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Target Stimuli (target + stimulus)
Selected AbstractsNeural correlates of exemplar novelty processing under different spatial attention conditionsHUMAN BRAIN MAPPING, Issue 11 2009Christian Michael Stoppel Abstract The detection of novel events and their identification is a basic prerequisite in a rapidly changing environment. Recently, the processing of novelty has been shown to rely on the hippocampus and to be associated with activity in reward-related areas. The present study investigated the influence of spatial attention on neural processing of novel relative to frequently presented standard and target stimuli. Never-before-seen Mandelbrot-fractals absent of semantic content were employed as stimulus material. Consistent with current theories, novelty activated a widespread network of brain areas including the hippocampus. No activity, however, could be observed in reward-related areas with the novel stimuli absent of a semantic meaning employed here. In the perceptual part of the novelty-processing network a region in the lingual gyrus was found to specifically process novel events when they occurred outside the focus of spatial attention. These findings indicate that the initial detection of unexpected novel events generally occurs in specialized perceptual areas within the ventral visual stream, whereas activation of reward-related areas appears to be restricted to events that do possess a semantic content indicative of the biological relevance of the stimulus. Hum Brain Mapp, 2009. © 2009 Wiley-Liss, Inc. [source] Measurement of development of cognitive and attention functions in children using continuous performance testPSYCHIATRY AND CLINICAL NEUROSCIENCES, Issue 2 2008Noriko Kanaka ba Aim:, The development of attention function in children is still not sufficiently clear. Although it is difficult to objectively assess attention function, continuous performance tests (CPT) can be used to objectively assess cognitive function along with attention. The development of cognitive and attention functions was examined in children using a CPT. Methods:, A total of 541 healthy girls aged 5,12 years participated. Ten parameters were calculated: numbers of cancellations for either target stimuli (T-cancel) or non-target stimuli (N-cancel), numbers of omission errors (Omission) and commission errors (Commission), hit rate (Hit), false alarm rate (False), mean reaction time for correct response (RT), coefficient of variance for mean reaction time (CVRT), sensitivity index (d,), and ln,. Results:, The parameters were divided into three types based on pattern of change. T-cancel, False, and Commission, which are related to inhibition of response, N-cancel, Hit, and Omission, which are related to inattention to stimuli, and CVRT, which is related to stability of processing time, exhibited significant change until 5 or 6 years of age. d,, which is related to ability to discriminate between target or non-target, exhibited significant change until 8 years of age. RT, which is related to processing time, exhibited significant change until 11 years of age. ln, exhibited no significant differences among age groups. Conclusions:, These findings indicate that inhibition function, inattention to stimuli, and stability of processing time develop first. Discrimination ability subsequently increases based on these developments, and finally processing time is reduced. [source] To PE or not to PE: A P3-like ERP component reflecting the processing of response errorsPSYCHOPHYSIOLOGY, Issue 3 2009K. Richard Ridderinkhof Abstract ERP studies have highlighted several electrocortical components that can be observed when people make errors. We propose that the PE reflects processes functionally similar to those reflected in the P3 and that the PE and P3 should covary. We speculate that these processes refer to the motivational significance of rare target stimuli in case of the P3 and of salient performance errors in case of the PE. Here we investigated whether PE amplitude after errors in a Simon task is correlated specifically to varying target,target intervals in a visual oddball task, a factor known to parametrically affect P3 amplitude. The amplitude of the PE, but not the NE, was observed to covary with the effect of target,target interval on P3 amplitude. The specificity of this novel finding supports the notion that the PE and P3 reflect similar neurocognitive processes as possibly involved in the conscious processing of motivationally significant events. [source] The effect of stimulus probability on P3 in the respiratory-related evoked potentialPSYCHOPHYSIOLOGY, Issue 1 2002Kate E. Webster The present study investigated the effect of target stimulus