Motor control in old age: evidence of impaired low-level inhibition

In the masked prime task, responses to supraliminal targets are influenced by previously presented subliminal primes. When targets follow primes immediately, positive compatibility effects are obtained such that performance is better when prime and target are compatible (mapped to the same response) than when they are incompatible (mapped to opposite responses). In young adults, this pattern reverses with longer interstimulus intervals (negative compatibility effect). These effects reflect an activation-followed-by-inhibition process: Primes trigger an initial activation of their corresponding motor response, which is subsequently inhibited. The present study demonstrates that healthy older adults (M = 76 years) show a substantial positive compatibility effect with a short prime-target interval, but they fail to produce reliable negative compatibility effects with longer intervals, indicating an age-related impairment in low-level motor control.

Non-conscious modulation of cardiac defense by masked phobic pictures

The present study investigated the modulation of cardiac defense by presenting emotional pictures under both effective and non-effective masking procedures. The aim was to test Ohman's model of pre-attentive processing of fear. Participants were 48 women volunteers with intense fear of spiders. The stimulus to elicit cardiac defense was a white noise of 105 dB, 500 ms duration and instantaneous risetime. Subjects had two trials of picture-noise presentation-one with a picture of a spider and one with a picture of a flower-, either under an effective masking procedure (30 ms duration) or a non-effective masking procedure (500 ms duration). Order of presentation was counterbalanced. Dependent variables were heart rate and subjective assessment of the noise. Results showed an increased cardiac response in the first trial and a less reduced cardiac response in the second trial when the noise was preceded by the phobic picture under both masking procedures. The response was accompanied by an increase in the subjective unpleasantness of the noise. These results provide support to Ohman's theoretical model.

Subliminal Convergence of Kanji and Kana Words: Further Evidence for Functional Parcellation of the Posterior Temporal Cortex in Visual Word Perception

Recent evidence has suggested that the human occipito-temporal region comprises several subregions, each sensitive to a distinct processing level of visual words. To further explore the functional architecture of visual word recognition, we employed a subliminal priming method with functional magnetic resonance imaging (fMRI) during semantic judgments of words presented in two different Japanese scripts, Kanji and Kana. Each target word was preceded by a subliminal presentation of either the same or a different word, and in the same or a different script. Behaviorally, word repetition produced significant priming regardless of whether the words were presented in the same or different script. At the neural level, this cross-script priming was associated with repetition suppression in the left inferior temporal cortex anterior and dorsal to the visual word form area hypothesized for alphabetical writing systems, suggesting that cross-script convergence occurred at a semantic level. fMRI also evidenced a shared visual occipito-temporal activation for words in the two scripts, with slightly more mesial and right-predominant activation for Kanji and with greater occipital activation for Kana. These results thus allow us to separate script-specific and script-independent regions in the posterior temporal lobe, while demonstrating that both can be activated subliminally.

A direct intracranial record of emotions evoked by subliminal words

A classical but still open issue in cognitive psychology concerns the depth of subliminal processing. Can the meaning of undetected words be accessed in the absence of consciousness? Subliminal priming experiments in normal subjects have revealed only small effects whose interpretation remains controversial. Here, we provide a direct demonstration of semantic access for unseen masked words. In three epileptic patients with intracranial electrodes, we recorded brain potentials from the amygdala, a neural structure that responds to fearful or threatening stimuli presented in various modalities, including written words. We show that the subliminal presentation of emotional words modulates the activity of the amygdala at a long latency (>800 ms). Our result indicates that subliminal words can trigger long-lasting cerebral processes, including semantic access to emotional valence.

Implicit Associative Learning Engages the Hippocampus and Interacts with Explicit Associative Learning

The hippocampus is crucial for conscious, explicit memory, but whether it is also involved in nonconscious, implicit memory is uncertain. We investigated with functional magnetic resonance imaging whether implicit learning engages the hippocampus and interacts with subsequent explicit learning. The presentation of subliminal faces-written profession pairs for implicit learning was followed by the explicit learning of supraliminal pairs composed of the same faces combined with written professions semantically incongruous to those presented subliminally (experiment 1), semantically congruous professions (experiment 2), or identical professions (experiment 3). We found that implicit face-profession learning interacted with explicit face-profession learning in all experiments, impairing the explicit retrieval of the associations. Hippocampal activity increased during the subliminal presentation of face-profession pairs versus face-nonword pairs and correlated with the later impairment of explicit retrieval. These findings suggest that implicit semantic associative learning engages the hippocampus and influences explicit memory.

Attentional biases to pain and social threat in children with recurrent abdominal pain

OBJECTIVES

To test whether children with recurrent abdominal pain (RAP) exhibit subliminal (nonconscious) and supraliminal (conscious) attentional biases to pain-related words, and to determine correlates of these biases. Previous research indicates that individuals attend to disorder-relevant threat words, and in this study, attentional biases to disorder-relevant threat (pain), alternative threat (social threat), and neutral words were compared.

