K.B.E. Böcker

Cortical Measures of Anticipation

Abstract Anticipation increases the efficiency of cognitive processes by partial advance activation of the neural substrate involved in those processes. In the case of perceptual anticipation, a slow cortical potential named Stimulus-Preceding Negativity (SPN) has been identified. The SPN has been observed preceding four types of stimuli: (1) stimuli providing knowledge-of-results (KR) about past performance, (2) stimuli conveying an instruction about a future task, (3) probe stimuli against which the outcome of a previous task has to be matched, and (4) affective stimuli. The morphology and scalp distribution of the SPN is different in each of these cases, suggesting the presence of separable components. This article reviews more than 15 years of SPN research. Possible neurophysiological generators are considered, as well as models that may describe the generation of the SPN. Suggestions for future research into anticipatory processes and the associated psychophysiological measures are made.

Cognitive basis of hallucinations in schizophrenia: role of top-down information processing

Hallucinations in schizophrenia have been regarded to result from the erroneous attribution of internally generated information to an external source. Distortions in mental imagery may underlie such confusions. We investigated performance of 77 subjects on multiple behavioral measures of auditory and visual mental imagery and perception, and a measure of reality monitoring. Comparisons were made between performance of schizophrenia patients with (N=22) and without (N=35) hallucinations and matched normal comparison subjects (N=20), after controlling for attentional factors. No differences emerged on any of the mental imagery measures, nor on reality monitoring accuracy. This suggests that there is no stable disposition towards abnormal mental imagery associated with hallucinations. However, for patients with active hallucinations (N=12), hallucination severity correlated positively with a measure of imagery-perception interaction in the auditory modality, r=0.70, p=0.01. Although preliminary, this finding is consistent with recent theoretical proposals in which hallucinations have been suggested to result from an increased influence of top-down sensory expectations on conscious perception.

Music training and mental imagery ability

Neuroimaging studies have suggested that the auditory cortex is involved in music processing as well as in auditory imagery. We hypothesized that music training may be associated with improved auditory imagery ability. In this study, performance of musically trained and musically naive subjects was compared on: (1) a musical mental imagery task (in which subjects had to mentally compare pitches of notes corresponding to lyrics taken from familiar songs); (2) a non-musical auditory imagery task (in which subjects had to mentally compare the acoustic characteristics of everyday sounds); and (3) a comparable measure of visual imagery (in which subjects had to mentally compare visual forms of objects). The musically trained group did not only perform better on the musical imagery task, but also outperformed musically naive subjects on the non-musical auditory imagery task. In contrast, the two groups did not differ on the visual imagery task. This finding is discussed in relation to theoretical proposals about music processing and brain activity.

Prepulse inhibition and P50 suppression: Commonalities and dissociations

Patients with schizophrenia exhibit reduced levels of both prepulse inhibition of the startle reflex (PPI) and condition-test suppression of the P50 event-related potential. This study investigated the extent to which PPI and P50 suppression, which exhibit similar parametric sensitivities, are intrinsically auditory phenomena or can be induced cross-modally, and reflect common or distinct neural mechanisms of inhibition. PPI, N100, and P50 were assessed in 20 healthy male volunteers, using auditory test probes and both visual and auditory lead stimuli, separated by 100- or 500-ms interstimulus intervals (ISIs). PPI was found in the auditory-lead condition across the complete group, and with visual-lead stimuli in approximately half of the subjects. Intra-modal auditory PPI was significantly higher with the 100-ms ISI than with the 500-ms ISI. P50 suppression was found only with the 500-ms ISI, with no difference between the auditory and visual conditions. Source analyses revealed that suppression was associated with frontal cortical activity. N100 suppression was found only in the auditory condition, with no difference between 100- and 500-ms ISIs. Although both phenomena are considered to provide operational measures of gating, PPI and P50 suppression are differentially sensitive to ISI and therefore reflect partly different neural mechanisms. They are not intrinsically auditory phenomena, and both appear to involve frontal cortical activity. In contrast, N100 suppression is most likely based on refractory mechanisms intrinsic to the auditory system.

Threat-induced cortical processing and startle potentiation

This paper presents cortical responses as reflected in event- related potentials (ERP) in an instructed fear paradigm. Safe cues and threat cues that predict shock were presented at an unprecedented fast rate (mean SOA of 2.1 s). Startle and subjective measures confirmed that threat relative to safe cues elicited fear. Several ERP correlates of fear processing were predicted and confirmed: modulation of exogenous sensory components, frontal selection positivity, and increase of P3. Furthermore, a frontal negative slow wave was observed. These results are discussed in relation to attentional selection models and emotional processing.

