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      Normative Variation of P3a and P3b from a Large Sample : Gender, Topography, and Response Time

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          Abstract

          Abstract. The P3a and P3b components were elicited in 120 (60 females, 60 males) young adults using a visual three-stimulus event-related brain potential (ERP) oddball paradigm in which subjects responded to an infrequent target. The major purpose of the paper was to provide a statistically strong characterization of these related P300 subcomponents. P3a components were obtained from the infrequently presented distracter stimulus, which was a large blue square. P3b components were obtained from the target stimulus, which was a blue circle that differed slightly in diameter from the standard stimulus blue circle. Amplitude measures demonstrated that P3a was maximum at Cz, and P3b was maximum at Pz; latency measures increased for both potentials from frontal to parietal recording sites. P3a and P3b from females were larger and later than those from male subjects, with topographic and appreciable individual difference variability observed. P3a was generally unrelated to response time. P3b amplitude was negatively correlated over right frontal areas with P3b latency and positively correlated over right parietal areas to response time. Theoretical implications are discussed.

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          Most cited references67

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          Two varieties of long-latency positive waves evoked by unpredictable auditory stimuli in man.

          Two distinct late-positive components of the scalp-recorded auditory evoked potential were identified which differed in their latency, scalp topography and psychological correlates. The earlier component, called "P3a" (latency about 240 msec), was elicited by infrequent, unpredictable shifts of either intensity or frequency in a train of tone pips whether the subject was ignoring (reading a book) or attending to the tones (counting). The later component, called "P3a" (mean latency about 350 msec), occurred only when the subject was actively attending to the tones; it was evoked by the infrequent, unpredictable stimulus shifts, regardless of whether the subject was counting that stimulus or the more frequently occurring stimulus. Both of these distinct psychophysiological entities have previously been refered to as the "P3" or "P300" in the literature.
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            Neural mechanisms of involuntary attention to acoustic novelty and change.

            Behavioral and event-related brain potential (ERP) measures were used to elucidate the neural mechanisms of involuntary engagement of attention by novelty and change in the acoustic environment. The behavioral measures consisted of the reaction time (RT) and performance accuracy (hit rate) in a forced-choice visual RT task where subjects were to discriminate between odd and even numbers. Each visual stimulus was preceded by an irrelevant auditory stimulus, which was randomly either a "standard" tone (80%), a slightly higher "deviant" tone (10%), or a natural, "novel" sound (10%). Novel sounds prolonged the RT to successive visual stimuli by 17 msec as compared with the RT to visual stimuli that followed standard tones. Deviant tones, in turn, decreased the hit rate but did not significantly affect the RT. In the ERPs to deviant tones, the mismatch negativity (MMN), peaking at 150 msec, and a second negativity, peaking at 400 msec, could be observed. Novel sounds elicited an enhanced N1, with a probable overlap by the MMN, and a large positive P3a response with two different subcomponents: an early centrally dominant P3a, peaking at 230 msec, and a late P3a, peaking at 315 msec with a right-frontal scalp maximum. The present results suggest the involvement of two different neural mechanisms in triggering involuntary attention to acoustic novelty and change: a transient-detector mechanism activated by novel sounds and reflected in the N1 and a stimulus-change detector mechanism activated by deviant tones and novel sounds and reflected in the MMN. The observed differential distracting effects by slightly deviant tones and widely deviant novel sounds support the notion of two separate mechanisms of involuntary attention.
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              Localization of a human system for sustained attention by positron emission tomography.

              Positron emission tomographic (PET) studies of human attention have begun to dissect isolable components of this complex higher brain function, including a midline attentional system in a region of the anterior cingulate cortex. The right hemisphere may play a special part in human attention; neglect, an important phenomenon associated with damage to attentional systems, is more severe, extensive and long-lasting after lesions to the right hemisphere. Here we use PET measurements of brain blood flow in healthy subjects to identify changes in regional brain activity during simple visual and somatosensory tasks of sustained attention or vigilance. We find localized increases in blood flow in the prefrontal and superior parietal cortex primarily in the right hemisphere, regardless of the modality or laterality of sensory input. The anterior cingulate was not activated during either task. These data localize the vigilance aspects of normal human attention to sensory stimuli, thereby clarifying the biology underlying asymmetries of attention to such stimuli that have been reported in clinical lesions.
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                Author and article information

                Journal
                jop
                Journal of Psychophysiology
                An International Journal
                Hogrefe Publishing
                0269-8803
                January 2007
                : 21
                : 1
                : 22-32
                Affiliations
                [ 1 ] Molecular and Integrative Neurosciences Department, The Scripps Research Institute, La Jolla, CA, USA
                Author notes
                Polich John, Cognitive Electrophysiology Laboratory Molecular Integrative Neurosciences Dept. TPC-10, The Scripps Research Institute, 10550 North Torrey Pines Road, CA 92037, La Jolla, USA, +1 858 784-8176, +1 858 784-9293, polich@ 123456scripps.edu
                Article
                jop2101022
                10.1027/0269-8803.21.1.22
                73716d25-38ec-4194-8177-684f9a81e86c
                Copyright @ 2007
                History
                : 15 September 2006
                Categories
                Articles

                Psychology,Anatomy & Physiology,Neurosciences
                variability,response time,P3a,event-related potential,P3b,topography,gender

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