What is Behavioural Neuroscience?

Introduction

Behavioural neuroscience, also known as biological psychology, biopsychology, or psychobiology, is the application of the principles of biology to the study of physiological, genetic, and developmental mechanisms of behaviour in humans and other animals.

Brief History

Behavioural neuroscience as a scientific discipline emerged from a variety of scientific and philosophical traditions in the 18th and 19th centuries. In philosophy, people like René Descartes proposed physical models to explain animal as well as human behaviour. Descartes suggested that the pineal gland, a midline unpaired structure in the brain of many organisms, was the point of contact between mind and body. Descartes also elaborated on a theory in which the pneumatics of bodily fluids could explain reflexes and other motor behaviour. This theory was inspired by moving statues in a garden in Paris. Electrical stimulation and lesions can also show the affect of motor behaviour of humans. They can record the electrical activity of actions, hormones, chemicals and effects drugs have in the body system all which affect ones daily behaviour.

Other philosophers also helped give birth to psychology. One of the earliest textbooks in the new field, The Principles of Psychology by William James, argues that the scientific study of psychology should be grounded in an understanding of biology.

The emergence of psychology and behavioural neuroscience as legitimate sciences can be traced from the emergence of physiology from anatomy, particularly neuroanatomy. Physiologists conducted experiments on living organisms, a practice that was distrusted by the dominant anatomists of the 18th and 19th centuries. The influential work of Claude Bernard, Charles Bell, and William Harvey helped to convince the scientific community that reliable data could be obtained from living subjects.

Even before the 18th and 19th century, behavioural neuroscience was beginning to take form as far back as 1700 B.C. The question that seems to continually arise is: what is the connection between the mind and body? The debate is formally referred to as the mind-body problem. There are two major schools of thought that attempt to resolve the mind–body problem; monism and dualism. Plato and Aristotle are two of several philosophers who participated in this debate. Plato believed that the brain was where all mental thought and processes happened. In contrast, Aristotle believed the brain served the purpose of cooling down the emotions derived from the heart. The mind-body problem was a stepping stone toward attempting to understand the connection between the mind and body.

Another debate arose about localisation of function or functional specialisation versus equipotentiality which played a significant role in the development in behavioural neuroscience. As a result of localisation of function research, many famous people found within psychology have come to various different conclusions. Wilder Penfield was able to develop a map of the cerebral cortex through studying epileptic patients along with Rassmussen. Research on localisation of function has led behavioural neuroscientists to a better understanding of which parts of the brain control behaviour. This is best exemplified through the case study of Phineas Gage.

The term “psychobiology” has been used in a variety of contexts, emphasizing the importance of biology, which is the discipline that studies organic, neural and cellular modifications in behaviour, plasticity in neuroscience, and biological diseases in all aspects, in addition, biology focuses and analyses behaviour and all the subjects it is concerned about, from a scientific point of view. In this context, psychology helps as a complementary, but important discipline in the neurobiological sciences. The role of psychology in this questions is that of a social tool that backs up the main or strongest biological science. The term “psychobiology” was first used in its modern sense by Knight Dunlap in his book An Outline of Psychobiology (1914). Dunlap also was the founder and editor-in-chief of the journal Psychobiology. In the announcement of that journal, Dunlap writes that the journal will publish research “…bearing on the interconnection of mental and physiological functions”, which describes the field of behavioural neuroscience even in its modern sense.

Relationship to Other Fields of Psychology and Biology

In many cases, humans may serve as experimental subjects in behavioural neuroscience experiments; however, a great deal of the experimental literature in behavioural neuroscience comes from the study of non-human species, most frequently rats, mice, and monkeys. As a result, a critical assumption in behavioural neuroscience is that organisms share biological and behavioural similarities, enough to permit extrapolations across species. This allies behavioural neuroscience closely with comparative psychology, evolutionary psychology, evolutionary biology, and neurobiology. Behavioural neuroscience also has paradigmatic and methodological similarities to neuropsychology, which relies heavily on the study of the behaviour of humans with nervous system dysfunction (i.e. a non-experimentally based biological manipulation).

Synonyms for behavioural neuroscience include biopsychology, biological psychology, and psychobiology. Physiological psychology is a subfield of behavioural neuroscience, with an appropriately narrower definition.

Research Methods

The distinguishing characteristic of a behavioural neuroscience experiment is that either the independent variable of the experiment is biological, or some dependent variable is biological. In other words, the nervous system of the organism under study is permanently or temporarily altered, or some aspect of the nervous system is measured (usually to be related to a behavioural variable).

