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Arne Ohman

Publications and source records attributed to Arne Ohman.

17 recordsLinked to original sources
PubMed2006

Skin conductance responses to masked conditioned stimuli: phylogenetic/ontogenetic factors versus direction of threat?

Evolutionarily old threat stimuli are likely to require less conscious information processing than threat stimuli of a more recent date. To test this proposal two differential conditioning experiments, with biological threat stimuli (e.g. snakes) in half the groups and cultural threat stimuli (e.g. guns) in the other half, were conducted. The conditioned (CS+) and the control (CS-) stimuli were backward masked during the extinction phase to prevent conscious recognition. The differential skin conductance responding for both biological and cultural threat stimuli survived the masking procedure when the conditioned stimuli were directed towards the participants (Experiment 1), but for neither type of CS when stimuli were not directed towards the participants (Experiment 2). These findings are discussed in relation to the previous finding by Ohman and co-workers and in relation to imminence of threat.

Adult↗
PubMed2006

Predictability modulates the affective and sensory-discriminative neural processing of pain.

Knowing what is going to happen next, that is, the capacity to predict upcoming events, modulates the extent to which aversive stimuli induce stress and anxiety. We explored this issue by manipulating the temporal predictability of aversive events by means of a visual cue, which was either correlated or uncorrelated with pain stimuli (electric shocks). Subjects reported lower levels of anxiety, negative valence and pain intensity when shocks were predictable. In addition to attenuate focus on danger, predictability allows for correct temporal estimation of, and selective attention to, the sensory input. With functional magnetic resonance imaging, we found that predictability was related to enhanced activity in relevant sensory-discriminative processing areas, such as the primary and secondary sensory cortex and posterior insula. In contrast, the unpredictable more aversive context was correlated to brain activity in the anterior insula and the orbitofrontal cortex, areas associated with affective pain processing. This context also prompted increased activity in the posterior parietal cortex and lateral prefrontal cortex that we attribute to enhanced alertness and sustained attention during unpredictability.

Adult↗
PubMed2005

Visual masking in magnetic resonance imaging.

When a brief target picture is followed by another picture (mask), people often report that they are not consciously aware of the target. Thus, visual masking can be used to manipulate perceptual awareness of target pictures. To avoid interference with magnetic resonance imaging, pictures have been presented on liquid crystal device (LCD) and thin film transistor (TFT) projectors that were placed outside of the scanner room. However, we found that display devices with LCD/TFT technology exhibit poor accuracy in presenting pictures at brief durations [Wiens, S., Fransson, P., Dietrich, T., Lohmann, P., Ingvar, M., Ohman, A., 2004. Keeping it short: A comparison of methods for brief picture presentation. Psychological Science, 15, 282--285]. In this paper, we present a reliable and valid masking procedure involving two LCD/TFT projectors in combination with mechanical shutters. Because LCD/TFT projectors present pictures in steady state at longer durations (e.g., after 70 ms), picture presentation is more ecologically valid than for common cathode ray tube (CRT) monitors that present pictures in multiples of refresh cycles. Also, because picture presentation with mechanical shutters is instantaneous and reliable in terms of onset, rise time, and duration, shutters can be used to control picture durations precisely in steps of milliseconds. In this paper, we also discuss risks for confounding effects from unreliable picture presentations in masking. Our findings and arguments recommend the use of mechanical shutters in front of LCD/TFT projectors in imaging studies of visual masking.

Humans↗
PubMed2005

The role of the amygdala in human fear: automatic detection of threat.

Behavioral data suggest that fear stimuli automatically activate fear and capture attention. This effect is likely to be mediated by a subcortical brain network centered on the amygdala. Consistent with this view, brain imaging studies show that masked facial stimuli activate the amygdala as do masked pictures of threatening animals such as snakes and spiders. When the stimulus conditions allow conscious processing, the amygdala response to feared stimuli is enhanced and a cortical network that includes the anterior cingulate cortex and the anterior insula is activated. However, the initial amygdala response to a fear-relevant but non-feared stimulus (e.g. pictures of spiders for a snake phobic) disappears with conscious processing and the cortical network is not recruited. Instead there is activation of the dorsolateral and orbitofrontal cortices that appears to inhibit the amygdala response. The data suggest that activation of the amygdala is mediated by a subcortical pathway, which passes through the superior colliculi and the pulvinar nucleus of the thalamus before accessing the amygdala, and which operates on low spatial frequency information.

Amygdala↗
PubMed2005

Long-term effects of lifestyle behavior change in coronary artery disease: effects on recurrent coronary events after percutaneous coronary intervention.

