2.1 Electroencephalography (EEG)
Electroencephalography, or EEG for short, is a bio signaling technique that records electrical potential in brain cortex activities in real time to represent brain status [14]. EEG is one of many electrobiological measuring techniques, including ECG (Electrocardiography) for pulse measurement, EMG (Electromyography) for muscle contraction measurement, EOG (Electro-Optigraphy) for eye-dipole field measurement, and many other imaging methods based on bodily concepts, such as MRI (Magnetic Resonance Imaging) and CT-Scan (Computer Tomography) [14]. EEG is a type of electrical impulses measured by a conductor or meta on the scalp surface of the head.
The neutron summation of electrical events is included in the EEG [14]. Neutrons are excitable cells with unique intrinsic electrical properties that generate both electrical and magnetic fields when they interact. Electrodes are used to map these fields at a short distance from the cortical surface. The human brain is divided into three parts from an anatomical standpoint: the cerebrum, cerebellum, and brain stem. The brain is the most anterior and primary component of the human body; its surface is known as the cerebral cortex, and it is made up of the left and right hemispheres.
The electrical impulses of the brain are tracked by EEG electrodes [15]. The cerebrum is an essential component of the central nervous system (CNS), and it is responsible for feeling, complex analysis, emotion, and other functions [15]. The brain stem oversees heartbeat, hormone synthesis, and respiratory rate, while the cerebellum maintains equilibrium and voluntary muscle activity [15]. The different electrode scalp positions are defined using two globally accepted nomenclatures.
One, The naming scheme of 10-20 [16]: The 10-20 name was derived from the spacing of electrodes from each other with either 10% to 20% front-to-back electrode spacing or 10% to 20% left-to-right electrode spacing; the 10-20 name was derived from the spacing of electrodes with either 10% to 20% front-to-back electrode spacing or 10% to 20% left-to-right electrode spacing. Each electrode is designated by an alphabet and a number. F stands for Frontal Cortex, T for Temporal Cortex, and C for Central Cortex (It has no real purpose other than to identify). Similarly, P stands for the parietal region, and O stands for the occipital region. Positions on the left hemisphere of the head are denoted by odd numbers, while positions on the right side are denoted by even numbers.
Second, The Modified Combinatorial Nomenclature [16] consists of the following terms: When more electrodes were needed for more reliable recordings, the need for this arose. The intermediate points in the 10-20 naming scheme are used in this system to link the different electrode locations. FC denotes the point halfway between F and C. T7, T8, P7, P8 stands for T3, T4, T5, T6 in the 10 - 20 modified combinatorial nomenclature; TP stands for the intermediate position between T and P; CP stands for the intermediate location between C and P; PO stands for the intermediate location between P and O; T7, T8, P7, P8 stands for T3, T4, T5, T6 in the 10 - 20 modified combinatorial nomenclature.
EEG is one of the most difficult bio signals to interpret because of its low amplitude, which ranges from 0.5V to 100V. It does, however, have a major speed advantage since complex brain patterns can be recorded in real time. Multiple neutron potential aggregation is what EEG waves are made up of. Human behavior is depicted by these frequency bands. The gamma waves, which display alertness, wakefulness, and anxiety, have a lower amplitude than the high-frequency beta waves. The amplitude of an alpha wave is lower than that of a beta wave, indicating that the individual is awake, calm, and learning. Theta waves signify rapid eye movement sleep and mindfulness, while delta waves are the slowest and have the largest amplitude, indicating N.
2.2 EEG Waves and Types
Delta: Delta is equal to or less than 3 Hz. In terms of amplitude, it happens to be the strongest and slowest waves. As the dominant rhythm in infants up to one year old, as well as in sleep stages 3 and 4, it is completely normal. It may happen in a focal way with subcortical lesions and more often with diffuse lesions, hydrocephalus metabolic encephalopathy, or deep midline lesions. It is typically most noticeable frontally in adults (for example, FIRDA - Frontal Intermittent Rhythmic Delta) and then later in children (for example, OIRDA - Intermittent Rhythmic Delta Occipital) [17].
Theta: Theta has a frequency of 3.5 to 7.5 Hz and is considered "slow." It is completely common in children under the age of 13 while they are sleeping, but it is dangerous in awake adults. It is a symptom of focal sub-cortical lesions; diseases such as metabolic Encephalitic or certain forms of Hydrocephalus can also be seen in a wide range of people [17].
Alpha has a frequency range of 7.5 to 13 Hz. Is normally better seen in the back of the head on either side, with the dominant side's amplitude being higher. When the eyes are closed and comfortable, it appears. When some mechanism opens the eyes or warns, it vanishes. It's the most common rhythm in healthy adults who are comfortable. It is present for the majority of one's life after the thirteenth year [17].
