Chapter 1 - What is Behavioural Neuroscience?

Question 1

NEUROSCIENCE

Answer 1

Neuroscience is the scientific study of the brain and nervous system.

Question 2

LEVELS OF ANALYSIS IN NEUROSCIENCE

Answer 2

Neuroscience works on different levels of analysis, namely molecular neuroscience, cellular neuroscience, synaptic neuroscience, network neuroscience, and behavioural neuroscience. Computational neuroscience produces models of the nervous systems from the molecular up through the behavioural level of analysis.

Question 3

TREPHINING or TREPANATION

Answer 3

The prehistoric practice of drilling holes in the skull as brain surgery to treat afflictions. Evidence suggests that it originated as long as 7000 years ago. Regrowth of tissue around the holes shows that at least some of the patients undergoing trephination survived the procedure.

Question 4

The EDWIN SMITH SURGICAL PAPYRUS

Answer 4

It is the oldest known medical writing in history (1600 BCE). The author understood that paralysis and lack of sensation in the body resulted from nervous system damage.

Question 5

BEHAVIOURAL NEUROSCIENCE

Answer 5

Behavioural neuroscience uses all of the previous levels of analysis, from the molecular up to the network, in effort to understand the biological correlates of behavior. The relationship between biology and behaviour is reciprocal - biology can impact behaviour, and behaviour, including cognition and emotions, impacts biology.

Question 6

ANCIENT GREECE NEUROSCIENCE

Answer 6

The Greek scholars of the fourth century BCE proposed that the brain was the organ of sensation. HIPPOCRATES correctly identified epilepsy as originating in the brain. GALEN, who made careful dissections of both animals and men, proposed that NATURAL SPIRITS - produced in the liver after consumption of food - are turned into VITAL SPIRITS in the heart and then into ANIMAL SPIRITS by the brain, which are then stored in the ventricles.

Question 7

DESCARTES

Answer 7

Descartes strongly supported mind-body DUALISM. He believed that the mind is neither physical nor accessible to study through the natural sciences. In contrast, modern neuroscience is based on MONISM - the mind is the result of activity in the brain.

Question 8

LUIGI GALVANI

Answer 8

He established electricity as the mode of communication used by the nervous system by observing movement in frogs’ amputated limbs after electrical stimulation.

Question 9

the BELL-MAGENDIE LAW

Answer 9

Bell and Francois Magendie demonstrated that information travels in one direction and that sensation and movement are controlled by separate pathways.

Question 10

CAMILLO GOLGI

Answer 10

He developed a technique to stain neurons and proposed the RETICULAR THEORY which viewed the nervous system as a single, vast, continuous network.
He shared a Nobel prize with his academic nemesis, Ramon y Cayal.

Question 11

RAMON Y CAYAL

Answer 11

Supporter of the NEURON DOCTRINE which viewed the nervous system as composed of an array of separate, independent cells. He used the technique invented by Golgi -with whom he shared a Nobel prize - to prove that the reticular theory was wrong.

Question 12

PHRENOLOGY

Answer 12

Phrenology was a pseudoscientific theory that maintained that the structure of people’s skulls could be correlated with their individual personality, characteristics and abilities. Bumps on the skull were believed to indicate that the underlying trait was present. Even though misguided, this theory moved us away from the metaphysical approach to the brain and laid the basis for modern neuroscience.

Question 13

PAUL BROCA

Answer 13

He correlated damages he observed in patients with their behavior and concluded that language functions (especially language production) were localised in the brain - which provided support to the theory of localisation of functions in the brain.

Question 14

FRITSCH and HITZIG

Answer 14

They described how electrically stimulating the cortex of a rabbit and a dog produced movement on the opposite side of the body, thus localising motor functions in the cortex - which provided support to the theory of localisation of functions in the brain.

Question 15

JACKSON

Answer 15

Often considered as the founder of modern neuroscience, he proposed that the nervous system was organised as a hierarchy, with simpler processing carried out by lower levels and more sophisticated processing carried out by higher levels, such as the cerebral cortex.

Question 16

SHERRINGTON

Answer 16

He coined the term synapse and won a Nobel prize.

Question 17

KATZ

Answer 17

He was awarded a Nobel prize for his work on chemical transmission at the synapse.

Question 18

ERIC KANDEL

Answer 18

He received the Nobel prize for his study on neurobiology of learning.

Question 19

MICROSCOPIC METHODS

Answer 19

Microscopic methods provide means for observing the structure, organisation, and connections of individual cells. The first investigation of nerve tissue under a microscope was conducted by Leeuwenhoek in 1674. The naked eye can perceive objects that are at least 0.2 mm in size; anything smaller requires both MAGNIFICATION and RESOLUTION, which are provided by LIGHT MICROSCOPES, ELECTRON MICROSCOPY and FLUORESCENT MICROSCOPY. Observation of brain tissue requires it to be thin enough to allow light to pass through; since brain tissue is fragile and watery, the tissue is either frozen, dehydrated or treated with formaldehyde.