METHODS

Participants were 59 children with RAP who completed a computer-based attentional bias task. Participants and their parents also completed questionnaires measuring pain, somatic complaints, anxiety/depression, and body vigilance.

RESULTS

Children with RAP showed attentional biases toward subliminal pain-related words and attentional biases away from supraliminal pain-related words. Participants' attentional biases to social threat-related words were marginally significant and also reflected subliminal attention and supraliminal avoidance. Attentional biases were related to parent and child reports of pain, body vigilance, and anxiety/depression.

CONCLUSIONS

Children with RAP show nonconscious attention to and conscious avoidance of threat-related words. Their attentional biases relate to individual differences in symptom severity. Implications for models of pediatric pain and future studies are discussed.

Relationships between temperament dimensions in personality and unconscious emotional responses

BACKGROUND

In addition to character dimensions, personality includes temperament dimensions, defined as individual differences in implicit associative learning responses to environmental stimuli processed by unconscious memories. We examined whether temperament dimensions were associated with patterns of unconscious emotional responses of an autonomic nature.

METHODS

From 70 healthy men, high and low novelty-seeking (NS) groups and high and low harm-avoidance (HA) groups were selected using scores on the Tridimensional Personality Questionnaire measuring temperament dimensions. Emotionally negative, neutral, and positive visual stimuli were presented subliminally using backward masking, and skin conductance responses (SCRs) were measured as an autonomic index of emotional responses. Skin conductance responses to the three emotional stimulus conditions were compared between groups.

RESULTS

Skin conductance responses in the high NS group were significantly greater than in the low NS group when positive or negative emotional stimuli were presented but not neutral stimuli. Skin conductance responses in the high HA group were significantly greater than in the low HA group for stimuli of all three valences.

CONCLUSIONS

Autonomic response patterns to unconscious emotional perception differed between NS and HA, suggesting that different dimensions of temperament may be associated with different patterns of unconscious emotional responses. Novelty seeking and HA may be associated with specificity and susceptibility of preattentive emotional perception, respectively.

On the role of mask structure in subliminal priming

Choice reaction times to visual stimuli may be influenced by preceding subliminal stimuli (primes). Some authors reported a straight priming effect i.e., responses were faster when primes and targets called for the same response than when they called for different responses. Other authors found a reversed pattern of results. Our results suggest that the sign of the priming effect depends on mask structure. Inverse priming was obtained only for masks containing the searched-for feature even though informational content of the masks was neutral. With masks of irrelevant structure, straight priming effects were found. Thus, masks are not passive stimuli whose roles are limited to rendering the prime invisible. Processing of the mask may interact with prime and target processing. Implications of the results are discussed for two hypotheses trying to account for straight and inverse priming (the self-inhibition hypothesis and object-updating hypothesis).

A direct brainstem–amygdala–cortical ‘alarm’ system for subliminal signals of fear

We examined whether consciously undetected fear signals engage a collateral brainstem pathway to the amygdala and prefrontal cortex in the intact human brain, using functional neuroimaging. 'Blindsight' lesion patients can respond to visual fear signals independently from conscious experience, suggesting that these signals reach the amygdala via a direct pathway that bypasses the primary visual cortex. Electrophysiological evidence points to concomitant involvement of prefrontal regions in automatic orienting to subliminal signals of fear, which may reflect innervation arising from brainstem arousal systems. To approximate blindsight in 22 healthy subjects, facial signals of fear were presented briefly (16.7 ms) and masked such that conscious detection was prevented. Results revealed that subliminal fear signals elicited activity in the brainstem region encompassing the superior colliculus and locus coeruleus, pulvinar and amygdala, and in fronto-temporal regions associated with orienting. These findings suggest that crude sensory input from the superior colliculo-pulvinar visual pathway to the amygdala may allow for sufficient appraisal of fear signals to innervate the locus coeruleus. The engagement of the locus coeruleus could explain the observation of diffuse fronto-temporal cortical activity, given its role in evoking collateral ascending noradrenergic efferents to the subcortical amygdala and prefrontal cortex. This network may represent an evolutionary adaptive neural 'alarm' system for rapid alerting to sources of threat, without the need for conscious appraisal.

Subliminal attentional modulation in crowding condition

In the crowding phenomenon, recognition of a visual target is impaired by other similar visual stimuli (distracters) presented near the target. This effect may be due largely to insufficient resolution of spatial attention. We showed that attention could subliminally enhance orientation selective adaptation to illusory lines in the crowding condition where target-distractor separation is beyond the limit of spatial resolution of attention. Despite the traditionally held close link between attention and awareness, here we provided evidence for subliminal attentional modulation for orientation stimuli that could not have been consciously perceived.

