Nonconscious Stimuli Research Articles

Binocularly suppressed stimuli induce brain activities related to aesthetic emotions

IntroductionAesthetic emotions are a class of emotions aroused by evaluating aesthetically appealing objects or events. While evolutionary aesthetics suggests the adaptive roles of these emotions, empirical assessments are lacking. Previous neuroscientific studies have demonstrated that visual stimuli carrying evolutionarily important information induce neural responses even when presented non-consciously. To examine the evolutionary importance of aesthetic emotions, we conducted a neuroscientific study using magnetoencephalography (MEG) to measure induced neural responses to non-consciously presented portrait paintings categorised as biological and non-biological and examined associations between the induced responses and aesthetic ratings.MethodsMEG and pre-rating data were collected from 23 participants. The pre-rating included visual analogue scales for object saliency, facial saliency, liking, and beauty scores, in addition to ‘biologi-ness,’ which was used for subcategorising stimuli into biological and non-biological. The stimuli were presented non-consciously using a continuous flash suppression paradigm or consciously using binocular presentation without flashing masks, while dichotomic behavioural responses were obtained (beauty or non-beauty). Time-frequency decomposed MEG data were used for correlation analysis with pre-rating scores for each category.ResultsBehavioural data revealed that saliency scores of non-consciously presented stimuli influenced dichotomic responses (beauty or non-beauty). MEG data showed that non-consciously presented portrait paintings induced spatiotemporally distributed low-frequency brain activities associated with aesthetic ratings, which were distinct between the biological and non-biological categories and conscious and non-conscious conditions.ConclusionAesthetic emotion holds evolutionary significance for humans. Neural pathways are sensitive to visual images that arouse aesthetic emotion in distinct ways for biological and non-biological categories, which are further influenced by consciousness. These differences likely reflect the diversity in mechanisms of aesthetic processing, such as processing fluency, active elaboration, and predictive processing. The aesthetic processing of non-conscious stimuli appears to be characterised by fluency-driven affective processing, while top-down regulatory processes are suppressed. This study provides the first empirical evidence supporting the evolutionary significance of aesthetic processing.

Effects of Brand Priming on Sustainable Consumption Attitudes and Behaviors

Keywords: altruism brand priming branding consumer behavior materialism sustainability sustainable consumption non-conscious stimuli

Nonconscious information can be identified as task-relevant but not prioritized in working memory.

Two critical features of working memory are the identification and appropriate use of task-relevant information while avoiding distraction. Here, in 3 experiments, we explored if these features can be achieved also for nonconscious stimuli. Participants performed a delayed match-to-sample task in which task relevance of 2 competing stimuli was indicated by a cue, and continuous flash suppression was used to manipulate the conscious/nonconscious visual experience. Experiment 1 revealed better-than-chance performance with nonconscious stimuli, demonstrating goal-directed use of nonconscious task-relevant information. Experiment 2 demonstrated that the cue that defined task relevance must be conscious to allow such goal-directed use. In Experiment 3, multi-voxel pattern analyses of brain activity revealed that only the target was prioritized and maintained during conscious trials. Conversely, during nonconscious trials, both target and distractor were maintained. However, decoding of task relevance during the probe/test phase demonstrated identification of both target and distractor information. These results show that identification of task-relevant information can operate also on nonconscious material. However, they do not support the prioritization of nonconscious task-relevant information, thus suggesting a mismatch in the attentional mechanisms involved during conscious and nonconscious working memory.

Unconscious Bias Training Removes Bias Effect from Non-Conscious Stimuli, Restoring Choice Divergence

Unconscious Bias Training Removes Bias Effect from Non-Conscious Stimuli, Restoring Choice Divergence

Computational Psychiatry and Psychometrics Based on Non-Conscious Stimuli Input and Pupil Response Output.

Computational Psychiatry and Psychometrics Based on Non-Conscious Stimuli Input and Pupil Response Output.

Classical conditioning of analgesic and hyperalgesic pain responses without conscious awareness

Pain reduction and enhancement can be produced by means of conditioning procedures, yet the role of awareness during the acquisition stage of classical conditioning is unknown. We used psychophysical measures to establish whether conditioned analgesic and hyperalgesic responses could be acquired by unseen (subliminally presented) stimuli. A 2 × 2 factorial design, including subliminal/supraliminal exposures of conditioning stimuli (CS) during acquisition/extinction, was used. Results showed significant analgesic and hyperalgesic responses (P < 0.001), and responses were independent of CS awareness, as subliminal/supraliminal cues during acquisition/extinction led to comparable outcomes. The effect was significantly larger for hyperalgesic than analgesic responses (P < 0.001). Results demonstrate that conscious awareness of the CS is not required during either acquisition or extinction of conditioned analgesia or hyperalgesia. Our results support the notion that nonconscious stimuli have a pervasive effect on human brain function and behavior and may affect learning of complex cognitive processes such as psychologically mediated analgesic and hyperalgesic responses.