Disabling or Decreasing Neural Function

  • Lesions: A classic method in which a brain-region of interest is naturally or intentionally destroyed to observe any resulting changes such as degraded or enhanced performance on some behavioural measure. Lesions can be placed with relatively high accuracy “Thanks to a variety of brain ‘atlases’ which provide a map of brain regions in 3-dimensional “stereotactic coordinates.
    • Surgical lesions: Neural tissue is destroyed by removing it surgically.
    • Electrolytic lesions: Neural tissue is destroyed through the application of electrical shock trauma.
    • Chemical lesions: Neural tissue is destroyed by the infusion of a neurotoxin.
    • Temporary lesions: Neural tissue is temporarily disabled by cooling or by the use of anaesthetics such as tetrodotoxin.
  • Transcranial magnetic stimulation: A new technique usually used with human subjects in which a magnetic coil applied to the scalp causes unsystematic electrical activity in nearby cortical neurons which can be experimentally analysed as a functional lesion.
  • Synthetic ligand injection: A receptor activated solely by a synthetic ligand (RASSL) or Designer Receptor Exclusively Activated by Designer Drugs (DREADD), permits spatial and temporal control of G protein signalling in vivo. These systems utilise G protein-coupled receptors (GPCR) engineered to respond exclusively to synthetic small molecules ligands, like clozapine N-oxide (CNO), and not to their natural ligand(s). RASSL’s represent a GPCR-based chemogenetic tool. These synthetic ligands upon activation can decrease neural function by G-protein activation. This can with Potassium attenuating neural activity.
  • Psychopharmacological manipulations: A chemical receptor antagonist induces neural activity by interfering with neurotransmission. Antagonists can be delivered systemically (such as by intravenous injection) or locally (intracerebrally) during a surgical procedure into the ventricles or into specific brain structures. For example, NMDA antagonist AP5 has been shown to inhibit the initiation of long term potentiation of excitatory synaptic transmission (in rodent fear conditioning) which is believed to be a vital mechanism in learning and memory.
  • Optogenetic inhibition: A light activated inhibitory protein is expressed in cells of interest. Powerful millisecond timescale neuronal inhibition is instigated upon stimulation by the appropriate frequency of light delivered via fibre optics or implanted LEDs in the case of vertebrates, or via external illumination for small, sufficiently translucent invertebrates. Bacterial Halorhodopsins or Proton pumps are the two classes of proteins used for inhibitory optogenetics, achieving inhibition by increasing cytoplasmic levels of halides (Cl) or decreasing the cytoplasmic concentration of protons, respectively.

Enhancing Neural Function

  • Electrical stimulation: A classic method in which neural activity is enhanced by application of a small electric current (too small to cause significant cell death).
  • Psychopharmacological manipulations: A chemical receptor agonist facilitates neural activity by enhancing or replacing endogenous neurotransmitters. Agonists can be delivered systemically (such as by intravenous injection) or locally (intracerebrally) during a surgical procedure.
  • Synthetic Ligand Injection: Likewise, Gq-DREADDs can be used to modulate cellular function by innervation of brain regions such as Hippocampus. This innervation results in the amplification of γ-rhythms, which increases motor activity.
  • Transcranial magnetic stimulation: In some cases (for example, studies of motor cortex), this technique can be analysed as having a stimulatory effect (rather than as a functional lesion).
  • Optogenetic excitation: A light activated excitatory protein is expressed in select cells. Channelrhodopsin-2 (ChR2), a light activated cation channel, was the first bacterial opsin shown to excite neurons in response to light, though a number of new excitatory optogenetic tools have now been generated by improving and imparting novel properties to ChR2

