Márta Farkas

Associative learning in deficit and nondeficit schizophrenia.

When two stimuli are associated and treated as equivalent, generalization occurs between them (acquired equivalence). The feedback-guided learning of associations is related to the basal ganglia, whereas the medial temporal lobe participates in acquired equivalence learning. In this study, we investigated feedback-guided associative learning and acquired equivalence in deficit and nondeficit schizophrenia. Results revealed that acquired equivalence learning was similarly impaired in deficit and nondeficit patients, whereas feedback-guided associative learning was impaired only in deficit patients. Associative learning and acquired equivalence were not related to frontal lobe tests. These results suggest that the enduring negative symptoms of deficit patients may be related to decreased response to cognitive feedback and deficient basal ganglia functioning.

The predictive validity of the Leonhardean classification of endogenous psychoses: a 21-33-year follow-up of a prospective study ("BUDAPEST 2000").

To our knowledge, no previous long-term studies of the Leonhardean classification in the whole spectrum of endogenous psychoses have been conducted. This prospective study (n = 276; female patients n = 222; normal control persons n = 54) started in 1967–1976. The same population was followed-up by participation of a “blinded control” psychiatrist in 1997–2002 [patients available at follow-up = 125 (56.3%); available controls = 38 (70.4%)]. Patients for this investigation were selected by two independent diagnosticians from eight nosological groups based on full diagnostic agreement. Diagnostic agreement at follow-up (weighted-kappa) was 0.87. Predictive validity of the diagnostic categories was measured empirically and using a stochastic (Markovian) model, thus combining validity and reliability. Hebephrenias, group of normal persons and of schizophrenias proved to be valid categories, with diagnostic stabilities of 0.94, 0.91, and 0.93, for the three groups, respectively. In addition, bipolar manic-depressive psychoses and cycloid psychoses were also valid (diagnostic stability of 0.77 and 0.76, respectively). Unipolar depression was valid (diagnostic stability = 0.84) only by forming a “nosological family” based on diagnostic stability and on current status and clinical presentation during the period preceding the follow-up with regard to other mood-congruent disorders and outcome-diagnosis “normal control”. Validity of systematic paraphrenias (diagnostic stability = 0.69) was in the moderate range. Division of schizophrenias in “systematic versus non-systematic” nosological categories was inconclusive; the categories of affect-laden paraphrenia, periodic catatonia and systematic catatonias could not be confirmed reliably in this study.

Validity of reliability: Comparison of interrater reliabilities of psychopathological symptoms

We have tested the stability of interrater reliability of psychiatric symptoms over a quarter of century using 2 rating scales. Interrater reliabilities of items of 2 psychiatric rating scales employed by 2 consecutive follow-ups were compared. Interrater reliabilites proved to be by and large stable. Interrater reliability depends on the standard deviation of the items scores. In addition to the traditional approach, a new statistical method for unifying the assessments from multiple raters is also presented. Using this method, we demonstrated that probabilities of correct ratings are higher in the absence of manifest symptoms, or in the presence of symptoms, as compared with cases characterized by middle scores. To interpret the relationships revealed in the setting of the experiment, we introduce for its theoretical designation the term “validity of reliability.” It is recommended for evaluation of results of rating scales in the context of psychiatric nosology.