Seeing is believing: Utilization of subliminal symbols requires a visible relevant context

Sensory input that is not available for conscious report can still affect our behavior. Recent findings suggest that such subliminal information has the potency to influence behavior in a way that is dependent on the observer's current intentions. Here, we investigate whether conscious observation of stimulus relevance provides an incentive for the utilization of nonconscious stimuli. We manipulated the predictive power of directional cues to selectively affect the incentive to utilize them for a subsequent target detection task. Central arrow cues rendered invisible by interocular suppression elicited a facilitatory cuing effect, but only when intermixed with visible arrow cues that were highly predictive with respect to (i.e., 80 % congruent with) the subsequent target location. When the visible cues were nonpredictive (50 % congruent), no subliminal cuing effect was found. An analysis of learning effects corroborates these findings; Cuing effects elicited by both visible and invisible cues increased over the course of the experiment, but only when intermixed visible cues were highly predictive. In a second experiment, we demonstrated that the intrinsic relevance of invisible cues (either 50 % or 100 % congruent) has no effect on the utilization of visible cues. We conclude that conscious perception is required to make statistical inferences about the relevance of symbolic cues. Once statistical information is extracted consciously, it affects subsequent nonconscious processing in a way that fits the current context. Accordingly, one of the possible functions of consciousness could be to extract general rules out of the conscious information, to provide guidelines for future behavior.

Nonconscious activation of placebo and nocebo pain responses

The dominant theories of human placebo effects rely on a notion that consciously perceptible cues, such as verbal information or distinct stimuli in classical conditioning, provide signals that activate placebo effects. However, growing evidence suggest that behavior can be triggered by stimuli presented outside of conscious awareness. Here, we performed two experiments in which the responses to thermal pain stimuli were assessed. The first experiment assessed whether a conditioning paradigm, using clearly visible cues for high and low pain, could induce placebo and nocebo responses. The second experiment, in a separate group of subjects, assessed whether conditioned placebo and nocebo responses could be triggered in response to nonconscious (masked) exposures to the same cues. A total of 40 healthy volunteers (24 female, mean age 23 y) were investigated in a laboratory setting. Participants rated each pain stimulus on a numeric response scale, ranging from 0 = no pain to 100 = worst imaginable pain. Significant placebo and nocebo effects were found in both experiment 1 (using clearly visible stimuli) and experiment 2 (using nonconscious stimuli), indicating that the mechanisms responsible for placebo and nocebo effects can operate without conscious awareness of the triggering cues. This is a unique experimental verification of the influence of nonconscious conditioned stimuli on placebo/nocebo effects and the results challenge the exclusive role of awareness and conscious cognitions in placebo responses.

Subliminal food images compromise superior working memory performance in women with restricting anorexia nervosa

Prefrontal cortex (PFC) is dysregulated in women with restricting anorexia nervosa (RAN). It is not known whether appetitive non-conscious stimuli bias cognitive responses in those with RAN. Thirteen women with RAN and 20 healthy controls (HC) completed a dorsolateral PFC (DLPFC) working memory task and an anterior cingulate cortex (ACC) conflict task, while masked subliminal food, aversive and neutral images were presented. During the DLPFC task, accuracy was higher in the RAN compared to the HC group, but superior performance was compromised when subliminal food stimuli were presented: errors positively correlated with self-reported trait anxiety in the RAN group. These effects were not observed in the ACC task. Appetitive activation is intact and anxiogenic in women with RAN, and non-consciously interacts with working memory processes associated with the DLPFC. This interaction mechanism may underlie cognitive inhibition of appetitive processes that are anxiety inducing, in people with AN.

Nonconscious perception, conscious awareness and attention

Because it is unclear how a nonconscious stimulus is cognitively processed, there is uncertainty concerning variables that modulate the processing. In this context recent findings of a set of neuroimaging experiments are important. These findings suggest that conscious and nonconscious stimuli activate same areas of the brain during performance of a similar task. Further, different areas are activated when a task is performed with or without awareness of processing. It appears that the neural network involved in cognitive processing depends on the awareness of processing rather than awareness of perception. Since conscious and nonconscious cognitive processing use separate neural networks, each processing is modulated by different variables. Attention modulates most conscious cognitive processing and most, but not all, nonconscious processing is attention dependent. Nonconscious tasks that require attentional resources, with or without conscious awareness, are processed using the attention dependent system. Further, because attention dependent and attention independent tasks are processed by separate neural networks, the cognitive processing and modulating variables can be understood better if cognitive tasks are defined as attention dependent or attention independent, rather than conscious or nonconscious.

Why the brain knows more than we do: non-conscious representations and their role in the construction of conscious experience.

