1. Introduction
Autism Spectrum Disorder (ASD) is a neurodevelopmental condition characterized by impairments in several domains of social functioning, particularly social interaction and communication, as well as restricted and repetitive behaviors [
1]. Over the past decades, the diagnosis of ASD has steadily increased, with current global prevalence estimates ranging between 0.6% and 1.0%, varying according to geographical area, socioeconomic context, and availability of healthcare services [
2,
3]. The clinical presentation of ASD is markedly heterogeneous, encompassing a wide range of symptoms that differ substantially in severity and configuration, resulting in distinct clinical profiles. Despite this variability, symptoms typically emerge in early childhood and significantly compromise multiple functional domains and overall quality of life [
4,
5]. Although the clinical manifestations may evolve across development, ASD is a lifelong condition; its persistence and phenotypic heterogeneity make early diagnosis both essential and particularly challenging. Furthermore, ASD affects individuals across all ethnicities and socioeconomic backgrounds, and its etiology is multifactorial, involving genetic, environmental, and neurobiological factors that remain only partially understood [
6,
7].
Current international diagnostic guidelines rely primarily on clinical and behavioral assessments based on semi-structured interviews and direct observation, such as the Autism Diagnostic Interview-Revised (ADI-R) [
8] and the Autism Diagnostic Observation Schedule-Second Edition (ADOS-2) [
9]. While these instruments represent the gold standard for ASD diagnosis, their sensitivity may be influenced by several factors, including clinician expertise, age at symptom manifestation, and individual cognitive and language abilities [
10,
11]. Moreover, reliance on the emergence of clearly observable behavioral symptoms often limits diagnostic accuracy during the earliest developmental stages, when clinical interventions are known to be most effective [
12,
13,
14]. Consequently, there is growing interest within both clinical and neuroscientific communities in identifying objective biomarkers that can support diagnostic procedures and capture shared neurobiological substrates underlying the broad spectrum of ASD phenotypes [
15,
16].
Within this framework, electroencephalography (EEG) has emerged as a promising and widely accessible tool for the identification of objective neurophysiological biomarkers of ASD and atypical brain functioning. EEG is commonly used in the assessment of neurodevelopmental disorders, which often co-occur with neurological atypies, and is typically available in clinical settings. Moreover, EEG is a low-cost and non-invasive technique, making it particularly suitable for pediatric populations [
17,
18,
19]. Owing to its high temporal resolution and relative ease of acquisition, EEG represents a valuable tool for investigating functional neural characteristics associated with ASD, facilitating the discrimination between autistic and neurotypical individuals and supporting diagnostic procedures [
20,
21]. A growing body of literature has documented atypical patterns of brain oscillatory activity, inter-regional functional connectivity, and event-related potentials (ERP) in individuals with ASD compared to typically developing (TD) peers [
13,
21]. In particular, several studies have reported an atypical spectral profile in ASD, commonly referred to as a “U-shaped” power distribution [
22,
23]. This pattern is characterized by increased power in low- and high-frequency bands, including delta (1–3 Hz), theta (4–7 Hz), beta (13–35 Hz), and gamma (>35 Hz), alongside a reduction in alpha power (8–12 Hz) [
23,
24,
25,
26]. These alterations have been associated with atypical neural development and are thought to contribute to the cognitive, social, and sensory impairments commonly observed in ASD [
25,
26,
27,
28,
29,
30]. Importantly, evidence from pediatric populations indicates that early alterations in functional connectivity, observable as early as three months of age, may predict later severity of autistic symptoms [
22,
31]. This finding underscores the potential role of EEG-derived measures as screening tools and as support for early diagnosis [
17,
32].
The increasing relevance of EEG in ASD research has driven the adoption of Artificial Intelligence (AI) methodologies, particularly Machine Learning (ML) and Deep Learning (DL) approaches, for the analysis of EEG recordings. These models are capable of processing large-scale, high-dimensional datasets and extracting complex patterns that may not be detectable through traditional analytical methods. By overcoming some of the limitations of conventional clinical and diagnostic tools [
33,
34,
35], AI-based approaches have enabled the identification of latent neural signatures that differentiate individuals with ASD from neurotypical controls, achieving classification accuracies ranging from 80% to 98% [
33,
36]. Despite these promising findings, many AI models are affected by the so-called “black box” problem, as they offer limited insight into the mechanisms underlying their decision-making processes. In clinical settings, however, AI-based models must be interpretable, reproducible, and grounded in neurobiological plausibility in order to be considered reliable and clinically meaningful.