Question 20

BEHAVIOURAL NEUROSCIENCE RESEARCH METHODS

Answer 20

Research methods include microscopic methods, imaging, recording, brain stimulation, lesion studies, biochemical methods, and genetic methods.

Question 21

IMAGING METHODS

Answer 21

Imaging methods include COMPUTERIZED TOMOGRAPHY (CT), POSITRON EMISSION TOMOGRAPHY (PET), MAGNETIC RESONANCE IMAGING (MRI), FUNCTIONAL MRI (fMRI), and DIFFUSION TENSOR IMAGIN (DTI).

Question 22

COMPUTERIZED TOMOGRAPHY (CT)

Answer 22

An imaging technique, CT uses modern computers to interpret data obtained through X-RAYS scans. This provides excellent structural information - even though x-rays do not do a very good job at imaging soft tissue - but provides no information regarding activity levels in the brain.

Question 23

POSITRON EMISSION TOMOGRAPHY (PET)

Answer 23

An imaging technique, PET scans do not provide good information about brain structure, but provide information about brain activity - PET allowed researchers to observe brain activity for the first time. In PET scans, a radioactive tracer is injected into the patient’s bloodstream, where it combines with a wide variety of molecules. Radiation released by decay of this tracer is detected by gamma cameras and fed to a computer, by which the data are reconstructed into images.

Question 24

MAGNETIC RESONANCE (MRI)

Answer 24

MRI is an imaging technique which uses powerful magnets to align HYDROGEN ATOMS within a magnetic field. Next, RADIO FREQUENCY PULSES are directed at the part of the body to be imaged, which forces hydrogen atoms to change alignment. When the pulses cease, the hydrogen atoms return to their natural alignment. As the atoms realign, they emit a pulse that is detected by the scanner. MRI is able to differentiate tissues based on how quickly they release energy after the pulses are turned off.

Question 25

FUNCTIONAL MAGNETIC RESONANCE (fMRI)

Answer 25

fMRI is an imaging technique that allows to correlate brain activity with the presentation of a stimulus, the presence of an emotional state, or the performance of a particular task in living humans. It takes advantage of the fact that active neurons require more OXYGEN than less active neurons, and that variations in blood flow to a particular area reflect this need. It relies on the fact that HEMOGLOBIN, the protein molecule that carries oxygen within the blood, has different magnetic properties when combined with oxygen or not.

Question 26

DIFFUSION TENSOR IMAGING

Answer 26

DTI is an imaging technique which uses the same machinery used for MRI and fMRI - it allows researchers to map connectivity in the brain by tracking the movement of water in the fiber pathways of the nervous system. DTI cannot, however, tell us about the direction of information flow.

Question 27

RECORDING TECHNIQUES

Answer 27

Recording methods take advantage of the fact that electrical and mag­netic activity can be recorded using electrodes either on the surface of the skull or brain or imbedded within the brain tissue itself. They include electroencephalograms (EEG), event related potentials (ERPS) recordings, magnetoencephalography (MEG), and single-cell recordings.

Question 28

ELECTROENCEPHALOGRAM (EEG)

Answer 28

This recording technique measures voltage fluctuations resulting from ionic currents within the neurons of the brain through several electrodes placed on the scalp. It has been extensively used to study different states of consciousness. It offers a wonderful temporal resolution fort it records electric fluctuations in real time, yet a poor spatial resolution for the placement of electrodes allows for poor spatial sensitivity.

Question 29

EVENT-RELATED POTENTIALS (ERPS) recording

Answer 29

This recording technique associate EEG with the presentation of some stimulus. The brain's electrical activity in response to a stimulus is quite small compared to its baseline activity, so responses to many presentations of a stimulus are averaged.

Question 30

MAGNETOENCELOGRAPHY

Answer 30

MEG is a recording technique that detects magnetic activity in the brain. Electrical signals in active neurons generate small magnetic fields - MEG measures and locates these fields. Since it does not provide any structural information, it is usually paired with fMRI. The major advantage of recording magnetism rather than electrical activity from the brain is that the skull bones and tissues allow magnetism to pass through without any reduction.

Question 31

SINGLE CELL RECORDINGS

Answer 31

Single-cell recordings provide neuroscientists with the ability to assess the rate of action potentials of single neurons using tiny microelectrodes. Living animals are usually studied using extracellular recordings, in which a microelec­trode is placed just outside a cell of interest.

Question 32

BRAIN STIMULATION TECHNIQUES

Answer 32

One way to study the localisation of function in the brain is by artificially stimulating an area and watching for resulting behavior. Brain stimulation techniques include deep brain stimulation, repeated transcranial magnetic stimulation (rTMS) and optogenetics.

