Sustained Endogenous Attention Deficits in Attention Deficit Hyperactivity Disorder

Recently, a distinction has been recognized between external sustained attention and internal sustained attention. Internal sustained attention is defined as the ability to maintain attention over time on neurocognitive processes that, rather than processing external information, act on information stored in memory. The "Sustained-Paced Finger Tapping" test was developed and used in experimental research protocols in international literature to assess internal sustained attention in typically developing children. While numerous studies confirm that ADHD is associated with deficits in external sustained attention, the international literature emphasizes that internal attention has been underexplored in ADHD. A pilot study conducted by the University of Salento revealed preliminary data showing that children with ADHD exhibit significantly lower performance compared to control subjects in the "Sustained-Paced Finger Tapping." Despite these preliminary data suggesting that the "Sustained-Paced Finger Tapping" test has the ability to discriminate between children with and without ADHD, there are no published studies formally investigating this hypothesis. Two subject samples will be recruited: one sample of subjects with ADHD and one sample of subjects without ADHD and with typical development. The ADHD diagnosis will be made based on the concordance of four data sources: 1) the detection of diagnostic criteria indicated in the DSM-5 through interviews, medical history, and observation during a neuropsychiatric and psychological visit; 2) high and/or medium-high scores, i.e., ≥ 65/70 T, on the ADHD symptom subscales of both the Conners-3-Parent and the CBCL-Parent; 3) high and/or medium-high scores, i.e., ≥ 65/70 T, on the ADHD symptom subscales of at least one questionnaire (Conners-3 or CBCL) administered to teachers; 4) the presence of all DSM-5 symptoms for ADHD on the Conners-3 scale for both parents and teachers.

Inclusion criteria:

ADHD Group:

Subjects with a diagnosis of ADHD (of any severity level and subtype) aged between 6 and 10 years; "Medication-naive" ADHD subjects, i.e., subjects who have not been prescribed and/or have not yet started taking any medication for ADHD; IQ ≥ 70.

Non-ADHD Group:

Normal IQ; Aged between 6 and 10 years.

Exclusion criteria:

Exclusion criteria for both groups:

Symptoms suggestive of autism spectrum disorders, psychotic disorders, mood disorders, and anxiety disorders; Use of psychotropic drugs; Subjects with cerebral palsy and/or neuromotor and neuromuscular disorders; CNS diseases (e.g., epilepsy and/or neurodegenerative diseases) or CNS injuries due to, for example, head trauma or stroke.

The assessment of autism spectrum disorder symptoms will be carried out using the SRS-2 questionnaire, while the evaluation of other exclusion criteria will be done through medical history and clinical interview during enrollment.

Exclusion criteria for the non-ADHD group:

Presence of ADHD symptoms as identified through clinical interview and administration of a questionnaire (questionnaire from the BIA battery).

Both groups of subjects will be administered the "Sustained-Paced Finger Tapping". It is a computerized test that lasts approximately 10 minutes. It consists of maintaining and reproducing for a certain period of time (10 minutes) the rhythm of a sound presentation (auditory version).

Depending on the variables to be analyzed, non-parametric statistics or the Student's t-test and/or ANOVA will be used. ANCOVA will be employed to assess significant differences between the study variables, accounting for variables that could influence the potential differences (e.g., demographic differences between groups). ROC curve analysis, the Youden Index, and the specific formulas for calculating the diagnostic characteristics of the test will be used. The discriminant validity and the presence of any deficits in the performance related to the test will be evaluated in two ways:

1. by comparing the performances obtained from subjects with and without ADHD. To this end, the Student's t-test and/or analysis of variance (ANOVA) will be used, and if significant differences are found between the two groups regarding variables other than the dependent variables, ANCOVA will be implemented;
2. by calculating sensitivity, specificity, accuracy indices, and test cut-offs. These parameters will be calculated using the ADHD diagnosis as the gold standard for the subjects with ADHD.

The cut-off will be calculated through ROC curve analysis and the Youden Index. By "cut-off" of the test, we mean the score that best discriminates, with a certain degree of accuracy, the optimal balance between sensitivity and specificity, separating subjects with ADHD from those without ADHD. In this sense, the cut-off is considered a measure of discriminant validity, similar to statistically significant differences that can be identified using other statistical techniques.

Ecological validity will be assessed by calculating correlations and regressions between the test scores and the scores obtained on the Conners scales. Finally, simple and partial correlations will be calculated between the Sustained-Paced Finger Tapping scores and the scores from other neuropsychological tests and questionnaires administered in order to gather information on various types of validity of the instrument (construct validity, divergent, and convergent validity).