A psychophysiological investigation of the interplay between orienting and executive control during stimulus conflict: A heart rate variability study.

BACKGROUND: It has been hypothesized that resting state cardiac vagal activity (CVA) - an indicator of parasympathetic nervous system activity - is a specific psychophysiological marker of executive control function. Here, we propose an alternative hypothesis - that CVA is associated with early stage attention orientation, promoting the flexible uptake of new information, on which the later operation of such executive control functions depends. We therefore predicted that CVA would predict the interaction between orienting and executive control. This was tested using the revised version of the Attention Network Test (ANT-R) that was developed to distinguish between orienting and executive attention during a stimulus conflict task. METHODS: Healthy adults (N = 48) performed the ANT-R and their resting CVA was measured over a 5 min period using ECG recordings. RESULTS: Multiple regression analyses indicated that, when other factors were controlled for, CVA was more strongly associated with the interaction between the orienting and executive control terms than with either factor individually. CONCLUSION: Higher levels of CVA are specifically implicated in the modulation of executive control by intrinsic orientation operating at early stages of conflict detection. These initial findings of higher CVA on orienting attention in conflict detection need to be replicated in larger samples.

Effects of psychological defense on processing of neutral stimuli indicated by event-related potentials (ERPs).

The Defense Mechanism Test (DMT) is claimed to identify personnel with a high risk for accidents. A new explanation for why the DMT seems to predict performance when survival depends on split second decisions is proposed. Sixteen right-handed, adult male students were tested with the DMT and with an ERP paradigm (two sine wave tones, presented binaurally). Each subject was tested with a one-stimulus paradigm, and a passive and an active oddball paradigm. Under the passive oddball condition, High defensive subjects differed from Low, having significantly smaller N2 amplitudes (low immediate perception), and significantly larger P3 amplitudes (rely on later associative mechanisms). High defensive subjects seem to have less ability to perceive the environment correctly immediately. This slowness may be fatal when life depends on split second decisions. The fundamental neurophysiological difference may also be the basis for the very complex cognitive and perceptual mechanisms involved in psychological defense mechanisms.

Information processing deficits in head injury assessed with ERPs reflecting early and late processing stages.

ERPs provide informative measures of slowed information processing in head injury. While several studies have reported changes in long latency ERPs (N2, P3) in head injury, the data on early ERP components related to attention selection are inconclusive. The problem may be partly methodological because the standard oddball paradigm does not give an adequate basis for discriminating components contributing to the N1 and P2 waveforms. Following a suggestion by Garcia-Larrea et al. [10: Garcia-Larrea L, Lukasziewicz A-C, Maugière F. Revisiting the oddball paradigm. Non-target vs neutral stimuli and the evaluation of ERP attention effects. Neuropsychologia 1992;30:723-741] we used an extended oddball paradigm to study measures of early processing (N1-average, P250) as well as conventional cognitive ERPs (N1, P2, N2, P3) in a group of head injured patients and controls. We found evidence of deficits in early processing of neutral and non-target stimuli in the patient group, and interpret the findings as an indication that the patients are less efficient in terminating processing of irrelevant stimuli. The results further indicate that processing deviations affect both target and non-target stimuli in the oddball paradigm and thus the allocation of attention in the task as a whole.

Alcoholics' selective attention to alcohol stimuli: automated processing?

OBJECTIVE: This study investigated alcoholics' selective attention to alcohol words in a version of the Stroop color-naming task. METHOD: Alcoholic subjects (n = 23) and nonalcoholic control subjects (n = 23) identified the color of Stroop versions of alcohol, emotional, neutral and color words. Manual reaction times (RTs), skin conductance responses (SCRs) and heart rate (HR) were recorded. RESULTS: Alcoholics showed overall longer RTs than controls while both groups were slower in responding to the incongruent color words than to the other words. Alcoholics showed longer RTs to both alcohol (1522.7 milliseconds [ms]) and emotional words (1523.7 ms) than to neutral words (1450.8 ms) which suggests that the content of these words interfered with the ability to attend to the color of the words. There was also a negative correlation (r = -.41) between RT and response accuracy to alcohol words for the alcoholics, reflecting that the longer time the alcoholics used to respond to the color of the alcohol words, the more incorrect their responses were. The alcoholics also showed significantly greater SCRs to alcohol words (0.16 microSiemens) than to any of the other words (ranging from 0.04-0.08 microSiemens), probably reflecting the emotional significance of the alcohol words. Finally, the alcoholics evidenced smaller HR acceleration to alcohol (1.9 delta bpm) compared to neutral (2.8 delta bpm), which could be related to difficulties alcoholics experience in terminating their attention to the alcohol words. CONCLUSIONS: These findings indicate that it is difficult for alcoholics to regulate their attention to alcohol stimuli, suggesting that alcoholics' processing of alcohol information is automated.

