 80% of the oxytocin-receptive areas are located close to the ventricular or subarachnoid CSF, including the hypothalamic 'Behavior Control Column' (L.W.Swanson, 2003). As a conclusion we suggest that 'CSF-oxytocin' contributes considerably to the non-synaptic communication processes involved in hypothalamic-, brainstem- and olfactory brain areas and behavioral states and that the flowing CSF is used as a 'broadcasting system' to send coordinated messages to a wide variety of nearby and distant brain areas.
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Affiliation(s)
- Jan G Veening
- Department of Anatomy (109), UMC St Radboud, Nijmegen, The Netherlands.
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12
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Understanding wiring and volume transmission. ACTA ACUST UNITED AC 2010; 64:137-59. [PMID: 20347870 DOI: 10.1016/j.brainresrev.2010.03.003] [Citation(s) in RCA: 189] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2009] [Revised: 03/17/2010] [Accepted: 03/17/2010] [Indexed: 11/23/2022]
Abstract
The proposal on the existence of two main modes of intercellular communication in the central nervous system (CNS) was introduced in 1986 and called wiring transmission (WT) and volume transmission (VT). The major criterion for this classification was the different characteristics of the communication channel with physical boundaries well delimited in the case of WT (axons and their synapses; gap junctions) but not in the case of VT (the extracellular fluid filled tortuous channels of the extracellular space and the cerebrospinal fluid filled ventricular space and sub-arachnoidal space). The basic dichotomic classification of intercellular communication in the brain is still considered valid, but recent evidence on the existence of unsuspected specialized structures for intercellular communication, such as microvesicles (exosomes and shedding vesicles) and tunnelling nanotubes, calls for a refinement of the original classification model. The proposed updating is based on criteria which are deduced not only from these new findings but also from concepts offered by informatics to classify the communication networks in the CNS. These criteria allowed the identification also of new sub-classes of WT and VT, namely the "tunnelling nanotube type of WT" and the "Roamer type of VT." In this novel type of VT microvesicles are safe vesicular carriers for targeted intercellular communication of proteins, mtDNA and RNA in the CNS flowing in the extracellular fluid along energy gradients to reach target cells. In the tunnelling nanotubes proteins, mtDNA and RNA can migrate as well as entire organelles such as mitochondria. Although the existence and the role of these new types of intercellular communication in the CNS are still a matter of investigation and remain to be fully demonstrated, the potential importance of these novel types of WT and VT for brain function in health and disease is discussed.
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Veening JG, Barendregt HP. The regulation of brain states by neuroactive substances distributed via the cerebrospinal fluid; a review. Cerebrospinal Fluid Res 2010; 7:1. [PMID: 20157443 PMCID: PMC2821375 DOI: 10.1186/1743-8454-7-1] [Citation(s) in RCA: 101] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2009] [Accepted: 01/06/2010] [Indexed: 01/04/2023] Open
Abstract
The cerebrospinal fluid (CSF) system provides nutrients to and removes waste products from the brain. Recent findings suggest, however, that in addition, the CSF contains message molecules in the form of actively released neuroactive substances. The concentrations of these vary between locations, suggesting they are important for the changes in brain activity that underlie different brain states, and induce different sensory input and behavioral output relationships.The cranial CSF displays a rapid caudally-directed ventricular flow followed by a slower rostrally-directed subarachnoid flow (mainly towards the cribriform plate and from there into the nasal lymphatics). Thus, many brain areas are exposed to and can be influenced by substances contained in the CSF. In this review we discuss the production and flow of the CSF, including the mechanisms involved in the regulation of its composition. In addition, the available evidence for the release of neuropeptides and other neuroactive substances into the CSF is reviewed, with particular attention to the selective effects of these on distant downstream receptive brain areas. As a conclusion we suggest that (1) the flowing CSF is involved in more than just nutrient and waste control, but is also used as a broadcasting system consisting of coordinated messages to a variety of nearby and distant brain areas; (2) this special form of volume transmission underlies changes in behavioral states.
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Affiliation(s)
- Jan G Veening
- Department of Anatomy, (109) UMC St Radboud, Nijmegen, the Netherlands.
