# Neuroscience

**Neuroscience** is the scientific study of the nervous system, including the brain, the spinal cord, and the networks of nerve cells, or neurons, throughout the body.<sup>[1](https://www.nichd.nih.gov/health/topics/neuro)</sup> The National Library of Medicine defines it as the study of the physiological, cellular, molecular, and genetic processes underlying the function of the brain and nervous system, and collects work on all aspects of the field as applied to any species.<sup>[2](https://www.ncbi.nlm.nih.gov/books/NBK518776/pdf/Bookshelf_NBK518776.pdf)</sup> In medicine, the related term "neurosciences" refers to the branch of medicine that focuses on the nervous system, while neuroscience as a science seeks to understand how the nervous system works in health and disease.<sup>[3](https://medlineplus.gov/ency/article/007456.htm)</sup>

| Key fact | Detail |
|---|---|
| Definition | The study of the nervous system: brain, spinal cord, and networks of neurons throughout the body<sup>[1](https://www.nichd.nih.gov/health/topics/neuro)</sup> |
| Scale of study | From atomic and molecular events on the order of one-tenth to one nanometer up to the entire nervous system on the order of a meter or more<sup>[4](https://www.ncbi.nlm.nih.gov/books/n/nap11480/pdf/)</sup> |
| Cell composition | Glia constitute over half the cells in the mammalian brain<sup>[5](https://www.nature.com/articles/s41583-023-00702-z)</sup> |
| Neuron count | The human brain contains, on average, about 100 billion neurons, with many more neuroglia supporting and protecting them<sup>[6](https://arxiv.org/abs/1906.01703)</sup> |
| Major US program | The NIH BRAIN Initiative, established April 2013, managed by 10 NIH Institutes and Centers, with $402 million appropriated in FY24<sup>[7](https://www.nih.gov/brain/about)</sup> |
| Professional society | The Society for Neuroscience, whose first 50 years (1969-2019) are documented as the history of a still-young field<sup>[8](https://www.sfn.org/about/history-of-sfn)</sup> |
| NIH intramural research | More than 180 laboratories across 14 NIH Institutes and Centers, with over 80 facilities in the John Edward Porter Neuroscience Research Center<sup>[9](https://irp.nih.gov/our-research/scientific-focus-areas/neuroscience)</sup> |

## Scope and organization of the field

Neuroscience examines everything from the inside of cells to cell networks to behavior, seeking to understand how people move, mature, learn, and remember.<sup>[1](https://www.nichd.nih.gov/health/topics/neuro)</sup> Its branches include developmental, behavioral, and molecular neuroscience, and NIH institutes organize research around themes such as typical and atypical development, rehabilitation, and nervous system diseases and disorders.<sup>[1](https://www.nichd.nih.gov/health/topics/neuro)</sup><sup> • </sup><sup>[10](https://www.nichd.nih.gov/sites/default/files/news/resources/links/infographics/Documents/infographic_neuroscience.pdf)</sup> The MeSH thesaurus of the National Library of Medicine places the field among the scientific disciplines concerned with the embryology, anatomy, physiology, biochemistry, and pharmacology of the nervous system, with cognitive neuroscience as one of its subdivisions.<sup>[11](https://meshb.nlm.nih.gov/record/ui?ui=D009488)</sup>

The subject of study is organized into two major subdivisions. The central nervous system consists of the brain and spinal cord; the peripheral nervous system consists of all nerve tissue outside them, divided into the autonomic nervous system, which controls internal processes such as blood pressure, breathing, and digestion, and the somatic nervous system, which carries messages between the central nervous system and the body's sensory organs and voluntary muscles.<sup>[3](https://medlineplus.gov/ency/article/007456.htm)</sup><sup> • </sup><sup>[12](https://www.ncbi.nlm.nih.gov/books/NBK20367/)</sup> The nervous system interacts with all other organ systems and, with limited capacity for self-repair, is particularly vulnerable to damage from injury or infection, which is one reason research spans basic science, translational therapy development, and clinical trials.<sup>[13](https://dpcpsi.nih.gov/sites/default/files/NIH_Biennial_FY0809-opt.pdf)</sup>