Effects of hypnotizability on performance of a Stroop task and event-related potentials.

The effect of hypnotizability on verbal reaction times and event-related potentials during performance of a Stroop color-naming task was studied. The Stroop stimuli (colored words) were randomly presented to 5 high and 5 low hypnotizable subjects in the right and left peripheral visual fields during both waking state and hypnotic induction conditions. Unlike studies in which the Stroop stimuli were foveally presented to the subjects, the highly hypnotizable subjects did not show prolonged verbal reaction times in either waking or hypnotic conditions. There was a marked deterioration in performance accuracy, however, for highly hypnotizable subjects during hypnosis. Event-related potentials indicated that the highly hypnotizable subjects showed a reduced P3a amplitude and a decreased N2b latency to the visual stimuli in both waking and hypnotic conditions, suggesting a lack of orienting to or disengagement from peripherally occurring stimuli.

Heart rate responses indicate locked-in attention in alcoholics immediately prior to drinking.

Twenty alcohol-dependent subjects and 10 social drinkers were tested in two experimental conditions: (a) when they were informed that their drinks contained alcohol and (b) when they were informed that their drinks were soft drinks. When told "alcohol," alcoholics evidenced a heart rate (HR) acceleration, whereas control subjects were unaffected by the instruction. Moreover, severely dependent (SD) alcoholics' HR remained elevated within the evaluation period whereas moderately dependent (MD) alcoholics' HR returned to baseline levels. The sustained HR acceleration in SD alcoholics suggests that their attention became "locked in" on the alcohol information immediately prior to drinking in the "told-alcohol" condition. Such an inward focus of attention will seriously reduce the alcoholic's ability to shift attention away from alcohol information, which may explain the difficulties alcoholics experience in coping with high-risk situations for drinking. In the SD alcoholics, HR acceleration correlated with the time it took to start drinking subsequent beverages containing alcohol in the told-alcohol instruction. In the MD alcoholics, HR responses were related to the reported urge to drink, whereas it was only in the nondependent subjects that self-reported urge to drink was related to the actual alcohol-use behavior.

Central auditory processing, MRI morphometry and brain laterality: applications to dyslexia.

We review data from our laboratory related to a view of dyslexia as a biological disorder, or deficit, caused by both structural and functional brain abnormalities. The review is focused on central auditory processing in dyslexia, and the possibility that impairments in the auditory or acoustic features of the phonological code may be at the heart of the impairments seen in dyslexia. Three methodological approaches by which to investigate central auditory processing deficits are outlined: dichotic listening (DL) to consonant-vowel syllables; magnetic resonance imaging (MRI), and the use of event-related potentials (ERPs). Consonant-vowel syllable DL is a technique for probing the functional status of phonological processing areas in the superior temporal gyrus, particularly in the left hemisphere. MRI is a corresponding structural, or morphological, measure of anatomical abnormalities in the same brain region, particularly covering the planum temporale area. The ERP technique, and particularly the mismatch negativity (MMN) component, reveals cortical dysfunctions in sensory processing and memory related to basic acoustic events. For all three approaches, the dyslexic children were seen to differ from their control counterparts, including absence of modulation of the right ear advantage (REA), in DL through shifting of attention, smaller left-sided planum temporale asymmetry, and prolonged latency in the MMN ERP complex, particularly in the time-deviant stimulus condition.

Event-related potential (ERP) asymmetries to emotional stimuli in a visual half-field paradigm.