Measuring Neural Activity

  • Optical techniques: Optical methods for recording neuronal activity rely on methods that modify the optical properties of neurons in response to the cellular events associated with action potentials or neurotransmitter release.
    • Voltage sensitive dyes (VSDs) were among the earliest method for optically detecting neuronal activity. VSDs commonly changed their fluorescent properties in response to a voltage change across the neuron’s membrane, rendering membrane sub-threshold and supra-threshold (action potentials) electrical activity detectable. Genetically encoded voltage sensitive fluorescent proteins have also been developed.
    • Calcium imaging relies on dyes or genetically encoded proteins that fluoresce upon binding to the calcium that is transiently present during an action potential.
    • Synapto-pHluorin is a technique that relies on a fusion protein that combines a synaptic vesicle membrane protein and a pH sensitive fluorescent protein. Upon synaptic vesicle release, the chimeric protein is exposed to the higher pH of the synaptic cleft, causing a measurable change in fluorescence.
  • Single-unit recording: A method whereby an electrode is introduced into the brain of a living animal to detect electrical activity that is generated by the neurons adjacent to the electrode tip. Normally this is performed with sedated animals but sometimes it is performed on awake animals engaged in a behavioural event, such as a thirsty rat whisking a particular sandpaper grade previously paired with water in order to measure the corresponding patterns of neuronal firing at the decision point.
  • Multielectrode recording: The use of a bundle of fine electrodes to record the simultaneous activity of up to hundreds of neurons.
  • fMRI: Functional magnetic resonance imaging, a technique most frequently applied on human subjects, in which changes in cerebral blood flow can be detected in an MRI apparatus and are taken to indicate relative activity of larger scale brain regions (i.e., on the order of hundreds of thousands of neurons).
  • PET: Positron Emission Tomography detects particles called photons using a 3-D nuclear medicine examination. These particles are emitted by injections of radioisotopes such as fluorine. PET imaging reveal the pathological processes which predict anatomic changes making it important for detecting, diagnosing and characterising many pathologies.
  • Electroencephalography: Or EEG; and the derivative technique of event-related potentials, in which scalp electrodes monitor the average activity of neurons in the cortex (again, used most frequently with human subjects). This technique uses different types of electrodes for recording systems such as needle electrodes and saline-based electrodes. EEG allows for the investigation of mental disorders, sleep disorders and physiology. It can monitor brain development and cognitive engagement.
  • Functional neuroanatomy: A more complex counterpart of phrenology. The expression of some anatomical marker is taken to reflect neural activity. For example, the expression of immediate early genes is thought to be caused by vigorous neural activity. Likewise, the injection of 2-deoxyglucose prior to some behavioural task can be followed by anatomical localisation of that chemical; it is taken up by neurons that are electrically active.
  • MEG: Magnetoencephalography shows the functioning of the human brain through the measurement of electromagnetic activity. Measuring the magnetic fields created by the electric current flowing within the neurons identifies brain activity associated with various human functions in real time, with millimetre spatial accuracy. Clinicians can noninvasively obtain data to help them assess neurological disorders and plan surgical treatments.

Genetic Techniques

  • QTL mapping: The influence of a gene in some behaviour can be statistically inferred by studying inbred strains of some species, most commonly mice. The recent sequencing of the genome of many species, most notably mice, has facilitated this technique.
  • Selective breeding: Organisms, often mice, may be bred selectively among inbred strains to create a recombinant congenic strain. This might be done to isolate an experimentally interesting stretch of DNA derived from one strain on the background genome of another strain to allow stronger inferences about the role of that stretch of DNA.
  • Genetic engineering: The genome may also be experimentally-manipulated; for example, knockout mice can be engineered to lack a particular gene, or a gene may be expressed in a strain which does not normally do so (the ‘transgenic’). Advanced techniques may also permit the expression or suppression of a gene to occur by injection of some regulating chemical.

Other Research Methods

Computational models, i.e. using a computer to formulate real-world problems to develop solutions. Although this method is often focused in computer science, it has begun to move towards other areas of study. For example, psychology is one of these areas. Computational models allow researchers in psychology to enhance their understanding of the functions and developments in nervous systems. Examples of methods include the modelling of neurons, networks and brain systems and theoretical analysis. Computational methods have a wide variety of roles including clarifying experiments, hypothesis testing and generating new insights. These techniques play an increasing role in the advancement of biological psychology.

Limitations and Advantages

Different manipulations have advantages and limitations. Neural tissue destroyed as a primary consequence of a surgery, electric shock or neurotoxin can confound the results so that the physical trauma masks changes in the fundamental neurophysiological processes of interest. For example, when using an electrolytic probe to create a purposeful lesion in a distinct region of the rat brain, surrounding tissue can be affected: so, a change in behaviour exhibited by the experimental group post-surgery is to some degree a result of damage to surrounding neural tissue, rather than by a lesion of a distinct brain region. Most genetic manipulation techniques are also considered permanent. Temporary lesions can be achieved with advanced in genetic manipulations, for example, certain genes can now be switched on and off with diet. Pharmacological manipulations also allow blocking of certain neurotransmitters temporarily as the function returns to its previous state after the drug has been metabolised.

Topic Areas

In general, behavioural neuroscientists study similar themes and issues as academic psychologists, though limited by the need to use nonhuman animals. As a result, the bulk of literature in behavioural neuroscience deals with mental processes and behaviours that are shared across different animal models such as:

  • Sensation and perception.
  • Motivated behaviour (hunger, thirst, sex).
  • Control of movement.
  • Learning and memory.
  • Sleep and biological rhythms.
  • Emotion.

However, with increasing technical sophistication and with the development of more precise non-invasive methods that can be applied to human subjects, behavioural neuroscientists are beginning to contribute to other classical topic areas of psychology, philosophy, and linguistics, such as:

  • Language.
  • Reasoning and decision making.
  • Consciousness.