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Bach-Y-Rita P. EMERGING CONCEPTS OF BRAIN FUNCTION. J Integr Neurosci 2005; 4:183-205. [PMID: 15988797 DOI: 10.1142/s0219635205000768] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2004] [Accepted: 12/24/2004] [Indexed: 11/18/2022] Open
Abstract
For over 40 years, since I first obtained evidence for nonsynaptic diffusion neurotransmission (most scientists call it Volume Transmission), I have been convinced that we scientists were ignoring organizational dynamics other than the mechanistic synaptic organization of the brain. For many years it was an uneasy feeling, since I was aware there are so many avenues to explore in brain function. I have wondered how much we scientists have ignored, in our quest to understand how the brain really works, due to our efforts to "be scientific". In addition to the difficulty of understanding how the brain functions, how could we even begin to explore the human experience? In this paper I will first discuss some emerging concepts of brain function. I will then comment on the development of concepts that have been a part of my own research experience.
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Affiliation(s)
- Paul Bach-Y-Rita
- Departments of Orthopedics and Rehabilitation Medicine and of Biomedical Engineering, 1300 University Avenue, Room 2756, University of Wisconsin, Madison, WI, USA.
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Bach-y-Rita P. Late postacute neurologic rehabilitation: neuroscience, engineering, and clinical programs. Arch Phys Med Rehabil 2003; 84:1100-8. [PMID: 12917846 DOI: 10.1016/s0003-9993(03)00312-5] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
This lecture highlights my career in rehabilitation research. My principal efforts in rehabilitation have been to study (1) mechanisms of brain plasticity related to reorganization of the brain and recovery of function; (2) late postacute rehabilitation; (3) sensory substitution; and (4) rehabilitation engineering. A principal goal has been to aid in the development of a strong scientific base in rehabilitation.
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Affiliation(s)
- Paul Bach-y-Rita
- Department of Orthopedics and Rehabilitation Medicine, University of Wisconsin, Madison, WI, USA
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16
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Lacalli TC, Kelly SJ. Ventral neurons in the anterior nerve cord of amphioxus larvae. I. An inventory of cell types and synaptic patterns. J Morphol 2003; 257:190-211. [PMID: 12833380 DOI: 10.1002/jmor.10114] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Serial sections were used to map the ventrally positioned neurons of the anterior nerve cord of a 12.5-day amphioxus larva from the infundibular region to the end of somite 2. Synaptic patterns reveal five categories of descending pathways, four of which are associated with the ventral compartment (VC) motoneurons responsible for escape swimming. 1) Pre-, para-, and postinfundibular (tegmental) neurons with large varicosities and mixed vesicle populations provide both synaptic and paracrine input to various components of the tegmental neuropile and primary motor center. Four categories of these neurons are distinguished on the basis of their vesicles. 2) Multiple anterior sensory pathways converge on the large paired neurons (LPNs) located near the junction of somites 1 and 2. LPN synaptic output is almost exclusively contralateral. This, together with the evidence for cross-innervation between the third pair of LPNs, is consistent with the latter acting as locomotory pacemakers. 3) Axons from several classes of tegmental neurons converge in the paraxial region on each side of the cord where they form distinct tracts, the upper paraxial bundles. The right bundle is larger than the left, which suggests a role during early development when myotome contractions are biased to one side. 4) Fibers in the ventral tracts from ipsilateral projection neurons, sensory neurons, and additional ascending fibers synapse repeatedly with VC motoneurons. This may be how the overall level of excitation of the latter is controlled so as to modulate their response to pacemaker input. The fifth pathway consists of fibers involved in controlling the dorsal compartment (DC) motoneurons responsible for slow swimming, which are largely isolated from inputs to the VC locomotory system. The ventral neurons of the primary motor center form a more or less continuous file on either side of the floor plate, with certain cell types showing a tendency to cluster. There are, however, few obvious patterns of the kind expected if development were controlled by a rigid, lineage-based mechanism. The evolutionary implications of the involvement of a midbrain-level pacemaker in controlling larval swimming in amphioxus is discussed.
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Affiliation(s)
- T C Lacalli
- Biology Department, University of Saskatchewan, Saskatoon, Saskatchewan, Canada, S7N-5E2.
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18
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Voogd J. Home of the Mind and More. Science 2003. [DOI: 10.1126/science.1085567] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Brain Architecture
Understanding the Basic Plan. Larry W. Swanson. Oxford University Press, New York, 2003. 281 pp. $59.50, £44.99 ISBN 0-19-510504-4. Paper, $29.95, £21.99. ISBN 0-19-510505-2.
Building on findings from theoretical and experimental morphology, embryology, and evolutionary biology, Swanson provides a balanced overview of the structure and function of the brain.
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Affiliation(s)
- Jan Voogd
- The reviewer is at the Department of Neuroscience, Erasmus Medisch Centrum, Box 1738, 3000 DR Rotterdam, Netherlands
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