Gricel Orellana

Executive Functioning in Schizophrenia

The executive function (EF) is a set of abilities, which allows us to invoke voluntary control of our behavioral responses. These functions enable human beings to develop and carry out plans, make up analogies, obey social rules, solve problems, adapt to unexpected circumstances, do many tasks simultaneously, and locate episodes in time and place. EF includes divided attention and sustained attention, working memory (WM), set-shifting, flexibility, planning, and the regulation of goal directed behavior and can be defined as a brain function underlying the human faculty to act or think not only in reaction to external events but also in relation with internal goals and states. EF is mostly associated with dorsolateral prefrontal cortex (PFC). Besides EF, PFC is involved in self-regulation of behavior, i.e., the ability to regulate behavior according to internal goals and constraints, particularly in less structured situations. Self-regulation of behavior is subtended by ventral medial/orbital PFC. Impairment of EF is one of the most commonly observed deficits in schizophrenia through the various disease stages. Impairment in tasks measuring conceptualization, planning, cognitive flexibility, verbal fluency, ability to solve complex problems, and WM occur in schizophrenia. Disorders detected by executive tests are consistent with evidence from functional neuroimaging, which have shown PFC dysfunction in patients while performing these kinds of tasks. Schizophrenics also exhibit deficit in odor identifying, decision-making, and self-regulation of behavior suggesting dysfunction of the orbital PFC. However, impairment in executive tests is explained by dysfunction of prefronto-striato-thalamic, prefronto-parietal, and prefronto-temporal neural networks mainly. Disorders in EFs may be considered central facts with respect to schizophrenia and it has been suggested that negative symptoms may be explained by that executive dysfunction.

Córtex prefrontal y trastornos del comportamiento: Modelos explicativos y métodos de evaluación

Los trastornos del cortex prefrontal (CPF) permiten explicar la sintomatologia de importantes cuadros neurologicos y psiquiatricos, tales como las secuelas de traumatismos encefalo-craneanos y las esquizofrenias. Sin embargo, y a pesar de la gran importancia de sus funciones, su estudio se ha visto dificultado por razones teoricas, experimentales y clinicas. Recientemente han surgido dos nuevos modelos que intentan explicar los mecanismos a la base del funcionamiento del CPF. Presentamos una revision de las principales manifestaciones clinicas ante su disfuncion, los modelos explicativos postulados tradicionalmente, ademas de las dos propuestas recientes de Koechlin y Mesulam, para finalizar con una revision de los instrumentos mas utilizados en el ambito clinico para la evaluacion de las funciones propias de esta region, denominadas funciones ejecutivas y de autorregulacion del comportamiento

Executive attention impairment in first-episode schizophrenia

BackgroundWe compared the attention abilities of a group of first-episode schizophrenia (FES) patients and a group of healthy participants using the Attention Network Test (ANT), a standard procedure that estimates the functional state of three neural networks controlling the efficiency of three different attentional behaviors, i.e., alerting (achieving and maintaining a state of high sensitivity to incoming stimuli), orienting (ability to select information from sensory input), and executive attention (mechanisms for resolving conflict among thoughts, feelings, and actions).MethodsWe evaluated 22 FES patients from 17 to 29 years of age with a recent history of a single psychotic episode treated only with atypical neuroleptics, and 20 healthy persons matched with FES patients by sex, age, and educational level as the control group. Attention was estimated using the ANT in which participants indicate whether a central horizontal arrow is pointing to the left or the right. The central arrow may be preceded by spatial or temporal cues denoting where and when the arrow will appear, and may be flanked by other arrows (hereafter, flankers) pointing in the same or the opposite direction.ResultsThe efficiency of the alerting, orienting, and executive networks was estimated by measuring how reaction time was influenced by congruency between temporal, spatial, and flanker cues. We found that the control group only demonstrated significantly greater attention efficiency than FES patients in the executive attention network.ConclusionsFES patients are impaired in executive attention but not in alerting or orienting attention, suggesting that executive attention deficit may be a primary impairment during the progression of the disease.

Trastornos de ansiedad en pacientes hospitalizados en Medicina Interna

BACKGROUND Anxiety symptoms and anxiety disorders are common among medical patients, however few studies differentiate both and consider the psychiatric comorbidity of anxiety disorders among such patients. AIM To evaluate the presence of anxiety disorders among patients admitted to a medical ward. PATIENTS AND METHODS Random selection of 406 patients (mean age 56 years, 203 female), hospitalized in a medical ward of a public hospital, mainly for cardiovascular, genitourinary and digestive diseases. All were assessed using an structured interview for DSM-III-R. RESULTS Twenty six percent of women and 13% of men had anxiety disorders. Fifteen percent of women and 6% of men had specific phobias, 7% of women and 4% of men had generalized anxiety, 5% of women and 0.5% of men had agoraphobia, 3% of women and 0.5% of men had social phobia, 1% of men and 0.5% of women had panic disorders and 0.5% of women had a post traumatic stress. Specific phobias and social phobias started during childhood. Anxiety and agoraphobia started during adulthood. Among patients with anxiety disorders, 43% of women and 34% of men did not have other psychiatric ailment, 34% of women and 19% of men had an associated depression and 34% of men had disorders due to use of alcohol. CONCLUSIONS A high proportion of patients hospitalized in medical wards have anxiety disorders, that once identified it may help to treat the medical ailments.