Behavioural neuroscience has also had a strong history of contributing to the understanding of medical disorders, including those that fall under the purview of clinical psychology and biological psychopathology (also known as abnormal psychology). Although animal models do not exist for all mental illnesses, the field has contributed important therapeutic data on a variety of conditions, including:

  • Parkinson’s disease, a degenerative disorder of the central nervous system that often impairs the sufferer’s motor skills and speech.
  • Huntington’s disease, a rare inherited neurological disorder whose most obvious symptoms are abnormal body movements and a lack of coordination. It also affects a number of mental abilities and some aspects of personality.
  • Alzheimer’s disease, a neurodegenerative disease that, in its most common form, is found in people over the age of 65 and is characterised by progressive cognitive deterioration, together with declining activities of daily living and by neuropsychiatric symptoms or behavioural changes.
  • Clinical depression, a common psychiatric disorder, characterised by a persistent lowering of mood, loss of interest in usual activities and diminished ability to experience pleasure.
  • Schizophrenia, a psychiatric diagnosis that describes a mental illness characterised by impairments in the perception or expression of reality, most commonly manifesting as auditory hallucinations, paranoid or bizarre delusions or disorganised speech and thinking in the context of significant social or occupational dysfunction.
  • Autism, a brain development disorder that impairs social interaction and communication, and causes restricted and repetitive behaviour, all starting before a child is three years old.
  • Anxiety, a physiological state characterised by cognitive, somatic, emotional, and behavioural components. These components combine to create the feelings that are typically recognised as fear, apprehension, or worry.
  • Drug abuse, including alcoholism.

What is Neuroscience?

Introduction

Neuroscience (or neurobiology) is the scientific study of the nervous system. It is a multidisciplinary science that combines physiology, anatomy, molecular biology, developmental biology, cytology, mathematical modelling, and psychology to understand the fundamental and emergent properties of neurons and neural circuits. The understanding of the biological basis of learning, memory, behaviour, perception, and consciousness has been described by Eric Kandel as the “ultimate challenge” of the biological sciences.

The scope of neuroscience has broadened over time to include different approaches used to study the nervous system at different scales and the techniques used by neuroscientists have expanded enormously, from molecular and cellular studies of individual neurons to imaging of sensory, motor and cognitive tasks in the brain.

Brief History

The earliest study of the nervous system dates to ancient Egypt. Trepanation, the surgical practice of either drilling or scraping a hole into the skull for the purpose of curing head injuries or mental disorders, or relieving cranial pressure, was first recorded during the Neolithic period. Manuscripts dating to 1700 BC indicate that the Egyptians had some knowledge about symptoms of brain damage.

Early views on the function of the brain regarded it to be a “cranial stuffing” of sorts. In Egypt, from the late Middle Kingdom onwards, the brain was regularly removed in preparation for mummification. It was believed at the time that the heart was the seat of intelligence. According to Herodotus, the first step of mummification was to “take a crooked piece of iron, and with it draw out the brain through the nostrils, thus getting rid of a portion, while the skull is cleared of the rest by rinsing with drugs.”

The view that the heart was the source of consciousness was not challenged until the time of the Greek physician Hippocrates. He believed that the brain was not only involved with sensation – since most specialised organs (e.g. eyes, ears, tongue) are located in the head near the brain – but was also the seat of intelligence. Plato also speculated that the brain was the seat of the rational part of the soul. Aristotle, however, believed the heart was the centre of intelligence and that the brain regulated the amount of heat from the heart. This view was generally accepted until the Roman physician Galen, a follower of Hippocrates and physician to Roman gladiators, observed that his patients lost their mental faculties when they had sustained damage to their brains.

Abulcasis, Averroes, Avicenna, Avenzoar, and Maimonides, active in the Medieval Muslim world, described a number of medical problems related to the brain. In Renaissance Europe, Vesalius (1514-1564), René Descartes (1596-1650), Thomas Willis (1621-1675) and Jan Swammerdam (1637-1680) also made several contributions to neuroscience.

Luigi Galvani’s pioneering work in the late 1700s set the stage for studying the electrical excitability of muscles and neurons. In the first half of the 19th century, Jean Pierre Flourens pioneered the experimental method of carrying out localised lesions of the brain in living animals describing their effects on motricity, sensibility and behaviour. In 1843 Emil du Bois-Reymond demonstrated the electrical nature of the nerve signal, whose speed Hermann von Helmholtz proceeded to measure, and in 1875 Richard Caton found electrical phenomena in the cerebral hemispheres of rabbits and monkeys. Adolf Beck published in 1890 similar observations of spontaneous electrical activity of the brain of rabbits and dogs. Studies of the brain became more sophisticated after the invention of the microscope and the development of a staining procedure by Camillo Golgi during the late 1890s. The procedure used a silver chromate salt to reveal the intricate structures of individual neurons. His technique was used by Santiago Ramón y Cajal and led to the formation of the neuron doctrine, the hypothesis that the functional unit of the brain is the neuron. Golgi and Ramón y Cajal shared the Nobel Prize in Physiology or Medicine in 1906 for their extensive observations, descriptions, and categorizations of neurons throughout the brain.

