Introduction

Developmental dyslexia (DD) is a neurobiological disorder characterized by significant deficits in the acquisition and development of reading and writing skills whose diagnosis should be done by an interdisciplinary team based on the patient's clinical profile and according to international guidelines (^{American Psychiatric Association [APA], 2023}; World Health Organization [WHO], 2022).

The neuropsychological profile of individuals with DD shows difficulties in different cognitive domains relative to that of proficient readers (^{Cruz-Rodrigues et al., 2014}; ^{Lima et al., 2013}; ^{Mingozzi et al., 2024}; ^{Zoubrinetzky et al., 2014}). In addition to cognitive deficits in phonological processing5, (^{de Groot et al., 2015}; ^{Navas et al., 2014}) children with DD also have difficulties in executive function (EF) domains, including inhibitory control, mental flexibility, working memory, strategy use, and verbal fluency (^{Barbosa et al., 2019}; ^{Lima, et al., 2013}; ^{Moura et al., 2014}; ^{Zoubrinetzky et al., 2014}).

EFs are a family of cognitive abilities that help the individual to make decisions autonomously (^{Diamond, 2013}, ²⁰²⁰) and thus are linked to the development of self-regulated behaviors (^{Bjork et al., 2013}). From a functional standpoint, academic areas that depend on EF processes, including written production and reading comprehension, homework, long-term projects, and taking tests and notes, can be adversely affected by executive deficits (^{Meltzer, 2010}; ^{Nouwens et al., 2021}; ^{Ruffini et al., 2024}; ^{Spiegel et al., 2021}).

The main treatment for dyslexia is based on the phonological approach, combining phonological awareness training and reading fluency training (^{Darrot et al., 2023}; ^{Galuschka et al., 2014}; ^{Harrar-Eskinazi et al., 2022}; ^{Martins et al., 2020}). Nevertheless, neuropsychological intervention has also shown positive results to minimize cognitive and behavioral deficits in individuals with acquired brain injuries (^{Starrfelt et al., 2013}; ^{Gazzellini et al., 2012}) or dysfunctions, as in the case of DD (^{Lorusso et al., 2011}; ^{Nukari et al., 2020}; ^{Robertson, 2000}).

Neuropsychological rehabilitation (NR) aims to reduce the impact caused by cognitive deficits, increasing the individual's repertoire of strategies. NR can also assist in psychological adaptation by expanding coping strategies, and enhancing self- understanding and acceptance (^{Nukari et al., 2020}; ^{Wilson, 2009}). Previous studies on neuropsychological interventions with young dyslexics has shown effective for improved performance in reading accuracy and comprehension through stimulation of sensory processing, visual attention, and executive functions (^{Goldstein & Obrzut, 2001}; ^{Lorusso et al., 2011}; ^{Taran et al., 2023}).

Single-case experimental design (SCED) studies have been used to investigate the validity of intervention programs in neuropsychology (^{Evans et al., 2014}; ^{Krasny-Pacini, 2023}). Statistical methods for estimating parameters and assessing the quality and internal validity of SCED studies have been specifically developed for such studies (^{Mcintosh & Rittmo, 2021}). For instance, a meta-analysis of single-subject- design intervention studies for students with learning disabilities showed that direction instruction models and cognitive strategies yielded more robust effect sizes on academic skills such as reading (^{Swanson & Sachse-Lee, 2000}). Another study indicates that the association between cognitive training of executive functions (EF) and phonological-based treatment was more effective in enhancing reading skills in groups with dyslexia. This suggests that gains in reading may be linked to improvements in executive functions (^{Pasqualotto & Venuti, 2020}).

Despite the positive results, few studies have addressed more complex reading processes, including comprehension and its underlying cognitive mechanisms such as EFs, using a neuropsychological approach. Thus, this single-case experimental study aimed to investigate the applicability of adopting a neuropsychological rehabilitation program for executive functions in a patient with developmental dyslexia.

Methods

Results

Tables 1 and 2 show pre- and post-intervention comparisons for the different EF instruments between the patient and controls. Significant differences between patient and controls were observed in pre-treatment SCWT (time), TMT-B (time), Letter-Number Sequencing, WMI, ToL, WCST (perseverative), EAVAP (cognitive, metacognitive, and total), EFSI (patient, parents, and teacher), cloze test, reading speed, and question answering (Table 1). Marginally significant differences in Backward Digit, FAS (phonology), and MARSI (total) were observed between case and controls. Pre-intervention reading by the patient was predominantly phonological and at the alphabetic level, MARSI score was low, and cloze was poor.

Significant differences persisted between case and controls in post-intervention Letter-Number Sequencing, WCST (perseverative), FAS (phonology), EFSI, reading speed, and cloze test (Table 2).

Reading by the patient was predominantly lexical and at the orthographic level, MARSI score was medium, and cloze was average. No comparisons were made for TMT-B and WCST (categories) because both case and controls made no errors in the TMT-B and completed the six WSCT categories in pre- and post-intervention tests. Figure 1 shows the pre- and post-intervention case's scores for oral retelling, question answering, and cloze test.

Figure 1 Pre- and post-intervention case's scores for oral retelling, question answering, and cloze 

Discussion

The patient obtained lower pre-intervention scores than controls on neuropsychological (inhibitory control, cognitive flexibility, phonological loop in working memory, phonological verbal fluency, and planning), and ecological (cognitive and metacognitive learning strategies, reading comprehension strategies, EFs applied to the school and family settings) measures of EFs and reading parameters (reading speed and comprehension). EF deficits (^{Barbosa et al., 2019}; ^{Cruz-Rodrigues et al., 2014}; ^{Lima et al., 2013}; ^{Moura et al., 2014}; ^{Zoubrinetzky et al., 2014}) may be an integral part of the neuropsychological profile of DD and should be considered for diagnosis and intervention.