Beta: Beta has 14 and higher Hz frequencies. Both sides are distributed symmetrically and is most obvious on the front. Sedative - hypnotic drugs, especially benzodiazepines and barbiturates, accentuate it. In neuronal damage locations, it may be missing or reduced. It is generally regarded as a steady rhythm. It is the dominant for patients that are alert and have their eyes open [17]
2.3 EEG Recording
Electrodes are small metal disks that are normally made of stainless steel and protected with a silver chloride coating. They are put on the scalp in specific places. These positions are specified by the International 10-20 framework [16]. A letter post with a number is fixed to each electrode spot. The alphabet is related to the brain (For Example, F- Frontal lobe). The right side of the head is represented by even numerals, while the left side is represented by odd numerals. The electrodes of the disks are added to the electrode gel and applied to the subject's scalp using EEG cables. A cap with electrodes encapsulated in it is used in many technologies to enable recording when electrode arrays are present.
Electrode Gel: Electrode gel serves as a malleable extension of the electrode, preventing objects from being generated by the electrode cables' movement. It optimizes direct communication and allows for the recording of low resistance. The electrolytic gel is placed in each cavity until a small amount of the hole in the mount is released. With a small amount of downward pressure, the syringe is easily rocked back and forth.
Electrode Positioning: We're adapting the 10/20 electrode positioning system from around the world. It's been very popular to provide a standardized positioning of electrodes for a classic EEG since the 10-20 arrangement was adopted. The distance between Nasion Inion and other fixed points in percentages in the 10-20 range [16] is the essence of this scheme. Fp, C, P, O, and T are the names given to these points. The midline electrodes are indicated by a subscript ‘z'. Points to the left as a subscription are represented by odd numerals, while points to the right are represented by evens.
EEG Montages: Montages are rational and orderly channel arrangements [16]. A referential or bi-polar installation may be used to observe the EEG. Each channel in bipolar has a reference electrode [16]. Both channels would have a shared reference thanks to the referential assembly.
Artifacts: Recognizing and eliminating artifacts is a big challenge in EEG tracking [17]. There are subject-related artifacts (for example, eye or muscle movements) as well as technical artifacts (for example, static caused by cable movements) [17] that must be handled differently. There are several resources that can be used to locate the objects. Measurements of FEMG and impedance, for example, may be used to detect a polluted signal [17]. Another source of interference can be discovered by examining different variables on a monitor. The electrodes used in EEG recording do not discriminate against the electrical signals they receive [17].
An artifact is any documented behavior that is not of cerebral origin. It is divided into physiological activity (activity produced by the subject other than the brain) and extra physiological objects (equipment such as electrodes and environment) that originate from outside the body.
Eye movement: With a cornea and a retina (+ and - poles, respectively), the eyeball serves as a dipole [16]. A broad amplitude alternating current field is produced as the globe rotates around its axis, which can be detected by any of the near-eye electrodes. The cornea (+ Pole) moves closer to the two frontopolar electrodes while the eye is blinking [17].
2.4 Role of Eye Blinks
Blinking is one of several identified human physiological functions [18]. It is best described as the involuntary rapid closing of the eyelids. It has also been discovered to play a key role in high-order cognitive efficiency, in addition to its protection feature of shielding the eye from potentially harmful external contamination and drying. The Central Nervous System (CNS) is said to be in charge of controlling eye blinking [18], with dopamine being the main neurotransmitter involved, especially in the Globus pallidus region. In terms of higher order functioning, blinking and its frequency have also been linked to consciousness, intelligence, and overall day-to-day functioning.
In a clinical research study conducted by SA Chermahini and B Hommel, it was discovered that eye blink rate (EBR) was negatively correlated with convergent thought ('Remote Association Task') and had a positive relationship with intelligence [19]. Although they discovered that divergent thinking was strongly linked to average EBR [19], they also discovered that divergent thinking was strongly linked to average EBR.
2.5 Addictions
Addiction is described as a state of compulsive desire [3]. It continues to relapse after therapy and other efforts to control drug use. Addiction is the malignant abdication of neuronal pathways that usually serve to reward, according to medical and research facilities [3].
Almost all addictions cause the neurotransmitter dopamine to be released in excess and at irregular levels, affecting the Limbic System of the brain (Rewarding). Chronic opioid and alcohol users have destroyed receptors in the brain for dopamine and other main neurotransmitters, which must be restored during addiction recovery. Furthermore, each narcotic drug has a distinct negative impact on the brain. How can one assess the brain's addiction to internet media? Behavioral addictions, including opioid addictions, disrupt and pervert reward processes in the brain. Impulsivity modulation is also linked to behavioral addictions. Changes in prefrontal cortex activation and frontal striatal pathway activation were seen in FMRI internet addiction studies.