# Deep Learning for EEG-Based Preference Classification in Neuromarketing
## 3 Literature Review
### Neural Correlations of the Preference  
This subsection explains the neural elements correlated with the preferences. Certain areas of the brain are responsible for various cognitive and mental functions. To determine the positions of EEG electrodes, the underlying brain regions that are responsible for preference processing must be understood. Studies have demonstrated that the preference is linked to the frontal brain regions, specifically, the medial prefrontal cortex, nucleus accumbens [19; 25], and medial orbitofrontal cortex [19; 26].  
[PERSON] et al. [25] linked the choice prediction of the products to the nucleus accumbens. When a consumer views the product, a higher activation of this region indicates a higher probability of the consumer purchasing that product. Furthermore, [PERSON] et al. [26] proved the relationship between the contextual preference and the medial orbitofrontal cortex; a higher activation in this region is related to higher level of preferences.  
Recording the neural activity correlated with a certain function requires placing the electrodes directly above the corresponding brain area. Figure 2 shows the main electrode positions and the associated neural activity according to the 10-20 [27].  
Figure 2: EEG electrodes and related neural functions.  
Although many researchers [24; 25; 26] have proved that the medial-frontal cortex is responsible for the preference function, no consensus exists on which electrodes should be used within the same brain area. Table 3 summarizes the electrode positions used in the preference recognition research.  
The authors of [24] proved that the medial-frontal cortex is linked to the individual preference in the beta range (16-18 Hz) on the mid-frontal areas on electrodes AFz, F2, FC1, and FCz. Moreover, the authors proved that the population preference is linked to the frontocentral areas in the theta range (60-100 Hz) on electrodes F1, F2, F4, FC3, FC1, FCz, FC2, FC4, C5, C3, C1, C4, and CP5.  
[PERSON] et al. [27] linked preference attributes such as attention, emotions, and liking to electrodes F3, C3, P3, Pz, Fz, Cz, and C4.  
[PERSON] et al. [28] found that asymmetrical increments of the theta and alpha bands are linked to watching pleasant (unpleasant) advertisements, as noted in the left (right) brain areas at electrodes Fp1 (Fp2), AF7 (AF8), F7 (F8), and F1 (F2). The spectral power for alpha bands increases noticeably for liked advertisements at electrode F1 and for the disliked advertisements at electrodes AF8 and AF4. In the theta band, increased activity occurs at electrodes F2, AF8, and F3 for the disliked advertisements and at Fp1 for the liked advertisements.  
[PERSON] et al. [29] found that the frontal asymmetry in the alpha band is linked to the consumers' unconscious reactions to the product attractiveness at electrodes F3 and F4. [PERSON] et al. [28] found that the asymmetrical frontal activity is statistically significantly positive in the alpha and theta bands between F1 and F2. In addition, this activity is significantly negative in the theta band between Fp2 and Fp1, AF8 and AF7, and F8 and F7.