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PubMed2005

Automatic and effortful emotional information processing regulates different aspects of the stress response.

There is increasing evidence that stress and self-regulation are important factors in the development and treatment of psychopathology. A key issue is to determine how cognitive-emotional systems modulate the stress response. We sought to determine whether effortful and automatic processing were differentially associated with subsequent mood and cortisol levels during a stressful challenge. We examined this question by having clinically anxious, depressed, and control participants perform a modified spatial cueing task with supraliminal and masked pictorial stimuli during a stressful challenge and control condition. The stressful challenge, relative to the control condition, lowered mood, but did not influence cortisol levels. In the full sample, disengagement from supraliminal dysphoric pictures was associated with subsequent mood ratings, whereas disengagement from masked pictures depicting threat was associated with subsequent cortisol levels. Effortful and automatic processing appears to regulate different aspects of the stress response.

Adaptation, Psychological↗
PubMed2006

Paracingulate sulcus morphology and fMRI activation detection in schizophrenia patients.

OBJECTIVE: Altered anterior cingulate cortex activity has been consistently detected by functional imaging in schizophrenia patients. In the present study, we hypothesized that the detection of such local hypoactivity varies when the subjects' local gyrification is monitored. Using a group-statistical approach, we investigated whether the presence or absence of a paracingulate sulcus (PCS) does influence the detection of the activation patterns in the cognitive division of the anterior cingulate cortex (ACcd). METHOD: fMRI data were acquired using an event-related paradigm during a task involving both priming and interference between stimuli. In the fMRI dataset collected from 13 schizophrenia patients and 16 healthy subjects, subgroups were defined according to the presence or absence of a PCS. Regional activations during interference between stimuli were examined in the ACcd of each hemisphere, using for each region of interest both voxel-based random-effects and non-parametric analyses. RESULTS: ACcd activation was left-sided in healthy subjects with a PCS, and right-sided in healthy subjects devoid of a PCS. ACcd activations were detected bilaterally in schizophrenia patients with a PCS, whereas left ACcd was deactivated in patients without a PCS. Subgroup comparisons revealed no difference between healthy subjects with a PCS and patients with a PCS, whereas in the subgroups devoid of PCS, the patients exhibited a bilateral ACcd hypoactivation relative to healthy subjects. CONCLUSIONS: PCS presence or absence influences the detection of ACcd activations in group-analysis of schizophrenia patients.

Adult↗
PubMed1999

Facilitatory and inhibitory effects of masked prime stimuli on motor activation and behavioural performance.

Three experiments investigated the impact of information provided by masked stimuli on motor activation. Masked primes were presented prior to target stimuli and these primes were identical to the target on compatible trials, identical to the target mapped to the opposite response on incompatible trials and task-irrelevant on neutral trials. A previous study [Eimer, M., & Schlaghecken, F. (1998). Effects of masked stimuli on motor activation: Behavioural and electrophysiological evidence. Journal of Experimental Psychology: Human Perception and Performance, 24, 1737-1747] found performance costs for compatible trials and benefits for incompatible trials. Experiment 1 showed that these effects are not due to 'perceptual repetition blindness'. Experiments 2 and 3 obtained evidence for an initial response facilitation triggered by the primes that was followed by inhibition. With short intervals between prime presentation and response execution, performance benefits were found for compatible trials and these turned into costs at longer intervals. It is argued that an early response facilitation mediated by direct perceptuo-motor links is subsequently inhibited by a central mechanism operating to prevent behaviour from being controlled by irrelevant information.

Adult↗
PubMed2002

Preconscious processing of body image cues. Impact on body percept and concept.

