The
scientific study of the nervous system increased significantly during the second half of the twentieth century, principally due to advances in
molecular biology,
electrophysiology, and
computational neuroscience. This has allowed neuroscientists to study the
nervous system in all its aspects: how it is structured, how it works, how it develops, how it malfunctions, and how it can be changed. For example, it has become possible to understand, in much detail, the complex processes occurring within a single
neuron. Neurons are cells specialized for communication. They are able to communicate with neurons and other cell types through specialized junctions called
synapses, at which electrical or electrochemical signals can be transmitted from one cell to another. Many neurons extrude a long thin filament of
axoplasm called an
axon, which may extend to distant parts of the body and are capable of rapidly carrying electrical signals, influencing the activity of other neurons, muscles, or glands at their termination points. A nervous
system emerges from the assemblage of neurons that are connected to each other in
neural circuits, and
networks. The vertebrate nervous system can be split into two parts: the
central nervous system (defined as the
brain and
spinal cord), and the
peripheral nervous system. In many species—including all vertebrates—the nervous system is the most
complex organ system in the body, with most of the complexity residing in the brain. The
human brain alone contains around one hundred billion neurons and one hundred trillion synapses; it consists of thousands of distinguishable substructures, connected to each other in synaptic networks whose intricacies have only begun to be unraveled. At least one out of three of the approximately 20,000 genes belonging to the human genome is expressed mainly in the brain. Due to the high degree of
plasticity of the human brain, the structure of its synapses and their resulting functions change throughout life. Making sense of the nervous system's dynamic complexity is a formidable research challenge. Ultimately, neuroscientists would like to understand every aspect of the nervous system, including how it works, how it develops, how it malfunctions, and how it can be altered or repaired. Analysis of the nervous system is therefore performed at multiple levels, ranging from the molecular and cellular levels to the systems and cognitive levels. The specific topics that form the main focus of research change over time, driven by an ever-expanding base of knowledge and the availability of increasingly sophisticated technical methods. Improvements in technology have been the primary drivers of progress. Developments in
electron microscopy,
computer science,
electronics,
functional neuroimaging, and
genetics and
genomics have all been major drivers of progress. Advances in the classification of
brain cells have been enabled by electrophysiological recording,
single-cell genetic sequencing, and high-quality microscopy, which have combined into a single method pipeline called
patch-sequencing in which all three methods are simultaneously applied using miniature tools. The efficiency of this method and the large amounts of data that is generated has allowed researchers to make some general conclusions about cell types; for example that the human and mouse brain have different versions of fundamentally the same cell types.
Molecular and cellular neuroscience in a chicken embryo Basic questions addressed in
molecular neuroscience include the mechanisms by which neurons express and respond to molecular signals and how
axons form complex connectivity patterns. At this level, tools from
molecular biology and
genetics are used to understand how neurons develop and how genetic changes affect biological functions. The
morphology, molecular identity, and physiological characteristics of neurons and how they relate to different types of behavior are also of considerable interest. Questions addressed in
cellular neuroscience include the mechanisms of how neurons process
signals physiologically and electrochemically. These questions include how signals are processed by neurites and somas and how
neurotransmitters and electrical signals are used to process information in a neuron. Neurites are thin extensions from a neuronal
cell body, consisting of
dendrites (specialized to receive synaptic inputs from other neurons) and
axons (specialized to conduct nerve impulses called
action potentials). Somas are the cell bodies of the neurons and contain the nucleus. Another major area of cellular neuroscience is the investigation of the
development of the nervous system. Questions include the
patterning and regionalization of the nervous system, axonal and dendritic development,
trophic interactions,
synapse formation and the implication of
fractones in
neural stem cells,
differentiation of neurons and glia (
neurogenesis and
gliogenesis), and
neuronal migration.
Computational neurogenetic modeling is concerned with the development of dynamic neuronal models for modeling brain functions with respect to genes and dynamic interactions between genes, on the cellular level (Computational Neurogenetic Modeling (CNGM) can also be used to model neural systems).
Neural circuits and systems Systems neuroscience research centers on the structural and functional architecture of the developing human brain, and the functions of
large-scale brain networks, or functionally-connected systems within the brain. Alongside brain development, systems neuroscience also focuses on how the structure and function of the brain enables or restricts the processing of sensory information, using learned
mental models of the world, to motivate behavior. Questions in systems neuroscience include how
neural circuits are formed and used anatomically and physiologically to produce functions such as
reflexes,
multisensory integration,
motor coordination,
circadian rhythms,
emotional responses,
learning, and
memory. In other words, this area of research studies how connections are made and morphed in the brain, and the effect it has on human sensation, movement, attention, inhibitory control, decision-making, reasoning, memory formation, reward, and emotion regulation. Specific areas of interest for the field include observations of how the structure of neural circuits effect skill acquisition, how specialized regions of the brain develop and change (
neuroplasticity), and the development of brain atlases, or wiring diagrams of individual developing brains. The related fields of
neuroethology and
neuropsychology address the question of how neural substrates underlie specific
animal and
human behaviors.
