EEG-Based Processing Approach for Pain Detection

Abstract-To unmask the affliction inveteadmonish on EEG salines variability, diverse efforts has been made except no irresolute conclusion has been closed at-last. In this con-over, we tender opposed signs to adequitable pan. EEG salines of 28 robust tends were narrative uninterruptedly occasion they knowledge affliction through the public ice-infiltrate paradigm. To advent the de-correlated EEG fountains, Inrelative Constituent Decomposition(ICA) theory was rightd. Shapeless them, the artievent and uproar fountains were oustd and hence affliction relative fountains were strong and contemplated end. Before the group, some signs were extracted from the EEG saline. To excellent the best signs, sequential bold excellention (SFS) was applied which too elucidates the plethora. The group conclusions get 89% , 90% and 94% faultlessness when undivided correct neighbor (1NN), 3NN and buttress vector proceedings (SVM) were rightd, heedively.

Keywords: EEG fountains, affliction relative signs, entropy, sign excellention.

  1. Introduction

Backonja et al. [1] tenderd an ice-infiltrate bath as a continuous afflictionful promotement, termed as the inirrelative presser experiment (CPT). in this con-over, CPT is applied as the affliction inducing paradigm. Some studies, inveatigated the transmutes during affliction. The conclusion of some antecedent studies[2-5] was reputed as an acception in the Delta and Beta firmenings and a lower in the Alpha firmening during affliction.

In another con-over, a tonic affliction promotement [6] acceptiond the sway of Delta, Beta-III and Gamma firmenings and lowerd the Theta, Alpha-I and Alpha-II firmening sways. Intramuscular injection of hypertonic saline acceptions the Beta sway[7]. In another learning, inducing Capsaicin caused no indicative transmute in the EEG firmenings. Another con-balance indicated transmutes of Alpha firmening activities interact in affliction-cognizance arrangement [8]. In another learning, brace levels of affliction were assortified by Naïve Bayes assortifier which produces 86.3±8.4% group faultlessness [21]. In a opposed approximation, fMRI images of the sundericipants’ brain were observed occasion they were experiencing affliction by excitement collation which conclusioned in 94% faultlessness [9].

The most sordid furnishings of these studies is a open acception in the sway of Beta firmening synchronous to a lower in the Alpha firmening with a practicable continuity acceptions balance opposed firmenings, as the brain confutation to affliction.

In Section 2, the events proceedingsing and the preprocessing are explained; In Section 3, the rules are picturesquely in detail; in Section 4, the conclusions are presented. Section 5 concludes the conclusions.

  1. Facts Proceedingsing and Preprocessing

2.1. Events Proceedingsing

Coercion proceedingsing EEG salines, 30 electrodes were rightd by Scanlt EEG proceedingsing rule. A cap inveteadmonish on 10-20 electrode importation rule was rightd coercion proceedingsing. The impedance of integral electrodes was near than 5 kilo ohms. The sampling admonish was adjusted at 250 hertz and a firmeningpass defecate with skin frequencies adjusted in 0.5 and 47 hertz was implemented to the saline.

In antecedent studies, laser, cuff exigency, hot/ice infiltrate, Electrocutaneous stimulation [10]-[13], feel been rightd to promote affliction. In this con-over, the ice-infiltrate (too firm CPT) was excellented to feel narrowness side-effect. The proceedingsing progress took attribute in a calm occasion. First, to close a deepline proceedingsing coercion each tend, a 30 remedy EEG saline were narrative in the relying standing, which is firm no-affliction assort. Then, by depositting their laborer in the inirrelative infiltrate (1.7±0.2centigrad) following a occasion, they reputed the affliction. The proceedingsing continues plow the tolerating occasion coercion each material.

With heed to the event of artifacts closeness in the EEG salines and to proceedings the uproars with conspicuous tendency, some electrodes on the aspect muscles were deposit to unmask EMG artifacts. Too, EOG is undivided of the other artievent fountains in EEG.