Small Saccades and Image Complexity during Free Viewing of Natural Images in Schizophrenia.

In schizophrenia, patients display dysfunctions during the execution of simple visual tasks such as antisaccade or smooth pursuit. In more ecological scenarios, such as free viewing of natural images, patients appear to make fewer and longer visual fixations and display shorter scanpaths. It is not clear whether these measurements reflect alterations in their proficiency to perform basic eye movements, such as saccades and fixations, or are related to high-level mechanisms, such as exploration or attention. We utilized free exploration of natural images of different complexities as a model of an ecological context where normally operative mechanisms of visual control can be accurately measured. We quantified visual exploration as Euclidean distance, scanpaths, saccades, and visual fixation, using the standard SR-Research eye tracker algorithm (SR). We then compared this result with a computation that includes microsaccades (EM). We evaluated eight schizophrenia patients and corresponding healthy controls (HC). Next, we tested whether the decrement in the number of saccades and fixations, as well as their increment in duration reported previously in schizophrenia patients, resulted from the increasing occurrence of undetected microsaccades. We found that when utilizing the standard SR algorithm, patients displayed shorter scanpaths as well as fewer and shorter saccades and fixations. When we employed the EM algorithm, the differences in these parameters between patients and HC were no longer significant. On the other hand, we found that image complexity plays an important role in exploratory behaviors, demonstrating that this factor explains most of differences between eye-movement behaviors in schizophrenia patients. These results help elucidate the mechanisms of visual motor control that are affected in schizophrenia and contribute to the finding of adequate markers for diagnosis and treatment for this condition.

Prevalencia de trastornos psiquiátricos por uso de alcohol y otras sustancias en hombres y mujeres hospitalizados en medicina interna de un hospital de Santiago de Chile

Background: Studies done in Chile and abroad report a high frequency of substance abuse among patients hospitalized in general medical services. Aim: To report the frequency of substance abuse in a sample of patients hospitalized in a public hospital of Santiago. Material and methods: A structured psychiatric interview for the Third Revised Version of The Diagnostic and Statistical Manual (DSM-III-R) was applied to 203 males, aged 58.5 years and 203 females, aged 52,9 years, hospitalized in an internal medicine Service of a public hospital. All subjects had a low educational and income level. Results: The discharge diagnoses of studied patients were digestive diseases in 32%, circulatory diseases in 19%, cancer, diabetes mellitus and genitourinary diseases in 11% respectively and mental or behavioral diseases in 5%. Thirty eight percent of males and 6% of females qualified for alcohol dependency or abuse in some moment of their lives. The figures for benzodiazepine dependency were 1% among males and 6% among females. The figures for cannabis, cocaine or stimulant abuse were 1.5% for males and 1% for females. Other conditions of the axis 1 of DSM-IIIR were diagnosed in 47% of males and 65% of females with substance abuse. Conclusions: Substance abuse underlies medical conditions in a high proportion of patients admitted to medical services in general hospitals (Rev Med Chile 2002; 130: 651-660)

Avances en la clínica de las adicciones: el rol del aprendizaje y la dopamina

There are two parallel explanatory models for addictions. One is the homeostatic model, that explains tolerance and the abstinence syndrome. Tolerance and abstinence are reversible phenomena that mask sensitization. These appear more commonly with the continued use of drugs, and are based in the up-regulation of cyclic AMP. The other is the plasticity model, that explains sensitization and compulsive use of drugs or addiction. Addiction is probably irreversible, underlies tolerance, appears more frequently with intermittent use of drugs, and is based in learning and memory mechanisms. Both are boldly linked to environmental and behavioral elements. In the plasticity model, dopamine (DA) has an outstanding role. Its phasic discharge is a temporal reward prediction error marker. It is the prediction error that generates learning. All the addictive drugs provoke a very strong increase of phasic DA discharge in some cerebral nuclei by direct or indirect paths. This increase is interpreted by cerebral circuits as prediction errors that generate learning behaviors. Pavlovian and operating type learning is involved. It is clinically observed as the prominence of environmental cues that are related to drug consumption, and the appearance of behaviors directed to the search and use of drugs, that are mainly involuntary and triggered by these cues. Pleasure (primary reinforcement) plays a role in this model, only in the initial stages of addiction. Understanding this double parallel model allows to design therapeutic interventions directed towards a conscious control of involuntary, environmental and affective cues that trigger drug search and use (Rev Med Chile 2007; 135: 384-91). (Key words: Dopamine; Drug addiction; Learning; Substance addiction)