Scientific studies have shown that non-conscious stimuli and representations influence information processing during conscious experience. In the light of such evidence, questions about potential functional links between non-conscious brain representations and conscious experience arise. This article discusses neural model capable of explaining how statistical learning mechanisms in dedicated resonant circuits could generate specific temporal activity traces of non-conscious representations in the brain. How reentrant signaling, top-down matching, and statistical coincidence of such activity traces may lead to the progressive consolidation of temporal patterns that constitute the neural signatures of conscious experience in networks extending across large distances beyond functionally specialized brain regions is then explained.

The neural processing of fearful faces without attention and consciousness: An event-related potential study

To investigate whether the non-conscious processing of fearful faces exist in unattended condition, event-related potentials (ERPs) were recorded in a facial expression detection task. Participants were asked to discriminate the facial expressions (fearful or neutral) at the attended location. Unattended faces were associated with a response that was either congruent or in conflict with the response to the attended face. ERP results showed that the trials with response conflict between attended and unattended faces enhanced the amplitude of the P3 component when the neutral face was presented at attended location and the fearful face was presented at the unattended location. Our findings imply that the non-conscious fearful faces can be processed in the unattended condition.

Timing of the earliest ERP correlate of visual awareness

The earliest reliably occurring event-related brain potential (ERP) correlate of visual awareness (visual awareness negativity, VAN) emerges after 100 ms and peaks between 200 and 300 ms from stimulus onset. In a study using low-contrast stimuli, VAN was significantly delayed, peaking at 460 ms (V. Ojanen, A. Revonsuo, & M. Sams, 2003). In that study physical differences between the conscious and nonconscious stimuli may have confounded the results. Here we explored whether VAN is similarly delayed for physically identical stimuli. We presented low-contrast stimuli near an individually determined subjective contrast threshold. A delayed VAN peaked at 400 ms at occipito-temporal sites to subjectively perceived stimuli. Our results support the interpretation that VAN is the earliest ERP correlate of phenomenal visual awareness. The electrophysiological processes eliciting VAN may become delayed as a function of the difficulty of the early perceptual discrimination.

Can One Suppress Subliminal Words?

Subliminal words cause behavioral priming, yet the depth of their processing remains debated. Using transcranial magnetic stimulation (TMS), Nakamura et al. demonstrate in this issue of Neuron that this subliminal priming effect can be selectively disrupted. Distinct TMS sites disrupt priming in lexical decision and pronunciation tasks, suggesting that task set influences subliminal processing.

Trends and styles in visual masking

Advances in Cognitive PsychologyProcessing of nonconscious stimuli has a long history as a research topic of experimental vision research. The recent past has seen an increasing number of research articles that address questions of noncon-scious vision. One starting point for this renewed interest has been the provision of visual masking paradigms – the topic of the present edition – as powerful tools for demonstrating the processing of nonconscious visual information (cf. Neumann & Klotz, 1994; Klotz & Neumann, 1999). Neumann and Klotz impeded con-scious perception of visual stimuli (‘primes’) by tem-porally trailing, spatially adjacent visual masks (meta--contrast masking; cf. Exner, 1868; Stigler, 1910). They further demonstrated that the prime influencesspeed and accuracy of responses towards the visible mask (“metacontrast dissociation”). Since Neumann and Klotz’s original report, numerous studies have replicated the basic finding,includingdemonstrationsof priming in electrophysiological measures of re-sponse activation and the shifting of visuospatial at-tention (see, for instance, Breitmeyer, Ro, & Singhal, 2004; Eimer & Schlaghecken, 1998; Jaśkowski, van der Lubbe, Schlotterbeck, & Verleger, 2002; Leuthold & Kopp, 1998; Schaghecken & Eimer, 2004; Vorberg, Mattler, Heinecke, Schmidt, & Schwarzbach, 2003).Occasionally, the processing of conscious and nonconscious information was assumed to be ac-complished by separate systems, as for example, the dorsal and the ventral stream of the cortical visual system (Milner & Goodale, 1995). Recent results, how-ever, show that there is no single and uniform system for the processing of conscious, or the processing of nonconscious information, even in vision. Instead, it seems that nonconscious stimuli are processed partly like conscious stimuli, especially during early stages of processing, and that the processing diverges only in some respects, at later, reentrant or feedback stages (cf. Aron et al., 2003; Haynes, Driver, & Rees, 2005; Lamme & Roelfsema, 2001; Morris, Ohman, & Dolan, 1999; Ogmen & Breitmeyer, 2006; Pinel, Riviere, Le Bihan, & Dehaene, 2001). These results suggest a shifting of the research focus towards two general questions: (a) the extent to which processing of conscious and nonconscious information contributes to any specificvisualfunc-tion, and (b) the identificationoftemporalstagescharacteristic of the processing of conscious and nonconscious visual information, respectively. These research questions have been addressed in a variety of forms, concerning the temporal dynamics of prim-ing and masking, the comparison of semantic and sensorimotor processing, or the role of intentions for the processing of nonconscious information.