This study evaluated the effects of a behaviorally oriented cardiac rehabilitation and secondary prevention program on lifestyle changes and on coronary recurrence rates. Patients recently treated with percutaneous coronary intervention (PCI) were randomized to an intervention with an aggressive focus on lifestyle changes (smoking, diet, exercise, and stress; n=46) or to a standard-care control group (n=42). Results showed that the intervention group had significantly larger overall lifestyle changes than the control group after 12, 24, 36, and 60 months. The intervention group had significantly lower rates of all coronary events (acute myocardial infarction, coronary artery bypass graft, PCI, cardiac death; 30.4% vs. 53.7%), and of cardiovascular mortality (2.2% vs. 14.6%). The need for future large-scale and long-term evaluations of lifestyle-oriented secondary prevention interventions of this kind is emphasized.

Ambulatory Care↗
PubMed2005

Looking for foes and friends: perceptual and emotional factors when finding a face in the crowd.

In a face-in-the-crowd setting, the authors examined visual search for photographically reproduced happy, angry, and fearful target faces among neutral distractor faces in 3 separate experiments. Contrary to the hypothesis, happy targets were consistently detected more quickly and accurately than angry and fearful targets, as were directed compared with averted targets. There was no consistent effect of social anxiety. A facial emotion recognition experiment suggested that the happy search advantage could be due to the ease of processing happy faces. In the final experiment with perceptually controlled schematic faces, the authors reported more effective detection of angry than happy faces. This angry advantage was most obvious for highly socially anxious individuals when their social fear was experimentally enhanced.

Adult↗
PubMed2004

Neural systems supporting interoceptive awareness.

Influential theories of human emotion argue that subjective feeling states involve representation of bodily responses elicited by emotional events. Within this framework, individual differences in intensity of emotional experience reflect variation in sensitivity to internal bodily responses. We measured regional brain activity by functional magnetic resonance imaging (fMRI) during an interoceptive task wherein subjects judged the timing of their own heartbeats. We observed enhanced activity in insula, somatomotor and cingulate cortices. In right anterior insular/opercular cortex, neural activity predicted subjects' accuracy in the heartbeat detection task. Furthermore, local gray matter volume in the same region correlated with both interoceptive accuracy and subjective ratings of visceral awareness. Indices of negative emotional experience correlated with interoceptive accuracy across subjects. These findings indicate that right anterior insula supports a representation of visceral responses accessible to awareness, providing a substrate for subjective feeling states.

Acoustic Stimulation↗
PubMed2004

The facilitated processing of threatening faces: an ERP analysis.

Threatening, friendly, and neutral faces were presented to test the hypothesis of the facilitated perceptual processing of threatening faces. Dense sensor event-related brain potentials were measured while subjects viewed facial stimuli. Subjects had no explicit task for emotional categorization of the faces. Assessing early perceptual stimulus processing, threatening faces elicited an early posterior negativity compared with nonthreatening neutral or friendly expressions. Moreover, at later stages of stimulus processing, facial threat also elicited augmented late positive potentials relative to the other facial expressions, indicating the more elaborate perceptual analysis of these stimuli. Taken together, these data demonstrate the facilitated perceptual processing of threatening faces. Results are discussed within the context of an evolved module of fear (A. Ohman & S. Mineka, 2001).

Adult↗
PubMed2004

Fear and the amygdala: manipulation of awareness generates differential cerebral responses to phobic and fear-relevant (but nonfeared) stimuli.

Rapid response to danger holds an evolutionary advantage. In this positron emission tomography study, phobics were exposed to masked visual stimuli with timings that either allowed awareness or not of either phobic, fear-relevant (e.g., spiders to snake phobics), or neutral images. When the timing did not permit awareness, the amygdala responded to both phobic and fear-relevant stimuli. With time for more elaborate processing, phobic stimuli resulted in an addition of an affective processing network to the amygdala activity, whereas no activity was found in response to fear-relevant stimuli. Also, right prefrontal areas appeared deactivated, comparing aware phobic and fear-relevant conditions. Thus, a shift from top-down control to an affectively driven system optimized for speed was observed in phobic relative to fear-relevant aware processing.

Adult↗
PubMed2004

Keeping it short: a comparison of methods for brief picture presentation.

Research has shown that backward masking is a powerful tool for studying unconscious mental processes. Whereas studies have traditionally presented stimuli using cathode-ray tube (CRT) monitors or mechanical shutters together with slide projectors, recent studies (mainly in functional magnetic resonance imaging, fMRI) have begun to use methods based on liquid crystal displays (LCDs) and thin-film transistor (TFT) technology. However, because of differences in technology, all methods may not be equally suited for masking. When methods were compared for their accuracy in presenting pictures at short durations, LCD and TFT presentations had poor accuracy, but shutter and CRT presentations had better accuracy. Because CRTs interfere with the imaging process in fMRI, we recommend the use of mechanical shutters. However, our results may not generally apply to all displays, so we advise researchers to validate the presentation parameters of their displays. The procedure described here may be useful for that purpose.

