Classification of EEG Signals

The types of EEG waves[2,3] are identified according to their frequency range – delta: below 3.5 Hz (0.1–3.5 Hz), theta: 4–7.5 Hz, alpha: 8–13 Hz, beta: 14–40 Hz, and gamma: above 40 Hz. The EEG may show unusual electrical discharge when some abnormality occurs in the brain.

What are the features in EEG signals?

The simplest features of the EEG signal are statistical features, like mean, median, variance, standard deviation, skewness, kurtosis, and similar [50].

What are the different rhythms of EEG signals?

δ rhythms, found in the frequency bands of 1–4 Hz (δ band) θ rhythms, found in the frequency bands of 4–8 Hz (θ band) α rhythms, found in the frequency bands of 8–13 Hz (α band) β rhythms, found in the frequency bands of 13–30 Hz (β band)

How many signal frequencies are there in EEG?

EEG signal has five frequency bands; delta (0.5-4Hz), theta (4-8 Hz), alpha (8-14 Hz), beta (14-30Hz) and gamma (above 30Hz) (Abo-Zahhad et al., 2015) . …

How do you analyze EEG signals?

There are two important methods for time domain EEG analysis: Linear Prediction and Component Analysis. Generally, Linear Prediction gives the estimated value equal to a linear combination of the past output value with the present and past input value.

What is signal amplitude of EEG?

The amplitude of the EEG is about 100 µV when measured on the scalp, and about 1-2 mV when measured on the surface of the brain. The bandwidth of this signal is from under 1 Hz to about 50 Hz, as demonstrated in Figure 13.1.

What does amplitude mean in EEG?

The amplitude of the EEG pattern is the strength of the pattern in terms of microvolts of electrical energy. There are four basic EEG frequency patterns as follows: Beta (14-30 Hz), Alpha (8-13 Hz), Theta (4-7 Hz), and Delta (1-3 Hz). In general, the amplitude of the EEG increases as the frequency decreases.

What is synchrony and alpha block?

synchrony: when there is an alpha rhythm (patient is relaxed with eyes closed), the waves are uniform, in amplitude and frequency. Alpha block is when beta waves start to interfere with the alpha rhythm; the patient is stimulated by different kinds of stimuli from the environment.

What does Hz mean in EEG?

Hertz

Frequency (Hertz, Hz) is a key characteristic used to define normal or abnormal EEG rhythms. Most waves of 8 Hz and higher frequencies are normal findings in the EEG of an awake adult.

What does asynchronous mean in EEG?

Asynchrony The noncoherent occurrence of EEG activities over regions on the same or opposite sides (hemispheres) of the head. For example, two similar waveforms occurring at separate electrodes or channels, but not simultaneously due to a time lag between the channels.

Are EEGs accurate?

EEG review yielded 1-week accuracy in 10–52% of recordings, and 2-week accuracy in 28–75% of recordings (n = 146; Fig. 3E and F).

What is attenuation on EEG?

Attenuation: Reduction in amplitude of EEG activity (for example, the alpha rhythm is usually attenuated or blocked on eye opening).

How many electrodes does an EEG have?

An array of 25 electrodes is recommended for standard EEGs with inferior temporal electrodes. Due to thinner skulls (spatial aliasing), pediatric EEG requires as many scalp electrodes as in adults. Arrays with higher electrode numbers (64–256 electrodes) allow source imaging at sublobar level.

What electrode is used in EEG?

Also, low electrode-skin impedance can help to reduce the power line interference and also make EEG signals more immune to movement artifacts, including cable motion. Today, the most commonly used electrode is the silver/silver chloride (Ag/AgCl) electrode.

What is an active EEG electrode?

Active electrodes (AEs), i.e., electrodes with built-in readout circuitry, are increasingly being implemented in wearable healthcare and lifestyle applications due to AEs’ robustness to environmental interference. An AE locally amplifies and buffers μV-level EEG signals before driving any cabling.

What is the difference between active and passive electrodes?

Conclusion: Active electrodes perform better than passive ones at all impedances other than very low ones; however, this is qualified by the additional finding that during fast voltage fluctuations, such as those most desirable in most ERP studies, active electrodes are less able to accurately follow the EEG than …

What is an inert electrode?

Inert electrodes are those do not participate in the reactions. There is function is just to provide an interface for reaction. You must be familiar with galvanic cell. In this cell both zinc and copper electodes participate in the reactions and electrons are taken or given to this electrodes.

What is active and indifferent electrode?

It is measured as a voltage (i.e. potential difference) between two electrodes. From the functional point of view, ECG electrodes are divided into 2 types – active (or exploring) and indifferent (reference or zero) electrodes. The active electrode measures the variable potential of the cardiac electric field.

What is exploring electrode?

an electrode placed on or near an excitable tissue; in unipolar electrocardiography, the electrode is placed on the chest in the region of the heart and paired with an indifferent electrode.

Is active electrode red or black?

Muscle Relaxants and Monitoring of Relaxant Activity

The black electrode of the stimulator is negatively charged, and the red electrode is positively charged. The black electrode depolarizes the membrane, and the red electrode hyperpolarizes the membrane.

Is active electrode positive or negative?

In most familiar electric devices, current flows from the terminal at higher electric potential (the positive electrode) to the terminal at lower electric potential (the negative electrode); therefore, the anode is usually the positive electrode and the cathode the negative electrode.

What are the 5 types of electrodes?