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The C1 and P1 (also called the P100) are two human scalp-recorded event-related brain potential (event-related potential (ERP)) components, collected by means of a technique called electroencephalography (EEG). The C1 is named so because it was the first component in a series of components found to respond to visual stimuli when it was first discovered. It can be a negative-going component (when using a mastoid reference point) or a positive going component with its peak normally observed in the 65–90 ms range post-stimulus onset. The P1 is called the P1 because it is the first positive-going component (when also using a mastoid reference point) and its peak is normally observed in around 100 ms. Both components are related to processing of visual stimuli and are under the category of potentials called visually evoked potentials (VEPs). Both components are theorized to be evoked within the visual cortices of the brain with C1 being linked to the primary visual cortex (striate cortex) of the human brain and the P1 being linked to other visual areas (Extrastriate cortex). One of the primary distinctions between these two components is that, whereas the P1 can be modulated by attention, the C1 has been typically found to be invariable to different levels of attention. ==History== The different components within the category of VEPs was first described by Spehlmann in 1965 who compared human ERPs when viewing patterned and diffuse stimuli that were quickly flashed on the screen while a person was viewing the general area where the flash was to appear. However, it was not until Jeffreys and Axford (1972) that the earliest individual components of those VEPs where delineated, including the C1 component. Jeffreys and Axford had human participants view stimulus patterns of squares for a very short time (25ms), aperiodically, in different parts of the participant’s visual fields while being recorded using electrodes placed towards the back of the head. Specifically, they recorded from three electrode sites placed on the longitudinal midline of the head: one 3 cm anterior to the inion (the bony projection at the posterioinferior part of the skull), and two 3 cm to either side of the midline. After averaging between like trials (trials where the stimuli were presented in the same part of the visual field) and looking at the ERPs, Jeffreys and Axford postulated that there are two distinct components in the first 150msm, the C1 and the C2. But of the two components, the C1 tended to show polarity shifts across the scalp for trials where a stimulus was shown on one side of the visual field was compared to trials where stimuli were shown on the opposite side of the visual field. The C1’s polarity is also inverted whenever trials where the stimuli were presented in the top half of the visual field versus when stimuli were presented in the lower half of the visual field. Based on this evidence, Jeffreys and Axford proposed that the C1 reflected activity in the striate cortex as the activity tends to reflect a retinotopic map very similar to the one in the striate cortex. Since its initial discovery, the common theory about the C1 continues to state that it is an early component when viewing stimuli and that it represents activity in the primary visual cortex. One of the initial descriptions of the P1 can be credited to Spehlmann (1965) with his categorization of components within the VEPs. Whereas previous papers had looked at human ERPs to visual stimuli, and, undoubtedly, recorded P1 components as can be seen by visually inspecting the waveforms in the early articles (e.g. Cobb & Dawson, 1960), Spehlmann was one of the first to describe a “surface positive component at 80-120ms.” In his experiment, Spehlmann showed participants patterns of black and white squares, arranged in a checkerboard manner. These patterns were flashed to the participant by using a strobe light that had a frequency of 1-2 flashes per second. Averaging across trials, Spehlmann noted two different positivites, the first of which would later go on to be known as the P1. In the last quarter of the 20th century, the P1 started to be studied looking at what is called the P1 “effect” in the selective attention domain. In 1977 Van Voorhis and Hillyard found modulations in the P1 due to attention using the famous paradigm used by Eason, Harter, and White (1969). For their experiment, Van Voorhis and Hillyard (1977) had participants view circular flashes of light to the left and to the right of a central fixation with the right and left flashes occurring independently with each side having flashes 2 to 8 seconds apart (a replication of Eason et al., 1969), the flashes occurring randomly with 1 to 4 seconds between each flash (left or right), or the flashes occurring randomly with 300 to 600ms between each flash. Participants were instructed to either attend to the left visual field, the right visual hemisphere, or both visual hemispheres for a double flash (two flashes within 70ms of each other). Participants were also instructed to either look for the target passively or press a button whenever the double flash occurs. To record the ERPs, they had two electrodes down the midline (Cz and Oz) all referenced to the right mastoid. Van Voorhis and Hillyard found that the P1 had a greater positive amplitude when the target was presented in the attended field than when it was presented outside the attended field across all conditions. This was one of the first papers to show that attention could modulate a visually evoked potential as early on as the P1. Ever since this experiment, the difference between the P1 amplitude when the participant is attending in the correct and incorrect visual field (or the P1 effect) has been extensively studied as part of selective attention. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「C1 and P1 (neuroscience)」の詳細全文を読む スポンサード リンク
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