In parallel with this research, work with brain-damaged patients by Paul Broca suggested that certain regions of the brain were responsible for certain functions. At the time, Broca’s findings were seen as a confirmation of Franz Joseph Gall’s theory that language was localised and that certain psychological functions were localised in specific areas of the cerebral cortex. The localisation of function hypothesis was supported by observations of epileptic patients conducted by John Hughlings Jackson, who correctly inferred the organisation of the motor cortex by watching the progression of seizures through the body. Carl Wernicke further developed the theory of the specialisation of specific brain structures in language comprehension and production. Modern research through neuroimaging techniques, still uses the Brodmann cerebral cytoarchitectonic map (referring to study of cell structure) anatomical definitions from this era in continuing to show that distinct areas of the cortex are activated in the execution of specific tasks.

During the 20th century, neuroscience began to be recognised as a distinct academic discipline in its own right, rather than as studies of the nervous system within other disciplines. Eric Kandel and collaborators have cited David Rioch, Francis O. Schmitt, and Stephen Kuffler as having played critical roles in establishing the field. Rioch originated the integration of basic anatomical and physiological research with clinical psychiatry at the Walter Reed Army Institute of Research, starting in the 1950s. During the same period, Schmitt established a neuroscience research programme within the Biology Department at the Massachusetts Institute of Technology, bringing together biology, chemistry, physics, and mathematics. The first freestanding neuroscience department (then called Psychobiology) was founded in 1964 at the University of California, Irvine by James L. McGaugh. This was followed by the Department of Neurobiology at Harvard Medical School, which was founded in 1966 by Stephen Kuffler.

The understanding of neurons and of nervous system function became increasingly precise and molecular during the 20th century. For example, in 1952, Alan Lloyd Hodgkin and Andrew Huxley presented a mathematical model for transmission of electrical signals in neurons of the giant axon of a squid, which they called “action potentials”, and how they are initiated and propagated, known as the Hodgkin-Huxley model. In 1961–1962, Richard FitzHugh and J. Nagumo simplified Hodgkin-Huxley, in what is called the FitzHugh-Nagumo model. In 1962, Bernard Katz modelled neurotransmission across the space between neurons known as synapses. Beginning in 1966, Eric Kandel and collaborators examined biochemical changes in neurons associated with learning and memory storage in Aplysia. In 1981 Catherine Morris and Harold Lecar combined these models in the Morris-Lecar model. Such increasingly quantitative work gave rise to numerous biological neuron models and models of neural computation.

As a result of the increasing interest about the nervous system, several prominent neuroscience organizations have been formed to provide a forum to all neuroscientist during the 20th century. For example, the International Brain Research Organisation was founded in 1961, the International Society for Neurochemistry in 1963, the European Brain and Behaviour Society in 1968, and the Society for Neuroscience in 1969. Recently, the application of neuroscience research results has also given rise to applied disciplines as neuroeconomics, neuroeducation, neuroethics, and neurolaw.

Over time, brain research has gone through philosophical, experimental, and theoretical phases, with work on brain simulation predicted to be important in the future.

Modern Neuroscience

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 specialised for communication. They are able to communicate with neurons and other cell types through specialised 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.

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 unravelled. 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 foci 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.

Molecular and Cellular Neuroscience

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 behaviour 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 (specialised to receive synaptic inputs from other neurons) and axons (specialised 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 regionalisation of the nervous system, neural stem cells, differentiation of neurons and glia (neurogenesis and gliogenesis), neuronal migration, axonal and dendritic development, trophic interactions, and synapse formation.

Computational neurogenetic modelling is concerned with the development of dynamic neuronal models for modelling brain functions with respect to genes and dynamic interactions between genes.

Neural Circuits and Systems

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, they address how these neural circuits function in large-scale brain networks, and the mechanisms through which behaviours are generated. For example, systems level analysis addresses questions concerning specific sensory and motor modalities: how does vision work? How do songbirds learn new songs and bats localize with ultrasound? How does the somatosensory system process tactile information? The related fields of neuroethology and neuropsychology address the question of how neural substrates underlie specific animal and human behaviours. 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 behaviours is still poorly understood.