Explainable Artificial Intelligence (XAI) has been proposed as a strategy to address this limitation by enhancing model transparency and enabling the interpretation of algorithmic decision-making processes. In this manuscript, we distinguish between interpretability, explainability, and the broader concept of XAI. Interpretability refers to the intrinsic transparency of a model; that is, the extent to which its internal structure and parameters can be directly understood by human observers without additional processing. Explainability refers to the set of techniques designed to provide insight into the behavior of complex models, either by analyzing their internal representations or by approximating their decision logic. The term XAI is used here as an umbrella concept encompassing both inherently interpretable models and post hoc explanation methods. From a methodological perspective, XAI approaches can be broadly categorized into (i) intrinsically interpretable models, where transparency is embedded in the model design, and (ii) post hoc explanation methods applied after model training. Post hoc methods can further be divided into model-specific techniques, which require access to internal model parameters (e.g., gradient-based attribution), and model-agnostic techniques, which treat the model as a black box and rely solely on input–output behavior. Inherently interpretable models are necessarily model-specific, as their transparency depends on their internal structure [
37,
38,
39,
40].
In the context of EEG analysis, XAI approaches can offer valuable insights into which neural signal features, such as frequency bands, channels, or cortical regions, contribute most strongly to model predictions. Routine clinical EEG is primarily oriented toward the identification of overt pathological abnormalities and it is not designed to detect subtle electrophysiological patterns, reflecting atypical, yet non-pathological, neural functioning. In contrast, XAI-based methods enable comparisons of such patterns and support predictive modeling in population with neurodevelopmental disorders [
34,
41]. Recent studies have demonstrated the potential of XAI methods for clinical and diagnostic applications. In particular, inherently interpretable Convolutional Neural Networks (CNNs) and post hoc explanation techniques such as SHapley Additive exPlanations (SHAP) applied to EEG data have been employed to quantify the contribution of specific EEG features to ASD discrimination [
21,
33,
41]. Notably, findings derived from these approaches are largely consistent with existing behavioral and neurophysiological evidence. Studies leveraging SHAP analyses have highlighted the role of atypical theta and alpha activity in individuals with ASD [
33,
41], thereby supporting the neurobiological relevance of the extracted features.
By leveraging objective neurophysiological data and increasing the transparency of AI-driven decision-making processes, XAI approaches hold considerable potential for improving both the timing and accuracy of ASD diagnosis, while also providing novel insights into neurophysiological subprofiles within the autism spectrum. Given the increasing emphasis on multidimensional frameworks that integrate subjective clinical assessments with objective biomarkers, such as genetic information and EEG measures, XAI represents a particularly promising avenue for supporting clinical decision-making [
37,
38,
42]. Nevertheless, despite the growing body of research in this area, a comprehensive synthesis of studies applying XAI techniques to EEG data in ASD is still lacking. Existing investigations show substantial heterogeneity in sample characteristics, EEG features (e.g., frequency bands, power spectra, and ERPs), methodological designs, and applied XAI approaches.
This systematic review aims to address this gap by examining and synthesizing studies that apply XAI approaches to EEG data analysis in individuals with ASD. Specifically, the main contributions of this review are: (i) to provide a systematic overview of AI-based approaches applied to EEG data in ASD; (ii) to categorize these approaches by distinguishing between intrinsically interpretable models and black-box models augmented with post hoc explanation methods; (iii) to critically analyze current XAI techniques applied to EEG in ASD; and (iv) to discuss methodological gaps and future directions for interpretable and clinically grounded AI models.
2. Methods
2.1. Study Design and Reporting
This review followed internationally recognized standards for the reporting of systematic reviews, as outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 statement [
43]. The study selection process is illustrated using a PRISMA flow diagram (
Figure 1), detailing the identification, screening, eligibility, and inclusion of records. The PRISMA 2020 checklists are provided in the
Supplementary Materials (Tables S1 and S2). Details of the protocol for this systematic review were registered in PROSPERO (registration number: CRD420251231630).
