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PubMed1998

On demonstrating unconscious perception: comment on Draine and Greenwald (1998)

S. C. Draine and A. G. Greenwald (1998) have described a methodology based on regression analysis for demonstrating unconscious perception. They have suggested that their methodology represents a major improvement over existing methodologies. An analysis of their methodology reveals that it is closely related to the classic dissociation paradigm. As such, interpretation of their results is compromised by the same issues concerning the measurement of awareness that have plagued all previous attempts to use the dissociation paradigm to demonstrate unconscious perception in the complete absence of conscious perception.

Cognition↗
PubMed1998

Correcting for measurement error in detecting unconscious cognition: comment on Draine and Greenwald (1998)

A. G. Greenwald, M. R. Klinger, and E. S. Schuh (1995) have proposed a regression method for detecting unconscious cognition in experiments that obtain measures of indirect and direct effects of stimuli with suspected unconscious effects. Their indirect-on-direct-measure regression approach can produce misleading evidence for indirect effects in the absence of direct effects when the direct-effect measure has typical measurement error. This article describes an errors-in-variables variant of the regression method that corrects for error in the direct-effect measure. Applied to the uses of the regression method by S. C. Draine and A. G. Greenwald (1998) in this issue, the errors-in-variables method affirms substantial evidence for indirect effects in the absence of direct effects.

Cognition↗
PubMed1995

Unconscious priming of association judgments.

Participants judged whether pairs of target words were associated or not-associated in meaning (association judgment task). Target pairs were preceded by a brief (200 ms) related or unrelated (prime) word presented to the nondominant eye. Each participant performed 2 blocks of association judgment task trials: 1 with primes that were legible, and 1 with primes that were masked by a pattern simultaneously presented to the dominant eye. Across 2 experiments, significantly larger masked priming effects were observed for participants who could not detect priming words (low-d' participants) than for participants who could partially see priming words (high-d' participants). This result suggests that undetectable masked primes can activate word meaning and that conscious attempts to process masked primes may inhibit unconscious activation. Additionally, evidence is presented that supports claims that spreading activation is the crucial mechanism responsible for unconscious priming.

Eye Movements↗
PubMed2006

On the status of unconscious memory: Merikle and Reingold (1991) revisited.

Four experiments are reported that reevaluate P. M. Merikle and E. M. Reingold's (1991) demonstration of unconscious memory: the greater sensitivity to familiarity (repetition) of an indirect (implicit) memory task than of a comparable direct (explicit) task. At study, participants named the cued member of a pair of visually presented words. At test, new and uncued study words were presented against a background mask. Participants judged whether each word was old or new (direct task) or whether the contrast between the word and the background was high or low (indirect task). Contrary to the original findings, the sensitivity of the indirect task to familiarity never exceeded that of the direct task. These findings pose a challenge to a key pillar of evidence for unconscious influences of memory.

Adolescent↗
PubMed1999

Use of midlatency auditory-evoked potentials as indicator of unconsciousness in the dog: characterisation of the effects of acepromazine-thiopentone, medetomidine-thiopentone and medetomidine-butorphanol-midazolam combinations.

Middle latency auditory-evoked potentials were measured in sedated and anaestetised dogs to determine their possible usefulness in monitoring of unconsciousness during anaesthesia and to compare the effects of anaesthetic protocols. There were three groups of five dogs: group I received acepromazine; groups 2 and 3 received medetomidine; 30 minutes later, groups 1 and 2 received thiopentone and group 3 received midazolam and butorphanol. Groups 2 and 3 received atipamezole 60 minutes after medetomidine was administered. Auditory-evoked potentials were recorded at time 15, 40 and 75 minutes. Thiopentone administration resulted in a profound modification of the pattern of response, and several peaks were no longer identified. In group 3, the administration of midazolam-butorphanol tended to increase the latency of the different peaks, but lesser than thiopentone did. Middle latency-evoked potentials appeared to be potentially useful in the monitoring of unconsciousness in the dog.

Acepromazine↗
PubMed2004

Extrageniculate mediation of unconscious vision in transcranial magnetic stimulation-induced blindsight.