## Levels of investigation

Research in neuroscience spans many levels of organization, from molecular events measured in fractions of a nanometer to the entire nervous system measured in meters, and the mechanisms are nonlinear across a wide range of spatial and temporal scales.<sup>[4](https://www.ncbi.nlm.nih.gov/books/n/nap11480/pdf/)</sup> Accordingly, the field draws on many disciplines, from genetics to physiology to psychology, and applies tools from molecular biology, anatomy, computer science, and imaging technologies.<sup>[13](https://dpcpsi.nih.gov/sites/default/files/NIH_Biennial_FY0809-opt.pdf)</sup> [Understanding](https://www.edgepedia.org/understanding) how the brain works therefore requires an interdisciplinary approach to integrating experimental data, computational data, and theory across scales.<sup>[4](https://www.ncbi.nlm.nih.gov/books/n/nap11480/pdf/)</sup>

**Reductionism and its limits.** A long-running methodological discussion concerns how much of behavior can be explained by cellular and molecular mechanisms. Reductionist experiments, such as interventions into cells using optogenetics, can contribute to theories that integrate data across levels, and the successes of cellular and molecular intervention are sometimes cited as support for a reductionist program.<sup>[14](https://pmc.ncbi.nlm.nih.gov/articles/PMC13096671/)</sup> Critics answer that cellular and molecular mechanisms are overwhelmingly complex and that complexity can give rise to emergent properties not found in the lower-level processes; Ebitz and Hayden (2021), for example, give an account of neuronal populations as the fundamental computational unit in the brain.<sup>[14](https://pmc.ncbi.nlm.nih.gov/articles/PMC13096671/)</sup> A ten-year follow-up by an interdisciplinary group of researchers argued that an integrative, multi-perspective approach is a precondition for progress in understanding and treating neuro-psychiatric disorders, while observing that many research programs remain reductionist and fail to acknowledge differences between system levels.<sup>[15](https://pmc.ncbi.nlm.nih.gov/articles/PMC13224105/)</sup>

## Cells and circuits beyond neurons

For many years the widely held assumption was that neurons are the only brain cells able to participate in synaptic communication, supporting the notion that they are uniquely capable of computation. That idea has been increasingly challenged over the past twenty years by growing appreciation of the contributions of glia to circuit function.<sup>[5](https://www.nature.com/articles/s41583-023-00702-z)</sup> More than half of the cells in the mammalian brain are glia, which engage heavily with synapses and play an indispensable role in establishing how neural circuits connect.<sup>[5](https://www.nature.com/articles/s41583-023-00702-z)</sup> Reviews of astrocyte function describe close structural and functional interactions with synapses in which astrocytes can both promote and dampen synaptic efficacy, acting as boosters or gatekeepers of synaptic circuits depending on their properties and activity.<sup>[16](https://www.nature.com/articles/s41583-018-0080-6)</sup>

Non-neuronal cells also participate in plasticity. Beyond synaptic plasticity, recent work has revealed plasticity affecting oligodendrocytes and the myelin sheaths they produce, which plays a crucial role in learning and memory, with evidence of oligodendrocyte and myelin dysfunction in neurodevelopmental disorders with cognitive symptoms.<sup>[17](https://www.nature.com/articles/s41583-020-00379-8)</sup> [Oligodendrocyte](https://www.edgepedia.org/oligodendrocyte) precursor cells, a proliferative progenitor pool that gives rise to myelinating oligodendrocytes, are retained across the lifespan and are suspected to have roles beyond myelination that remain incompletely understood.<sup>[5](https://www.nature.com/articles/s41583-023-00702-z)</sup>