2.2. Eligibility Criteria
Studies were included if they met the following criteria: (a) original empirical research published in English or with an available English translation; (b) investigations conducted in populations diagnosed with ASD; (c) use of EEG data; and (d) application of AI-based methods, such as ML or DL approaches, incorporating explicit elements of model explainability or interpretability (e.g., XAI). Studies were excluded if they met any of the following criteria: (a) absence of participants with ASD; (b) lack of EEG data; (c) no explicit adoption of XAI methodologies; or (d) publication types including reviews, meta-analyses, books or book chapters, editorials, letters, commentaries, case reports, and case series.
To ensure conceptual precision, eligibility criteria were restricted to studies that explicitly adopted and described their interpretability strategies within a formal XAI framework. The aim of this review is not to survey all forms of model interpretability in EEG-based ASD research, but specifically to examine how XAI methodologies are implemented and evaluated in this domain. Approaches limited to feature importance reporting, ablation analyses, or other post hoc heuristic interpretations were not considered sufficient for inclusion unless they were explicitly embedded within a declared XAI framework. This distinction reflects the methodological scope of the review: XAI methods are characterized by structured explanatory mechanisms that aim to make model decision processes transparent, rather than by generic measures of variable relevance or model sensitivity.
2.3. Information Sources
A comprehensive literature search was conducted across the following databases to identify studies available up to November 2025: PubMed, Scopus, APA PsycArticles, APA PsycInfo, MEDLINE, CINAHL Plus with Full Text, Psychology and Behavioral Sciences Collection, Web of Science, Cochrane Library, and IEEE Xplore. In addition, reference lists of relevant reviews and included articles were manually screened to identify further eligible studies not captured through database searches. The final search across all sources was completed on 16 November 2025.
2.4. Search Strategy
A structured search strategy was implemented across all databases using combinations of terms related to electrophysiological measures (EEG/ERP), ASD, AI-based approaches, and XAI. Search terms included free-text keywords and database-specific fields, and were combined using Boolean operators (AND/OR). The strategy was adapted to the syntax and indexing requirements of each database (e.g., Title/Abstract, Keywords, All Fields). Keywords and controlled vocabulary terms (e.g., MeSH, where applicable) were included to maximize sensitivity. The complete search strings for each database are reported in
Table 1.
2.5. Selection Process
Three reviewers independently assessed all retrieved records using a two-step selection process. Initially, titles and abstracts were evaluated for relevance; subsequently, potentially eligible articles underwent full-text assessment according to predefined inclusion and exclusion criteria. Exclusions at the full-text stage were recorded with explicit justification. Any disagreements were resolved through collegial discussion, with involvement of an additional reviewer when consensus was not immediately achieved. Overall, 301 records were identified. After screening and full-text assessment, 11 studies met the eligibility criteria and were included in the final synthesis.
2.6. Data Collection Process and Data Items
Data were independently extracted by three reviewers using a standardized Excel spreadsheet developed according to the PICO framework (Population, Intervention/Exposure, Comparison, Outcome). A fourth reviewer verified the extracted data for completeness and accuracy. The following information was collected for each included study: study design and methodological approach; country and research setting; sample characteristics (sample size, age range or mean age, sex distribution, and presence and type of control groups); ASD diagnostic criteria or assessment instruments; EEG acquisition characteristics (recording condition, task-based or resting-state paradigm, and number of electrodes); AI-based analytical methods (including ML or DL models); the type of XAI strategy adopted, distinguishing between intrinsically interpretable models and post hoc explanation techniques; main electrophysiological features analyzed (spectral, temporal, and functional connectivity measures); primary outcomes; and key findings. In addition, information regarding the level of clinical characterization (e.g., cognitive functioning, symptom severity, comorbidities, and medication status, when available) and reporting of socioeconomic and demographic variables was extracted. Additional bibliographic information included first author, year of publication, and country of origin.
2.7. Quality Assessment
Given the substantial heterogeneity of study designs and analytical approaches, a structured assessment of methodological rigor and potential sources of bias was performed by systematically evaluating multiple dimensions, including (i) diagnostic procedures, (ii) EEG preprocessing, (iii) validation frameworks, (iv) handling of class imbalance and confounding variables, as well as (v) the integration of XAI methods and (vi) code or data availability. All domains were assessed qualitatively and they were not weighted or prioritized. The criteria were applied systematically to all included studies and the results of this assessment are summarized in
Table 2. This table enables comparison of methodological strengths, limitations, and potential sources of bias across the included studies.
