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ABSTRACT: Behavioral and electrophysiological data related to performance in an auditory Go/NoGo task were analyzed in young and older adults in the present study. Especially, differences in within-person variability in behavior and neural activity between young and older adults and changes in topography of slow event-related oscillations (EROs) were of interest. Within-person variability in behavior was assessed by reaction time (RT) variability. Event-related delta and theta oscillations were analyzed using time-frequency transformation, which can give information on the time-course of single trial event-related EEG spectral power enhancement and intertrial phase-locking (ITC). In contrast to our previous visual Go/NoGo study, no under-recruitment of task-relevant brain regions was found for the auditory theta and delta EROs. Young did not differ from older adults in RT variability or in single trial delta/theta ITC. Altered recruitment of brain activity at advanced age was indicated, first, by stronger early theta phase-locking in older compared to young adults and, second, by a Go-specific lateralization of delta/theta activity. We conclude that within-person variability may increase with age, but the degree depends on performance level and the modality investigated.
Neuroscience Letters 03/2011; 495(2):159-63. · 2.11 Impact Factor
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ABSTRACT: This study investigated changes in gamma oscillations during auditory sensory processing (auditory-evoked gamma responses, AEGR) and target detection (auditory event-related gamma responses, AERGR) in healthy controls (n=10) and patients with schizophrenia (n=10) using both single-trial and averaged time-frequency data analysis. The results show that single-trial gamma responses in patients were altered in magnitude and topographic pattern for both the AEGR and the AERGR experimental conditions, whereas no differences were found for the averaged evoked gamma response. At the single-trial level, auditory stimuli elicited higher gamma responses at both anterior and occipital sites in patients with schizophrenia compared to controls. Furthermore, in patients with schizophrenia target detection compared to passive listening to stimuli was related to increased single-trial gamma power at frontal sites. In controls enhancement of the gamma response was only apparent for the averaged gamma response, with a distribution largely restricted to anterior sites. The differences in oscillatory activity between healthy controls and patients with schizophrenia were not reflected in the behavioral measure (i.e., counting targets). We conclude that gamma activity triggered by auditory stimuli in schizophrenic patients might have less selectivity in timing and alterations in topography and may show changes in amplitude modulation with task demands. The present study may indicate that in patients with schizophrenia neuronal information is not adequately transferred, possibly due to an over-excitability of neuronal networks and excessive pruning of local connections in association cortex.
International journal of psychophysiology: official journal of the International Organization of Psychophysiology 11/2010; 79(1):3-8. · 3.05 Impact Factor
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ABSTRACT: Many studies suggest that separate retinocortical channels with different conduction speeds transmit the information about high and low spatial frequencies (SF). Similarly, separate callosal channels may be responsible for the transfer of different SFs. To test this hypothesis, interhemispheric transfer time (IHTT) was estimated using visual evoked potentials (VEPs) elicited by reversal of different SF checkerboard patterns, which were presented either in the right or left visual hemifield. VEPs were recorded from homologous occipital and parietal leads in 11 subjects. The P100 latencies obtained from directly stimulated hemispheres were defined as retinocortical conduction times. The difference in P100 latencies obtained from directly and indirectly stimulated hemispheres was defined as IHTT (i.e., contralateral P100 latency values subtracted from the ipsilateral latency values). The results, showing faster retinocortical transfer for low SF than for high SF, and the shortest transfer time at parietal leads only for low SF, indicate that the presented stimuli are transferred on separate retinocortical channels. Concerning the interhemispheric transfer (VEP-IHTT), faster right-to-left than left-to-right transfer for both low and high SF stimuli was found, which is in congruence with previous studies. Most important however, the VEP-IHTT was faster for low SF than high SF. These different interhemispheric transfer speeds support the hypothesis that transferring low SF, compared with high SF information, relies on larger callosal fibers. Thus, we conclude that indeed distinct callosal channels respond selectively to the SF content of visual stimuli.
Brain research 09/2009; 1296:85-93. · 2.46 Impact Factor
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ABSTRACT: Deficits in sustained attention and vigilance were assessed for oscillatory delta, theta, alpha, and gamma EEG activity during an auditory continuous performance task in patients with schizophrenia and healthy controls by quantifying peak-to-peak amplitudes of averaged and single-trial data. Averaged data indicated significantly reduced amplitudes in schizophrenia patients in all analyzed frequency bands, mainly at anterior locations. Single-trial analysis suggested that the amplitude reductions observed in the averaged delta, theta, and alpha response in patients originated from increased inter-trial phase variability. Gamma activity maximum amplitudes were reduced at the single-trial level. The findings imply that EEG activity in patients with schizophrenia can be characterized by multiple deficits in oscillatory networks, which indicates a disturbance in the temporal integration and interaction of all frequency components and their inter-trial variability.
International Journal of Psychophysiology 08/2008; 71(1):75-83. · 2.14 Impact Factor
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ABSTRACT: Previous studies have shown a close interrelation between emotional processing and memory processes using facial stimuli and applying the concept of oscillatory brain dynamics. Amending prior findings the influence of neural correlates related to the emotional state termed "romantic love" was investigated. Specifically, the effect of feelings of love on face perception was of interest. Pictures of a "loved person" were presented to female subjects and the elicited responses were compared with responses to pictures showing faces of a "known and appreciated person" or an "unknown person" during EEG recordings (n=20 females). As a control condition light stimulation was employed. The sequence of faces shown was presented in random and block-design. EEG data was analyzed considering maximum amplitudes and topographical differences within the conventional frequency bands of delta, theta, alpha, beta and gamma. Differences between light and face stimuli were found in the delta and theta bands and differences between the face types and the two designs were found in the delta band. The delta response to the picture of the "loved person" showed significantly higher amplitude values, not only in comparison with the "unknown person", but also with the picture of the "appreciated person". Frontal lobes appear to react to different types of facial stimuli with specific increases in delta responses. The difference between the response to the "loved person" and of the "known and appreciated person" reflects the component of the emotion denoted as love. The findings and their interpretations are discussed within the framework of event-related oscillations and complex stimulus processing emphasizing the concept of dynamic localization.
Brain Research 07/2008; 1214:105-15. · 2.73 Impact Factor
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ABSTRACT: This study investigated event-related oscillations associated with a Simon task in 11 Parkinson's disease patients, 11 age-matched, and 11 young participants. During this task, participants respond faster when the relative spatial positions of stimulus and response match (no response conflict exists) than when they do not match (response conflict exists). An increased response conflict (increase in reaction times known as Simon effect) was found in elderly control and Parkinson's patients compared with young participants. Group and condition differences were found in the delta and theta frequency range, which may reflect that Parkinson's patients and matched controls use different cognitive strategies for stimulus-response processing than young controls and neurophysiological correlates of such strategy are deficient in patients compared with age-matched controls.
Neuroreport 03/2007; 18(3):277-81. · 1.66 Impact Factor