probability on the P3 component of the respiratory-related evoked potential (RREP). A single respiratory stimulus paradigm was employed where normal breaths served as standard stimuli and occluded breaths presented at various probability levels served as target stimuli. EEG was recorded from 29 channels in young adults in two conditions. In Condition 1, occlusions were presented at target probabilities of 0.5, 0.33, 0.25, 0.2, 0.1, and 0.05, that is, every 2nd, 3rd, 4th, 5th, 10th, and 20th breath. Order of target probability presentation varied randomly. Condition 2 used the same target probabilities, but held breathing rate constant by using a paced respiration task. Results indicated that P3 amplitude was significantly affected by stimulus probability, such that the component showed an inverse relationship with probability. This effect was similar between conditions. However, P3 amplitude reduced and latency increased when the secondary task of paced respiration was introduced. These data suggest that models developed to describe the effect of stimulus probability on the amplitude of visual and auditory P3 components are applicable to the respiratory somatosensory modality. [source] Nonspatial intermodal selective attention is mediated by sensory brain areas: Evidence from event-related potentialsPSYCHOPHYSIOLOGY, Issue 5 2001Durk Talsma The present study focuses on the question of whether inter- and intramodal forms of attention are reflected in activation of the same or different brain areas. ERPs were recorded while subjects were presented a random sequence of visual and auditory stimuli. They were instructed to attend to nonspatial attributes of either auditory or visual stimuli and to detect occasional target stimuli within the attended channel. An occipital selection negativity was found for intramodal attention to visual stimuli. Visual intermodal attention was also manifested in a similar negativity. A symmetrical dipole pair in the medial inferior occipital areas could account for the intramodal effects. Dipole pairs for the intermodal attention effect had a slightly more posterior location compared to the dipole pair for the intramodal effect. Auditory intermodal attention was manifested in an early enhanced negativity overlapping with the N1 and P2 components, which was localized using a symmetrical dipole pair in the lateral auditory cortex. The onset of the intramodal attention effect was somewhat later (around 200 ms), and was reflected in a frontal processing negativity. The present results indicate that intra- and intermodal forms of attention were indeed similar for visual stimuli. Auditory data suggest the involvement of multiple brain areas. [source] Visuospatial attention disturbance in Duchenne muscular dystrophyDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 2 2010MARIA CLARA DRUMMOND SOARES DE MOURA Aim, The cognitive deficits present in the Duchenne muscular dystrophy (DMD) are not yet well characterized. Attention, considered to be the brain mechanism responsible for the selection of sensory stimuli, could be disturbed in DMD, contributing, at least partially, to the observed global cognitive deficit. The aim of this study was to investigate attentional function in individuals with DMD. Method, Twenty-five males (mean age 12y; SD 2y 2mo) with DMD and 25 healthy males (mean age 12y; SD 2y) were tested in a visuospatial task (Posner computerized test). They were instructed to respond as quickly as possible to a lateralized visual target stimulus with the ipsilateral hand. Their attention was automatically orientated by a peripheral prime stimulus or, alternatively, voluntarily orientated by a central spatially informative cue. Results, The main result obtained was that the attentional effect (sum of the benefit and the cost of attention) did not differ between the two groups in the case of automatic attention (p=0.846) but was much larger for individuals with DMD than for comparison individuals in the case of voluntary attention (p<0.001). Interpretation, The large voluntary attentional effect exhibited by the participants with DMD seems similar to that of younger children, suggesting that the disease is associated with delayed maturation of voluntary attention mechanisms. [source] Delayed visual P3 in unilateral thalamic strokeEUROPEAN JOURNAL OF NEUROLOGY, Issue 5 2000E. Trinka The P3 potential is accepted as a neurophysiological correlate of memory and attention. Delayed latencies were reported in different forms of dementias. Although the generator sites are still under debate, the thalamus may play a crucial role. The aim of this study was to investigate the influence of an unilateral thalamic ischaemic infarction on P3 generation. The event-related