Deficiencias mnésicas, ejecutivas y atencionales como endofenotipos neurocognitivos en el trastorno bipolar: una revisión
Marisol Castañeda Franco,1 Elsa Tirado Durán,1
Actualización por temas
Although many studies have demonstrated that bipolar disorder (BD) isheritable, the disorder´s genetic basis remains elusive despite the substantial evidence. Hence, indicators of processes mediating between genotype and phenotype, known as endophenotypes, may be necessary to provide more information about this issue. Given that endophenotypes could provide information for elucidating the genetic underpinnings of BD, many studies have focused on one class of endophenotypicmarker, the neuropsychological measures. In order for a cognitive measure to be considered an endophenotype, it has to 1. be highly heritable, 2. be associated with the illness, 3. be independent of the clinical state and, 4. the impairment must co-segregate with the illness within a family, with non-affected family members showing impairment relative to general population. In this sense, failuresin attention, executive functions and verbal memory are the most consistently reported deficits with the characteristics for endophenotypes. With these factors in mind, the primary interest of this paper was to review the existing literature on neurocognitive functioning in BD as possible endophenotypes. Studies were identified by searching the major databases (MEDLINE and PSYCINFO) from 1990 to2007 with the following key words: endophenotype, neurocognitive assessment, bipolar disorder, attention, memory, executive functions, neuropsychological assessment and neuroimaging. The titles and abstracts of the articles identified were examined and those that appeared to fullfil our inclusion criteria were retrieved. Articles were included if they met the following criteria: 1. included adultpatients (aged: 16-65), 2. included a psychiatric or normal comparison group, 3. used well-established diagnostic criteria to ascertain diagnosis (DSM, 3rd. and 4th. eds.), 4. provided information about the clinical status of the patients being assessmed and 5. cognitive assessment was based on standardized or well established cognitive tasks. Declarative memory has been studied in BD patientsthrough tests that imply learning of words and stories to evaluate immediate memory, delayed recall and recognition, also considering the kind of strategies that the patients use to evoke verbal material. It seems that BD patients in depressive phase present deficits in immediate memory and delayed recall, but recognition memory is preserved. This impairment is due to difficulties in the planning andevoking strategies used, associated to prefrontal dysfunction. In manic phase, the patients make a lot of irrelevant associations because the
failure in the system to control impulses. In the absence of the depressive and maniac symptoms, patients continue with anomalies in memory. Euthymic patient can use a similar semantic clustering strategy so that they can recall and recognize fewerwords than controls, suggesting impaired encoding of verbal information and there is lack of rapid forgetting, which suggests a relative absence of a storage deficit. Results of studies in declarative memory impairment in BD suggests that the impairments are consistent with deficits in learning, but do not appear to be related to different organizational strategies during learning, and do not appearto be secondary to clinical state. Rather, they are associated with the underlying pathophysiology of the illness. Regarding executive functions, patients with BD have deficiencies related to planning, organizational strategies, lack of control in the action, conceptual formation and cognitive flexibility. In depressive phase, patients have problems with concept formation, meanwhile the deficit...