## 1 Introduction
### New Challenges in the Evaluation of Executive Functions
#### 1.2.2 Nonverbal Physiological Indices  
Over the years, executive functioning has been further explored by the identification new nonverbal physiological indices obtained with different devices, such as the eye tracker (ET) and electroencephalogram (EEG). ETs allow for online tracking and recording of subjects' eye movements (e.g., saccadic and antisaccadic movements, and fixations). Physiological indices obtained with ETs (e.g., pupil dilation, eye movements, fixation, and gaze direction) are generally considered reliable indicators of executive dysfunction (e.g., inhibitory control) [37]. For example, [PERSON] and colleagues demonstrated that antisaccadic movements are a sensitive marker of ED and frontal-lobe structure in cognitively and functionally healthy older adults [52]. Recently, [PERSON] and co-workers demonstrated the suitability of the antisaccades test (AST) as a cognitive marker of ETs in aging and PD populations [53]. AST performance was a good predictor of decision-making and visual-memory abilities for both older adults and PD patients, while it predicted visual search performance to a larger extent in PD patients. The advantages of ET and VR/360\({}^{\circ}\) environments (e.g., natural stimuli, natural movement, controlled environment, and controlled data collection) make it possible to answer many research questions in a radically innovative way. It allows for calculating the subject's gaze in the 3D virtual environment and observing where the subject is looking during the session. Moreover, ET allows for the definition of regions of interest in 3D space and fixation time of each area [54]. EEG, on the other hand, can be used to analyse, monitor, and record electrical activity and any functional anomalies in the prefrontal cortex and associated cortico-subcorticalcircuits, responsible for EFs [55; 56]. \"Dysexecutive syndrome\" is common in neurological patients due to damage to the frontal lobe, such as following head trauma or related to specific conditions such as PD [57]. Slower oscillations within the theta frequency band in the frontal cortex, generally observed between 4 and 8 Hz, are associated with the involvement of the neural resources involved in executive tasks. EEG can be used to estimate the complexity of executive dysfunction in several clinical populations (e.g., [58; 59]). For example, a study conducted by [PERSON] and colleagues showed that decreased resting-state functional connectivity between the frontal and parietal cortex, especially in the left side, was related to executive dysfunction in PD [59]. Interestingly, recent technological advances allowed for the development of portable, wearable, and wireless EEG headsets [60; 61; 62]. These inexpensive and easy-to-use EEG devices, with few channels and/or dry-electrodes, could be interesting for the evaluation of EFs outside of the laboratory in real-world environments. However, additional studies need to be performed to validate their use to evaluate EFs. In light of all these advantages and innovations, the integration of immersive, virtual, or 360\({}^{\circ}\) environments has the potential to simultaneously evaluate different components of executive functioning in a real-life setting via the use of ETs and EEGs. To date, only a few studies have integrated these methods, focusing mainly on executive dysfunctions in developmental age [63; 64]. Our work evaluates the convergent validity, usability, and efficacy of the EXecutive-Functions Innovative Tool 360\({}^{\circ}\) (EXIT 360\({}^{\circ}\)) to assess EFs in Parkinson's disease. This 360\({}^{\circ}\) instrument will consist of a new 360\({}^{\circ}\) task for EFs delivered via a technological device: a head-mounted display (HDM) that integrates an ET and an EEG. The EXIT 360\({}^{\circ}\) assessment tool will go beyond the effectiveness of standard tests, VR-based tools, or ET and EEG studies by combining different components and data for a multidimensional and multicomponent assessment of executive functioning with high clinical usability and ecological validity.