2.8. Synthesis Methods
Given the substantial heterogeneity across study designs, participant characteristics, EEG paradigms, analytical approaches, and outcome measures, a quantitative meta-analysis was not feasible. Therefore, a qualitative narrative synthesis was conducted. Studies were grouped according to key methodological and conceptual dimensions relevant to the aims of the review, including: (1) EEG acquisition paradigm (resting-state versus task-based); (2) electrophysiological features analyzed (spectral, temporal, and functional connectivity measures); (3) AI methodologies (ML versus DL models); and (4) explainability or interpretability approaches applied. Within each domain, patterns of findings were summarized and compared across studies, with particular attention to convergent electrophysiological markers, consistency of model interpretability, and clinical relevance of the extracted features. This approach allowed for the integration of results across heterogeneous methodologies while highlighting methodological trends, sources of variability, and gaps in the existing literature.
5. Discussion
The concurrent increase in the prevalence of neurodevelopmental disorders and the rapid advancement of technological tools have driven the growing adoption of sensitive and minimally invasive techniques to characterize these conditions and investigate their developmental trajectories. In this context, EEG has become a widely used technique in clinical practice. Both resting-state and task-based EEG analyses have enabled the identification of common and disorder-specific neurofunctional characteristics, which are increasingly considered objective markers of atypical brain functioning. The application of AI technologies has further enhanced EEG signal analysis by enabling the detection of complex patterns that are not readily identifiable through traditional analytical approaches or clinical inspection alone. However, the limited transparency of many AI models represents a critical barrier to their clinical adoption, particularly in neurodevelopmental research, where neurophysiological plausibility is essential. In this context, XAI approaches offer a substantial added value by providing insights into the electrophysiological features, temporal dynamics, and functional interactions that drive model predictions. By bridging the gap between predictive performance and mechanistic understanding, XAI frameworks facilitate the translation of AI-based EEG findings into clinically meaningful knowledge, supporting hypothesis generation, diagnostic decision-making, and the development of personalized and preventive intervention strategies. Accordingly, the present review systematically collected and analyzed the available literature on XAI methods applied to the study of electrophysiological correlates in populations with ASD, identifying a total of 11 eligible studies. From a methodological perspective, the reviewed literature predominantly focused on EEG data acquired during resting-state conditions, typically involving eyes-open or eyes-closed relaxation paradigms. To facilitate compliance, especially in pediatric populations, some studies collected EEG recordings during exposure to low-demand, relaxing stimuli such as soap bubbles [
52].
Only a limited number of studies [
44,
45,
48,
50,
51] employed task-based paradigms, indicating a prevailing emphasis on the investigation of spontaneous brain activity. Resting-state experimental designs are particularly suitable for pediatric and clinically vulnerable populations, including individuals with adaptive difficulties, as they allow the examination of intrinsic neural dynamics and functional connectivity networks with minimal task demands. Furthermore, resting-state paradigms are generally more reproducible over time and less susceptible to confounding sources of variability, thereby facilitating the construction of large and comparable datasets.
Across the included studies, EEG data were acquired using both high- and low-density systems, with the number of electrodes ranging from 4 to 129. Analyses primarily focused on specific regions of interest, particularly frontal and central areas, where abnormalities in functional connectivity and spectral organization have been consistently reported [
132]. Overall, the 11 studies identified convergent electrophysiological differences between individuals with ASD and TD controls across spectral, temporal, and functional connectivity domains. These differences enabled robust discrimination between ASD and TD groups and supported neuropsychological interpretations of ASD-related brain functioning. Notably, an imbalance between alpha and gamma oscillations emerged as a consistent finding. In line with previous literature, individuals with ASD exhibited increased gamma-band activity and reduced alpha power compared to TD controls [
49,
51,
52]. Such spectral alterations are consistent with sensory processing abnormalities, including hyper- or hyporeactivity to environmental stimuli, as well as attentional regulation difficulties frequently observed in ASD.
