Difficulties with concentration are frequent complaints of patients with depersonalization disorder (DPD). Standard neuropsychological tests suggested alterations of the attentional and perceptual systems. To investigate this, the well-validated Spatial Cueing paradigm was used with two different tasks, consisting either in the detection or in the discrimination of visual stimuli. At the start of each trial a cue indicated either the correct (valid) or the incorrect (invalid) position of the upcoming stimulus or was uninformative (neutral). Only under the condition of increased task difficulty (discrimination task) differences between DPD patients and controls were observed. DPD patients showed a smaller total attention directing effect (RT in valid vs. invalid trials) compared to healthy controls only in the discrimination condition. RT costs (i.e., prolonged RT in neutral vs. invalid trials) mainly accounted for this difference. These results indicate that DPD is associated with altered attentional mechanisms, especially with a stronger responsiveness to unexpected events. From an evolutionary perspective this may be advantageous in a dangerous environment, in daily life it may be experienced as high distractibility.
Depersonalization disorder (DPD) is characterized by persistent or recurrent feelings of depersonalization (i.e. experiences of unreality, detachment, or being an outside observer with respect to one׳s thoughts, feelings, sensations, body, etc.) and/or derealization (individuals or objects are experienced as unreal, dreamlike, foggy, lifeless, or visually distorted). During these experiences reality testing remains intact. The symptoms are not caused by direct physiological effects of drugs or other medical conditions and are not better accounted for by another mental disorder (e.g. panic disorder or depression). Finally, these symptoms cause clinically significant distress or impairment (Spiegel et al., 2011 and American-Psychiatric-Association, 2013). The prevalence of DPD in the general population is around 1% (Lee et al., 2012). Both genders are equally affected (Simeon, 2004). The onset of the disorder is usually before age 25, the course is typically chronic (Baker et al., 2003 and Simeon et al., 2003). DPD has a high comorbidity with depression and anxiety disorders, however, comorbidity does not explain the severity of depersonalization (Simeon, 2004, Medford et al., 2005 and Sierra et al., 2012). Impairment of cognitive functions is among the main complaints of DPD patients: patients complain about mind emptiness, racing thoughts, memory impairments, impairment of visual imagery and concentration (Lambert et al., 2001, Hunter et al., 2003 and American-Psychiatric-Association, 2013). With regard to functions in DPD patients two previous studies demonstrated subtle alterations of the attentional and perceptual systems, but only little cognitive disturbances (Giesbrecht et al., 2008). In their first study, Guralnik et al. (2000) found a worse performance of DPD patients as compared to healthy persons for measures of attention, short-term visual and verbal memory, and spatial reasoning (Guralnik et al., 2000). In their second study they found an intact general intelligence and working memory for DPD patients. However, subtle impairments in tasks of short-term memory and selective attention emerged, as severity of depersonalization was correlated with increased distractibility during recall. Important to note, these findings were not mediated by the severity of anxiety and/or depression. The authors concluded that DPD may be associated with disruptions in the early perceptual and attentional processes (Guralnik et al., 2007). Impairments of short-term memory tasks were attributed to problems in processing new information. However, due to methodological limitations of the applied standard neuropsychological tests, it was not possible to differentiate, whether these cognitive impairments were due to deficits of short-term memory or attention.
The aim of the present study was to test whether DPD affects attentional processing stages as hypothesized by Guralnik et al. (2007). More specifically, we investigated whether DPD is associated with altered mechanisms of selective spatial attention. Selective attention is defined as the ability to select the behavioral relevant information from the vast amount of internal and/or external information (enhancement of processing) and to ignore the rest (suppression of processing) (Posner, 1980 and Hillyard et al., 1998). A common and well established experimental task for investigating selective attention is the “Spatial Cueing Paradigm” by Posner and Cohen (1984). In the Spatial Cueing paradigm participants are instructed to detect and to respond to targets presented on the left or right side of a fixation cross on a screen. Prior to the target, a centrally located cue indicates the most likely location for the subsequent target. In most of the trials the prediction of the cue is valid, i.e. it indicates the correct target location. However, in some of the trials invalid cues are given, indicating the incorrect location of the target. By testing the responses to targets following a non-directional (i.e. neutral) cue, a baseline score of the participants׳ reaction time can be measured. A common finding is that response times (RTs) to targets are shorter after valid cues as compared to targets after invalid cues (e.g. Eimer, 1996; Luck et al., 1994; Mangun and Buck, 1998). This effect is considered as the result of a covert shift of attention to the expected target location. This total attention directing effect can be caused either by enhanced target processing at cued location (“RT benefits”) or by suppression of processing of targets at uncued location (“RT costs”). RT benefits of directing attention are reflected in faster RTs for valid as compared to neutral trials, whereas RT costs are reflected in increased RTs for invalid compared to neutral trials (see Fig. 1).