Cognitive and Behavioural 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 still hold a reductionist stance looking for the neurobiological basis of cognitive phenomena, recent research shows that there is an interesting interplay between neuroscientific findings and conceptual research, soliciting and integrating both perspectives. For example, neuroscience research on empathy solicited an interesting 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 behavioural sciences as well as nascent interdisciplinary fields such as 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 utilises 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 behaviour of single neurons as well as the dynamics of neural networks. Computational neuroscience is often referred to as theoretical neuroscience.

Nanoparticles in medicine are versatile in treating neurological disorders showing promising results in mediating drug transport across the blood brain barrier. Implementing nanoparticles in antiepileptic drugs enhances their medical efficacy by increasing bioavailability in the bloodstream, as well as offering a measure of control in release time concentration. Although nanoparticles can assist therapeutic drugs by adjusting physical properties to achieve desirable effects, inadvertent increases in toxicity often occur in preliminary drug trials. Furthermore, production of nanomedicine for drug trials is economically consuming, hindering progress in their implementation. Computational models in nanoneuroscience provide alternatives to study the efficacy of nanotechnology-based medicines in neurological disorders while mitigating potential side effects and development costs.

Nanomaterials often operate at length scales between classical and quantum regimes. Due to the associated uncertainties at the length scales that nanomaterials operate, it is difficult to predict their behaviour prior to in vivo studies. Classically, the physical processes which occur throughout neurons are analogous to electrical circuits. Designers focus on such analogies and model brain activity as a neural circuit. Success in computational modelling of neurons have led to the development of stereochemical models that accurately predict acetylcholine receptor-based synapses operating at microsecond time scales.

Ultrafine nanoneedles for cellular manipulations are thinner than the smallest single walled carbon nanotubes. Computational quantum chemistry is used to design ultrafine nanomaterials with highly symmetrical structures to optimise geometry, reactivity and stability.

Behaviour of nanomaterials are dominated by long ranged non-bonding interactions. Electrochemical processes that occur throughout the brain generate an electric field which can inadvertently affect the behaviour of some nanomaterials. Molecular dynamics simulations can mitigate the development phase of nanomaterials as well as prevent neural toxicity of nanomaterials following in vivo clinical trials. Testing nanomaterials using molecular dynamics optimizes nano characteristics for therapeutic purposes by testing different environment conditions, nanomaterial shape fabrications, nanomaterial surface properties, etc without the need for in vivo experimentation. Flexibility in molecular dynamic simulations allows medical practitioners to personalise treatment. Nanoparticle related data from translational nanoinformatics links neurological patient specific data to predict treatment response.

Nano-Neurotechnology

The visualization of neuronal activity is of key importance in the study of neurology. Nano-imaging tools with nanoscale resolution help in these areas. These optical imaging tools are PALM and STORM which helps visualise nanoscale objects within cells. Pampaloni states that, so far, these imaging tools revealed the dynamic behaviour and organisation of the actin cytoskeleton inside the cells, which will assist in understanding how neurons probe their involvement during neuronal outgrowth and in response to injury, and how they differentiate axonal processes and characterisation of receptor clustering and stoichiometry at the plasma inside the synapses, which are critical for understanding how synapses respond to changes in neuronal activity. These past works focused on devices for stimulation or inhibition of neural activity, but the crucial aspect is the ability for the device to simultaneously monitor neural activity. The major aspect that is to be improved in the nano imaging tools is the effective collection of the light as a major problem is that biological tissue are dispersive media that do not allow a straightforward propagation and control of light. These devices use nanoneedle and nanowire (NWs) for probing and stimulation.

NWs are artificial nano- or micro-sized “needles” that can provide high-fidelity electrophysiological recordings if used as microscopic electrodes for neuronal recordings. NWs are an attractive as they are highly functional structures that offer unique electronic properties that are affected by biological/chemical species adsorbed on their surface; mostly the conductivity. This conductivity variance depending on chemical species present allows enhanced sensing performances. NWs are also able to act as non-invasive and highly local probes. These versatility of NWs makes it optimal for interfacing with neurons due to the fact that the contact length along the axon (or the dendrite projection crossing a NW) is just about 20 nm.

Neuroscience and Medicine

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, behavioural, cognitive, and perceptual disorders. Anaesthesiology 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.

Translational Research

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.

Nanoneuroscience

One of the main goals of nanoneuroscience is to gain a detailed understanding of how the nervous system operates and, thus, how neurons organise themselves in the brain. Consequently, creating drugs and devices that are able to cross the blood brain barrier (BBB) are essential to allow for detailed imaging and diagnoses. The blood brain barrier functions as a highly specialised semipermeable membrane surrounding the brain, preventing harmful molecules that may be dissolved in the circulation blood from entering the central nervous system.

