What are the main neuroscience research areas? Many fields of study are currently in full development, for example:

– The development of the human brain in the baby and the child,

– The processing of information that results in coordinated bodily responses,

– Mental states that are all controlled and regulated by the brain, for which considerable progress has been made in recent years,

– Memory and learning related to cognitive neuroscience.

– and also the brain in the conquest of space.

All this is accompanied by extraordinary progress in the field applied to medicine.

More deeply in the lines that follow we will study some main neuroscience research areas.

1 – Neuroscience Research on Genetic Factors

Neuroscience research

Neuroscience research

In classical genetics, we associate a gene with a factor (Mendelian inheritance). In the year 2000, the human genome was fully sequenced but it is still very far from knowing the role of all genes described. The genome has only 30,000 genes in humans (and the mouse), which is much less than expected, there are indeed very large “empty” parts.

Genetics is not only a science; it affects our way of life because it questions our very nature, if we have cancer it is not because of food or a carcinogenic product, but because we have the cancer gene! We will think “genetics” more and more. We can see the special issue of La Recherche (July-August 1998): “Are we driven by our genes? ” And Newsweek Magazine did not hesitate to make a headline recently on the imperialism of genetics.

Some examples of this research are given.

• Disorders of Mental Development and Language

Oligophrenias are known as developmental delays or mental retardation.

The fragile chromosome X syndrome corresponds to a more or less strong intellectual level; it is linked to an abnormality of a gene carried by the X chromosome, which explains why it is more common in boys. We are now talking about MRLX (Mental Retardation Linked to the X chromosome). At least 60 disease entities have been identified. They are known to be related to neuronal migration problems during brain development. Prenatal diagnosis is difficult because the expression of the mutation is variable.

We also know the very rare cases of a mental retardation associated with an extraordinary talent for the conversation: it is the Williams syndrome. Children with this condition have an intelligence quotient of 50 (unable to find their way, tie their laces, difficulty reading, writing, adding, etc.). On the other hand, they possess remarkable linguistic abilities, a good recognition of the faces, they are good musicians (but incapable of deciphering music!) and very sociable. This is a rare disorder (1/20,000). It corresponds to the absence of several genes of chromosome 7. There are numerous modifications in the brain, in particular, an absence of specialization of the hemispheres for language.

Two gene-bearing areas have been identified recently on chromosome 7 that cause language disorders and possibly autism.

• Neuroscience Research on Neurodegenerative Diseases

Huntington’s Chorea

Huntington’s chorea or Saint-Guy dance affects around 6,000 people in France. It was described in Venezuela in 1884. It begins with emotional instability, tics on the face, clumsiness, then thrills and bursts of the entire body to result in profound dementia. She declares herself between 30 and 45 years old. We know that it corresponds to a degeneration of the central gray nuclei (especially the caudate nucleus and putamen) which regulate the movements, hence the motor abnormalities. Inhibitory GABA neurons are involved. It is a dominantly inherited disease that is fatal in about fifteen years. By studying the genetic inheritance of consanguineous families, we found a genetic marker that is a gene mutation of a protein called huntingtin (which then contains an excess of glutamic acid). There is the formation of protein clusters that cause the death of neurons of the caudate nucleus. This mutation is not specific because it is found for 5 other neurodegenerative diseases nearby. This makes it possible to identify, in the families at risk, the people who will be reached towards the quarantine of the first symptoms of the disease.

Parkinson Disease

This is a neurodegenerative condition described in 1817 by an English doctor. It affects the dopamine neurons of the brain’s dark substance that contains projections on the basal ganglia. It is characterized by tremors when 70% of the neurons are destroyed. The problem is trying to protect the remaining third. There is a hereditary form whose gene was discovered in 1996 in an Italian-American family where the disease occurs with a very high frequency: 10% of patients (out of 600 people studied in Italy and the USA). The gene is dominant and is on chromosome 4. There is an animal model obtained by injection into the brain of rats of a dopamine specific toxicant (a neurotransmitter involved in this disease …).  We have just discovered on rats that pesticides could induce symptoms similar to those of Parkinson’s disease.

Alzheimer’s Disease

Alzheimer’s disease (senile dementia: the progressive decline of intellectual functions begins with the loss of memory of recent events). An “Apo E4” gene has been identified that predisposes the disease to otherwise rare early forms. The Americans will put on the market over the counter a kit to diagnose this gene.

Described in 1906 by Alois Alzheimer, a German psychiatrist (1864 -1917)  – on a patient Auguste D., who suffered from progressive deterioration of cognition, hallucinations and mental confusion. His brain that was found in Munich confirms the neurological origin of the disease. Recent data show the appearance of senile lesions or plaques first in the limbic system (memory disorders) and then in the neocortex (disorders of the higher functions) as well as degeneration of neurons that are invaded by neurofibrils and form plaques senile.

