# DIVA Meets EEG: Model Validation Using Formant-Shift Reflex
## 3 Results  
### DIVA Model Simulation  
The activation of the cortical maps of the DIVA model during the vocalization of the phoneme /e/ with undisturbed auditory feedback is illustrated in Figure 4. DIVA maps provided by the model activated at different times with respect to the onset of the simulated vocalization. The first maps were activated at t = 0 (onset of the vocalization) and were the motivation, initiation, speech, somatosensory target (somato-t) and auditory target (auditory-t) maps (Figure 4A). While the activity of the motivation map reduced to 0 directly following the vocalization onset, the activity of the initiation map remained constant (value of 1) throughout the vocalization. The articulator map (articulator) activated 10 ms after the onset of the vocalization. This was followed by the activation of the somatosensory state map (somato-s) (25 ms), the somatosensory error (somato-e) (30 ms), the feedback map (35 ms), and the auditory state (auditory-s) (55 ms after the vocalization onset). As the auditory feedback was not disturbed, the auditory error map was not activated.  
Cortical activations feed into the EEG generative model, which resulted in EEG scalp distributions that characterized the different phases (stages) of the cortical dynamics (Figure 4B). Current density maps in the cerebral cortex were estimated from the EEG scalp distributions using sLORETA (Figure 4B). The EEG sources estimated with the inverse solution method closely resembled the brain distribution of DIVA maps (cortical seeds used for the EEG generation). Auditory feedback perturbations (both down- and up shift in F1) were reflected in the activity profile of the DIVA model (Figure 5A). While the activity changes of the Auditory state map clearly followed the direction of the perturbations, Somatosensory state maps changed minimally. Evident increases in the activity of the Feedback map were obtained in the presence of auditory feedback perturbation. Noteworthy, the feedback perturbation triggered the activation of both the Auditory error map and the Somatosensory error map, which are typically suppressed in undisturbed conditions.  
Due to the auditory feedback perturbation, differences were observed in both the EEG scalp distributions and the activity of the EEG generators estimated with sLORETA (Figure 5B). The shifts in F1 resulted in increased bilateral activation of frontal, temporal and parietal cortical areas (Figure 5C, left and middle panels), including the orbital, opercular and triangular parts of the inferior frontal gyrus, the middle and superior frontal gyri, the Rolandic operculum, the Heschl gyrus, the temporal pole, as well as the middle and superior temporal gyri (Table S2, Supplementary Materials). The downward and upward shifts in F1, although equal in magnitude, resulted in different EEG source-space maps (Figure 5C, right panel). This asymmetry was reflected as an increase in the cortical activity elicited by down-shifted feedback perturbations in comparison with that induced by up-shifted perturbations. The differences in activity were mainly observed in frontal and parietal brain areas (bilaterally), including the primary somatosensory and motor cortices (Table S2, Supplementary Materials).  
Figure 4: Simulations of the brain cortical activity associated with the different DIVA maps during the vocalization of the phoneme /e/ with undisturbed feedback: (**A**) Time course of activity of DIVA cortical maps. t: target, s: state, e: error (**B**) Topographic representations of cortical activity for time t = 0, 10, 25, 250, 510, 550 ms relative to the onset of the vocalization. top panel: cortical seeds. middle panel: simulated EEG. bottom panel: source space representation of the synthetic EEG.