2.2. EEG Artifacts Eliminating

Principal constituent decomposition (PCA) and retrogradation rules[14] are the rules rightd coercion eliminating the EEG artifacts such as muscle artifacts and glance artifacts. Too ICA has been introduced balance cogent coercion decomposing the narrative salines into uncorrelated fountains [14] which is applied here to oust the EEG artifacts.

2.2.1. Inrelative Constituent Decomposition (ICA)

The constituents x i {displaystyle x_{i}} of the observed casual vector x = ( x 1 , … , x m ) T {displaystyle x=(x_{1},ldots ,x_{m})^{T}} are generated as a incorporate of the inrelative constituents s k {displaystyle s_{k}} x i = a i , 1 s 1 + ⋯ + a i , k s k + ⋯ + a i , n s n {displaystyle x_{i}=a_{i,1}s_{1}+cdots +a_{i,k}s_{k}+cdots +a_{i,n}s_{n}} weighted by the mixing weights a i , k {displaystyle a_{i,k}} [15]:

X= AS (1)

Where S is fountains vector, X is the narrative salines (EEGs) matrix.

To compute its inverse or pseudo-inverse, termed as W, the equation(3) is rightd:

S =WX, where W=A-1 (2)

2.2.2. EOG Artievent

To oust the most grave EEG artifacts, which are EOG and EMG artifacts, the correspondent arrangement was manufactured. As the Fp1 tool is the most contained EEG tool, the apposition of this tool with integral strong fountains, was computed Eq.4 is the apposition coercionmula. If the estimate exceeded 0.7, the selfsame fountain was excellented as the mitigated EOG fountain[16].


Where Ri is the apposition of the ith fountain with the narrative saline at Fp1.

Fig.1 shows the illusionary map of the strong EOG fountain which is ce-the-most-sunder on coercioneahed interspace.

Shanon Entropy


Fractal Size

L(k)= (5)

Description: Term: Term: C:UsersghazalehDesktoppayaneeg1.jpg

Fig. 1. Illusionary map of EOG constituent

2.2.3. EMG Artifacts

To oust the EMG artifacts, the apposition of integral fountains with the frontalis and temporalis tools were computed and the undivideds which were balance than 0.7 were considered as the reasonable EMG fountains. Sordidly, EMG fountains feel conspicuous sway at excellent frequencies. Hence, to clearly unmask EMG fountains, in specification to the apposition touchstone, their brain map were investigated[17]. The scalp map and sway spectrum of undivided of the unmasked EMG artifacts is shown in Fig. 2.

Description: Term: I:figures3.a.tif

  1. (b)

Fig. 2. An EMG fountain (a)Scalp map,(b) Zeal Sway Illusionary

  1. Methods

This con-balance is agoing from the events wages sunder in which 28 robust materials sundericipated. We proceedings their EEG salines through the relying mode (externally striking any affliction promotement) and affliction mode.

Due to the closeness of artievent and uproar in the narrative salines, we right inrelative constituent decomposition (ICA) to EEG in manage to oust the chattels of electrooculogram (EOG), electromyogram (EMG) and move artifacts. Non-artievent fountains were contemplated end to electrode interinterillimitableness and diversified signs were extracted from them. To oust the plethora and increasing the discriminability, an approximation coercion excellenting discriminative undivideds, Sequential Bold Excellention(SFS) was applied. The solicitor assortifiers were buttress vector proceedings (SVM) and undivided correct neighbor (1NN).

3.1. Signs

The signs rightd in this learning are as follows; firmening sway of the affliction fountains in five firmenings (Delta, Theta, Alpha, Beta, Gamma), fractal size, Shannon entropy, trench entropy and illusionary entropy.

As a diminutive term to the signs, Five quantity firmenings including Delta (0-4 Hz), Theta (4-8 Hz), Alpha (8-13 Hz), Beta (13-30 Hz), and Gamma (>30Hz) were elicited coercion each occasion bring-about, from each tool. [17].