Neuroscience research is currently being conducted on a vaccine against Alzheimer’s disease from work on transgenic mice having incorporated the beta-amyloid protein gene responsible for the appearance of senile plaques.

Friedreich’s Ataxia

Friedreich’s ataxia is another hereditary, recessive degenerative disease, which is, therefore, rarer (200 families in France). There is degeneration of neurons, cardiac disorders and death occur in children between 5 and 15 years. The responsible gene has been identified, it is on chromosome 9, and is responsible for the mutation of a protein, frataxin.

Spongiform Encephalopathies

Spongiform encephalopathies (bovine BSE, Creutzfeldt-Jakob disease in humans, kuru in New Guinea, scrapie in sheep) are deadly diseases of brain degeneration. The brain is dotted with holes, where brain tissue and neurons have been destroyed. This disease is linked to genetic bases but to a very resistant and poorly known infectious agent prion.

• Mental Illnesses

We want to look everywhere from genetic origins to mental illnesses.

Manic-depressive psychosis is a serious mental illness. In 1987, a gene on chromosome 11 that affects the metabolism of tyrosine hydroxylase (1st stage of catecholamine metabolism) was found in North American Amish (where this disease is common, probably because of consanguinity). In fact, later studies have not confirmed the link between the disease and the gene.

It seems that susceptibility genes for schizophrenia are found on chromosomes 6,  8 and 22 (deletion = loss of a fragment of chromosome 22 in … 2% … cases of schizophrenia!). Until recently, in September 1998, a team of biostatisticians from the University of Baltimore, Maryland, isolated a small region of chromosome 13 that may harbor schizophrenia susceptibility genes.

However, currently the most common psychiatric diseases escape DNA analysis (See the special issue of July 1998, Research in Neuroscience), but for how long?

• Genetics of Intelligence

This is an immense problem, every day various researchers try to show that there is a genetic component more or less important in the intelligence. We will not tackle this debate here, which is strongly biased by ideological prejudices.

• Miscellaneous

Stuttering is thought to have predisposing factors and triggers.

At low doses, radioactivity leads to many changes in the gene pool, as in Chernobyl for “liquidators” who have entered the contaminated area without protection. We can expect a resurgence of mutations in the coming years in these people.

2 – Neuroscience Research on Endocrinology of Behavior

The search for hormonal determinism of behavior is difficult. In the simplest cases, the presence of a particular hormonal state allows the expression of a given behavior, for example, sexual activity. This is the case for most animals that are directly dependent on their hormonal status for reproduction.

The emancipation with respect to the sex hormones is not the specificity of the man, since already in the monkeys the sexuality is present independently of their sexual cycle. In many animals, factors of experience appear […]. There are also complex interactions between external stimuli and endocrine mechanisms. Lehrman (USA) on the turtledove and Hinde (England) on the canary have first looked for these interactions.

The techniques used in this field are the classic techniques of endocrinology: castrations, injections of hormones or antihormones, implantations of glands, …

3 – Neuroscience Research on Neurophysiology of Behaviors (Neuroethology) and Neurochemistry

There is a multitude of works in this area; they use the classical techniques of neurophysiology and electrophysiology.

At the behavioral level (Neuroethology) we have been able to dissect some simple models such as flight in fish or cricket singing, but these models are rare because the behavior cannot be reduced to activation more often than not of a single neuron system.

Stereotaxis

Stereotaxis is a technique that allows the implantation of electrodes in specific areas of the brain through a micromanipulation device. These areas can be stimulated, destroyed and even injected with micro amounts of substances.

Thus, Hess from 1932 introduced stimulation electrodes into the cat’s hypothalamus. It triggers zones of neurovegetative reactions, movements, emotions (fear, anger), flight, and sleep. The hypothalamus is a very important crossroads in controlling the main behaviors. Delgado made himself famous with radio transmitters commanding electrodes implanted into the amygdala of fighting bulls that become sweet as lambs.

Modern microdialysis techniques use porous membranes placed at the end of microcannulae, which let pass molecules such as mediators which allows them to be assayed in vivo on active animals.

Neurochemistry

Neurochemistry is currently experiencing considerable growth. Many neurotransmitters have been discovered, even though their number does not seem very large (about 50 at present). It is possible to draw up a real cartography of the different neuronal systems thanks to their neurotransmitters (by immunofluorescence or radioactivity), to destroy a system thanks to specific neurotoxic mediators. The electrolytic lesions in the brain have given way to specific destructions of localized neurochemical systems.