P3 component of six patients (2 male, four female; mean age 47 years, range 22,63 years) with unilateral thalamic ischaemic infarction was studied and compared to age-matched controls (five male, nine female; mean age 45.8 years; range 22,69 years). All patients underwent full clinical examination, CCT, and MRI scan. P3 potentials were recorded with a visual three stimulus discrimination paradigm. The mean P3 latency of the patient group to the target stimulus was delayed (469.7 ms, SD = 36.8) compared with the controls (378.8 ms, SD = 51.5; P < 0.05). The mean P3 latency to the unexpected stimulus was delayed in patients with thalamic infarction compared with controls [477 ms (SD = 46.6) vs. 381.2 ms (SD = 48.5); P < 0.001). Delayed P3 components of the event-related potential (ERP) were recorded in six patients with unilateral thalamic infarction, suggesting an important role of the thalamus in the generation of the P3 potential. [source] Using state-dependency of transcranial magnetic stimulation (TMS) to investigate letter selectivity in the left posterior parietal cortex: a comparison of TMS-priming and TMS-adaptation paradigmsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2008Zaira Cattaneo Abstract The state-dependency of transcranial magnetic stimulation (TMS) can be used to investigate the neural properties of subregions of the stimulated region. The objective of the present study was to determine whether state-dependency can reveal letter selectivity in the left posterior parietal cortex (PPC), a region known to contain letter-selective neurons. In two experiments, we used visual priming and adaptation to modulate the initial activation state of the left PPC prior to application of TMS. In the priming experiment, TMS was applied over the left PPC during the delay between the prime and the target stimulus on each experimental trial. Left PPC TMS reversed the effects of priming by facilitating the detection of non-primed letters, whereas detection of primed letters was unaffected. As neurons tuned to non-primed letters were less active at the time of TMS application than neurons tuned to the primed letters, this finding demonstrates that TMS preferentially facilitates the detection of attributes encoded by the less active neural populations. A similar facilitation of the less active neural populations was observed when adaptation was used to suppress letter-selective neurons prior to application of TMS. Our study demonstrates that TMS-priming and TMS-adaptation paradigms can reveal letter selectivity in the left PPC and thus be useful in the study of language processes. Our results also show that the state-dependent TMS effects obtained with visual priming are similar to those found with TMS adaptation: in both cases, attributes encoded by the less active neural populations are preferentially facilitated. [source] Processing of emotionally toned pictures in dementiaINTERNATIONAL JOURNAL OF GERIATRIC PSYCHIATRY, Issue 9 2006P. A. T. M. Eling Abstract Background Apathy is a common symptom in dementia and is often associated with reduced emotional reactivity. This study examined whether reduced emotional reactivity can be demonstrated in dementia patients using a picture viewing task. Methods The viewing time of three different types of visual stimuli was measured in 24 elderly participants, half of which suffered from dementia. The participants had to make a target response to an emotionally neutral target stimulus that was intermixed with a frequently occurring non-target or ,background' stimulus and infrequently presented emotional stimuli. All participants could control the presentation time of each stimulus, but one half of the participants were explicitly instructed to perform the task quickly. Results The main measure was a ratio score in which the viewing time for emotional stimuli was expressed relative to the viewing time for the neutral non-target stimulus. Using this measure, the instigation of a time-pressure condition proved to significantly reduce the viewing time for emotional stimuli in the healthy subjects. Irrespective of time-pressure condition, the dementia patients showed a similar short viewing time for emotional stimuli as did the healthy subjects in the time-pressure condition. However, both dementia patients and healthy controls displayed longer viewing times for unpleasant than for pleasant stimuli. Conclusion These results suggest the ability of the present task to reveal the simultaneous occurrence of an overall reduced interest for novel stimuli and an intact differential emotional reactivity to stimuli with a negative versus positive valence in the dementia patients. Copyright © 2006 John Wiley & Sons, Ltd. [source] | ||||||||||||||||||||||