The proposed neural mechanisms supporting blindsight, the above-chance performance of cortically blind patients on forced-choice visual discrimination tasks, are controversial. In this article, we show that although subjects were unable to perceive foveally presented visual stimuli when transcranial magnetic stimulation over the visual cortex induced a scotoma, responses nonetheless were delayed significantly by these unconscious distractors in a directed saccade but not in an indirect manual response task. These results suggest that the superior colliculus, which is involved with sensory encoding as well as with the generation of saccadic eye movements, is mediating the unconscious processing of the transcranial magnetic stimulation-suppressed distractors and implicate a role of the retinotectal pathway in many blindsight phenomena.

Adult↗
PubMed2005

Repression of unconscious information by conscious processing: evidence from affective blindsight induced by transcranial magnetic stimulation.

Some patients with a lesion to the primary visual cortex (V1) show "blindsight": the remarkable ability to guess correctly about attributes of stimuli presented to the blind hemifield. Here, we show that blindsight can be induced in normal observers by using transcranial magnetic stimulation of the occipital cortex but exclusively for the affective content of unseen stimuli. Surprisingly, access to the affective content of stimuli disappears upon prolonged task training or when stimulus visibility increases, allegedly increasing the subjects' confidence in their overall performance. This finding suggests that availability of conscious information suppresses access to unconscious information, supporting the idea of consciousness as a repressant of unconscious tendencies.

Adult↗
PubMed2005

Unconscious fear influences emotional awareness of faces and voices.

Nonconscious recognition of facial expressions opens an intriguing possibility that two emotions can be present together in one brain with unconsciously and consciously perceived inputs interacting. We investigated this interaction in three experiments by using a hemianope patient with residual nonconscious vision. During simultaneous presentation of facial expressions to the intact and the blind field, we measured interactions between conscious and nonconsciously recognized images. Fear-specific congruence effects were expressed as enhanced neuronal activity in fusiform gyrus, amygdala, and pulvinar. Nonconscious facial expressions also influenced processing of consciously recognized emotional voices. Emotional congruency between visual and an auditory input enhances activity in amygdala and superior colliculus for blind, relative to intact, field presentation of faces. Our findings indicate that recognition of fear is mandatory and independent of awareness. Most importantly, unconscious fear recognition remains robust even in the light of a concurrent incongruent happy facial expression or an emotional voice of which the observer is aware.

Auditory Perception↗
PubMed1995

The case for not interpreting unconscious mental life in consulting to organizations.

DESPITE differing theoretical orientations in psychoanalysis, there is general agreement that its distinctive feature among all therapies is its attempt to bring to consciousness mental conflict that is unconscious. Does this distinctive feature of psychoanalysis apply in organizational consultation? I argue that unlike clinical psychoanalysis, more harm than good occurs when consultants attempt to interpret unconscious material to clients in organizations. The main use of psychoanalytic psychology in consulting work is for observation and understanding on the part of the consultant, who as an advisor presents recommendations aimed at enhancing rationality.

Consultants↗
PubMed1993

Recurrent attacks of unconsciousness with diffuse EEG alpha activity.

A 45-year-old patient presented with recurrent attacks of unconsciousness, which resembled sleep. However, EEG recordings during these attacks showed diffuse, frontal-dominant 10-Hz alpha activity. Both the attacks and EEG changes reversed promptly with intravenous flumazenil, but not with methylphenidate, atropine or placebo. The attacks could not be prevented with methysergide, flumazenil, clonidine, piracetam or phenytoin. Laboratory investigations revealed a temporal lobe arachnoid cyst, a distal motor and sensory polyneuropathy, abnormal auditory evoked responses during the attack, an abnormal silent period latency and abnormal melatonin regulation. Similar attacks were reported by history in two siblings and in the proband's late father. It is postulated that the attacks of unconsciousness could involve gamma-aminobutyric acid- (GABA)-mediated mechanisms.

Alpha Rhythm↗
PubMed1993

Fentanyl-induced rigidity and unconsciousness in human volunteers. Incidence, duration, and plasma concentrations.