To investigate the hypothesis of a right hemispheric superiority in negative emotional processing, event-related potentials (ERPs) were recorded from 17 sites (Fz, Cz, Pz, F3/4, F7/8, C3/4, T7/8, P3/4, P7/8, O1/2) in a visual half-field paradigm. While maintaining fixation, right-handed women viewed pictures of patients with dermatological diseases before (negative) and after (neutral) cosmetic surgery. A principal components analysis with Varimax rotation performed on ERPs revealed factors identified as N1, N2, early P3, late P3, and slow wave. Repeated measures analyses of variance performed on factor scores revealed a significant effect of emotional content for all factors except for N1. However, asymmetries in emotional processing were restricted to N2 and early P3, with maximal effects over the right parietal region. N2-P3 amplitude was augmented for negative and reduced for neutral stimuli over right hemisphere regions. Visual field presentation interacted with these asymmetries in enhancing amplitudes contralaterally for early but ipsilaterally for late ERP components. Overall, findings for N2 and P3 support theories of an asymmetry in emotional processing.

Event-related potentials (ERPs) to deviant auditory stimuli during sleep and waking.

Using an oddball paradigm with two tones differing in pitch and probability, event-related potentials (ERPs) were compared during wake and two sleep stages. REM and NREM sleep stages were identified in nine subjects using the Nightcap which continuously records eye and body movements. The N1 occurred later and the P2 was larger during sleep than when awake. The N1 to the infrequent tones was larger during both sleep stages. A late negative wave was significantly larger to infrequent tones during REM sleep. It is concluded that representations of auditory stimuli occur in sleep, and most prominently during the REM phase. The prolonged latency of the ERP components indicates that processing of external sensory stimuli may be delayed.

Autonomic cued reactivity in alcoholics: the effect of olfactory stimuli.

The present study was designed to investigate autonomic cued reactivity to olfactory alcohol stimuli in alcoholics. Twenty outpatient alcoholics and 20 social drinkers were exposed to high- and low-potency alcohol and neutral odors. The alcoholics showed greater skin conductance responses and increased heart rate acceleration responses to the high-potency alcohol odor than social drinkers, while there was no difference between the groups' responses to the low-potency alcohol odor. Alcoholics also reported greater difficulties in resisting a potential offer for a drink after relative to before the experiment, while there was no change in the desire to drink. The results indicate that alcohol cues are perceived as emotionally aversive and elicit a defensive response to avoid further processing of these stimuli. The increased autonomic reactivity may thus reflect a shift of focus from the environmental alcohol cues to internal thoughts and feelings. A rigid internal focus may constrain the ability to resist alcohol consumption and thus be a critical determinant in promoting craving and relapse in alcoholics.

ERPs for infrequent omissions and inclusions of stimulus elements.

A negative event-related potential (ERP) wave called mismatch negativity (MMN) is elicited by an infrequent deviant stimulus in a sequence of frequent standard stimuli. Omission of a stimulus in a sequence of stimuli, however, has been considered to elicit a negativity different from MMN. The present study addressed this issue by examining ERPs for infrequent omissions and inclusions of compound stimuli or their elements. Three kinds of stimuli were presented: a 1000-Hz sine wave tone (Sine), white noise with the 1000-Hz frequency sharply filtered out (Noise), and a composite of the pure tone and the filtered white noise (SiNoise). All stimuli had 50 ms duration and were presented with a regular interstimulus interval of 650 ms. Intensities were 75 dB SPL for the tone and noise stimuli and slightly higher for the composite stimulus. The three kinds of stimuli were presented on separate runs, either as the frequent stimulus or one of two infrequent stimuli, each with 10% probability. Infrequent omission of the large stimulus element (Sine deviant to SiNoise) tended to elicit later MMN than inclusion of the same element (SiNoise deviant to Sine). Omission of the small stimulus element (Noise deviant to SiNoise) elicited a smaller and later MMN than did inclusion of the same element (SiNoise deviant to Noise). These data suggest that MMNs are also elicited by partial stimulus omissions, although they seem to be more sensitive to other kinds of stimulus deviances.

Electrophysiological correlates to cued attentional shifts in the visual and auditory modalities.

