Authors, such as Dewsbury (1991), define biopsychology as “the scientific study of the biology of behavior”. Field also known as psychobiology. However, other authors prefer the term biopsychology because “it indicates a biological approach to the study of psychology rather than a psychological approach to the study of biology”.
Thanks to scientific advances, research methods in biopsychology have undergone a huge revolution in recent years. How many old researchers thought they would come to observe the functioning of the brain live? Although the methods of research in biopsychology are many, emphasis will be placed on those who study what happens in the brain under certain conditions.
“Man is the most mysterious and the most disconcerting of objects discovered by science.”
Methods of stimulation and visualization of the human brain
Observing and recording brain activity in vivo is a milestone achieved thanks to the different techniques that have been developed throughout the 20th century. Techniques that, without a doubt, have supposed a great advance in the knowledge of our most unknown organ.
This technique consists in injecting in one of the compartments of the body a substance that absorbs X-rays. In this way, a contrast is observed between the compartment and the surrounding tissue.
Cerebral angiography is a contrast X-ray technique. To do this, a dull radio dye is introduced into a cerebral artery; The objective will be to observe the cerebral circulatory system while performing an X-ray. This technique is useful to locate vascular lesions and brain tumors.
Computed tomography (CT) scan
Through the CT scan, the brain structure can be visualized. During the test, the patient lies in the center of a large cylinder. While the patient is lying down, an X-ray tube and a receiver (placed diametrically opposite) take a large number of photographs separately. This occurs while transmitter and receiver revolve around the head of the subject.
The information of all the photographs is combined thanks to a computer. This unification allows exploration through a horizontal plane of the brain. Normally this exploration can be done through eight or nine horizontal brain sections (cuts). Once all the explorations are combined, a three-dimensional representation of the brain is achieved.
Nuclear magnetic resonance (NMR)
The NMR facilitates high resolution images thanks to the different waves that emit hydrogen atoms when they are activated by radiofrequency waves in a magnetic field. It provides high spatial resolution and produces images in three dimensions.
Positron emission tomography (PET) scan
The PET scan provides images of brain activity rather than the structure itself. To obtain these images, radioactive 2-deoxyglucose (2-DG) is injected into the carotid artery of the subject. The active neurons rapidly absorb 2-DG and as it is not metabolized by them, 2-DG accumulates until it gradually degrades. In this way, it is observed which neurons are active at a certain moment during different activities.
Functional magnetic resonance (fMRI)
The fMRI offers images of the increase of the oxygen supply in blood to the regions of the encephalon. Thanks to this, he enjoys great success in measuring brain activity. In comparison with the PET it has four advantages:
- The subject is not injected with anything.
- It provides both functional and structural information.
- It offers a better spatial resolution.
- It can provide three-dimensional images of the entire brain.
Measures the changes in the magnetic fields that occur on the surface of the scalp. These changes are produced by variations in the patterns that underlie neuronal activity.
Transcranial magnetic stimulation (TMS)
Walsh and Rothwell (2000) emphasize that the EMT “consists in a technique to alter the activity of an area of the cortex, creating a magnetic field under a bonina that is situated above the skull”. What the EMT does is temporarily “turn off” a part of the brain while evaluating the effect of black out on behavior and cognition.
The harmful methods are those that destroy some brain area to check what effect it has on the behavior.
- Aspiration injuries. This method is usually used to cause an injury in some area of the cortical tissue that is visible to the naked eye. The tissue is extracted through a thin-tipped glass pipette.
- Radiofrequency injuries. These are small subcortical lesions. For this, an electrode is used that channels a high frequency current through the tissue that is to be destroyed.
The size and shape of the lesion depends on three factors:
- Intensity of the current.
- Configuration of the tip of the electrode.
- Cuts with scalpel. Consists is to section the area of the brain that you want to destroy.
- Blocking by cold. This technique, although usually included in the lesive, is reversible.
Instead of destroying some structure, an area is cooled to keep it above the freezing point. The neurons stop emitting signals, so that the functioning of the cooled brain region is blocked. In this way, it can be observed which alterations in behavior provoke the intervened zones. Once the temperature returns to normal, normal brain function is restored.
Another method of research in biopsychology is through electrical stimulation. A structure of the nervous system is stimulated electrically to obtain data on its functioning. Usually a bipolar electrode is used.
This stimulation triggers the neurons and alters their behavior. In general, it usually causes the opposite effect of injuries. If, for example, an injury is achieved by someone drastically reducing their sleep, stimulating them can lead to disproportionate sleep behavior.
Harmful methods with electrophysiological recording
Intracellular record of a unit. This technique is carried out through the introduction of a microelectrode inside a neuron. It provides a record of the graduated fluctuations of the membrane potential of the same.
- Extracellular record of a unit. A microelectrode is placed in the extracellular fluid surrounding the neuron through which the neuron shots are collected. However, it does not collect information on membrane potency.
- Registration of multiple units. In this case the tip of the electrode is larger than that of a microelectrode, so it picks up signals from many neurons at the same time. The action potentials that are detected are led to a circuit that integrates them and adds them up.
- Invasive EEG registration. In this case, the electrodes are implanted. When looking for records of cortical EEG signals, stainless steel “nut” cranial electrodes are used. For sub-tic signals, cable electrodes implanted through stereotactic surgery are usually used.
“Anthropology, biology, physiology, psychology, have assembled true mountains of materials to erect before man, in all its amplitude, the tasks of his own corporal and spiritual perfection and of his further development”.
Research methods in biopsychology: a long way ahead
Throughout the article, the most representative research methods in biopsychology have been treated. However, mention that there are other research methods in biopsychology that studies other areas of the body. Among them we can find: the measurement of muscle tension, the registration of eye movements, the conductivity of the skin or cardiovascular activity.
Without a doubt, the advance in methods of research in biopsychology in recent years has been spectacular, but not for that reason. That is to say, in a few years new techniques may emerge that we can not even imagine right now. All this will contribute to the evolution of the neurosciences that, in turn, will help to improve the quality of life of so many people affected by some type of neuronal alteration.