Consciousness↗
PubMed2003

Effects of trial order and differential conditioning on acquisition of differential shock expectancy and skin conductance conditioning to masked stimuli.

Research suggests that when people are fear conditioned to masked spiders and snakes (electric shocks are contingent on only spiders or snakes), they acquire a conditional skin conductance response and can predict the occurrence of shocks even though they are unable to identify the masked spiders and snakes. Because in prior studies trial order was not completely random, it is unclear if findings were due to the contingencies from differential conditioning or a restricted trial order or both. When participants were assigned to four groups to disentangle effects of trial order and differential conditioning to masked pictures in acquisition, effects were obtained only for trial order. These findings demonstrate that trial order can result in conditioning. However, because effects were observed even for participants who reported unawareness of the contingency from trial order, results are consistent with the notion of hunches or gut feelings.

Adult↗
PubMed2003

Comparing multifactorial lifestyle interventions and stress management in coronary risk reduction.

The aim of this study was to compare the effects of residential multifactorial cardiac rehabilitation, outpatient multifactorial rehabilitation, stress management, and standard coronary rehabilitation, on cardiac risk reduction. Out of 144 eligible male patients recently treated with percantaneous transluminal coronary angiography (PTCA), coronary artery bypass graft (CABG), or acute myocardial infarction (AMI), 132 were randomized into this study. All interventions covered a 12-month active intervention, intense during the first months and subsequently leveled out. Main assessments were performed before randomization and after the intervention. Patients offered behavioral rehabilitation showed improved self-reported healthy diet habits and exercise frequency, and higher internal locus of control. Although blood lipids, exercise capacity, body mass, anxiety, depression, and Type A scores were changed in the expected direction, no significant difference emerged between active intervention and the standard care condition. Standard care of today appears to have great potential in particular if supplemented with some kind of stress management.

Angioplasty, Balloon, Coronary↗
PubMed2002

Phobias and preparedness: the selective, automatic, and encapsulated nature of fear.

We describe evidence for an evolved module for fear elicitation and fear learning with four primary characteristics. First, it is preferentially activated by stimuli related to survival threats in evolutionary history. Thus, fear-relevant stimuli lead to superior conditioning of aversive associations compared with fear-irrelevant stimuli. Second, the module is automatically activated by fear-relevant stimuli, meaning that fear activation occurs before conscious cognitive analysis of the stimulus can occur. Third, the fear module is relatively impenetrable to conscious cognitive control, and fear conditioning with fear-relevant stimuli can occur even with subliminal conditioned stimuli. Fourth, the amygdala seems to be the central brain area dedicated to the fear module. Finally, we propose that there are two levels of fear conditioning, with an emotional level that is relatively independent of the cognitive contingency level, each mediated by different brain areas.

Amygdala↗
PubMed2002

Born to fear: non-associative vs associative factors in the etiology of phobias.

Poulton and Menzies (Behaviour Research & Therapy 40 (2001) 127-149) review two lines of evidence as supporting a non-associative pathway to the origins of "evolutionary relevant phobias". First, in retrospective studies of mode of onset some recall they have always had this fear. We review here solid evidence that retrospective recall is notoriously unreliable. Second, they note as many nonphobics recall relevant associative learning experiences as do phobics. We argue such studies are very inconclusive because they fail to consider many experiential and personality vulnerability (and invulnerability) factors that strongly impact the outcome of any putative learning experience. Their argument also does not explain the transition from developmental fears to phobias that is central to their thesis. Overall, we call for major methodological improvements in this area, in the context of theoretical developments pointing to interacting vulnerability and invulnerability factors.

Conditioning, Psychological↗
PubMed2002

Unawareness is more than a chance event: comment on Lovibond and Shanks (2002).

P. F. Lovibond and D. R. Shanks (2002) suggested that expectancy of the unconditional stimulus and emotional ratings are valid indexes of awareness in Pavlovian conditioning and that participants are aware if they can discriminate the conditional stimuli. However, research suggests that processes that are irrelevant to awareness affect these measures. Further, as awareness refers to conscious experience, a valid measures needs to index subjective state rather than discrimination ability. In support, research using subjective measures has demonstrated qualitatively different effects depending on whether participants reported being aware or unaware of the stimuli. In this research, participants reported being unaware of the stimuli even though they were clearly able to discriminate the stimuli. These findings question the validity of Lovibond and Shanks' concept of awareness and their suggestion of a close association between conditioning and awareness.

Awareness↗