Attentional capture by physically salient stimuli in the gamma frequency is associated with schizophrenia symptoms

<p><b>Objectives:</b> Aberrant salience mainly is attributed to excessive dopaminergic processing in the ventral striatum. Increased gamma power during sensory processing of physical salience has been shown to be associated with positive trait schizotypy. In the present study, this is assessed in patients with schizophrenia.</p> <p><b>Methods:</b> The early evoked visual gamma-band response (GBR) at 40 Hz was assessed for a schizophrenia patient group (<i>N</i> = 22) and a matched healthy control group (<i>N</i> = 22) applying EEG time-frequency analysis. The GBR was assessed for two conditions within a visual detection paradigm: a target with or without a physically salient distracter and evaluated in relation to the PANSS.</p> <p><b>Results:</b> A 2 × 2 ANOVA revealed a significant main effect of condition and a trend interaction of group and condition for the GBR, with highest power for schizophrenia patients in the physically salient distracter condition. Moreover, evoked GBR power in this condition was correlated with positive (<i>r</i> = 0.664; <i>P</i> = 0.001**) and disorganised (<i>r</i> = 0.618; <i>P</i> = 0.002**) schizophrenia symptoms.</p> <p><b>Conclusions:</b> Evoked GBR power during processing of physical salience in schizophrenia was associated with positive symptoms. We suggest that abnormal processing of physically salient stimuli might be involved in the pathophysiological genesis of positive symptoms.</p

Oscillatory responses to reward processing in borderline personality disorder

<p><i>Objectives.</i> Previous electrophysiological studies have confirmed impaired reward processing in patients with BPD. However, it is not clear which aspects of reward processing are affected and which brain regions are involved. The present study investigated both evoked and induced event-related oscillations (EROs) to feedback events (thought to represent different aspects of feedback processing), and used source localization (sLORETA) to assess activity in two areas known to contribute to reward processing, the dorsomedial prefrontal/anterior cingulate cortex (dmPFC/ACC) and the orbitofrontal cortex (OFC). <i>Methods.</i> Eighteen patients with BPD and 22 healthy controls performed a gambling task, while 64-channel electroencephalographic activity was recorded. Evoked and induced theta and high-beta band EROs as well as activity in the two regions of interest were investigated depending on the valence and magnitude of feedback events. <i>Results.</i> Theta-band responses to negative feedback were reduced in BPD, an effect that involved only evoked responses and the dmPFC/ ACC region, and was associated with trait impulsivity in patients. sLORETA analyses revealed disturbed evoked responses depending on feedback magnitude in the theta (OFC) and high-beta (dmPFC/ACC and OFC) frequency range. <i>Conclusions.</i> The results indicate multiple dysfunctions of feedback processing in patients with BPD, implicating several distinct subsets of reward-processing mechanisms.</p

Feedback related negativity.

<p>Grand average waveforms of feedback-related visual evoked potentials for the maximum loss (red), maximum gain (black), minimum loss (green) and minimum gain (blue) condition showing the FRN effect with larger FRN amplitudes in response to loss feedback compared to gain feedback (onset of feedback stimuli at 0 ms). The scalp topography (derived from the peak amplitude of the difference waveform of maximum loss and maximum gain condition observed 270 ms after presentation of the feedback stimulus) shows a frontocentral maximum over Fz.</p

Paradigm.

<p>Schematic diagram showing the design of a trial of the gambling task used in this study.</p

Time frequency analysis.

<p>The comparison (difference) of the results of the time-frequency analysis of maximum loss and maximum gain conditions revealed theta, alpha and low-beta activity to be more pronounced in the maximum loss condition and delta and high-beta activity to be more pronounced in the maximum gain condition (onset of feedback stimuli at 0 ms). For all frequencies, we found frontocentral maxima of differences between conditions. The scalp topographies are derived from the peak amplitudes of the difference waveforms (maximum loss minus maximum gain condition) of the extracted frequency-specific wavelet layers (latencies: delta 150 ms; theta 340 ms; alpha 550 ms; low-beta 630 ms; high-beta 360 ms). The dotted lines indicate the frequencies of interest (from the bottom up: delta, theta, alpha, low-beta and high-beta).</p

Mean values of electrophysiological measures per condition and ANOVA results.

<p>Amplitudes are reported in µV; latencies are reported in milliseconds. n.s.  =  not significant.</p