Neuroendocrinology and
psychoneuroimmunology examine interactions between the nervous system and the
endocrine and
immune systems, respectively. Despite many advancements, the way that networks of neurons perform complex
cognitive processes and behaviors is still poorly understood.
Cognitive and behavioral neuroscience Cognitive neuroscience addresses the questions of how
psychological functions are produced by
neural circuitry. The emergence of powerful new measurement techniques such as
neuroimaging (e.g.,
fMRI,
PET,
SPECT),
EEG,
MEG,
electrophysiology,
optogenetics and
human genetic analysis combined with sophisticated
experimental techniques from
cognitive psychology allows
neuroscientists and
psychologists to address abstract questions such as how cognition and emotion are mapped to specific neural substrates. Although many studies hold a reductionist stance looking for the neurobiological basis of cognitive phenomena, recent research shows that there is an interplay between neuroscientific findings and conceptual research, soliciting and integrating both perspectives. For example, neuroscience research on empathy solicited an interdisciplinary debate involving philosophy, psychology and psychopathology. Moreover, the neuroscientific identification of multiple memory systems related to different brain areas has challenged the idea of
memory as a literal reproduction of the past, supporting a view of memory as a generative, constructive and dynamic process. Neuroscience is also allied with the
social and
behavioral sciences, as well as with nascent interdisciplinary fields. Examples of such alliances include
neuroeconomics,
decision theory,
social neuroscience, and
neuromarketing to address complex questions about interactions of the brain with its environment. A study into consumer responses for example uses EEG to investigate neural correlates associated with
narrative transportation into stories about
energy efficiency.
Computational neuroscience Questions in computational neuroscience can span a wide range of levels of traditional analysis, such as
development,
structure, and
cognitive functions of the brain. Research in this field utilizes
mathematical models, theoretical analysis, and
computer simulation to describe and verify biologically plausible neurons and nervous systems. For example,
biological neuron models are mathematical descriptions of spiking neurons which can be used to describe both the behavior of single neurons as well as the dynamics of
neural networks. Computational neuroscience is often referred to as theoretical neuroscience.
Neuroscience and medicine Clinical neuroscience Neurology, psychiatry, neurosurgery, psychosurgery, anesthesiology and
pain medicine, neuropathology,
neuroradiology,
ophthalmology,
otolaryngology,
clinical neurophysiology,
addiction medicine, and
sleep medicine are some medical specialties that specifically address the diseases of the nervous system. These terms also refer to clinical disciplines involving diagnosis and treatment of these diseases.
Neurology works with diseases of the central and peripheral nervous systems, such as
amyotrophic lateral sclerosis (ALS) and
stroke, and their medical treatment.
Psychiatry focuses on
affective, behavioral,
cognitive, and
perceptual disorders.
Anesthesiology focuses on perception of pain, and pharmacologic alteration of consciousness.
Neuropathology focuses upon the classification and underlying pathogenic mechanisms of central and peripheral nervous system and muscle diseases, with an emphasis on morphologic, microscopic, and chemically observable alterations.
Neurosurgery and
psychosurgery work primarily with surgical treatment of diseases of the central and peripheral nervous systems. Neuroscience underlies the development of various
neurotherapy methods to treat diseases of the nervous system.
Translational research of a human head showing
benign familial macrocephaly (head circumference > 60 cm) Recently, the boundaries between various specialties have blurred, as they are all influenced by
basic research in neuroscience. For example,
brain imaging enables objective biological insight into mental illnesses, which can lead to faster diagnosis, more accurate prognosis, and improved monitoring of patient progress over time.
Integrative neuroscience describes the effort to combine models and information from multiple levels of research to develop a coherent model of the nervous system. For example, brain imaging coupled with physiological numerical models and theories of fundamental mechanisms may shed light on psychiatric disorders. Another important area of translational research is
brain–computer interfaces (BCIs), or machines that are able to communicate and influence the brain. They are currently being researched for their potential to repair neural systems and restore certain cognitive functions. Translational BCI research is supported by specialized neurotechnology platforms that enable high-resolution neural signal acquisition, real-time processing, and experimental validation in clinical and laboratory settings. Such platforms are developed by academic groups as well as industry partners, including systems produced by g.tec medical engineering GmbH. ==Major branches==