Brain potentials evoked to non-targets in an auditory target detection task changed in amplitude, duration, polarity, and scalp topography as a function of position in the stimulus sequence relative to the target. (1) A negative prestimulus readiness like-potential, or RP, the poststimulus N100, and a late slow wave to non-targets immediately after the target were reduced in amplitude compared to non-targets immediately before the target. The amplitudes of these potentials after the target then increased in size as a linear function of the number of non-targets in the sequence. (2) The amplitudes of the positive components, P50 and P200, were larger to non-targets immediately after the target than to non-targets immediately before the targets. P50 amplitude then decreased to subsequent non-targets in the sequence in a linear manner; P200 amplitude was reduced equivalently to all subsequent non-targets. (3) The duration of the P200 component could extend into the time domain when the P300 to targets would occur. The P200 component to non-targets was therefore designated 'P200/300'. The duration of the P200/300 component was shorter to non-targets immediately after the target than to non-targets immediately before the targets. P200/300 duration then extended in a linear manner to subsequent non-targets in the sequence and approached the peak latency of the P300 evoked by targets. (4) The anterior/posterior scalp distribution of P50 and the polarity of the late slow wave to non-targets changed as a function of non-target position in the sequence. The subject's response to the targets (button press or mental count) influenced these sequential effects. Linear trends for sequence were present in the press but not the count conditions for the amplitude of the RP, N100, and P300; linear trends for P50, P200/300 duration, and the late slow wave were found in both the press and count conditions. Reaction time was speeded as a function of the number of preceding targets. These dynamic changes in the processing of auditory signals were attributed to an interaction of attention and the subjective expectancies for both the appearance of a target stimulus and the requirement to make a motor response.
"In this short-term memory task, participants memorise a brief list of memory set items such as digits and a few seconds later indicate whether a target number was a member of the memory set or not (Sternberg, 1966). Early ERP components such as the N1 are sensitive to physical parameters of the stimuli, but also are affected by cognitive factors such as attention (Herrmann and Knight, 2001; Davis, 1964; Picton and Hillyard, 1974; Correa et al., 2006; Fu et al., 2008), expectancy (Starr et al., 1997), and tasks involving short-term memory (Kaufman et al., 1991). The N1 is a negative component peaking around 100–150 ms after stimulus onset with a fronto-central maximum. "
[Show abstract][Hide abstract] ABSTRACT: In the present study, we investigated how the electrical activity in the sensorimotor cortex contributes to improved cognitive processing capabilities and how SMR (sensorimotor rhythm, 12-15Hz) neurofeedback training modulates it. Previous evidence indicates that higher levels of SMR activity reduce sensorimotor interference and thereby promote cognitive processing.
Participants were randomly assigned to two groups, one experimental (N=10) group receiving SMR neurofeedback training, in which they learned to voluntarily increase SMR, and one control group (N=10) receiving sham feedback. Multiple cognitive functions and electrophysiological correlates of cognitive processing were assessed before and after 10 neurofeedback training sessions.
The experimental group but not the control group showed linear increases in SMR power over training runs, which was associated with behavioural improvements in memory and attentional performance. Additionally, increasing SMR led to a more salient stimulus processing as indicated by increased N1 and P3 event-related potential amplitudes after the training as compared to the pre-test. Finally, functional brain connectivity between motor areas and visual processing areas was reduced after SMR training indicating reduced sensorimotor interference.
These results indicate that SMR neurofeedback improves stimulus processing capabilities and consequently leads to improvements in cognitive performance.
The present findings contribute to a better understanding of the mechanisms underlying SMR neurofeedback training and cognitive processing and implicate that SMR neurofeedback might be an effective cognitive training tool.
Clinical neurophysiology: official journal of the International Federation of Clinical Neurophysiology 04/2014; 126(1). DOI:10.1016/j.clinph.2014.03.031 · 3.10 Impact Factor
"Recent findings show that the N100 reflects the process of attention activation, analysis of information based on the physical characteristics of sound, and the formation of memory trace with oscillators in the auditory cortex, prefrontal cortex, hippocampus, and cingulate cortex . Moreover, the amplitude of N100 was also reported to be associated with enhanced memory performance , attention , expectancy , and tasks involving short-term memory . "
[Show abstract][Hide abstract] ABSTRACT: The development of cognitive enhancers from plants possessing antioxidants has gained much attention due to the role of oxidative stress-induced cognitive impairment. Thus, this study aimed to determine the effect of ginger extract, or Zingiber officinale, on the cognitive function of middle-aged, healthy women. Sixty participants were randomly assigned to receive a placebo or standardized plant extract at doses of 400 and 800 mg once daily for 2 months. They were evaluated for working memory and cognitive function using computerized battery tests and the auditory oddball paradigm of event-related potentials at three different time periods: before receiving the intervention, one month, and two months. We found that the ginger-treated groups had significantly decreased P300 latencies, increased N100 and P300 amplitudes, and exhibited enhanced working memory. Therefore, ginger is a potential cognitive enhancer for middle-aged women.
Evidence-based Complementary and Alternative Medicine 01/2012; 2012:383062. DOI:10.1155/2012/383062 · 1.88 Impact Factor
"Negative shifts have been hypothesized to reflect anticipatory activity (Kotchoubey, 2006) that may well overlap the early part of the ERP to the following stimulus (Starr et al., 1995; Kotchoubey, 2006). For example, a late slow wave observed by Starr et al. (1997) in ERPs to standard tones showed negative polarity and a frontal distribution before the occurrence of an infrequent deviant tone, and was assumed to be related to listeners' attention to and expectation of the deviant tone. This explanation seems unlikely in the present study as the early negativity observed at the mastoid site was observed to both deviant and standard tones. "
[Show abstract][Hide abstract] ABSTRACT: Previous research suggests that our past experience of rhythmic structure in music results in a tendency for Western listeners to subjectively accent equitonal isochronous sequences. We have shown in an earlier study that the occurrence of a slightly softer tone in the 8th to 11th position of such a sequence evokes a P300 event-related potential (ERP) response of different amplitudes depending on whether the tone occurs in putatively subjectively accented or unaccented sequence positions (Brochard et al., 2003). One current theory of rhythm processing postulates that subjective accenting is the result of predictive modulations of perceptual processes by the attention system. If this is the case then ERP modulations should be observed at an earlier latency than the P300 and these should be observed in ERPs to both standard and softer tones. Such effects were not observed in our previous study. This was possibly due to the use of a linked-mastoid reference which may have obscured lateralized differences. The aim of the present study was to replicate the previous auditory P300 subjective accenting findings and to investigate the possibility that these effects are preceded by ERP changes that are indicative of rhythmic modulation of perceptual processing. Previous auditory P300 findings were replicated. In addition and consistent with current theories of rhythm processing, early brain ERP differences were observed both in standard and deviant tones from the onset of the stimulus. These left lateralized differences are consistent with a rhythmic, endogenously driven, modulation of perception that influences the conscious experience of equitonal isochronous sequences.
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