Neurocognitive mechanisms underlying identification of environmental risks

Abstract

Environmental risks threaten a large population and are more dreadful than personal risks that bring physical or health problems to individuals. To assess the neurocognitive processes involved in environmental risk identification, we recorded brain activities, using event-related potential (ERP) and functional magnetic resonance imaging (fMRI), from human adults while they identified risky and safe environmental and personal events depicted in words. We found that, relative to safe environmental events, the identification of risky environmental events induced larger amplitudes of an early positive ERP component at 180–260 ms over the frontal area (P200) and of a late positive wave at 420–660 ms over the central–parietal area (LPP). fMRI results showed that the identification of environmental risks was associated with increased activations in the ventral anterior cingulate cortex (vACC) and posterior cingulate cortex (PCC). The amplitudes of the LPP/P200 and the PCC activity positively correlated with subjective ratings of risk degree of and emotional responses to the risky environmental events. However, the identification of personal risks induced positive shift of ERPs at 280–320 ms over the frontal and parietal areas and increased activity in the left inferior and medial prefrontal cortex. Our findings suggest that identification of dreadful environmental risks is subserved by an early detection in vACC and a late retrieval of emotional experiences in PCC.

Introduction

Natural disasters such as floods and earthquakes may induce serious damages to a large population and constitute severe risks to the public. After entering the 20th century, human beings are also confronted with potential artificial disasters such as nuclear explosion and chemical pollution that can damage the environment and lead to catastrophic consequences to human society. These environmental risks have increasingly dominated individual and collective consciousness (Denney, 2005, Laudan, 1994) since perception of these environmental risks is crucial for making decisions on both individual behaviors and public policies.

Psychometric studies showed that risk perceptions are highly domain specific (Blais & Weber, 2001; Weber, Blais, & Betz, 2002). For example, risks related to an individual can be decomposed into subcategories such as those related to personal health/safety and social decisions (Weber et al., 2002). Our recent functional magnetic resonance imaging (fMRI) study showed that distinct neural substrates engage in identifications of personal risks that arise from interpersonal interactions in social contexts (social risks) and that come from situations that may give rise to physical discomfort (physical risks) (Qin & Han, in press). Specifically, the identification of social risks induced increased activities in the medial prefrontal cortex (MPFC), the dorsal anterior cingulate cortex (dACC), and bilateral posterior insula, whereas the identification of physical risks resulted in activations in the MPFC, the ventral anterior cingulate cortex (vACC), the right cuneus/precuneus and bilateral amygdala. The fMRI findings suggest that identifications of risks in the social and physical domains are different in both cognitive processes and emotional responses.

Researchers also categorized risks into environmental and individual personal domains (Gattig & Hendrickx, 2007; Schütz, Wiedemann, & Gray, 2000). The environmental risks arise from the natural processes and the use of technology, lack direct control by individuals (Schütz et al., 2000), and may generate catastrophic consequences relevant to the survival of a large population (Böhm & Pfister, 2000). In contrast, personal risks result from individual activities (e.g., smoking, drinking, or car driving) that influence individual health and safety (Schütz et al., 2000). It has been shown that humans may discount the ponderance of the same personal risks that may happen in the far than near future (Chapman, 1996; Chapman & Elstein, 1995), whereas evaluation of the severity of environmental risks is less influence by the temporal delay of outcome (Böhm & Pfister, 2000; Hendrickx & Nicolaij, 2004). Following our previous research (Qin & Han, in press), the current work further investigated neurocognitive mechanisms that may distinguish between the identifications of environmental and personal risks.