Reaction time (RT) is usually speeded and slowed to correctly and incorrectly cued target stimuli, respectively, in experiments on attention shift (Posner, 1988). When targets occur in a spatial location different from the cue, shifting attention from the cued location to the target location involves interrupt of ongoing activity, move attention to the new location, and reengage attention. The present study investigated whether the cognitive operations involved in cued vs uncued attentional shifts also were detectable in the event-related potentials (ERPs). Two experiments are reported, one with visual and one with auditory stimuli. In the visual modality, the cue and target were a lit-up square and an asterisk, respectively, shown on a computer screen. In the auditory modality, the cue was a tone in either the left or right ear, followed by the target noise in either the same or the opposite ear. The results from the visual experiment showed shorter RTs to correctly cued (Valid) targets and longer RTs to incorrectly cued (Invalid) targets. Invalidly cued targets elicited enhanced P3 amplitudes, with a frontocentral distribution. Reduced P3 amplitudes were observed on Valid trials, largest reduction for parietooccipital leads. The auditory experiment showed P3 enhancement frontally and reduced amplitudes at temporal and parietal leads. No RT differences were seen to Valid and Invalid trials. The existence of an anterior attention system involved in interrupt and disengage of attention, and a posterior attention facilitation system related to cue presentation is discussed.

Phototoxic coumarins in limes.

Coumarins in the rind and pulp of Persian and Key limes were quantified. In the rind of Persian limes, coumarin concentrations were in the order: limettin > bergapten > isopimpinellin > xanthotoxin > psoralen. In the rind of Key limes, psoralen and xanthotoxin were analytically absent; limettin was 10 times more concentrated than either bergapten or isopimpinellin, which were equal in concentration. Coumarin content in Persian lime pulp was in the order: isopimpinellin > limettin > bergapten > xanthotoxin > psoralen. For Key lime pulp, the concentrations of limettin, isopimpinellin and bergapten were equal; psoralen and xanthotoxin were not detected. Coumarins in lime pulp were 13 to 182 times less concentrated than those in the peel. Based on the amounts and types of coumarins, Persian limes appear to be potentially more phototoxic than Key limes. Although bergapten may be the main component of limes responsible for phytophotodermatitis, dermatological interaction assays with psoralen, bergapten, xanthotoxin and limettin should be conducted.

[Intraoperative ultrasonography in brain surgery]. / Peroperativ ultrasonografi i hjernekirurgi.

Intraoperative ultrasound was used in 33 patients. 19 lesions were primary malignant brain tumours, including 12 gliomas, three astrocytomas and four oligodendrogliomas. There were five metastases, three meningeomas, two dysembryoplastic neuroepithelial tumours and two angiomas. One patient had an arachnoid cyst, and another an infarct. The main advantage of carrying out intraoperative ultrasound examination is that it helps to localize the tumour, particularly in small subcortical lesions where the brain surface may appear normal. Ultrasound is less useful for characterizing the tumour, although the various tumours do show some differences. As a rule, the glioblastomas are inhomogeneous and poorly marginated, while low grade gliomas are more homogeneous and well marginated. Also meningeomas and metastases tend to be homogeneous and well marginated. Periofocal oedema is hyperechogenic compared with brain tissue, with an intensity between that of normal brain tissue and tumour mass. Cyst, calcification and haemorrhage are easily demonstrated.

Hemisphere differences in event-related potentials (ERPS) to monaural presentations of simple speech sounds.

The aim of the present study was to compare ERPs over the left and right hemispheres to monaural consonant-vowel (CV) syllables. It was predicted that, if the contralateral auditory representation is stronger than the ipsilateral one, then ERPs over the left hemisphere should be larger for right-ear stimulus input. Furthermore, if the hemispheres differ in efficiency in processing of speech sounds, then ERPs recorded at any given site should vary as a function of the ear to which the sound is presented. Twelve right-handed subjects participated. The CV-syllables used were /Ba/ and /Pa/ with 15 presentations of each syllable to each ear in a randomized order. EEG was recorded from F3, Fz, and F4 with linked ears as reference. The results showed no significant asymmetry in the ERP-leads. N1- and N2-amplitudes were, however, larger at Fz than at F3 and F4, and N1-latency was shorter for right-ear presentations, which also interacted with the /Pa/-syllable presentations. P3-latency was longer to the /Pa/-syllable compared to the /Ba/-syllable, while N4-latency was longer to the /Ba/-syllable. N4-amplitude was more negative for the /Pa/-syllable presented to the left ear. The results are discussed in terms of phonemic differences between the unvoiced /Pa/ and voiced /Ba/, and early versus late stages of processing. The results are also seen in relation to ear differences in dichotic listening.

Increased serum creatine kinase BB and neuron specific enolase following head injury indicates brain damage.