From a clinical standpoint, the NR program was effective for improving inhibitory control, cognitive flexibility, working memory, planning, use of learning and comprehension strategies, and reading comprehension. Post-intervention reading speed remained slow, but both predominant decoding strategy and reading level improved, from phonological to lexical and alphabetic to orthographic, respectively. It should be noted that the intervention did not include training for decoding skills such as phonological awareness (^{Darrot et al., 2023}; ^{Galuschka et al., 2014}; ^{Martins et al., 2020}) or reading parameters such as fluency (^{Galuschka et al., 2014}; ^{Tressoldi et al., 2008}). On the contrary, the intervention emphasized metacognitive reading strategies, i.e., increasing the use of comprehension strategies, represented by self-monitoring and self-evaluation activities. Thus, to be included in the study, the patient needed to have achieved at least the alphabetic reading level. Consequently, cognitive resources would be less implicated in decoding (recognition, grapheme-phoneme conversion) and more available to higher-order reading processes (i.e., reading comprehension).

The number of propositions (macro and microprocesses) recalled by patient on oral retelling was higher at post- than at pre-intervention, even though it was not significantly different from that of controls at baseline. Moreover, the post-intervention number of correct answers in question answering improved significantly. Conversely, reading performance on the cloze test remained significantly poorer than that of controls, even though percent correct answers was higher and overall cloze improved from poor to average. MARSI and EAVAPI results also showed that the patient started to use more comprehension strategies. Similarly, a study that investigated the effect of an intervention program on metacognitive reading processes in 5th and 6th grade students also reported positive results (^{Gayo et al., 2014}). Nevertheless, the current study describes the effects of a clinical and systematic NR program.

Some neuropsychological measures were not affected by NR. The Letter-Number Sequencing score remained unchanged (9) and was lower than that of controls, but fell within the average range for this subtest. Percent perseverative responses on WCST and mean number of words generated on FAS (phonology) were lower at post-intervention. It is possible that these difficulties persisted because of characteristics of the patient's clinical profile. For instance, only the semantic, but not the phonological category was impaired on FAS at pre- and post-intervention, suggesting that the patient had more difficulties in accessing the lexicon through phonological clues (^{Lima et al., 2013}; ^{Navas et al., 2014}).

The post-intervention changes promoted by the ecological measures of EFs administered to patient, parents, and teacher did not alleviate the differences between case and controls. These results are inconsistent with clinical observation and with the positive effects observed on other levels of reading and comprehension strategies. In the case of instruments administered to parents and teacher, the results may suggest increased pressure for improved performance in different school tasks. Thus, these findings cannot be interpreted solely as a lack of effect of the intervention on the school and family settings. These ecological measures have been used to determine the efficacy of clinical interventions because they resemble the patient's daily demands (^{Loschiavo-Alvares et al., 2013}). Future studies using standardized instruments that are capable of ranking performance may minimize this limitation.

Some characteristics of the NR program may explain the improvements achieved by the patient. First, the intervention aimed at stimulating EFs by promoting self-regulation in school situations and reading comprehension through explicit instruction and systematic learning of EF strategies so that the patient could deal with school demands. These principles have also been addressed in other interventions involving EF strategies, but from an educational point of view (^{Gayo et al., 2014}).

Secondly, we found that an emphasis on reading comprehension and its strategic aspects has proven effective for children with DD who have fewer decoding deficits. Thus, NR can complement other conventional therapeutic approaches for DD (^{Darrot et al., 2023}; ^{Galuschka et al., 2014}; ^{Pasqualotto & Venuti, 2020}) and the emphasis on EFs broadens the scope of treatment, which has been previously confined to sensory processing and attention (^{Lorusso et al., 2011}). Another NR approach for dyslexia showed positive effects for decoding, but not for reading comprehension (^{Lorusso et al., 2011}).

Thirdly, parental and school involvement in the psychoeducation and guidance intervention modules may have aided in the transfer of strategies learned to other contexts. The principle of transfer of effects is crucial to the efficacy of any intervention and has been recognized as one of the main challenges for NR (^{Barnett & Ceci, 2002}). Thus, parents and teachers acted as mediators of treatment response, overseeing the training, monitoring, and reinforcement of strategies.

SCED studies have wide applicability in the clinical setting and, in this study, this design enabled the observation of the patient's idiosyncrasies. Nevertheless, using appropriate statistical techniques for the comparison of an individual to a well-matched control sample is central to the success of such studies. Thus, the design (^{Crawford et al., 2010}) used in this study was appropriate to test the effectiveness of NR. Nevertheless, some limitations of this study and perspectives for future studies include: use of standardized ecological measures of EFs; matching case and controls by reading level; a future study with an experimental design for the analysis of the effects of EFs on reading comprehension; inclusion of performance measures in other cognitive domains to evaluate the possible transfer of effects to untrained skills; and follow-up measures to determine the long-term persistence of effects.

Considerations

In conclusion, this study demonstrated the efficacy of a neuropsychological rehabilitation program for developmental dyslexia in a single-case experimental design. Neuropsychological rehabilitation emphasized executive functions and was effective in improving cognitive performance measures, ecological measures of executive functions, and reading parameters. Thus, neuropsychological rehabilitation can be part of the intervention process of individuals with dyslexia, helping minimize deficits and develop compensatory strategies for dealing with difficulties in the school and family settings.