The main two hurdles for drug-delivering molecules to access the brain are size (must have a molecular weight < 400 Da) and lipid solubility. Physicians hope to circumvent difficulties in accessing the central nervous system through viral gene therapy. This often involves direct injection into the patient’s brain or cerebral spinal fluid. The drawback of this therapy is that it is invasive and carries a high risk factor due to the necessity of surgery for the treatment to be administered. Because of this, only 3.6% of clinical trials in this field have progressed to stage III since the concept of gene therapy was developed in the 1980s.

Another proposed way to cross the BBB is through temporary intentional disruption of the barrier. This method was first inspired by certain pathological conditions that were discovered to break down this barrier by themselves, such as Alzheimer’s disease, Parkinson’s disease, stroke, and seizure conditions.

Nanoparticles are unique from macromolecules because their surface properties are dependent on their size, allowing for strategic manipulation of these properties (or, “programming”) by scientists that would not be possible otherwise. Likewise, nanoparticle shape can also be varied to give a different set of characteristics based on the surface area to volume ratio of the particle.

Nanoparticles have promising therapeutic effects when treating neurodegenerative diseases. Oxygen reactive polymer (ORP) is a nano-platform programmed to react with oxygen and has been shown to detect and reduce the presence of reactive oxygen species (ROS) formed immediately after traumatic brain injuries. Nanoparticles have also been employed as a “neuroprotective” measure, as is the case with Alzheimer’s disease and stroke models. Alzheimer’s disease results in toxic aggregates of the amyloid beta protein formed in the brain. In one study, gold nanoparticles were programmed to attach themselves to these aggregates and were successful in breaking them up. Likewise, with ischemic stroke models, cells in the affected region of the brain undergo apoptosis, dramatically reducing blood flow to important parts of the brain and often resulting in death or severe mental and physical changes. Platinum nanoparticles have been shown to act as ROS, serving as “biological antioxidants” and significantly reducing oxidation in the brain as a result of stroke. Nanoparticles can also lead to neurotoxicity and cause permanent BBB damage either from brain oedema or from unrelated molecules crossing the BBB and causing brain damage. This proves further long term in vivo studies are needed to gain enough understanding to allow for successful clinical trials.

One of the most common nano-based drug delivery platforms is liposome-based delivery. They are both lipid-soluble and nano-scale and thus are permitted through a fully functioning BBB. Additionally, lipids themselves are biological molecules, making them highly biocompatible, which in turn lowers the risk of cell toxicity. The bilayer that is formed allows the molecule to fully encapsulate any drug, protecting it while it is travelling through the body. One drawback to shielding the drug from the outside cells is that it no longer has specificity, and requires coupling to extra antibodies to be able to target a biological site. Due to their low stability, liposome-based nanoparticles for drug delivery have a short shelf life.

Targeted therapy using magnetic nanoparticles (MNPs) is also a popular topic of research and has led to several stage III clinical trials. Invasiveness is not an issue here because a magnetic force can be applied from the outside of a patient’s body to interact and direct the MNPs. This strategy has been proven successful in delivering Brain-derived neurotropic factor, a naturally occurring gene thought to promote neurorehabilitation, across the BBB.

Major Branches

Modern neuroscience education and research activities can be very roughly categorised into the following major branches, based on the subject and scale of the system in examination as well as distinct experimental or curricular approaches. Individual neuroscientists, however, often work on questions that span several distinct subfields.