BACKGROUND: Muscle rigidity frequently accompanies induction of anesthesia with opioids. The authors sought to determine whether unconsciousness and amnesia occur when humans develop rigidity and apnea after intravenous fentanyl (without other concomitant anesthetics). METHODS: The incidence and duration of rigidity and level of consciousness were evaluated and associated plasma concentrations of fentanyl were measured in 12 healthy adult male volunteers given only intravenous fentanyl. Fentanyl was infused at a rate of 150 micrograms/min until a total of 15 micrograms/kg had been administered. Arterial blood samples for fentanyl assay were drawn and responsiveness, heart rate (HR), and systolic and diastolic arterial blood pressures were determined at frequent intervals during and after infusion. If rigidity was accompanied by an Spo2 < 90%, positive pressure ventilation with 100% O2 with a mask was instituted until spontaneous ventilation resumed. RESULTS: The incidence of muscular rigidity was 50% (6/12). All subjects who developed rigidity were apneic, unresponsive, and had no recall of commands to breathe or of positive pressure ventilation. Subjects not developing rigidity remained awake and responsive. No subject developing rigidity required neuromuscular blockade to allow positive pressure ventilation and adequate oxygenation (Spo2 > 90%). When rigidity occurred, it started 3 +/- 0.9 (range 1-4) min after the peak plasma fentanyl concentration and lasted for 11.5 +/- 5.8 (range 7-23) min. Rigidity started at a plasma fentanyl concentration of 21.5 +/- 4.4 (range 16-28) ng/ml and ended at 6.9 +/- 1.5 (range 5.2-8.7) ng/ml. Baseline HR was less in the subjects who subsequently developed rigidity (56.7 +/- 7.8 vs. 67.2 +/- 7.8 P = 0.04). No differences in fentanyl plasma concentrations or predicted effect site concentrations for rigidity were detected between subjects who developed rigidity and those who did not. CONCLUSIONS: These findings support the hypothesis that unconsciousness occurs in the unstimulated subject during fentanyl-induced apnea and rigidity.

Adult↗
PubMed2004

Narcotrend does not adequately detect the transition between awareness and unconsciousness in surgical patients.

BACKGROUND: The Narcotrend index (MonitorTechnik, Bad Bramstedt, Germany) is a dimensionless number between 0 and 100 that is calculated from the electroencephalogram and inversely correlates with depth of hypnosis. The current study evaluates the capability of the Narcotrend to separate awareness from unconsciousness at the transition between these levels. METHODS: Electroencephalographic recordings of 40 unpremedicated patients undergoing elective surgery were analyzed. Patients were randomly assigned to receive (1) sevoflurane-remifentanil (</= 0.1 microg . kg . min), (2) sevoflurane-remifentanil (>/= 0.2 microg . kg . min), (3) propofol-remifentanil (</= 0.1 microg . kg . min), or (4) propofol-remifentanil (>/= 0.2 microg . kg . min). Remifentanil and sevoflurane or propofol were given until loss of consciousness. After tracheal intubation, propofol or sevoflurane was stopped until return of consciousness and then restarted to induce loss of consciousness. After surgery, drugs were discontinued. Narcotrend values at loss and return of consciousness were compared with each other, and anesthetic groups were compared. Prediction probability was calculated from values at the last command before and at loss and return of consciousness. RESULTS: At 105 of 316 analyzed time points, the Narcotrend did not calculate an index, and the closest calculated value was analyzed. No significant differences between loss and return of consciousness were found. In group 1, Narcotrend values were significantly higher than in group 3. Prediction probability was 0.501. CONCLUSIONS: In these challenging data, the Narcotrend did not differentiate between awareness and unconsciousness. In addition, Narcotrend values were not independent from the anesthetic regimen.

Adult↗
PubMed1994

Early definitive abdominal evaluation in the triage of unconscious normotensive blunt trauma patients.

The need for simultaneous diagnosis and treatment of life-threatening intracranial mass lesions and intra-abdominal injury results in controversy over the appropriate triage of unconscious blunt trauma patients with stable vital signs. To aid in early decisions for these patients, a retrospective analysis of 290 patients with Glasgow Coma Scale (GCS) scores < or = 8 and systolic blood pressures (SBP) > 90 mm Hg was undertaken. The hypothesis of this study was that life-threatening abdominal injury frequently occurs in these patients and injuries cannot be consistently identified from vital signs alone. Data were analyzed for injury mechanism, SBP, heart rate (HR), Injury Severity Score (ISS), Revised Trauma Score (RTS), Abbreviated Injury Scale score for the abdomen and brain (A-AIS, CNS-AIS), and the need for emergent laparotomy. Patients with concurrent injuries were more likely to come from motor vehicle crashes than falls (p < 0.001). Although severe abdominal injuries (A-AIS > or = 3) were frequently identified based on SBP and HR, the use of clinical signs alone resulted in more missed injuries than did using the results diagnostic peritoneal lavage (DPL). This study suggests that all unconscious normotensive blunt trauma patients undergo immediate DPL to prevent missing life-threatening injuries.

