Neuropsychological and neuroimaging markers and their potential use for schizophrenia diagnosis

Resumen

Basic cognitive processes and social cognition (SC) have been identified as being impaired in patients with schizophrenia. However, nowadays, these variables are not included in the common used diagnostic manuals for diagnosis the disease. Using cognitive impairment as diagnostic marker for schizophrenia presents different challenges such as: 1) the difficulties when accounting for patient’s premorbid functioning in order to stablish the presence of cognitive impairment and 2) the lack of adapted and reliable measures for assessing cognition in these patients, mainly in Spanish-speaking samples. This last challenge is particularly problematic in the case of SC and especially regarding social perception (SP), one of the most impaired SC domains in schizophrenia. Besides cognition, white matter (WM) integrity, and more concretely WM asymmetry, has shown abnormalities in patients with schizophrenia. However, up to date, no study has assessed the role of WM integrity asymmetry in cognition in schizophrenia. The present thesis is composed by four scientific contributions. The first study assessed the discriminant capability of both raw and discrepancy (controlling for sociodemographic and premorbid characteristics) cognitive scores when comparing patients and healthy controls (HC). The second study aimed to adapt and validate a well-known SP test (the Social Feature Recognition Test-2, SFRT-2) into Spanishspeaking patients with schizophrenia and HC. The third study presented two shortened and equivalent forms of the SFRT-2 as well as their psychometric properties. The fourth study investigated the WM asymmetry abnormalities in two frontal and occipital WM tracts as well as their relationship with cognition in patients with schizophrenia. Results showed that verbal memory and processing speed raw scores discriminated better than discrepancy scores between patients and HC, being verbal 28 memory the best classifier. Moreover, the Spanish adaptation and validation of the SFRT-2 as well as the obtained shortened forms showed satisfactory psychometric characteristics. Finally, patients with schizophrenia showed an abnormal asymmetry pattern of a frontal WM tract showing greater integrity in the right compared to the left hemisphere. WM integrity of the right frontal tract showed to correlate with verbal memory performance in patients with schizophrenia. This thesis provides an adapted and validated SP measure as well as its two shortened forms for Spanish-speaking patients with schizophrenia allowing stablishing a reliable SP impairment profile in these patients. In addition, results support the inclusion of cognitive impairment, especially verbal memory alterations, and frontal WM asymmetry abnormalities as potential diagnostic markers for schizophrenia diagnosis.