At the neurophysiological level, atypical gamma and alpha oscillatory activity has been interpreted as potentially reflecting a disruption in cortical excitation–inhibition balance, likely associated with alterations in neurotransmitter systems, particularly GABAergic circuits [
22,
26,
108]. These findings further supported the view of ASD as a complex, multicomponent, and fundamentally neurobiological condition. In addition to spectral alterations, several studies highlighted atypical patterns of neural connectivity in ASD populations. These connectivity abnormalities may play a critical role in distinguishing ASD from TD individuals and are characterized by simplified hierarchical network structures, with a predominance of short-range connections at the expense of long-range integration [
47]. Reduced global efficiency and functional integration appear to be hallmark features of ASD-related brain networks and may contribute to the cognitive and social impairments commonly associated with the condition [
8,
71,
115,
116,
117,
118]. Importantly, altered alpha-band coherence has been shown to predict symptom severity at later developmental stages, highlighting its potential prognostic value [
32].
Task-based studies further may contribute to corroborate differences in neural functioning between ASD and TD individuals, revealing right-hemispheric asymmetries involving regions implicated in attentional modulation and social stimulus processing [
44,
50,
64,
119,
120,
121,
124,
125,
126,
127,
128]. Within this context, XAI techniques such as SHAP, LRP, and ELI5 demonstrated particular promise in identifying objective spectral, spatial, and temporal features relevant for ASD classification and in providing clinically meaningful interpretations of model decisions [
44]. The reviewed studies illustrated the potential of XAI approaches to identify novel biomarkers, validate existing neuroscientific hypotheses, and address clinical heterogeneity. For example, XAI methods enabled the detection of associations between ERP and clinical severity scores measured using the ADOS-2, which are not readily identifiable using conventional analytical techniques [
44]. Additionally, these approaches facilitated the evaluation of feature relevance in distinguishing between clinical conditions [
50] and supported the identification of potential clinical subgroups characterized by distinct electrophysiological patterns [
49].
Importantly, these interpretative advances cannot be attributed to model architecture alone, but rather to the interaction between modeling strategies, data representations, and the explainability frameworks adopted across studies. Although most reviewed approaches relied on post hoc explanation techniques, these methods differed in their degree of model dependence. Model-specific approaches, such as Layer-wise Relevance Propagation (LRP) and gradient-based saliency methods, required access to internal network parameters, whereas model-agnostic techniques, including certain implementations of SHAP, operated by probing the input–output behavior of the trained model [
38,
42]. Regardless of this distinction, the stability and neurophysiological plausibility of the resulting explanations were strongly influenced by feature representation and model constraints. ML frameworks operating on explicitly defined spectral or functional connectivity features tended to produce more stable and physiologically interpretable explanations, as their representations preserved a direct correspondence with EEG markers. In contrast, DL approaches, while capable of capturing richer spatiotemporal dependencies, often generated attribution patterns that were more sensitive to architectural design choices and input variability. Overall, these findings indicate that explainability in EEG-based ASD research depends not only on the choice of explanatory technique, but also on how that technique interacts with model structure and data representation [
50].
Despite these findings, the application of XAI approaches to EEG analysis in ASD remains in an early and evolving stage. The innovative nature of XAI methodologies is reflected in the substantial heterogeneity and limited systematicity observed across experimental designs. Many studies provided only partial descriptions of sample characteristics, with insufficient clinical characterization of ASD developmental profiles. Key parameters—including symptom severity, cognitive and verbal functioning, and, in some cases, participant age range—were frequently absent, imprecise, or not integrated into EEG analyses. These limitations affect both resting-state and task-based studies and hinder the identification of clinically meaningful subgroups and the prediction of developmental trajectories. This issue is particularly relevant given the high rate of comorbidity in ASD, including conditions such as attention-deficit/hyperactivity disorder (ADHD), which is itself associated with electrophysiological alterations [
133,
134]. Such comorbidities contribute additional sources of variability and complicate the attribution of observed EEG abnormalities specifically to ASD [
135,
136].
Another important source of heterogeneity concerns the EEG acquisition systems and channel density employed across studies. While some variability is expected in emerging research fields, these methodological differences may limit the robustness, comparability, and generalizability of findings. As XAI-based EEG research continues to expand, it is anticipated that the growing diffusion of these approaches will promote the adoption of more rigorous, transparent, and reproducible experimental designs. Substantial methodological consolidation and rigorous validation will be essential before XAI-based approaches could be considered reliable in clinical-decision making procedures.