## Institutional history and major programs

The field is young by the standards of the natural sciences. The [Society for Neuroscience](https://www.edgepedia.org/society-for-neuroscience) (SfN) traces the modern field's development from "Neuroscience Before Neuroscience, 1945-1969" through the establishment of the society in 1968-1970 and its subsequent growth, and maintains autobiographical chapters and videos documenting the struggles and accomplishments of a still-young field.<sup>[8](https://www.sfn.org/about/history-of-sfn)</sup><sup> • </sup><sup>[18](https://www.sfn.org/about/history-of-neuroscience)</sup>

In the United States, federal investment is substantial and organized. The NIH Intramural Research Program has conducted neuroscience research since 1949, when the [National Institute of Mental Health](https://www.edgepedia.org/national-institute-of-mental-health) was established, followed in 1950 by the National Institute of Neurological Disorders and Stroke; today more than 180 laboratories across 14 NIH Institutes and Centers study the brain, with over 80 facilities located together in the John Edward Porter Neuroscience Research Center.<sup>[9](https://irp.nih.gov/our-research/scientific-focus-areas/neuroscience)</sup>

**The BRAIN Initiative.** The Brain Research Through Advancing Innovative Neurotechnologies® Initiative, established April 2013, is a partnership between federal and non-federal partners aimed at accelerating the development of innovative neurotechnologies, so that researchers can produce a dynamic picture of the brain showing how individual cells and complex neural circuits interact in both time and space.<sup>[7](https://www.nih.gov/brain/about)</sup> It is managed by 10 NIH Institutes and Centers, led by Director John Ngai with Deputy Director Andrea Beckel-Mitchener, and received $402 million in appropriations in FY24.<sup>[7](https://www.nih.gov/brain/about)</sup> Its founding BRAIN 2025 report recommended a ten-year program beginning in FY2016, with a primary focus on technology development in the first five years and a shift to integrating technologies for fundamental discoveries about the brain in the second five years, identifying the analysis of circuits of interacting neurons as particularly rich in opportunity.<sup>[19](https://braininitiative.nih.gov/sites/default/files/documents/brain2025_508c_2.pdf)</sup> Priority areas now include neural recording and modulation, human neuroscience, neuroethics, neuroimaging across scales, systems neuroscience, data science, and training.<sup>[20](https://grants.nih.gov/funding/find-a-fit-for-your-research/nih-institutes-centers-offices/BRAIN)</sup> The initiative also carries a neuroethics component, including a research portfolio and an NIH-external Neuroethics Working Group.<sup>[21](https://www.ninds.nih.gov/sites/default/files/2025-08/NINDS_Interim_Strategic_Plan_2025-2026_508c_20250730.pdf)</sup>

## Why the field matters

Understanding how the brain and nervous system work can help in understanding, preventing, and treating injury and disease and improving health.<sup>[1](https://www.nichd.nih.gov/health/topics/neuro)</sup> Many conditions affect the nervous system, including degenerative diseases such as Alzheimer and Parkinson disease, epilepsy, stroke, demyelinating diseases such as multiple sclerosis, and mental disorders such as schizophrenia, and diagnosis draws on tests from computed tomography and magnetic resonance imaging to electroencephalography and positron emission tomography.<sup>[3](https://medlineplus.gov/ency/article/007456.htm)</sup> Fundamental neuroscience, defined as research to understand the structure and functions of the normal nervous system over the lifespan, is described by a NINDS working group as the cornerstone for scientific advances underlying neurological health, therapeutic development, and clinical care.<sup>[22](https://www.ninds.nih.gov/sites/default/files/documents/Advancing%20Fundamental%20Neuroscience%20Research_Report%20of%20the%20Fundamental%20Neuroscience%20Working%20Group%20of%20the%20NANDS%20Council_508C.pdf)</sup>