Molecular Neurobiology

These discoveries lead directly to molecular neurobiology: analysis of the receptors and genes of these receptors that can be cloned. Five types of dopamine receptors (Dopa) have thus been identified; these receptors are known only by their different genes and their pharmacological properties. In the case of serotonin, there are 7 classes (5HT1 to 5HT7 with 14 different types! – figure probably exceeded). Finally, Knock Out (KO) mutants are known in which receptor genes are inactivated. Most of the time these mutants are not viable, but mutated mice without a dopamine D2 receptor were made, these mice have problems of motor coordination and therefore of locomotion.

4 – Functional Exploration of the Brain

What kind of neuroscience research we have in this area? The classical functional exploration was EEG or electroencephalography, the recording of electrical potentials on the surface of the skull. The brain has slow spontaneous rhythms of a few Hertz (Hz) to a few tens of Hz.

The electrical activity related to the various tasks of the brain is superimposed on these rhythms and is therefore embedded in a background noise so uninformative. More recently, with the progress of computer science, it has been possible to extract from the background noise the signals specific to a task, they have been called evoked potentials (auditory, visual, etc.). The electrical activity of certain areas of the brain is also recorded with electrodes implanted for therapeutic purposes, for example in epileptics. It has recently been discovered that the brain has a chaotic activity in normal times, with short synchronous of 30 to 80 Hertz. An epileptic fit is a generalized synchronization, which can be expected with the electrodes. It is possible to envisage a treatment device by electrostimulation of drug-resistant forms (350,000 people suffer from epilepsy in France).

In recent years a real revolution has emerged, with new non-invasive techniques that allow observing the active brain (See Special Research No. 289 “Seeing in the brain”, July-August 1996):

– the X-Ray or  X-Ray Scanner:

We make “cuts” of the brain, which allows us to see tumors or cerebrovascular accidents.

– PET, Positron Emission Tomography (Or Positron)

Is a detector of micro radioactivity (from 1981). Oxygen {15 O} * or {11 C} * are injected and emit positrons (positively charged particles, the inverse of the electron). The areas where these particles will be metabolized can be located, meaning that the areas in question are active at the time of testing. We can see the brain in action and locate the areas of cognitive functions or any other activity.

MRI, Magnetic Resonance Imaging

Uses the property of hydrogen to behave like a small magnet, so we will detect micro-variations of magnetism in the brain.

PET has made it possible to film live the various areas of the brain involved in the emotions.

Example of the Cerebral Lateralisation:

Neuroscience research shows that our brain is not symmetrical: sensory and motor areas project into areas each corresponding to one half of the body. The left hemisphere is specialized in language and speech (Broca and Wernicke’s areas), it is the rational hemisphere (for example, the exact calculation of musical analysis) but also that of laughter and happy thoughts. ; the right hemisphere in the space, the forms, the emotions, the perceptions (music, tact, …), it is the artistic hemisphere. The intuitions emitted by the Right Hemisphere (RH) of the brain and the more rational productions of the LH (Left Hemisphere) are complementary. “It is from the balance between one and the other that our vision of the world is born and affirmed” (J.-M. Pelt, Plants, and transgenic foods, Fayard 1998, 167). Every being is thus lateralized, one can recognize the laterality by the hand of spontaneous throwing. We know that left-handers have a later puberty, a shorter life expectancy than right-handers and yet we still find 10% left-handed in all cultures and this rate has not changed in 50 centuries.

Japanese Writing Systems

The Japanese use two writing systems: the alphabetic kana and the ideographic kanji (on the Chinese model). The left parieto-occipital cortical lesions suppress the kana reading but the kanji is preserved, while right temporal lesions suppress the kanji and not the other system. All these data were verified by MRI.

Jacques Mehler and Emmanuel Depoux

Jacques Mehler and Emmanuel Depoux “To be born human” (O. Jacob 1990): in the newborn RH (right hemisphere) is from the start specialized in the recognition of the forms and faces, the LH (left hemisphere) in the language. Cerebral specialization already exists at birth.

Sperry

Patients followed by Sperry (1975) had a section of the corpus callosum to treat epileptic seizures. These patients had a normal life in appearance, but their vision and prehension were split as evidenced by the famous test of the key. If the patient is presented with the keyword on a screen in his left visual field, he will say he sees nothing.

If he is told to choose among several objects out of his sight with his left hand he will take the key without being able to say what is the object he has chosen! The explanation is that the subject reads the keyword with his RH, but as the center of the language is in the LH he cannot say what he saw. On the other hand, the gripping of the left hand depends on its RH which has the “key” information and it will be able to make the right choice with its tactile recognition. In these particular conditions, the two hemispheres operate autonomously, which is why these patients have been called “slipt-brain” or split-brain.