Stimulus-preceding negativity induced by fear: a manifestation of affective anticipation

The Stimulus-Preceding Negativity (SPN), a slow cortical potential, has been studied in relation to anticipatory attention. A review of the literature suggests that most instances of SPN are observed in anticipation of motivational stimuli, such as aversive stimuli and stimuli that provide Knowledge of Results. In the present study, SPN was recorded in 12 subjects in a threat-of-shock experiment. This manipulation induced fear, as shown by subjective ratings and potentiation of the eyeblink startle. The fear-induced SPN showed a frontocentral maximum and coarse source analysis suggested that it was generated in midline frontal areas, possibly by the anterior cingulate cortex. It is concluded that the fear-induced SPN is a manifestation of affective anticipation. Possible thalamocortical and amygdalocortical contributions to its generation are discussed.

The effectiveness of EEG-feedback on attention, impulsivity and EEG: a sham feedback controlled study.

EEG-feedback, also called neurofeedback, is a training procedure aimed at altering brain activity, and is used as a treatment for disorders like Attention Deficit/Hyperactivity Disorder (ADHD). Studies have reported positive effects of neurofeedback on attention and other dependent variables. However, double-blind studies including a sham neurofeedback control group are lacking. The inclusion of such group is crucial to control for unspecific effects. The current work presents a sham-controlled, double-blind evaluation. The hypothesis was that neurofeedback enhances attention and decreases impulsive behavior. Participants (n=27) were students selected on relatively high scores on impulsivity/inattention questionnaires (Barrat Impulsivity Scale and Broadbent CFQ). They were assigned to a neurofeedback treatment or a sham group. (sham)Neurofeedback training was planned for 15 weeks consisting of a total of 30 sessions, each lasting 22 min. Before and after 16 sessions (i.e., interim analyses), qEEG was recorded and impulsivity and inattention was assessed using a stop signal task and reversed continuous performance task and two questionnaires. Results of the interim analyses showed that participants were blind with respect to group inclusion, but no trend towards an effect of neurofeedback on behavioral measures was observed. Therefore in line with ethical guidelines the experiment was ceased. These results implicate a possible lack of effect of neurofeedback when one accounts for non-specific effects. However, the specific form of feedback and application of the sham-controlled double-blind design may have diminished the effect of neurofeedback.

Acute effects of nicotine on attention and response inhibition

Smoking is highly prevalent among patients with Attention Deficit Hyperactivity Disorder (ADHD). Previous studies using the reversed continuous performance task (R-CPT) have suggested that nicotine reduces inattention. Since especially adults with ADHD have been claimed to suffer from a core deficit in inhibitory control, this study aimed at determining whether nicotine improves response inhibition in addition to attention. Sixteen healthy regular smokers participated in a pre/post treatment design in which transdermal patches containing 7 and 21 mg nicotine per day were administered in a counterbalanced, double-blind manner. In a second study, patches containing 0 mg (placebo) and 21 mg per day were administered to a different group of regular smokers. For replication purposes, the R-CPT and the profile of mood states (POMS) were administered. Furthermore, a different version of the continuous performance task (CPT-AX) and the stop-signal task, traditionally used to measure response inhibition, were presented. The high dose of nicotine was found to relieve self-reported Depression in Study 1 and Fatigue in Study 2. Performance data indicated acute effects of nicotine on attention-related, but not on inhibition-related measures. Especially the comparison with placebo revealed decreases in reaction time and variability of responding. The results imply that patients with ADHD smoke to reduce inattention.

Event-related potentials and secondary task performance during simulated driving

Inattention and distraction account for a substantial number of traffic accidents. Therefore, we examined the impact of secondary task performance (an auditory oddball task) on a primary driving task (lane keeping). Twenty healthy participants performed two 20-min tests in the Divided Attention Steering Simulator (DASS). The visual secondary task of the DASS was replaced by an auditory oddball task to allow recording of brain activity. The driving task and the secondary (distracting) oddball task were presented in isolation and simultaneously, to assess their mutual interference. In addition to performance measures (lane keeping in the primary driving task and reaction speed in the secondary oddball task), brain activity, i.e. event-related potentials (ERPs), was recorded. Performance parameters on the driving test and the secondary oddball task did not differ between performance in isolation and simultaneous performance. However, when both tasks were performed simultaneously, reaction time variability increased in the secondary oddball task. Analysis of brain activity indicated that ERP amplitude (P3a amplitude) related to the secondary task, was significantly reduced when the task was performed simultaneously with the driving test. This study shows that when performing a simple secondary task during driving, performance of the driving task and this secondary task are both unaffected. However, analysis of brain activity shows reduced cortical processing of irrelevant, potentially distracting stimuli from the secondary task during driving.

Multi-dimensionality of hallucinatory predisposition: factor structure of the Launay–Slade Hallucination Scale in a normal sample

Abstract A substantial percentage of normal people has been documented to report hallucinatory experiences. We investigated the multi-dimensionality of such experiences in 243 subjects from the normal population who completed the Launay–Slade Hallucination Scale. Principal components analysis with oblique rotation was performed on the data. Three factors were obtained loading on items reflecting (1) tendency towards hallucinatory experiences, (2) subjective externality of thought, and (3) vivid daydreams. An additional exploratory factor analysis revealed highly similar factors. The results support the concept of hallucinatory disposition as a multi-dimensional construct.