## References

1. [Neuroscience, Eunice Kennedy Shriver National Institute of Child Health and Human Development](https://www.nichd.nih.gov/health/topics/neuro)
2. [Neuroscience, Collection Development Guidelines of the National Library of Medicine](https://www.ncbi.nlm.nih.gov/books/NBK518776/pdf/Bookshelf_NBK518776.pdf)
3. [Neurosciences, MedlinePlus Medical Encyclopedia](https://medlineplus.gov/ency/article/007456.htm)
4. [Free Executive Summary, National Academies (NCBI Bookshelf)](https://www.ncbi.nlm.nih.gov/books/n/nap11480/pdf/)
5. [Cheadle, L. Neuron–glia communication through bona fide synapses. Nature Reviews Neuroscience 24, 395 (2023)](https://www.nature.com/articles/s41583-023-00702-z)
6. [Basic Neural Units of the Brain: Neurons, Synapses and Action Potential, arXiv](https://arxiv.org/abs/1906.01703)
7. [About the BRAIN Initiative, National Institutes of Health](https://www.nih.gov/brain/about)
8. [1969-2019: History of the Society for Neuroscience](https://www.sfn.org/about/history-of-sfn)
9. [Neuroscience, NIH Intramural Research Program](https://irp.nih.gov/our-research/scientific-focus-areas/neuroscience)
10. [Why Do We Study Neuroscience?, NICHD infographic](https://www.nichd.nih.gov/sites/default/files/news/resources/links/infographics/Documents/infographic_neuroscience.pdf)
11. [MeSH Browser record D009488, National Library of Medicine](https://meshb.nlm.nih.gov/record/ui?ui=D009488)
12. [Information about the Brain, NIH Curriculum Supplement Series, NCBI Bookshelf](https://www.ncbi.nlm.nih.gov/books/NBK20367/)
13. [Neuroscience and Disorders of the Nervous System, NIH Biennial Report FY2008-2009](https://dpcpsi.nih.gov/sites/default/files/NIH_Biennial_FY0809-opt.pdf)
14. [Reductionism in Engram Neuroscience, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC13096671/)
15. [Progress and ongoing conceptual challenges "on the way to integrative human neuroscience" – ten years after, PMC](https://pmc.ncbi.nlm.nih.gov/articles/PMC13224105/)
16. [Dallérac, G., Zapata, J. & Rouach, N. Versatile control of synaptic circuits by astrocytes. Nature Reviews Neuroscience 19, 729-743 (2018)](https://www.nature.com/articles/s41583-018-0080-6)
17. [Myelin plasticity: sculpting circuits in learning and memory. Nature Reviews Neuroscience 21, 682-694 (2020)](https://www.nature.com/articles/s41583-020-00379-8)
18. [History of Neuroscience, Society for Neuroscience](https://www.sfn.org/about/history-of-neuroscience)
19. [BRAIN 2025: A Scientific Vision, NIH BRAIN Initiative](https://braininitiative.nih.gov/sites/default/files/documents/brain2025_508c_2.pdf)
20. [NIH BRAIN Initiative, Grants & Funding](https://grants.nih.gov/funding/find-a-fit-for-your-research/nih-institutes-centers-offices/BRAIN)
21. [NINDS Interim Strategic Plan 2025-2026](https://www.ninds.nih.gov/sites/default/files/2025-08/NINDS_Interim_Strategic_Plan_2025-2026_508c_20250730.pdf)
22. [Advancing Fundamental Neuroscience Research, Report of the Fundamental Neuroscience Working Group of the NANDS Council](https://www.ninds.nih.gov/sites/default/files/documents/Advancing%20Fundamental%20Neuroscience%20Research_Report%20of%20the%20Fundamental%20Neuroscience%20Working%20Group%20of%20the%20NANDS%20Council_508C.pdf)

---
*Topic: Encyclopedia › Life and health › Biological foundations › Development and comparative physiology › Cellular, regenerative, and comparative physiology › Comparative physiology › Comparative neuro- and sensory physiology*

*Initially written Sep 17, 2026 · Reviewed: Sep 30, 2026; Oct 21, 2026 · Edited: Sep 30, 2026; Oct 21, 2026 · Last review: Oct 21, 2026*

*Copyright 2026 EdgeChat AI, a subsidiary of Biostate AI.*

License: Edgepedia Community License 1.0, https://www.edgepedia.org/edgepedia/license