On the inference of personal authorship: enhancing experienced agency by priming effect information

Three experiments examined whether the mere priming of potential action effects enhances people's feeling of causing these effects when they occur. In a computer task, participants and the computer independently moved a rapidly moving square on a display. Participants had to press a key, thereby stopping the movement. However, the participant or the computer could have caused the square to stop on the observed position, and accordingly, the stopped position of the square could be conceived of as the potential effect resulting from participants' action of pressing the stop key. The location of this position was primed or not just before participants had to stop the movement. Results showed that (subliminal as well as supraliminal) priming of the position enhanced experienced authorship of stopping the square. Additional experimentation demonstrated that this priming of agency was not mediated by the goal or intention to produce the effect.

Comments on "Rapid motor adaptations to subliminal frequency shifts during syncopated rhythmic sensorimotor synchronization" by Michael H. Thaut and Gary P. Kenyon (Human Movement Science 22 [2003] 321-338)

Thaut and Kenyon [Human Movement Sci. 22 (2003) 321] have shown that, in a task requiring tapping in antiphase with a metronome, the response period adapts rapidly to a small (+/-2%) change in the stimulus period, whereas the relative phase between stimulus and response returns to its pre-change value only very gradually. On the basis of these and earlier findings, Thaut and Kenyon argue that period adaptation is rapid and subconscious, whereas phase adaptation is slow and dependent on awareness of a phase error. This interpretation is at variance with results in the literature suggesting that phase correction is rapid and subconscious, whereas period correction is slow and dependent on awareness of a period mismatch. Although differences in terminology (adaptation versus correction) play a role in this conflict, it primarily reflects different conceptions of sensorimotor synchronization and different interpretations of empirical findings. By excluding from their model a central timekeeper or oscillator with a flexible period, Thaut and Kenyon have omitted an essential component of human timing control that is needed for a proper explanation of their results.

Attentional and evaluative biases for smoking cues in nicotine dependence: component processes of biases in visual orienting

The present study investigated attentional and evaluative biases for smoking-related cues in cigarette smokers and non-smokers. Using a visual probe task, we manipulated the presentation conditions of the stimuli to examine: (1). whether smokers have a bias to allocate attention towards smoking-related pictures that appear below the threshold of conscious awareness; and (2). whether attentional biases for smoking-related pictures that appear above the threshold of awareness operate both in initial orienting and in the maintenance of attention. We also obtained explicit and implicit measures of the valence of the smoking-related pictures from pleasantness ratings and from behavioural responses on a stimulus-response compatibility (SRC) task. Results showed that smokers, but not non-smokers, had an attentional bias for smoking-related pictures which had been presented at two exposure durations (200 and 2000 ms). The bias was not found in a brief (17 ms) masked exposure condition, so there was no evidence that it operated preconsciously. Smokers also showed greater preferences for smoking-related than control cues, compared with non-smokers, on both the explicit and implicit indices of stimulus valence. Results are discussed with reference to incentive and cognitive models of addiction.

Absence of increasing cortical fMRI activity volume in response to increasing visceral stimulation in IBS patients

Cerebral cortical activity associated with perceived visceral sensation represents registration of afferent transduction and cognitive processes related to perception. Abnormalities of gut sensory function can involve either or both of these processes. Cortical registration of subliminal viscerosensory signals represents cerebral cortical activity induced by stimulation of intestinal sensory neurocircuitry without the influence of perception-related cortical activity, whereas those associated with perception represent both neural circuitry and cognitive processes. Our aims were to determine and compare quantitatively cerebral cortical functional magnetic resonance imaging (fMRI) activity in response to subliminal, liminal, and nonpainful supraliminal rectal distension between a group of irritable bowel syndrome (IBS) patients and age/gender-matched controls. Eight female IBS patients and eight age-matched healthy female control subjects were studied using brain fMRI techniques. Three barostat-controlled distension levels were tested: 1) 10 mmHg below perception (subliminal), 2) at perception (liminal), and 3) 10 mmHg above perception (supraliminal). In control subjects, there was a direct relationship between stimulus intensity and cortical activity volumes, ie., the volume of fMRI cortical activity in response to subliminal (3,226 +/- 335 microl), liminal (5,751 +/- 396 microl), and supraliminal nonpainful stimulation (8,246 +/- 624 microl) were significantly different (P < 0.05). In contrast, in IBS patients this relationship was absent and fMRI activity volumes for subliminal (2,985 +/- 332 microl), liminal (2,457 +/- 342 microl), and supraliminal nonpainful stimulation (2,493 +/- 351 microl) were similar. Additional recruitment of cortical fMRI activity volume in response to increasing stimulation from subliminal to liminal and supraliminal domains is absent in IBS patients, suggesting a difference in the processing of perceived stimulation compared with controls.

[Effects of mere subliminal exposure on trait judgments and the role of stereotyped knowledge]

This study investigated the effects of repeated exposures to male and female targets on trait impressions and the role of stereotyped knowledge for the target's social category in impression formation process. The participants were repeatedly exposed to slides of male and female faces for subliminal durations. For each of 12 pairs containing both previously presented slide and newly presented slide, the participants made forced-choice liking judgments (Experiment 1), trait judgments (Experiment 2) and recognition judgments (Experiments 1 and 2). It was found that participants' attitude toward the targets became more positive, even though target recognition was not significantly greater than the chance level. Yet, when the dimension of judgment was stereotypically associated with the target's social category, exposure effects were obtained for the targets whose social category and its dimension were inferentially matched, but not obtained for the targets whose social category and its dimension were not inferentially matched. Some theoretical implications of the role of social category information in the mere exposure phenomenon are discussed.