BranchDescription
Affective NeuroscienceAffective neuroscience is the study of the neural mechanisms involved in emotion, typically through experimentation on animal models.
Behavioural NeuroscienceBehavioural neuroscience (also known as biological psychology, physiological psychology, biopsychology, or psychobiology) is the application of the principles of biology to the study of genetic, physiological, and developmental mechanisms of behaviour in humans and non-human animals.
Cellular NeuroscienceCellular neuroscience is the study of neurons at a cellular level including morphology and physiological properties.
Clinical NeuroscienceThe scientific study of the biological mechanisms that underlie the disorders and diseases of the nervous system.
Cognitive NeuroscienceCognitive neuroscience is the study of the biological mechanisms underlying cognition.
Computational NeuroscienceComputational neuroscience is the theoretical study of the nervous system.
Cultural NeuroscienceCultural neuroscience is the study of how cultural values, practices and beliefs shape and are shaped by the mind, brain and genes across multiple timescales.
Developmental NeuroscienceDevelopmental neuroscience studies the processes that generate, shape, and reshape the nervous system and seeks to describe the cellular basis of neural development to address underlying mechanisms.
Evolutionary NeuroscienceEvolutionary neuroscience studies the evolution of nervous systems.
Molecular NeuroscienceMolecular neuroscience studies the nervous system with molecular biology, molecular genetics, protein chemistry, and related methodologies.
Neural NeuroscienceNeural engineering uses engineering techniques to interact with, understand, repair, replace, or enhance neural systems.
NeuroanatomyNeuroanatomy is the study of the anatomy of nervous systems.
NeurochemistryNeurochemistry is the study of how neurochemicals interact and influence the function of neurons.
NeuroethologyNeuroethology is the study of the neural basis of non-human animals behaviour.
NeurogastronomyNeurogastronomy is the study of flavour and how it affects sensation, cognition, and memory.
NeurogeneticsNeurogenetics is the study of the genetical basis of the development and function of the nervous system.
NeuroimagingNeuroimaging includes the use of various techniques to either directly or indirectly image the structure and function of the brain.
NeuroimmunologyNeuroimmunology is concerned with the interactions between the nervous and the immune system.
NeuroinformaticsNeuroinformatics is a discipline within bioinformatics that conducts the organisation of neuroscience data and application of computational models and analytical tools.
NeurolinguisticsNeurolinguistics is the study of the neural mechanisms in the human brain that control the comprehension, production, and acquisition of language.
NeurophysicsNeurophysics deals with the development of physical experimental tools to gain information about the brain.
NeurophysiologyNeurophysiology is the study of the functioning of the nervous system, generally using physiological techniques that include measurement and stimulation with electrodes or optically with ion- or voltage-sensitive dyes or light-sensitive channels.
NeuropsychologyNeuropsychology is a discipline that resides under the umbrellas of both psychology and neuroscience, and is involved in activities in the arenas of both basic science and applied science. In psychology, it is most closely associated with biopsychology, clinical psychology, cognitive psychology, and developmental psychology. In neuroscience, it is most closely associated with the cognitive, behavioural, social, and affective neuroscience areas. In the applied and medical domain, it is related to neurology and psychiatry.
PaleoneurobiologyPaleoneurobiology is a field which combines techniques used in palaeontology and archaeology to study brain evolution, especially that of the human brain.
Social NeuroscienceSocial neuroscience is an interdisciplinary field devoted to understanding how biological systems implement social processes and behaviour, and to using biological concepts and methods to inform and refine theories of social processes and behaviour.
Systems NeuroscienceSystems neuroscience is the study of the function of neural circuits and systems.

Neuroscience Organisations

The largest professional neuroscience organisation is the Society for Neuroscience (SFN), which is based in the United States but includes many members from other countries. Since its founding in 1969 the SFN has grown steadily: as of 2010 it recorded 40,290 members from 83 different countries. Annual meetings, held each year in a different American city, draw attendance from researchers, postdoctoral fellows, graduate students, and undergraduates, as well as educational institutions, funding agencies, publishers, and hundreds of businesses that supply products used in research.

Other major organisations devoted to neuroscience include the International Brain Research Organisation (IBRO), which holds its meetings in a country from a different part of the world each year, and the Federation of European Neuroscience Societies (FENS), which holds a meeting in a different European city every two years. FENS comprises a set of 32 national-level organisations, including the British Neuroscience Association, the German Neuroscience Society (Neurowissenschaftliche Gesellschaft), and the French Société des Neurosciences. The first National Honour Society in Neuroscience, Nu Rho Psi, was founded in 2006. Numerous youth neuroscience societies which support undergraduates, graduates and early career researchers also exist, like Project Encephalon.

In 2013, the BRAIN Initiative was announced in the US. An International Brain Initiative was created in 2017, currently integrated by more than seven national-level brain research initiatives (US, Europe, Allen Institute, Japan, China, Australia, Canada, Korea, Israel) spanning four continents.

Public Education and Outreach

In addition to conducting traditional research in laboratory settings, neuroscientists have also been involved in the promotion of awareness and knowledge about the nervous system among the general public and government officials. Such promotions have been done by both individual neuroscientists and large organisations. For example, individual neuroscientists have promoted neuroscience education among young students by organising the International Brain Bee, which is an academic competition for high school or secondary school students worldwide. In the United States, large organisations such as the Society for Neuroscience have promoted neuroscience education by developing a primer called Brain Facts, collaborating with public school teachers to develop Neuroscience Core Concepts for K-12 teachers and students, and cosponsoring a campaign with the Dana Foundation called Brain Awareness Week to increase public awareness about the progress and benefits of brain research. In Canada, the CIHR Canadian National Brain Bee is held annually at McMaster University.

Neuroscience educators formed Faculty for Undergraduate Neuroscience (FUN) in 1992 to share best practices and provide travel awards for undergraduates presenting at Society for Neuroscience meetings.

Finally, neuroscientists have also collaborated with other education experts to study and refine educational techniques to optimise learning among students, an emerging field called educational neuroscience. Federal agencies in the United States, such as the National Institute of Health (NIH) and National Science Foundation (NSF), have also funded research that pertains to best practices in teaching and learning of neuroscience concepts.