OBJECTIVE: There is considerable evidence that body image is an elastic construct, which can be influenced by environmental and internal factors. The present study used a visual subliminal processing paradigm, with the aim of determining the impact of preconscious processing of verbal cues upon body image (percept and concept). METHOD: Forty nonclinical women completed measures of body percept and concept before and after being exposed to very rapid presentations (4 ms) of fatness and thinness cues. RESULTS: The women with relatively unhealthy eating attitudes were influenced by the fatness stimulus, with a worsening of their body percept and concept. In contrast, the women with healthier eating attitudes showed an improvement in their body percept in response to the thinness stimulus. CONCLUSION: The findings support the centrality of body image schemata in eating psychopathology, although there is a need for replication and extension in other groups.

Adult↗
PubMed2006

Subliminal emotion perception in brain imaging: findings, issues, and recommendations.

Many theories of emotion propose that emotional input is processed preferentially due to its relevance for the organism. Further, because consciousness has limited capacity, these considerations imply that emotional input ought to be processed even if participants are perceptually unaware of the input (subliminal perception). Although brain imaging has studied effects of unattended, suppressed (in binocular rivalry), and visually masked emotional pictures, conclusions regarding subliminal perception have been mixed. The reason is that subliminal perception demands a concept of an awareness threshold or limen, but there is no agreement on how to define and measure this threshold. Although different threshold concepts can be identified in psychophysics (signal detection theory), none maps directly onto perceptual awareness. Whereas it may be tempting to equate unawareness with the complete absence of objective discrimination ability (d'=0), this approach is incompatible with lessons from blindsight and denies the subjective nature of consciousness. This review argues that perceptual awareness is better viewed as a continuum of sensory states than a binary state. When levels of awareness are characterized carefully in terms of objective discrimination and subjective experience, findings can be informative regarding the relative independence of effects from awareness and the potentially moderating role of awareness in processing emotional input. Thus, because the issue of a threshold concept may never be resolved completely, the emphasis is to not prove subliminal perception but to compare effects at various levels of awareness.

Attention↗
PubMed2001

Event-related brain potentials differentiate positive and negative mood adjectives during both supraliminal and subliminal visual processing.

This experiment provides brain event-related potential (ERP) evidence for differential processing of visually presented pleasant and unpleasant affectively valent words (mood adjectives) for both supraliminal (40 ms) and subliminal (unmasked, 1 ms) stimulus durations. Unpleasant words elicited a more positive amplitude than pleasant words in both durations. ERP components (P1, N1, P2, P3, and a late positive potential; LP) were measured at six electrode sites (F3, F4, P3, P4, CzPz, Oz). ERPs to subliminal stimuli demonstrated differences between pleasant and unpleasant words in the left hemisphere across all measured components. Supraliminal processing showed similar differences in the left hemisphere for early components (P1 and N1), but bilateral differences for late components (P3 and LP). Activity in the P2 time window was associated with the divergence between supraliminal and subliminal affective responses. Implications for the study of affect and consciousness are discussed.

Adolescent↗
PubMed2001

Event-related markers of unconscious processes.

A series of studies is reviewed strongly suggesting that event-related potentials (ERPs) may provide markers for unconscious processes. In one study it was shown that, although smaller in amplitude by a least a factor of four, ERPs to subliminal stimuli have a similar component structure to ERPs to supraliminal stimuli. In another study, it was shown that an oddball P300 could be obtained for subliminal stimuli. In two additional studies, it was shown that aversive conditioning could be established unconsciously. The implications for our understanding of the role of unconscious processes in phobias and post-traumatic stress disorders are discussed, as well as more general implications for memory formation.

Animals↗
PubMed2003

Rapid motor adaptations to subliminal frequency shifts during syncopated rhythmic sensorimotor synchronization.