Another Neuroscience Research

Another neuroscience research shows their problems: if we present a scary film to the patient’s left eye, he will be afraid but will be unable to describe the scene; the same scene presented to the right eye will not produce any emotional effect but he can describe it. It is quite obvious that, in the usual situations, the two hemispheres work in harmony and constantly inform each other. All of these experimental data were confirmed by MRI or PET.

Mathematical calculation (for example, making an addition head) would involve the left frontal lobe which houses the center of the language, whereas mathematical intuition (an approximation of a result) would rather involve the parietal lobes responsible for visual representations and space according to the works of Stanislas Dehaene. For this author, our mathematical competence depends on the architecture of our brain, but nothing indicates the existence of a bump of maths (see, the bump of maths, S. Dehaene, O. Jacob ed., 1997). However, neurobiologists have just re-examined Einstein’s brain and found an increase in the volume of the parietal lobes!

It also seems that we are getting closer to a better understanding of the functioning of the brain of dyslexics. One wonders if they would not have a bad lateralization of the language area but especially a defect in the cerebellum.

5 – Does the Brain Have a Sex?

What kind of neuroscience research we have on this subject?

Since the beginning of the 70s, many works have been done on possible differences in the organization of the brain between men and women. It is known that performance at events varies statistically according to sex. For example, in space recognition tests, men are generally better, whereas the reverse is true for image matching tests.

In men the lateralization of the brain would be more decided: the HG would work alone in speech or listening activity, while in women the HD would work a little too at the same time.

It would be the same during a drawing activity or the examination of a map (spatial faculties involving RH). Lateralization would be more extensive in men than in women. These works have been the subject of intense controversy because we wanted to explain the professional success of men, the greatest scientists (language, mathematics …) and the greatest artists (forms, space…). These data are obviously excessive, but the difference in brain function is confirmed by the MRI and PET data.

The sexualization of the brain at the level of the hypothalamus is also now well known, it has been discovered that one of the nuclei (in the group of interstitial nuclei) is larger in the male, including human.

6 – Computer Models of Brain Function

The neuron was compared to a calculator, for example, Eccles in the 1950s considered dendrites as input and exit axon. Neural calculators have been designed from neural networks. In reality, the brain/computer analogy is false: the electrical impulse moves in the microprocessor at the speed of light while the nerve impulse moves at variable speeds depending on the types of neurons from 50 to 100m / s. The microprocessor connections are permanently fixed while the neural network is very malleable, etc.

7 – Biology of Consciousness


Neuroscience research shows the biology of consciousness also. Consciousness refers to mental states in a state of awakening but also of dreams. For a long time, it has been considered that material physical reality is distinct from spiritual reality. It was the dualism of Descartes and Galileo in the 16-17th centuries. For Descartes, the seat of the soul was the pineal gland now called epiphysis (The Treatise of Man, 1864). Neurobiologists like Eccles (Nobel Prize) are still dualistic (See the book Eccles “How consciousness controls the brain?”, Fayard 1997).

Jean Pierre Changeux

Jean Pierre Changeux in his book Neuronal Man(1983, published in pocket) is resolutely monistic reductionist, for him, a brain is a machine, all the signals propagated by the nervous system are integrally reducible to physicochemical mechanisms and nothing else. It is written “Human behavior seems to escape determinism simply because we do not know its internal mechanisms.” ; “All mental activity, whatever it may be, reflection or decision, emotion or feeling, self-consciousness … is determined by all the nerve impulses circulating in defined sets of nerve cells, in response or not to external signals. I will go even further and say that she is only that.” This is the theory of psychophysiologist identity.

Francis Crick

With Francis Crick (The Astonishing Hypothesis: The Scientific Search for the Soul, Plon, 1995), Gerald Edelman (Biology of Consciousness, 1994), Israel Rosenfield (Consciousness, a Self-Biology, Eshel Edition), Antonio Damasio (The error of Descartes, O. Jacob ed., 1995) all these researchers have the ambition to discover the biological bases of the conscience.

Changeux writes recently that every object is seen, every mental state results in the activation of a network and the formation of a mental image. This image is consolidated by its repeated use. Antonio Damasio, a specialist in medical imaging, comes to the same conclusions in his book “The same feeling of self: body, emotion, consciousness” (O. Jacob edition, 1999) and he writes in Pour La Science [For The Science]: “From here 2050 our knowledge of biological phenomena will have progressed enough for us to be rid of the traditional separations between the body and the brain, the body, and the mind, or even the brain and the mind “(PLS [FTS], January 2000, 81) .

Jean Delacour

Neuroscience research and MRI techniques begin to understand how some people develop exceptional artistic or scientific abilities. We are moving quickly towards a map of brain and thought. See “Brain and Consciousness” by Jean Delacour (DeBoeck University 2001).

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