Schizophrenia is a mental illness affecting 1% of the world population and has severe deleterious effects on quality of life; mainly because symptoms begin at an early age and full recovery has not been achieved with current therapies [1
]. Schizophrenia is characterized by multiple cognitive impairments including attention deficit [2
]. Most psychosocial problems in schizophrenia are associated with cognitive deficiency [3
The majority of studies on cognition in schizophrenia involve heterogeneous samples of adults suffering from chronic schizophrenia with long histories of somatic treatments including electroconvulsive therapy. Thus, the nature of neurocognitive dysfunction is potentially confounded by the effects of age, clinical symptoms, illness duration and severity, and/or treatment. Over the past 15 to 20
years, however, there has been a growing interest in the clinical and neurocognitive characteristics of the early phases of schizophrenia, an approach that has the potential to minimize many of the interpretive difficulties associated with studying chronically ill patients [7
Attention deficits have been reported in schizophrenia from the earliest descriptions of the disease [8
]. As one of the earliest clinical manifestations of schizophrenia, attention impairment may be a primary disorder in the neuropathology of schizophrenia [9
]. Most data on attention deficit in schizophrenia have involved chronic patients and have found that these patients demonstrate impairment in all three attention networks (evaluated with the Attention Network Test; ANT). Yet, studies of chronic schizophrenia provide little information to shed light on which attention capacity is primarily impaired and which may explain the first manifestations of the disease.
Attention is not a single unitary system but a set of integrated processes that act on all levels of cognitive processing from sensory entry to motor exit [9
]. As early as Bleuler’s (1911) articles, many authors have been led to consider attentional disorder as a basic manifestation of the development of the illness.
Attention in schizophrenia has been primarily studied with the Stroop test and the Continuous Performance Test (CPT). The Stroop test estimates how reaction time slows when a participant must deal with conflicting information. In the classic Stroop test, participants need to say, as fast as possible, the name of the color of words written in ink of the same or of a different color from that which is specified by the letters (e.g., the word “blue” written in green ink). Participants take longer to say the name of the color when the written words are different from the ink color. The Stroop test is presented on printed cards or on a computer screen. In the card version of this test, under conditions of conflict, patients suffering from chronic schizophrenia show slower reaction times and a higher error rate than control participants. Therefore, schizophrenic patients present an increase in degree of sensitivity to interference [12
]. Studies carried out with the computer version of the Stroop test have shown that, when compared to healthy control participants, schizophrenic patients present a higher error rate in situations ranging from the neutral to the incongruent or conflicting condition [12
]. Deficits in the execution of the CPT have been detected in chronic schizophrenia and in adolescent and adult patients during early stages of the illness, in nonpsychotic relatives of patients, and in offspring at risk of inheriting the illness from their schizophrenic parents [13
]. The totality of these studies suggest that the sustained attention deficit, as measured by the CPT, is stable during the course of the illness, does not improve with antipsychotic treatment, and has a strong genetic component. CPT deficits would appear to be specific to schizophrenia; they are not found in depression and in adolescents that are at risk of suffering affective illnesses [13
Current models have shown that attention is not a unitary function but the result of three different attentional networks, i.e., alerting, orienting, and executive function [14
], that can be independently evaluated using the ANT [15
]. Alerting is manifested by achieving and maintaining the alert state, orienting by the ability to direct attention to sensory events, and executive attention by efficient control of thoughts, actions, and feelings. The ANT has been widely validated across a number of cultures, ages, and morbid entities. Some recent studies exploring attention in chronic schizophrenia with the ANT have revealed contrasting results: One study reported impairment in orientation and executive attention [18
], whereas others referred exclusively to a deficit in executive attention [19
] or in alerting [22
]. Still other studies have produced controversial results, reporting smaller conflict effect scores in individuals with chronic schizophrenia measured behaviorally [23
] and by event-related potentials [24
]. Finally, another study observed that positive syndrome patients showed less efficiency than healthy controls in the orientation network [25
]. The discrepancy reported by these studies may be due to the heterogeneity of symptoms and syndromes in chronic schizophrenic patients. For example, the sample described by Gooding et al. [19
] consisted of chronic schizophrenia–spectrum patients including chronic schizophrenia and schizoaffective disorder. However, the inconsistency can also be a consequence of differences in the progression and treatment of the disease. Studying patients with first-episode schizophrenia (FES) provides the advantage of being able to control the different factors described above. A consistent impairment in attention exists in FES [7
]; nevertheless, to the best of our knowledge, attention networks in FES patients have not been evaluated with the ANT. The aim of our study was to establish which attentional network is impaired in schizophrenia during early stages of the disease treated only with one atypical antipsychotic.
Since schizophrenia is highly related to dopamine and prefrontal dysfunction in its earliest stages, we may expect that FES patients exhibit exclusive reduction in executive attention [26
]. Indeed, in monkeys, alerting is more influenced by norepinephrine [28
] and orienting by acetylcholine [29
]. We thus hypothesize that, contrary to patients with chronic schizophrenia, FES patients will only show a primary deficit in executive attention.