Shannon entropy [18] measures the aggregate of eccentricity in a sect.

Fractal sizemeasures the eccentricity or bluntness of a saline in a occasion bring-about[19].

The table beneath, demonstrates the diminutive progress of guarded the signs.

Where P()are the probabilities occurred in the ith bin.

is thethe mediocre extension, L(k) is the mediocre extension.

3.2. Sign excellention

The excellent calculate of signs extracted in this con-over, from 30 tools amid each occasion bring-about caused a excellent aggregate of plethora.

Exploration strategies want an extrinsic administration to excellent the adequate subregular of signs. This extrinsic administration is usually a statistical/ referableice/distance inveteadmonish touchstsingle or the assortifiers feedback, which are firm defecate and wrapper, heedively. Defecate rules are firm and does referable prepossession to the assortifier mold, occasion wrapper rules usually get correct conclusions at excellent computational complication absorb.

3.2.1. Sequential Bold Excellention (SFS)

Sequential bold excellention agency starts with vacuity regular of signs and commsolely adds the most indicative signs to aim the touchstone[20].

Here the touchstsingle is excellented as the group faultlessness with the extrinsic of SFS excellents the most discriminative algorithm.

3.3. Assortifiers

Brace well-public assortifiers, 1-NN and SVM, were rightd in this con-over. 1-NN is a summitical and nonlinear assortifier, which is own coercion adjusting multimodal as sorted samples[41]. From another predilection, SVM with a adequate meat is preferable of adjusting samples of brace assortes with balancelap, which gets a majestic openization ownty[21].

3.4. Group

Investigating brain map through CPT gives us costly referableice about the group possibility. Brace quantity ranges, centered at 2Hz (Delta) and 9.8Hz (Alpha), are observed as the most affliction relative signs [3]-[5],[8],[22],[23]. The mediocre brain map balance integral the materials, in the Delta (Fig. 3) and Alpha (Fig. 4) firmenings, are exhibited in affliction and no affliction assort.

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Description: Term: Term: C:UsersghazalehAppDataLocalMicrosoftWindowsTemporary Internet FilesContent.Wordintolerable2,4,12.jpg



Fig. 3. The mediocre brain map of materials at 2Hz (Delta firmening): a) Non-pain, b) affliction

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Description: Term: Term: C:UsersghazalehAppDataLocalMicrosoftWindowsTemporary Internet FilesContent.Wordintolerable spect6,10,22.jpg



Fig. 4. The mediocre brain map of materials at 9.8Hz (Alpha firmening): a) Non-pain, b)pain

Fig. 3 illustrates an acception in the sway of Delta firmening by sensibility the affliction, which transmutes the zeal centre country from summit to the correct hemisphere. These furnishings were antecedently reputed [3]-[5], [23]. In dissimilarity, by sensibility balance affliction, the sway of Alpha firmening is lowerd in the frontal lobe and acceptiond in occipital lobes, as shown in Fig. 4, which is as the conclusions obtained in coercionmer studies [3]-[5], [8], [22]-[23].

It is referableed that the deep of the assortifier was equitable built up according to the unmasked differences on the spatial sect of these brace firmening sway signs. To right the other EEG signs and furnish a divide subregular of signs, SFS was melt. Hence, by adding the other signs, which were excellented by SFS, it was expected to close a conspicuous group faultlessness.

  1. Results

EEG salines from 30 electrodes were narrative and then EOG and EMG artifacts were oustd by the ICA rule, picturesquely in Section 2. Through the preprocessing, EMG or EOG fountains and the fountains caused by the sick junction of an electrode on the scalp, was contemplated visible of the brain.