In addition, a further limitation concerns the definition-based inclusion boundary adopted in this review. By restricting eligibility to studies that explicitly framed their interpretability strategies within an XAI paradigm, we may have excluded investigations implementing functionally similar interpretative analyses without adopting explicit XAI terminology. This choice reflects the methodological focus of the review on the development and application of XAI as a defined framework, rather than on all forms of model interpretability in EEG-based ASD research. Consequently, the findings should be interpreted as mapping the current state of explicit XAI applications in this field. Taken together, these considerations highlight the need for clearer methodological standards to support the maturation of the field. In light of the evidence summarized in this review, a set of practical recommendations can be outlined to support the translation of XAI-based EEG approaches into clinically meaningful applications. These recommendations directly address the methodological and interpretative challenges identified across the reviewed studies and aim to provide concrete guidance for future research. First, external validation and cross-dataset evaluation should be prioritized whenever feasible. XAI-based EEG models should be tested on independent cohorts or across datasets acquired at different sites to assess generalizability and to reduce the risk of dataset-specific patterns or explanations. When external datasets are not available, cross-dataset or leave-site-out validation strategies should be considered as minimal requirements. Second, the stability and reproducibility of explanations should be treated as explicit outcome measures. Beyond predictive performance, future studies should systematically assess the robustness of XAI outputs across subjects, recording sessions, model initializations, and perturbations of the input data. Both quantitative metrics and qualitative evaluations of explanation consistency should be reported, as unstable or highly variable explanations limit clinical trust even in the presence of high classification accuracy. Third, XAI outputs should be explicitly linked to clinically relevant phenotypes. To enhance clinical interpretability, relevance patterns derived from XAI analyses should be related to symptom severity, developmental trajectories, cognitive or behavioral profiles, and task performance measures when available. Establishing such links is essential to move from descriptive model explanations toward actionable neurophysiological markers that can inform diagnosis, prognosis, and personalized intervention strategies.
Together, these steps provide a concise and operational roadmap for guiding future XAI-based EEG research toward robust, interpretable, and clinically translatable applications in ASD. Within this framework, minimal methodological expectations can also be articulated. Future studies applying XAI to EEG in ASD should demonstrate at least one form of robustness analysis and, whenever feasible, one form of external validation. Explanation plausibility alone, without empirical assessment of stability and generalizability, is insufficient to support clinical translation. By embedding these minimal standards into study design and reporting practices, the field may progressively move from visually compelling interpretations toward reproducible and clinically grounded explanatory frameworks.
6. Conclusions
This systematic review aimed to collect and analyze the current literature on the application of XAI technologies to the analysis of electrophysiological measures in populations with ASD. Overall, the findings highlight the substantial potential of XAI-based frameworks to advance EEG-driven neuroscience research and to support future clinical translation. In particular, the integration of EEG and XAI provides a non-invasive and interpretable approach for identifying novel neurophysiological patterns associated with neurodevelopmental disorders, validating previously reported electrophysiological features by quantifying their discriminative contribution relative to neurotypical populations, and detecting potential early biomarkers. Such biomarkers may be especially valuable during early developmental stages or in clinical contexts in which conventional diagnostic procedures are difficult to apply or lack sufficient sensitivity.
Beyond predictive performance, XAI methodologies enable the attribution of model decisions to specific EEG features across spectral, temporal, spatial, and connectivity-related dimensions. This capability facilitates a direct link between algorithmic outputs and underlying neurophysiological mechanisms and represents a key advantage over purely black-box AI models. As such, XAI is essential for enhancing understanding, trust, and applicability in clinical and translational settings. Based on the evidence summarized in this review, future research should prioritize larger and more comprehensively characterized clinical cohorts, together with rigorous evaluation of explanation stability, reproducibility, and neurophysiological plausibility. In addition, greater attention to developmental trajectories, cognitive profiles, and clinical heterogeneity will be crucial for refining neurodevelopmental subtyping within ASD and for guiding the development of reliable, interpretable, and clinically meaningful AI-based EEG tools.