A Temporal Dissociation of Subliminal versus Supraliminal Fear Perception: An Event-related Potential Study

Current theories of emotion suggest that threat-related stimuli are first processed via an automatically engaged neural mechanism, which occurs outside conscious awareness. This mechanism operates in conjunction with a slower and more comprehensive process that allows a detailed evaluation of the potentially harmful stimulus (LeDoux, 1998). We drew on the Halgren and Marinkovic (1995) model to examine these processes using event-related potentials (ERPs) within a backward masking paradigm. Stimuli used were faces with fear and neutral (as baseline control) expressions, presented above (supraliminal) and below (subliminal) the threshold for conscious detection. ERP data revealed a double dissociation for the supraliminal versus subliminal perception of fear. In the subliminal condition, responses to the perception of fear stimuli were enhanced relative to neutral for the N2 “excitatory” component, which is thought to represent orienting and automatic aspects of face processing. By contrast, supraliminal perception of fear was associated with relatively enhanced responses for the late P3 “inhibitory” component, implicated in the integration of emotional processes. These findings provide evidence in support of Halgren and Marinkovic's temporal model of emotion processing, and indicate that the neural mechanisms for appraising signals of threat may be initiated, not only automatically, but also without the need for conscious detection of these signals.

Activation of the amygdala and anterior cingulate during nonconscious processing of sad versus happy faces

Previous functional neuroimaging studies have demonstrated that the amygdala activates in response to fearful faces presented below the threshold of conscious visual perception. Using a backward masking procedure similar to that of previous studies, we used functional magnetic resonance imaging (fMRI) to study the amygdala and anterior cingulate gyrus during preattentive presentations of sad and happy facial affect. Twelve healthy adult females underwent blood oxygen level dependent (BOLD) fMRI while viewing sad and happy faces, each presented for 20 ms and "masked" immediately by a neutral face for 100 ms. Masked happy faces were associated with significant bilateral activation within the anterior cingulate gyrus and amygdala, whereas masked sadness yielded only limited activation within the left anterior cingulate gyrus. In a direct comparison, masked happy faces yielded significantly greater activation in the anterior cingulate and amygdala relative to identically masked sad faces. Conjunction analysis showed that masked affect perception, regardless of emotional valence, was associated with greater activation within the left amygdala and left anterior cingulate. Findings suggest that the amygdala and anterior cingulate are important components of a network involved in detecting and discriminating affective information presented below the normal threshold of conscious visual perception.

Differential neural responses to overt and covert presentations of facial expressions of fear and disgust

There is debate in cognitive neuroscience whether conscious versus unconscious processing represents a categorical or a quantitative distinction. The purpose of the study was to explore this matter using functional magnetic resonance imaging (fMRI). We first established objective thresholds of the critical temporal parameters for overt and covert presentations of fear and disgust. Next we applied these stimulus parameters in an fMRI experiment to determine whether non-consciously perceived (covert) facial expressions of fear and disgust show the same double dissociation (amygdala response to fear, insula to disgust) observed with consciously perceived (overt) stimuli. A backward masking paradigm was used. In the psychophysics experiment, the following parameters were established: 30-ms target duration for the covert condition, and 170-ms target duration for the overt condition. Results of the block-design fMRI study indicated substantial differences underlying the perception of fearful and disgusted facial expressions, with significant effects of both emotion and target duration. Findings for the overt condition (170 ms) confirm previous evidence of amygdala activation to fearful faces, and insula activation to disgusted faces, and a double dissociation between these two emotions. In the covert condition (30 ms), the amygdala was not activated to fear, nor was the insula activated to disgust. Overall, findings demonstrate significant differences between the neural responses to fear and to disgust, and between the covert presentations of these two emotions. These results therefore suggest distinct neural correlates of conscious and unconscious emotion perception.

Functional association of the amygdala and ventral prefrontal cortex during cognitive evaluation of facial expressions primed by masked angry faces: an event-related fMRI study

The present study examined the functional association of the amygdala and right ventral prefrontal cortex (PFC) during cognitive evaluation of facial expressions. A situation was created where emotional valence of the stimuli was unconsciously manipulated by using subliminal affective priming. Twelve healthy volunteers were asked to evaluate the facial expressions of a target face (500-ms duration) such as "anger", "neutral", or "happy". All target faces expressed relatively weak anger. Just before the presentation of the target face, a prime of three conditions of 35-ms duration, angry face, neutral face, and white blank was presented. The subjects could not consciously identify the primes in this procedure. Activity in the right amygdala was greater with subliminal presentation of the angry prime compared with subliminal presentation of a neutral face or white-blank stimuli. Most importantly, the degree of activation of the right amygdala was negatively correlated with that of the right ventral PFC only with the anger prime. Furthermore, activation of the amygdala was positively correlated with rate of judgment when the subjects recognized anger in the target faces. These results are discussed in terms of the functional association between the right PFC and the amygdala and its influence on cognitive processing.

