# Emotion Recognition: An Evaluation of ERP Features Acquired from Frontal EEG Electrodes
## 3 EEG Data Acquisition Methodology  
The classification of emotions along any of the domains, viz., arousal, valence and dominance, is possible by utilizing the orthogonal nature of emotions. To evoke emotions, the visuals from the International Affective Picture System (IAPS) were used [51]. The acquisition of ERP features requires the projection of an emotion-evoking stimulus on one computer system while simultaneously putting a mark on the second computer system acquiring EEG. A low-cost synchronization technique using two keyboards with a galvanically connected key was used in our experiments to synchronize EEG signals with the emotion-evoking stimulus [52].  
The experimentation performed is totally noninvasive and has approval from the University Ethics Committee. The EEG signals have been acquired using the MP150 data acquisition system provided by Biopac (please see [[https://www.biopac.com/product/mp150-data-acquisition-systems/](https://www.biopac.com/product/mp150-data-acquisition-systems/)]([https://www.biopac.com/product/mp150-data-acquisition-systems/](https://www.biopac.com/product/mp150-data-acquisition-systems/)) (accessed on 9 February 2021) for more details). The EEG cap EEG100C consists of 20 Ag/AgCl electrodes placed according to 10-20 International System. The EEG signals have been acquired from 10 electrodes, namely, Fz, Cz, Pz, Fp1, Fp2, F3, F4, P3, P4 and F8, in unipolar mode. The reference electrode has been fitted on the left mastoid. EEG signals time locked with the stimulus presented to subjects were acquired. To achieve this objective, we used two mechanical keyboards and mechanically connected the F5 function key of both the keyboards. We programmed and ran the Neurobs Presentation System in such a manner that pressing F5 starts the stimulus on one computer system while simultaneously inserting an event mark on data being acquired using Biopac provided Acq 4.2. Figure 1 shows the experimentation technique used for the acquisition of evoked EEG signals.  
Students from Thapar University above the age of 18 years and below 24 years volunteered to be our subjects. All the subjects were right-handed males with normal to corrected vision and none had any history of psychological illness. The process of acquisition was started after appraising the subjects about the source of images, the type of images as we did not reject arousal (above 18 years) images in the HVHA category, the acquisition protocol and the type of emotions we aimed to evoke for classification. The subjects signed an undertaking in this regard that they understand the procedure of EEG data acquisition which, of course, is totally non-invasive and they are voluntarily appearing for data acquisition. They also understood that some of the images are in the above 18 years category. We also acknowledged that their names would not be disclosed after experimentation. The given experiment is non-invasive and is approved by the university ethics committee. The emotion classification results have been obtained by acquiring data from frontal EEG electrodes, viz., Fp1, Fp2, F3, F4, F8 and Fz.