The synchronization of rhythmic arm movements to a syncopated metronome cue was studied in a step-change design whereby small tempo shifts were inserted at fixed time points into the metronome frequency. The cueing sequence involved three stimulus types: (1) target contact in synchrony with the metronome beats, (2) syncopated target contact midway in time between audible beats, and (3) syncopated target contact following either a +2% or -2% change in stimulus frequency. Analysis of normalized and aggregated data revealed that (1) during the syncopation condition the response period showed a rapid adaptation to the frequency-incremented stimulus period, (2) response period was less variable during syncopated movement, (3) mean synchronization error and variability, calculated during syncopation relative to the mathematical midpoint of the stimulus cycle, were reduced during syncopated movements, and (4) synchronization error following the frequency increment showed trends to return linearly to pre-increment values which was fully achieved in the -2% change condition only. The results suggest that frequency entrainment to stimulus period was possible during syncopated movement with the response and stimulus onsets 180 degrees out of phase. Most remarkably, 70-80% of the adaptation of the response period to the new stimulus period was immediately attained during the second half cycle of the syncopated movement. Finally, a mathematical model, based on recursion, was introduced that accurately modeled actual data as a function of the previous stimulus and response intervals and a weighted response of period error and synchronization error, which showed dominance of frequency entrainment over phase entrainment during rhythmic synchronization.

Adaptation, Physiological↗
PubMed2003

Response facilitation and inhibition in subliminal priming.

The research reviewed in this article has investigated with behavioural, electrophysiological, and functional imaging methods how subliminally presented masked prime stimuli affect response-related processes. An initial response activation triggered by these primes was found to be followed by an inhibition of this response tendency, provided that the initial activation was strong enough to exceed an 'inhibition threshold'. This biphasic pattern is assumed to reflect the presence of self-inhibitory circuits in motor control. In contrast to endogenous response inhibition, observed when response-relevant signals are consciously perceived, this exogenous mode of response inhibition appears to be mediated by corticostriate rather than by prefrontal mechanisms. Overall, results demonstrate that inhibitory mechanisms are involved in the control of response processes, even when motor activations are triggered by stimuli that are not accessible to conscious awareness.

Dominance, Cerebral↗
PubMed1998

Baseline salivary cortisol levels and preconscious selective attention for threat. A pilot study.

This study was conducted to examine the relationship between baseline salivary cortisol (CORT) levels and selective attention for displays of angry faces. Selective attention was investigated using a pictorial emotional Stroop task, comparing colournaming-speed of angry and neutral faces. The task was assessed in supraliminal (unmasked) and subliminal (masked) conditions to 28 non-clinical subjects (14 male and 14 female). Repeated measures analysis of variance revealed a significant interaction between median split CORT levels (low vs. high) and masked face valence (angry vs. neutral). The latter effect was mainly due to significant facilitation in the high CORT subject-group; these subjects seemed to allocate their attention away from the masked angry face. A relation between baseline CORT levels and fast withdrawal behavior is suggested.

Adult↗
PubMed2002

The emotional Stroop: a comparison of panic disorder patients, obsessive-compulsive patients, and normal controls, in two experiments.

An emotional Stroop task with four word types (panic threat, obsessive-compulsive threat, general threat, and neutral) and two presentation conditions (supraliminal, subliminal) was used in two experiments. The first experiment involved 21 panic disorder (PD) patients and 20 normal controls; the second experiment 20 PD patients and 20 obsessive-compulsive patients. PD patients, obsessive-compulsive patients, and normal controls did not differ in Stroop interferences. In addition, there were no significant correlations between reduction of PD symptoms and differences between pre- and post-treatment Stroop response latencies.

Adult↗
PubMed1999

Mental imaging of motor activity in humans.

Motor imagery corresponds to a subliminal activation of the motor system, a system that appears to be involved not only in producing movements, but also in imagining actions, recognising tools and learning by observation, as well as in understanding the behaviour of other people. Recent advances in the field include the use of techniques for mapping brain activity and probing cortical excitability, as well as observation of brain lesioned patients during imaging tasks; these advances provide new insights into the covert aspects of motor activity.

Humans↗
PubMed2004

Subliminal perception and its cognates: theory, indeterminacy, and time.