True and false memory in the absence of perceptual identification

Two experiments are reported in which, after attempting to identify a briefly flashed, masked test word, participants were asked to rate the likelihood that it had been presented in an earlier study list. Even when people were unable to identify such items, they demonstrated an ability to discriminate between those that were studied and those that were not studied; ratings given to studied items were significantly higher than ratings given to nonstudied items. This effect does not appear to be a data-driven phenomenon. In Experiment 1 it was found when the presentation modality was changed from study to test. In Experiment 2 false memory for unidentified items that were related to studied items was shown.

The effects of emotional content and aging on false memories

After studying a list of words related to a nonpresented lure word, people often falsely recall or recognize the nonpresented lure. Older adults are particularly susceptible to these forms of false memories. The age-related false memory enhancement likely occurs because older adults do not encode, or later retrieve, items in enough detail to allow them to discriminate between presented words and other associated but nonpresented items. Pesta, Murphy, and Sanders (2001) suggested that the emotional salience of the lures may provide distinctiveness, so that individuals would be less likely to endorse an emotional lure as a studied item than to endorse a neutral lure. In the present investigation, young and older adults were less likely to falsely recall or recognize emotional, as compared with neutral, lures. Both age groups appeared capable of using the distinctiveness of the emotional lures to reduce, although not to eliminate, false recall and recognition.

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.

Unconscious modulation of motor cortex excitability revealed with transcranial magnetic stimulation

The neuronal effects of sensory events that do not enter conscious awareness have been reported in numerous pathological conditions and in normal subjects. In the present study, unconscious modulation of corticospinal excitability was probed in healthy volunteers with transcranial magnetic stimulation (TMS). TMS-induced motor evoked potentials (MEPs) were collected from the first dorsal interosseus muscle while subjects performed a masked semantic priming task that has been shown to elicit covert motor cortex activations. Our data show that the amplitude of the MEPs is modulated by an unseen prime, in line with temporal patterns revealed with event related potentials. These data confirm previous reports showing specific motor neural responses associated with an unseen visual stimulus and establish TMS as a valuable tool in the study of the neural correlates of consciousness.

Emotional valence of words modulates the subliminal repetition priming effect in the left fusiform gyrus: an event-related fMRI study

The present study investigated if the emotional valence of words modulates the subliminal repetition priming effect in the brain, in particular, the occipitotemporal visual cortex, by adopting a rapid presentation event-related fMRI design. A masked repetition priming paradigm was adopted, in which, before the presentation of the target (either positive or negative or neutral in meaning), a masked prime word that was either a repetition or an unrelated word of the target was presented. The subject made a perceptual judgment on the target. The results revealed that the left mid-fusiform gyrus was sensitive to the emotional manipulation of the repetition priming effect and that the priming effect in the region was greater in the positive than in the negative word condition. The priming effect in the fusiform gyrus in neutral words was not significant, which might be a result of suppression caused by the emotional context. No effect of valence or repetition was found in the amygdala.

Hemispheric differences between left and right number representations: effects of conscious and unconscious priming

The contribution of each hemisphere to the generation of number representations was investigated by two lateralized priming experiments in which participants had to compare Arabic digits to a fixed standard of four. In Experiment 1, unmasked primes (Arabic digits or word numerals) were used. In Experiment 2, masked primes were presented consciously or subconsciously. In both experiments similar priming effects were found in the left (LH) and the right hemisphere (RH) when the prime was presented consciously. However, asymmetries emerged when the primes were presented subconsciously: while the priming effects of digits and word numbers were equally large in the right visual half field (RVF-LH), the influence of the word prime on the semantic and the response stage of the left visual half field (LVF-RH) was absent, indicating that a word prime was no longer processed when it was presented subconsciously in LVF-RH. We believe that the origin of the latter effect can be attributed to a failure to transfer word number primes from the RH to the LH when attentional resources are restricted.

The perception of microsound and its musical implications

Sound particles or microsounds last only a few milliseconds, near the threshold of auditory perception. We can easily analyze the physical properties of sound particles either individually or in masses. However, correlating these properties with human perception remains complicated. One cannot speak of a single time frame, or a "time constant" for the auditory system. The hearing mechanism involves many different agents, each of which operates on its own timescale. The signals being sent by diverse hearing agents are integrated by the brain into a coherent auditory picture. The pioneer of "sound quanta," Dennis Gabor (1900-1979), suggested that at least two mechanisms are at work in microevent detection: one that isolates events, and another that ascertains their pitch. Human hearing imposes a certain minimum duration in order to establish a firm sense of pitch, amplitude, and timbre. This paper traces disparate strands of literature on the topic and summarizes their meaning. Specifically, we examine the perception of intensity and pitch of microsounds, the phenomena of tone fusion and fission, temporal auditory acuity, and preattentive perception. The final section examines the musical implications of microsonic analysis, synthesis, and transformation.

