Helge Nordby

Attentional shifts to emotionally charged cues: Behavioural and erp data

Abstract When information activated in memory involves emotional associations, the ability to shift attention away from an emotional cue is impaired compared to an emotionally neutral cue. The purpose of the present study was to investigate how emotional stimuli modulate attentional processes, and how this is reflected in localised brain electrical activity. Eight emotion and eight neutral words served as cues in a covert attention spatial orienting task. The cues were either valid or invalid indicators of which hemifield the target would be presented to. In the remaining trials, no cue was presented prior to the target. Twenty subjects were instructed to manually respond to the target as fast as possible. Event-related potentials (ERPs) showed an enhanced P3 component to the emotion words. The ERPs to the target showed enhanced P1 and P3 components on invalid trials, with emotional cues. There were faster reaction times (RTs) to validly cued targets, but only when the emotion words served as cues. The re...

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.

Realignment parameter-informed artefact correction for simultaneous EEG–fMRI recordings ☆

In this work we introduce a new algorithm to correct the imaging artefacts in the EEG signal measured during fMRI acquisition. The correction techniques proposed so far cannot optimally represent transitions, i.e. when abrupt changes of the artefact properties due to head movements occur. The algorithm developed here takes the head movement parameters from the fMRI signal into account to calculate adequate EEG artefact templates and subsequently correct the distorted EEG data. The data reported in this work demonstrate that the realignment parameter-informed algorithm outperforms the commonly used moving average algorithm if head movements occur. The superiority is reflected by comparing the residual variance after artefact correction with either method. The residual variance is lower around head-movements that exceed head deflections of about 1 mm when applying the realignment parameter-informed algorithm. Additionally, the signal to noise ratio of a surrogate event-related potential (ERP) increased by 10-40% for head displacements larger than 1 mm. The algorithm developed here is particularly suited for studies where head movements of the subject cannot be prevented as in studies with patients, children, or during sleep. Furthermore, the enhanced signal to noise ratio of a single trial ERP indicates the power of the presented algorithm for single trial ERP-fMRI studies in which EEG signal quality is a critical factor.

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.

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.

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.

Disturbance of automatic auditory change detection in dementia associated with Parkinson's disease: A mismatch negativity study.

OBJECTIVE To investigate whether automatic auditory change detection, as measured by the mismatch negativity (MMN) event-related potential waveform, differs in dementia associated with Parkinsons disease (PDD) and dementia with Lewy-bodies (DLB) as compared to Alzheimers disease (AD), Parkinsons disease without dementia (PD) and healthy control subjects (HC). METHOD Seventeen DLB, 15 PDD, 16 PD, 16 AD patients and 18 HC subjects participated. A passive MMN event-related potential paradigm and an oddball-distractor reaction time paradigm were presented. RESULTS The PDD patients had reduced MMN area and amplitude compared to the DLB, PD, and the HC groups. The MMN area correlated significantly with number of missed target stimuli in the oddball-distractor task, and the PDD group missed targets significantly more often than the DLB group. CONCLUSION The results indicate that PDD patients to a larger degree than patients with DLB have a deficit of automatic auditory change detection that contributes to impairment in their ability to selectively attend and respond to deviant auditory stimuli.

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.

Trait Self-Compassion Reflects Emotional Flexibility Through an Association with High Vagally Mediated Heart Rate Variability

Converging evidence shows a positive effect of self-compassion on self-reported well-being and mental health. However, few studies have examined the relation between self-compassion and psychophysiological measures. In the present study, we therefore examined the relation between trait self-compassion and vagally mediated heart rate variability (vmHRV) in 53 students (39 female, mean age = 23.63). Trait self-compassion was assessed using the Self-Compassion Scale, and resting vmHRV was measured during a 5-min ECG baseline period. We hypothesized that higher levels of trait self-compassion would predict higher levels of resting vmHRV. Controlling for potential covariates (including age, gender, and BMI), the results confirmed our hypotheses, showing that higher levels of trait self-compassion predicted higher vmHRV. These results were validated with a 24-h measure of vmHRV, acquired from a subsample of the participants (n = 26, 16 female, mean age = 23.85), confirming the positive correlation between high trait self-compassion and higher vmHRV. The relation between trait self-compassion, vmHRV, self-reported trait anxiety (the trait scale of the State-Trait Anxiety Inventory; STAI) and self-reported rumination (the Rumination subscale of the Rumination-Reflection Questionnaire; RRQ-Rum) was also investigated. Higher levels of trait anxiety and rumination were highly correlated with low levels of trait self-compassion. Trait anxiety, but not rumination, correlated marginally significantly with the level of vmHRV. The findings of the present study indicate that trait self-compassion predicts a better ability to physiologically and psychologically adapt emotional responses. Possible implications and limitations of the study are discussed.

EEG Spectral Features Discriminate between Alzheimer's and Vascular Dementia.

Alzheimer’s disease (AD) and vascular dementia (VaD) present with similar clinical symptoms of cognitive decline, but the underlying pathophysiological mechanisms differ. To determine whether clinical electroencephalography (EEG) can provide information relevant to discriminate between these diagnoses, we used quantitative EEG analysis to compare the spectra between non-medicated patients with AD (n = 77) and VaD (n = 77) and healthy elderly normal controls (NC) (n = 77). We use curve-fitting with a combination of a power loss and Gaussian function to model the averaged resting-state spectra of each EEG channel extracting six parameters. We assessed the performance of our model and tested the extracted parameters for group differentiation. We performed regression analysis in a multivariate analysis of covariance with group, age, gender, and number of epochs as predictors and further explored the topographical group differences with pair-wise contrasts. Significant topographical differences between the groups were found in several of the extracted features. Both AD and VaD groups showed increased delta power when compared to NC, whereas the AD patients showed a decrease in alpha power for occipital and temporal regions when compared with NC. The VaD patients had higher alpha power than NC and AD. The AD and VaD groups showed slowing of the alpha rhythm. Variability of the alpha frequency was wider for both AD and VaD groups. There was a general decrease in beta power for both AD and VaD. The proposed model is useful to parameterize spectra, which allowed extracting relevant clinical EEG key features that move toward simple and interpretable diagnostic criteria.