Question 33

DEEP BRAIN STIMULATION

Answer 33

Electrical stimulation of the brain can be applied during neurosurgery - individual dif­ferences in function localisation frequently occur, and this technique allows surgeon to identify the functions of specific areas before the intervention. Most neurosurgery is conducted under local, rather than general, anaesthesia, for the tissues of the brain lack nociceptors.

Question 34

REPEATED TRANSCRANIAL MAGNETIC STIMULATION (rTMS)

Answer 34

Magnetic stimulation of the brain is obtained through a coil of wire which is placed on the scalp. The current through the wire generates a magnetic field - which passes freely through the skull bones to reach the brain, producing weak electrical cur­rents on its surface. This current can, in turn, either depolarise or hyperpolarize neurons at a specific site. Even though the stimulated superficial area of the brain can be excited or inactivated temporarily, deeper structures cannot be affected by this technique.

Question 35

OPTOGENETICS

Answer 35

Optogenetics is a stimulation technique that allows researchers to stimulate single neurons. It involves the use of molecules genetically inserted into specific neurons in the brain, which then allows neural function to be modified by light. It begins with the identification of light-sensitive proteins. Genetic material - modified to produce the protein in only one specific type of neural cell - is first inserted into a virus which is then injected in the animal's brain. Light stimulation is provided through optical fibers attached to the skull or surgically implanted.

Question 36

LESION STUDIES

Answer 36

A lesion is an injury to neural tissue that can be either naturally occurring (subject of clinical observation) or delib­erately produced (in animal models) Either way, the primary purpose of lesion analysis is to assess the probable function of an area by comparing behaviour prior to the lesion with behavior occurring after the lesion. Deliberate lesions can be divided in HEAT lesions and CHEMICAL lesions. Heat lesions are produced by means of surgically inserted microelectrodes, insulated except for the very tip - heat is generated at the tip, killing the surrounding cells. Chemical lesions are produced by applying neurotoxins, chemicals that specifically kill neurons, into the area of interest through a surgically implanted micropipette. They have the advantage of harming only the cell bodies of neurons while leaving the nerve fibers traveling through the area intact.

Question 37

BIOCHEMICAL METHODS - MICRODIALYSIS

Answer 37

Microdialysis is the analysis of extracellular fluid extracted from a specific brain area through an implanted micropipette. It is used to identify the chemicals that naturally exist in a particular location in the brain. Drug administration is useful if a researcher wants to investigate the effects of chemical stimulation in the brain - different methods (eating, inhaling, injecting the drug) result into the delivery of very different concentrations of a drug into the blood supply within a given period.

Question 38

GENETIC METHODS

Answer 38

Genetic methods are used to identify the interactions between hereditary and environ­mental variables on a particular behavior - they include twin studies, adoption studies and genetic screens.

Question 39

TWIN STUDIES

Answer 39

Twin studies compare identical and fraternal twins and provide some insight into the relative contributions of heredity and environment. Monozygotic twins share an identical set of genes, whereas fraternal twins ah about 50 percent of their genes in common, just like any other pair of non-identical siblings. The heritability of a trait or condition is often stated in the form of a CONCORDANCE RATE which, given the existence of a trait in one identical twin, estimates the probability of the other twin having the trait. An important methodological limit of twin studies is that most identical twins not only share identical genes, but also identical environments.

Question 40

ADOPTION STUDIES

Answer 40

Adoption studies compare the similarities of adopted individuals to their adoptive and biological parents to investigate the influence of heredity and environment. Adoption studies of twins adopted by different families provide information about individuals who share identical genes and different environments.

Question 41

GENETIC SCREENS

Answer 41

Genetic screens investigate the relationship between genes and the development of phenotypic traits, and can be divided in FORWARD and REVERSE genetic screens. Forward genetic screens are used to identify genes that seem important in the development of a phenotype. Researchers locate individuals with the phenotypical trait of interest and then attempt to identify the genes necessary for exhibiting the trait. This process usually considers thousands of genes at the same time, or in some cases, the entire genome, a procedure known as a GENOME-WIDE ASSOCIATION STUDY. In reverse genetic screens, a gene of interest is manipulated and the results of the manipulation on the phenotype are observed. Knockout genes - engineered, defective versions of genes - are inserted into the chromosomes of animals, where they take the place of the normal genes but fail to produce proteins.

Question 42

ANIMAL SUBJECTS GUIDELINES

Answer 42

Ethical guidelines for research with animal subjects follow the 3R PRINCIPLE - reduce, refine, and replace. REDUCE the number of animals used; REFINE methods that minimise the pain, suffering, distress or lasting harm that may be experienced by research animals, and which improve their welfare; REPLACE animal subjects if other options are available. Full replacement consists of avoiding use of research animals altogether, whereas partial replacement employs animal subjects that, based on current scientific thinking, are not considered capable of experiencing suffering.