The basal ganglia and inhibitory mechanisms in response selection: evidence from subliminal priming of motor responses in Parkinson's disease

Subliminal response priming was used to investigate inhibitory control processes relevant to response selection impairments in Parkinson's disease. Using a backward masking technique, covert activation of left- or right-hand responses was induced without subjects consciously perceiving the stimuli (right- or left-pointing arrows). The masked priming stimuli were followed by visible arrow stimuli, instructing for a left- or right-hand response, at a delay (interstimulus interval, ISI) of 0 or 100 ms. Motor cortex activation was recorded by means of the electroencephalographic lateralized readiness potential (LRP). Parkinson's disease patients (n = 12) were compared with age-matched controls (n = 12) and young controls (n = 10). In young controls, the ISI = 100 ms task effectively invoked inhibition of the subliminally primed responses, as demonstrated by a reversal of prime-target compatibility effects compared with the ISI = 0 ms task. This reversal implied that there was a so-called negative compatibility effect with faster responses and fewer errors when prime and target arrows pointed in opposite directions than when they required the same response. This negative compatibility effect turned into a positive compatibility effect in Parkinson's disease patients, while age-matched controls produced intermediate values. Together, these results support the view that response selection involves competitive, mutually inhibitory interactions between response alternatives, influenced by basal ganglia-thalamocortical mechanisms. As indicated by the reduced inhibition of partially activated responses, Parkinson's disease and, to a lesser degree, normal ageing affect the efficiency of these inhibitory interactions.

Processing of the arousal of subliminal and supraliminal emotional stimuli by the human amygdala

The amygdala is known to play an important role in conscious and unconscious processing of emotional and highly arousing stimuli. Neuroanatomical evidence suggests that the amygdala participates in the control of autonomic responses, such as skin conductance responses (SCRs), elicited by emotionally salient stimuli, but little is known regarding its functional role in such control. We investigated this issue by showing emotional visual stimuli of varying arousal to patients with left (n = 12), right (n = 8), and bilateral (n = 3) amygdala damage and compared their results with those from 38 normal controls. Stimuli were presented both subliminally (using backward masking) and supraliminally under lateralized presentation to one visual hemifield. We collected SCRs as a physiological index of emotional responses. Subjects subsequently rated each stimulus on valence and arousal under free viewing conditions. There were two key findings: (1) impaired overall SCR after right amygdala damage; and (2) impaired correlation of SCR with the rated arousal of the stimuli after left amygdala damage. The second finding was strengthened further by finding a positive correlation between the evoked SCR magnitude and postsurgery amygdala volume, indicating impaired autonomic responses with larger tissue damage. Bilateral amygdala damage resulted in severe impairments on both of the above measures. Our results provide support for the hypothesis that the left and right amygdalae subserve different functions in emotion processing: the left may decode the arousal signaled by the specific stimulus, whereas the right may provide a global level of autonomic activation triggered automatically by any arousing stimulus.

Semantic activation in the absence of perceptual awareness

Participants performed a semantic categorization task on a target that was preceded by a prime word belonging either to the same category (20% of trials) or to a different category (80% of trials). The prime was presented for 33 msec and followed either immediately or after a delay by a pattern mask. With the immediate mask, reaction times (RTs) were shorter on related than on unrelated trials. This facilitatory priming reached significance at prime-target stimulus onset asynchronies (SOAs) of 400 msec or less and remained unaffected by task practice. With the delayed mask, RTs were longer on related than on unrelated trials. This reversed (strategic) semantic priming proved to be significant (1) only at a prime-target SOA of 400 msec or longer and (2) after the participants had some practice with the task. The present findings provide further evidence that perceiving a stimulus with and without phenomenological awareness can lead to qualitatively different behavioral consequences.

Subjective measures of awareness and implicit cognition

In this article, we examine whether artificial grammar learning is implicit according to a subjective criterion of awareness based on confidence ratings. In four experiments, participants discriminated between grammatical and ungrammatical sequences in both the same (Experiment 1) and a novel (Experiments 2-4) vocabulary and indicated their confidence in each decision. Replicating earlier studies, confidence judgments reported on a continuous scale (50%-100%) were only weakly related to accuracy, suggesting that learning was implicit. In contrast, confidence judgments reported on a binary scale (high vs. low) revealed that confidence was related to accuracy. We show that participants are better able to place their phenomenal states on a binary scale, as compared with a continuous scale.

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.

Memories of mother, complementarity and shame: predicting response to subliminal stimulation with "Mommy and I are one"

A poorly understood finding with potentially wide-ranging implications is that subliminal stimulation with "Mommy and I are one" affects behavior. In this study (n= 62), "Mommy and I are one" lowered implicit mood (p= 0.0015) in comparison with a neutral stimulus ("People are walking"). The effect was most pronounced in shame-prone participants with less positive memories of their mother, and low self-mother complementarity (interaction p= 0.0044). Effects of a potentially shame-inducing stimulus ("I am completely isolated") were not significant (ps > 0.11). The results concerning less positive memories of mother replicate previous findings. We suggest that activation of unconscious associative networks explains the data. Though more research is needed, the cognitive content of these networks may involve representations of self-with-mother; for some, the affective content could involve shame.

