Background
Despite attempts to predict which clinical high risk (CHR) individuals will convert to schizophrenia (SCZ), current neurocognitive tests have yielded only modest results. Stress plays a pivotal role in the inception of psychotic symptoms. Accordingly, we have recently speculated that modest predictive success may be an outcome of the discrepancy between the neutral environment in which testing occurs and the stressful environments in which SCZ outbursts. According to this view, prediction of conversion to psychosis requires ‘stress’ tests analogous to those used in general medicine, such as examining cardiac activity under physical exertion. The purpose of this pilot study was to test this notion by developing and validating a ‘Stress-sensitive Self’ neurocognitive test. The focus on the self was chosen because disturbances of the basic self, such as impaired sense of agency (SoA) are central deficits in SCZ. We examined four hypotheses: (1) subjective ratings of stress will be associated with physiological markers of stress, (2) stress will impair judgments and metacognition of SoA, (3) the effect of stress on SoA will be related to the level of attenuated psychotic symptoms (APS), and (4) based on accumulating evidence relating cardiac signals to the bodily self, accuracy in SoA will be related to cardiac deceleration.
Methods
To test these hypotheses 14 healthy controls (HC) performed the ‘Virtual Hand’ (VH) task under two conditions; a neutral block and following a psychosocial stress induction in a ‘stress’ block. In the task they perform a movement with their hand, that is hidden from them, while on a monitor a VH is presented that performs the same movement. The movement is either presented synchronously or with temporal delays. Participants judge whether the VH’s movement is identical to their actual movement (i.e. agency question) and rate their confidence (i.e. metacognition question). Heart rate (HR) was continuously recorded. Presence and distress associated with APS were assessed via the brief version of the Prodromal Questionnaire (PQ-B).
Results
Consistent with our first hypothesis, HR variability captured subjective ratings of stress, and the two were strongly correlated (r = -.637, p = .014). Inconsistent with our second hypothesis, stress did not significantly alter sensitivity (d’) in recognition of the VH (F(1,12) < 1, p = .34). Moreover, it significantly improved, rather than impaired, metacognitive monitoring (i.e., the association between confidence judgments and the actual correctness of the answers) (F(1,12) = 10.64, p =.007, η²p = 0.47). Consistent with our third hypothesis, the beneficial effect of stress on metacognitive monitoring was smaller for HCs with high levels of APS, albeit not significantly so (r = -.28, p = .26). Finally, HR deceleration during VH presentation was significantly predictive of both SoA accuracy (F(1,12) = 13.3, p =.003, η²p = 0.53), and confidence in SoA judgments (F(1,12) = 10.64, p =.002, η²p = 0.52).
Discussion
The results of this pilot study provide mixed yet promising preliminary support for the notion of a ‘Stress-sensitive Self’ test’. More specifically, they suggest that mild stress improves metacognitive monitoring judgments of self-agency, whereas an opposite trend was observed for healthy participants that reported higher scores of APS. In addition, they provide preliminary evidence for a pre-reflexive implicit physiological mechanism supporting the basic self, a mechanism that may be disturbed in SCZ. Ongoing studies are examining CHR’s performance on the ‘Stress-sensitive Self’ test and replicating the current results in a larger sample of HCs.