Most of contemporary research on risk perception/evaluation emphasizes both probability and consequences of risks during decision making (Kahneman & Tversky, 1979; Sanfey, Loewenstein, McClure, & Cohen, 2006). Neuroimaging studies have shown evidence that the processing of probability and negative outcome are associated with the prefrontal cortex (ventral and medial prefrontal cortex: Longe, Elliott, & Deakin, 2001; ventral and dorsal prefrontal cortex: Casey et al., 2001; dorsal lateral prefrontal cortex: Huettel, Song, & McCarthy, 2005) and the ACC (Gehring & Willoughby, 2002; Yeung & Sanfey, 2004), respectively. However, memory of emotional experience and other factors may influence the way people evaluate risks in everyday life so that the probability of risky events may be ignored (Botterill & Mazur, 2004; Loewenstein, Weber, Hsee, & Welch, 2001; Sunstein, 2003). In this case, the evaluation of potential consequences or consequences that have already taken place may become extremely important for risk perception. The psychometric approach on risk perception showed that subjective rating of risks correlated with the severity and dreadfulness of hazards that reflect the consequences associated with risks (Slovic, 1987). These findings suggest that feelings of dread play an important role in risk perception (Fischhoff, Slovic, Lichtenstein, Read, & Combs, 1978; Slovic, 1987) and risk perception may be associated with emotional reactions (Loewenstein et al., 2001; Slovic, Finucane, Peters, & MacGregor, 2004).

Previous studies suggested that strong feelings of dread are induced by the risks that lack control by individuals and may induce severe consequences (Slovic, 1987). Environmental risks are out of control in most cases (Schütz et al., 2000) and may produce catastrophic consequences to the survival of a large population (Böhm & Pfister, 2000). In these senses, environmental risks are more dreadful than personal risks (Slovic, 1987). This is consistent with the stress-related theory of risk perception, which claims that perception of high risk or anticipation of serious negative consequences may elicit intense emotions such as dread or fear (Stallen & Tomas, 1985). Moreover, Böhm (2003) suggested that prospective consequence-based feelings such as dread and fear are the most intense emotion associated with the consequence-based evaluation of environmental risks. Based on these studies, we hypothesized that, relative to the process of personal risks, the identification of environmental risks may result in enhanced emotional processing. In addition, the identification of environmental risks may occur earlier than that of personal risks in order to avoid harms to humans. To test these hypotheses, we combined event-related potential (ERP) and fMRI to record neural activities from subjects who were asked to perform a risk identification task. The task required judgment of risky or safe environmental and personal events depicted in words or phrases. Personal risk identification task was employed in the current work in order to estimate the specificity of the neurocognitive processes linked to the identification of environmental risks. Both risky and safe items were included in risk identification tasks. The neural substrates underlying risk identifications were defined by contrasting the risky events with the safe ones, which ruled out any confounds such as semantic processing and motor responses.

ERPs with high temporal resolution were recorded to examine the time course of environmental risk identification. Previous research showed that a fronto-central positive ERP component peaking at about 200 ms after sensory stimulation (P200) is sensitive to presence of threatening images or angry faces (Carretié, Martín-Loeches, Hinojosa, & Mercado, 2001; Carretié, Mercado, Tapia, & Hinojosa, 2001; Eimer, Holmes, & McGlone, 2003). A late positive potential (LPP) over the centro-parietal area is engaged in evaluative categorizations (Cacioppo, Crites, & Gardner, 1996; Crites & Cacioppo, 1996; Ito & Cacioppo, 2000) and could differentiate emotional from neutral stimuli during active evaluation (Cacioppo et al., 1996, Schupp et al., 2000). We assessed whether the ERP component such as P200 and LPP could differentiate identification of environmental and personal risks by comparing risky and safe events in each domain. Blood oxygen level dependent (BOLD) signals with high spatial resolution were recorded using fMRI to localize neural substrates engaged in the identification of environmental and personal risks. Our recent research showed the vACC activity was greater to physical than social risks, parallel to the higher rating scores of physical than social risks (Qin & Han, in press). Moreover, the neural activity in the posterior cingulate cortex (PCC) positively correlated with subjective evaluations of the degree of physical risks. The higher subjective ratings of the physical risk degree, the greater activations were observed in this brain region. Thus the current study tested if, compared with processing of personal risks, identification of environmental risks may enhance neural activities in brain regions such as vACC and PCC since environmental risks induce higher dread than personal risks (Slovic, 1987).