The deep of the assortifier was equitable normal upon the indicative transmutes in the spatial sect of firmening sway signs through sensibility affliction (Fig. 4). gone genuineness is that righting equitable the excellented firmening sway signs does referable get convincing conclusions, the constitution occasion becaexplanation the other signs was tenderd. The conclusions of affliction group by the tenderd constitution and those firmening sway signs, which were excellented through visual superintendence, is shown in Table I. Coercion now and on, integral of the presented group conclusions in this monograph is closed by ten-times ten-folds ill-conditioned validation was done coercion the ill-conditioned validation appearance. The group accuracies are artistic in Table IV, uniformly SVM was considered coercion integral nodes and the other occasion 1-NN assortifier was assigned.

Table I. The affliction group conclusions of solely the excellented firmening sway signs





Affliction Versus Non-pain




Table II shows the group accuracies closed by righting svm to the signs that is introduced as the discriminative undivideds in antecedent studies [6]-[8], [10], [23]-[24].

Table II. The relatively conclusions of affliction and non-affliction group by righting the antecedent suggested signs[6]-[8], [10], [23]-[24].

Suggested Firmening Sway Signs

in the Antecedent Studies

Group Faultlessness (%)

Alpha firmening


Beta and Alpha firmenings


Delta and Alpha and Beta firmenings


Theta and Alpha firmenings


Delta and Beta firmenings


Alpha and Gamma firmenings


Delta, Beta and Alpha &Gamma firmenings


These muddy signs, in each occasion bring-about, were concatenated into successive sign vectors and hence the assortifiers were encountered with excellent-dimensional vectors. To oust the plethora and customize an optimized subregular of signs , SFS was adopted, to excellent the affliction relative signs and hence correct the last conclusions.

Nevertheless, occasion using wrapper rule, the excellented sign regular depends on the assortifier, the excellented subsets of signs are referable certain similar coercion SVM and 1-NN. SFS was melt coercion each assortifier individually. Too, gone the experiment and retinue regulars are transmuted through opposed folds, the excellented signs in opposed validation folds are referable selfsame. As integral of the reports which right wrapper approximation, to demonstadmonish the inventory of excellented signs, the sordid signs through folds were reputed. The excellented signs by SFS at each node are inventoryed in Table III. and coercion deploying SVM at integral nodes presented and the 1NN signs are inventoryed in Table IV.

Table III. The excellented signs by SFS coercion SVM and 1-NN


Inventory of the excellented signs


Alpha, Delta, Beta and Gamma firmenings, Shannon entropy, and fractal size


Alpha, Delta, Beta firmenings and Shannon entropy

The closed group conclusions by righting the EEG signs, customized using SFS, are artistic in Table VI.

Table VI. Group faultlessness of the affliction

Faultlessness (%)





Affliction vs. Non-Pain





As it is orderic the inventory of excellented signs depends on the mold of assortifier.

  1. Discussion

EEG salines is the solely non-invasive physiological-deep measuring events that quantitatively proceedingss the brain zeal. Too, the learning in affliction size is splow in the rise compared to other applications such as discourse arrangementing.

As it is mentioned, shapeless the artievent resolution theorys such as retrogradation with PCA, adaptive defecate and competition defecate, the best public rule is splow ICA. It gets this occasion to elucidate opposed uproar and artievent roots in the ICA interspace, where integral of the fountains were statistically rebellious. Some constraints were considered to uphold us that the mitigated stunning fountains were rightly excellented. In other vote, the alteration of spatial sect of the Delta and Alpha firmenings are visualized by brain map images through the occasion and this alteration was translated into a succesfull group.

We adept to excellent informative signs to disclose the affliction transmutes as excellentlight as practicable. In this heed, instead of eliciting signs from the correlated EEG salines on the scalp electrodes, miscellany of the public signs were extracted from the affliction relative EEG fountain salines. Balanceover, instead of ad-hoc rules, a heuristic exploration strategy, firm as SFS, was occupied to automatically excellent the adequate signs. The excellent group conclusion demnstarates the appropriateness of the complete arrangement.


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