The aim of this study was to examine whether an increase in the serum concentrations of the two brain enzymes creatine kinase BB (CK-BB) and neuron specific enolase (NSE) can be demonstrated in patients with acute head injury and whether such an increase reflects release from damaged brain tissue. In 60 patients who had suffered minor to severe head injury, serial blood samples were drawn during the first hours after impact, and CK-BB and NSE were measured by radioimmunoassay. Computed tomography (CT) was also performed shortly after admission to hospital, and was repeated 1-3 days later in selected patients. Increased serum concentrations of both CK-BB and NSE were found in 88% of the patients with moderate to severe head injury (group 1, n = 18) and in 23% of the patients with minor head injury (group 2, n = 42), whereas CT showed contusion in only 41% and 2% of the group 1 and 2 patients, respectively. The following findings suggest that the enzymes had been released from brain tissue: 1) The maximum concentrations of CK-BB and NSE correlated with the severity of injury as assessed clinically and with the volume of contusion as estimated from CT (r = 0.79 with CK-BB, r = 0.72 with NSE). 2) The maximum concentrations of CK-BB and NSE were closely correlated (r = 0.87).(ABSTRACT TRUNCATED AT 250 WORDS)

Anticipatory nausea and vomiting in cancer patients.

The present study reports on a mediating mechanism for anticipatory nausea and vomiting (ANV) in cancer chemotherapy. ANV is usually explained as a classically conditioned response. However, conditioning models have failed to explain individual variation in ANV susceptibility. On the basis of the positive correlation between degree of autonomic reactivity (AR) and conditionability, it is proposed that individual AR is predictive of ANV development. Of the 31 patients who participated in the study, 74% experienced postinfusion nausea and vomiting (PNV). Of the 23 patients who experienced PNV, 52% developed ANV. AR was recorded in a habituation paradigm before chemotherapy treatment was initiated. The patients in the ANV group showed significantly increased sympathetic reactivity as compared with the no-ANV group, implying that AR is a mediator of ANV development.

Hemisphere differences in conditional learning: an ERP-study.

The present ERP-experiment investigated brain asymmetry in encoding and representation of the formation of conditional associations in a Pavlovian framework. Two consonant-vowel syllables were used as conditional stimuli, one of them paired with an unconditional noise during the acquisition phase (CS+), the other never paired with noise (CS-). During a subsequent test phase, both CS cues were presented dichotically i.e. at the same time. Half of the subjects had the CS+ probe presented to the right ear (contralateral to the left hemisphere). The other half of the subjects had the CS+ presented to the left ear (contralateral to the right hemisphere). ERPs from F3, Fz and F4 leads were recorded. The paradigm used was an adaptation of the standard dichotic listening technique for the study of learned associations. The results showed that conditional associative learning occurred during the acquisition phase in both "groups". The P235 latency was furthermore delayed over the left hemisphere to the CS+ probe. During the dichotic test phase, there was a clear laterality or asymmetry effect between the groups for both the N125 and N450 components, possibly supporting an interpretation of asymmetry in encoding and cortical representation of a conditional association, although alternative interpretations remain open.

[Triage. Initial diagnosis of life-threatening injuries based on functional state and mechanism of injury]. / Triage. Initial diagnostikk av livstruende skader basert på funksjonstilstand og skademekanisme.

Functional status expressed as Trauma Score (TS) and mechanism of injury were evaluated as criteria for diagnosing severe trauma in 253 traffic accident victims. An Injury Severity Score (ISS) of greater than or equal to 16 was considered a severe, potentially life-threatening injury. In 67 patients with ISS greater than or equal to 16, either TS was less than or equal to 13 or the history suggested risk of high energy trauma in 72%. When one or both of these criteria were met, ISS was greater than or equal to 16 in 54%. In addition, five patients (3%) with ISS less than 16 had potentially life-threatening injuries in the abdomen or in the thorax. Of these, two had a history indicating high energy trauma. Identifying severely injured patients by assessment of function and mechanism of injury gave an overtriage of 46%, which is acceptable, and an undertriage of 12%. Caution should be exercised in excluding severe trauma on these criteria. Considered together, decreased TS and a history indicating high energy injury, gave high sensitivity (72%) and specificity (78%) for diagnosing severe trauma, ISS greater than or equal to 16.