How the Self Controls Its “Automatic Pilot” when Processing Subliminal Information

Human performance may be primed by information not consciously available. Can such priming become so overwhelming that observers cannot help but act accordingly? In the present study, well-visible stimuli were preceded by whole series of unidentifiable stimuli. These series had strong, additive priming effects on behavior. However, their effect depended on the frequency with which they provided information conflicting to the visible main stimuli. Thus, effects of subliminal priming are under observers' strategic control, with the criterion presumably set as a function of the openly observable error frequency. Electrical brain potentials show that this criterion acts simultaneously at the level of visual discrimination of the primes and at motor activation evoked by the primes, thereby shielding observers from unwanted information.

Persistent complex subliminal activation effects: first experimental observations

A strong recent focus on unconscious processes has increased interest in subliminal stimulation and other experimental activation technologies. Five experiments using male and female university students (N = 365) were carried out to compare 5-ms exposures of "mommy and I" stimuli with 5-ms control stimulation. Measures of self-mother similarity and other variables taken 7-14 days after exposure were more strongly correlated among experimental participants. Such complex, persistent effects may follow when powerfully activating stimuli administered under wholly unconscious conditions provokes schematic processing of social information and behavioral confirmation. These scientifically exciting and ethically problematic findings imply a need for further reduction of the role accorded to conscious volition and control in psychology.

Forgetting congruent and incongruent stereotypical information

In 2 studies, the authors investigated the directed-forgetting effects of stereotypically congruent, incongruent, and irrelevant information, after the in-group (Swedish) and out-group (immigrant) social categories had been subliminally primed. Because of recent theories of the role of attention and level of processing in the cognitive development of stereotypes, we hypothesized that directed-forgetting effects would be found for stereotype-congruent and irrelevant information but not for stereotype-incongruent information. The results supported our hypothesis, suggesting that the level of processing demanded by the type of information (regardless of whether congruent, incongruent, or irrelevant) may moderate directed-forgetting effects. The authors discussed the social implications of the results.

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.

Membrane Na+-K+ ATPase inhibition mediated quantal model for brain evolution

The hypothalamus secretes an endogenous membrane Na+-K+ ATPase inhibitor, digoxin. A digoxin-mediated model of quantal perception is proposed. In the quantal state, self replication of self-organized macromolecules is possible. This leads to the origin of molecular organisms like prions. Macromolecules group together to form organelle, which in evolutionary terms are independent bacteria. The organelle/bacteria symbiotically cluster together to form the cell. The human organism, including the brain, can be visualized as an organized cluster or colony of unicellular, symbiotically grouped flagellated bacteria. Synaptic connections form in the bacterial cluster leading to the evolution of the primitive neuronal networks, and later the human brain. The role of quantal perception and the observer function of consciousness in the origin of matter is important. Symbiotically clustered intergalactic magnetotactic bacterial networks are important in the evolution of the universe.

Interaction of prime and target in the subliminal affective priming effect

It has been found that an emotional stimulus such as a facial expression presented subliminally can affect subsequent information processing and behavior, usually by shifting evaluation of a subsequent stimulus to a valence congruent with the previous stimulus. This phenomenon is called subliminal affective priming. The present study was conducted to replicate and expand previous findings by investigating interaction of primes and targets in the affective priming effect. Two conditions were used. Prime (subliminal presentation 35 msec.) of an angry face of a woman and a No Prime control condition. Just after presentation of the prime, an ambiguous angry face or an emotionally neutral face was presented above the threshold of awareness (500 msec.). 12 female undergraduate women judged categories of facial expressions (Anger, Neutral, or Happiness) for the target faces. Analysis indicated that the Anger primes significantly facilitated judgment of anger for the ambiguous angry faces; however, the priming effect of the Anger primes was not observed for neutral faces. Consequently, the present finding suggested that a subliminal affective priming effect should be more prominent when affective valence of primes and targets is congruent.

Long-term semantic memory versus contextual memory in unconscious number processing

Subjects classified visible 2-digit numbers as larger or smaller than 55. Target numbers were preceded by masked 2-digit primes that were either congruent (same relation to 55) or incongruent. Experiments 1 and 2 showed prime congruency effects for stimuli never included in the set of classified visible targets, indicating subliminal priming based on long-term semantic memory. Experiments 2 and 3 went further to demonstrate paradoxical unconscious priming effects resulting from task context. For example, after repeated practice classifying 73 as larger than 55, the novel masked prime 37 paradoxically facilitated the "larger" response. In these experiments task context could induce subjects to unconsciously process only the leftmost masked prime digit, only the rightmost digit, or both independently. Across 3 experiments, subliminal priming was governed by both task context and long-term semantic memory.