Abdominal Injuries↗
PubMed2001

Evaluation of the Oxford protocol for total spinal clearance in the unconscious trauma patient.

BACKGROUND: Prolonged use of spinal precautions in unconscious trauma patients is associated with significant morbidity. The trauma service of the John Radcliffe Hospital uses full-length radiography, computed tomographic scanning, and dynamic screening of the cervical spine to clear the spine at the earliest opportunity. METHODS: The results in 210 consecutive patients were reviewed. Seventy-eight patients underwent dynamic screening of the cervical spine. RESULTS: Five of these patients had a cervical fracture or instability. One patient had demonstrated minor changes only on plain radiography but gross instability on dynamic screening. There were no neurologic sequelae from dynamic screening and no fractures were missed. Collar removal was possible in all but one patient a median 3 days before extubation and 1 day after admission to the intensive care unit. CONCLUSION: Full length spinal radiography and dynamic cervical screening may allow early and safe discontinuation of spinal precautions in the unconscious trauma patient in whom clinical signs are absent or unreliable.

Adolescent↗
PubMed2000

Parts outweigh the whole (word) in unconscious analysis of meaning.

In unconscious semantic priming, an unidentifiable visually masked word (the prime) facilitates semantic classification of a following visible related word (the target). Three experiments reported here provide evidence that masked primes are analyzed mainly at the level of word parts, not whole-word meaning. In Experiment 1, masked nonword primes composed of subword fragments of earlier-viewed targets functioned as effective evaluative primes. (For example, after repeated classification of the targets angel and warm, the nonword anrm acted as an evaluatively positive masked prime.) Experiment 2 showed that this part-word processing was potent enough to oppose analysis at the whole-word level. Thus, smile functioned as an evaluatively negative (!) masked prime after repeated classification of smut and bile. Experiment 3 found no priming when masked word primes contained no parts of earlier targets. These results suggest that robust unconscious priming (a) is driven by analysis of part-word information and (b) requires previous classification of visible targets that contain the fragments later serving as primes. Contrary to a widely held view, analysis of subliminal primes appears not to function at the level of analysis of complete words.

Adult↗
PubMed2004

Unconscious color priming occurs at stimulus- not percept-dependent levels of processing.

Although past studies have shown that visual information can be processed without awareness, the types and levels of this processing have yet to be determined. We used metacontrast masking to explore unconscious priming effects of white, blue, and green stimuli generated on a color video display. We found that a white prime tends to act more like a green than a blue one. Color confusions among unmasked and masked primes and calibrations of the display phosphors show that physical rather than perceptual properties of the stimuli best explain the white prime's effects. We conclude that unconscious color priming in normal observers occurs at early wavelength-dependent levels of processing prior to later color-percept-dependent levels.

Color Perception↗
PubMed2004

Clearing the cervical spine in unconscious polytrauma victims, balancing risks and effective screening.

Cervical spine injury occurs in 5-10% of cases of blunt polytrauma. A missed or delayed diagnosis of cervical spine injury may be associated with permanent neurological sequelae. However, there is no consensus about the ideal evaluation and management of the potentially injured cervical spine and, despite the publication of numerous clinical guidelines, this issue remains controversial. In addition, many studies are limited in their application to the obtunded or unconscious trauma victim. This review will provide the clinician managing unconscious trauma victims with an assessment of the actual performance of clinical examination and imaging modalities in detecting cervical spine and isolated ligamentous injury, a review of existing guidelines in light of the available evidence, relative risk estimates and a proposed management scheme.

Cervical Vertebrae↗
PubMed2004

Clearing the cervical spine after polytrauma: implementing unified management for unconscious victims in the intensive care unit.

Determining the best method for excluding cervical spine injury while a polytrauma victim is unconscious remains a controversial topic despite a number of published guidelines. A structured questionnaire demonstrated major differences between intensivists, neurosurgeons, orthopaedic surgeons and spinal surgeons with regard to the imaging modalities requested, the perception of their performance, the relative risks of missed injuries and the complications of immobilisation. Unconscious victims of polytrauma often come under the care of several subspecialties, with the direct consequence that management can be contradictory and lack standardisation. Advanced Trauma Life Support and Eastern Association for the Surgery of Trauma guidelines can reinforce and even contribute to non-standardised care. Having performed this clinician survey, we have now developed a multidisciplinary management protocol appropriate for Northern Ireland.

Cervical Vertebrae↗