Unconscious processes, by whatever name they may be known (e.g., "subliminal," "implicit"), are invariably operationalized by the dissociation paradigm, any situation involving the dissociation between two indicators (or sets of indicators), one of availability (epsilon) and the other, of accessibility (alpha), such that, epsilon>alpha. Subliminal perception has been traditionally defined by a special case of the dissociation paradigm in which availability exceeds accessibility when accessibility is null (epsilon>alpha/alpha=0). Construct validity issues bedevil all dissociation paradigms since it is not clear what might constitute appropriate indicators that, moreover, are pure and exhaustive. Semantic and theoretic drifts in the recent literature--e.g., the confusion of different versions of the dissociation paradigm, the equation of conscious-unconscious with direct-indirect tests, and the foisting of the criterion of qualitative differences--have tended to undermine emerging theoretic parsimony. On the other hand, a crucial factor has been left out of theory development: time. Both epsilon and alpha can rise and fall over time, often asynchronously, and so dissociations may wax and wane and, even, reverse over time. Some laboratory evidence suggests that accessibility measures (e.g., d'), as they approach chance, may actually dip below chance (subchance perception). If so, d'=0 (the chance-limen or objective threshold), could be an averaging artifact of positive and negative d's. Conscious accessibility is not either-or but more or less, and variable over time.

Cognition↗
PubMed2001

Intracerebral event-related potentials to subthreshold target stimuli.

OBJECTIVES: Event-related potentials (ERPs) elicited by subthreshold visual stimuli were recorded directly from human frontal and temporal lobe structures to study unconscious perception. METHODS: Thirteen intractable epileptic patients undergoing depth electrode recordings prior to their surgical treatment participated in the study. An original method of modified visual oddball paradigm with supraliminal and subliminal stimuli was applied, and the averaged responses to both kinds of stimuli were subsequently compared. RESULTS: The results clearly prove that, at least from an electrophysiological viewpoint, the mechanism of unaware processing of visual stimuli in the human brain does not differ substantially from the aware processing. Finding the subliminal P3 waveform in a number of cortical structures (hippocampus and parahippocampal gyrus bilaterally, and left-sided mesiofrontal, orbitofrontal and lateral temporal cortex) indicates their involvement in unconscious processing, in spite of the fact that typical large-scale neurocognitive networks are not completely activated. The absence of activation consistently observed bilaterally in dorsolateral prefrontal cortices, in connection with right-sided cortical frontal lobe structures and right-sided lateral temporal neocortex in unconscious perception, supports the importance of these structures for the awareness of visual stimuli. The proof of the significantly faster unaware information processing represents another distinctive feature of implicit visual perception. CONCLUSIONS: Based on the presented findings and comparisons with the results of previous ERP, functional magnetic resonance imaging, positron emission tomography, and clinical neuropsychological studies, a crucial role of the large-scale neural system for conscious experience of perception is suggested, which is distributed extensively among the dorsal posterior association areas and the prefrontal cortex, with the dominant part being that of the right hemisphere.

Adult↗
PubMed2001

Subliminal messages for increasing self-esteem: placebo effect.

Although experimental research has confirmed the capacity of the human cognitive system to process information that does not reach consciousness (unconscious perception), empirical evidence of the incidence of subliminal verbal messages included on audiotapes claiming to improve human resources and correct some behavioral problems is meager and inconsistent. Our study assesses the influence of "subliminal tapes" designed to increase self-esteem. Participants were randomly assigned to four experimental conditions. One group listened to a tape of music with supra- and subliminal messages; another listened to a tape of music with only subliminal messages; the third group's tape had only music, although the participants believed that it also included subliminal messages; a fourth ("waiting") group heard no tapes, but filled in the same self-esteem scales. Participants in the first three groups filled in the Tennessee Self-Concept Scale (Fitts, 1965) before and after listening to the tape for several days. All groups showed a similar pretest-posttest improvement in self-esteem (p < or = .003), except for the waiting group, which did not improve (p = .311). This implies that only a placebo effect took place. Our data are not in accordance with those obtained by other authors. We comment upon the possible reasons for these discrepancies.

Adolescent↗