The subliminal mere exposure effect does not generalize to structurally related stimuli

R.F. Bornstein (1994) questioned whether subliminal mere exposure effects might generalize to structurally related stimuli, thereby providing evidence for the existence of implicit learning. Two experiments examined this claim using letter string stimuli constructed according to the rules of an artificial grammar. Experiment 1 demonstrated that brief, masked exposure to grammatical strings impaired recognition but failed to produce a mere exposure effect on novel structurally related strings seen at test. Experiment 2 replicated this result but also demonstrated that a reliable mere exposure effect could be obtained, provided the same grammatical strings were presented at test. The results suggest that the structural relationship between training and test items prevents the mere exposure effect when participants are unaware of the exposure status of stimuli, and therefore provide no evidence for the existence of implicit learning.

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.

Comparison of two alternative measures of the boundary construct

'Mental boundaries' is a traditional concept in psychology, although attempts to conceptualize and measure such boundaries empirically have only recently been pursued. Two major efforts in this respect are Hartmann's Boundary Questionnaire and the Revised Transliminality Scale of Lange, Thalbourne, Houran, and Storm. We administered both along with the Briggs-Nebes Handedness Scale to a convenience sample of 268 participants to assess the convergent validity of the two boundary measures and to replicate previous evidence that the boundary construct involves body boundaries as well, such as a tendency toward mixed-handedness. As predicted, scores on the Revised Transliminality Scale correlated .66 positively with total scores on the Boundary Questionnaire, but neither measure was associated with the handedness scale. Each of the 12 domains of the Boundary Questionnaire correlated significantly with total scores on the Transliminality Scale, yet only five domains contributed significantly to the prediction of variance in transliminality scores in a standard multiple regression analysis. Analysis suggests that transliminality is related to specific domains of the Boundary Questionnaire, and we hypothesize that the other domains of the Boundary Questionnaire represent higher levels of the boundary construct than what is measured by the Revised Transliminality Scale. This idea is discussed within the context of Werner's 1948 theory of syncretic versus symbolic cognition.

The motivational looking glass: How significant others implicitly affect goal appraisals

Three studies manipulate the accessibility of significant-other representations to explore how these representations may automatically influence how goals are construed and experienced. Study 1 finds that the perceived attainment expectations of a significant other automatically affect participants' own task-goal expectations and their subsequent task performance and persistence. Study 2 finds that the general perceived value that a significant other places in attaining a task goal automatically affects participants' own attainment value appraisals, their task persistence and performance, and the magnitude of their reaction to success and failure feedback. Finally, Study 3 demonstrates that the regulatory focus prescribed by a significant other may automatically affect participants' own regulatory focus with regards to a task goal, with consequences for their cheerfulness-dejection and relaxation-agitation responses to success and failure feedback. The implications for our understanding of social influence and self-regulation are discussed.

On wildebeests and humans: the preferential detection of negative stimuli

On the basis of a functional perspective, we hypothesized that negative stimuli are detected faster than positive stimuli. In Experiment 1, participants were subliminally presented with positive and negative words or with no words at all. After each presentation, participants were asked whether they had seen a word. They detected negative words more accurately than positive words. In Experiment 2, participants were subliminally presented with negative or positive words. After each presentation, they were asked whether the presented word was positive or negative. Negative words were correctly categorized more often than positive words. Experiment 3 showed that although participants correctly categorized negative words more often than positive words. they could not guess the meaning of the words better than would be expected by chance. The results are discussed against the background of recent findings on basic affective processes.

Effects of nonconscious perception on motor response

The present study reviews the literature on the empirical evidence for the dissociation between perception and action. We first review several key studies on brain-damaged patients, such as those suffering from blindsight and visual/tactile agnosia, and on experimental findings examining pointing movements in normal people in response to a nonconsciously perceived stimulus. We then describe three experiments we conducted using simple reaction time (RT) tasks with backward masking, in which the first (weak) and second (strong) electric stimuli were consecutively presented with a 40-ms interstimulus interval (ISI). First, we compared simple RTs for three stimulus conditions: weak alone, strong alone, and double, i.e., weak plus strong (Experiment 1); then, we manipulated the intensity of the first stimulus from the threshold (T) to 1.2T and 2T, with the second stimulus at 4T (Experiment 2); finally, we tested three different ISIs (20, 40, and 60 ms) with the stimulus intensities at 1.2T and 4T for the first and second stimuli (Experiment 3). These experiments showed that simple RTs were shorter for the double condition than for the strong-alone condition, indicating that motor processes under the double condition may be triggered by sensory inputs arising from the first stimulus. Our results also showed that the first stimulus was perceived without conscious awareness. These findings suggested that motor processes may be dissociated from conscious perceptual processes and that these two processes may not take place in a series but, rather, in parallel. We discussed the likely mechanisms underlying nonconscious perception and motor response to a nonconsciously perceived stimulus.

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.