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  • 1
    Electronic Resource
    Electronic Resource
    Source locations of pattern-specific components of human visual evoked potentials. II. Component of extrastriate cortical origin (1972)
    Springer
    Experimental brain research 16 (1972), S. 22-40 
    Details
    ISSN: 1432-1106
    Keywords: Visual evoked potentials ; Cortical sources ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Further studies are reported on the influence of retinal stimulus location on the surface distributions of individual pattern-related VEP components. The following results were observed for stimulation of different central and annular regions of the upper and lower field in four subjects: 1. Consistent differences in polarity and form of the longitudinal distributions of (a) components C.I (peak latency 65–80 msec) and C.II (latency 90–110 msec) of the same VEPs; and (b) component C.II of the upper and lower half-field responses for the same subject. 2. Differences in the relative contributions from the central and outer regions of the stimulus field to (a) the C.I and C.II half-field distributions; and (b) the upper and lower half-field C.II distributions. 3. For C.II (as for C.I) an additive relationship was demonstrated between the half-field and constituent quadrant distributions. 4. The binocular and monocular distributions of C.I and C.II were found to be almost identical in form and comparable in magnitude. These results again indicate that C.I and C.II have spatially separate sources. The longitudinal distributions of C.II are shown to conform with those of a simple dipolar model based on the retinotopic organization of the extrastriate cortex on the outer surfaces of the occipital lobes. Also, the longitudinal distributions of C.I appear consistent with its proposed striate cortical origin. Both C.I and C.II are thought to originate from surface negative cortical activity. Experiments indicating that C.I and C.II are influenced differently by pattern pre-exposure provide supporting evidence for the separability of these components and suggest that they are produced in functionally different cortical regions. The implications of this work are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233372
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  • 2
    Electronic Resource
    Electronic Resource
    Source locations of pattern-specific components of human visual evoked potentials. I. Component of striate cortical origin (1972)
    Springer
    Experimental brain research 16 (1972), S. 1-21 
    Details
    ISSN: 1432-1106
    Keywords: Visual evoked potentials ; Cortical sources ; Man
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A study was made of the transverse distributions of human scalprecorded potentials evoked by the brief presentation of a pattern into different regions of a continuously illuminated diffuse field. The first two components of these visual evoked potentials (VEPs), designated C.I. (latency 65–80 msec) and C. II (latency 90–110 msec), were both greatly influenced by the retinal location of the stimulus pattern. In an initial study of the VEP waveforms with 12 subjects, followed by a more detailed investigation of the distribution of the individual components in 4 subjects, the following results were found. 1. Corresponding peaks (C. I and C. II) of the VEPs to stimulation of the upper and lower half-fields were inverted in polarity. 2. For the left and right half-field VEPs, the transverse distribution of C. I, but not of C. II, showed a polarity reversal across the midline. 3. Consistent differences were observed between the distributions of C. I for adjacent upper and lower quadrants, as well as between those for adjacent horizontal and vertical octants of the upper field. 4. Subjects differed in the degree of left-right asymmetry shown. There was also a much greater degree of interindividual consistency of quadrant and upper and lower half-field VEPs than for full-field or left and right half-field responses. 5. For C. I, an additive relationship was demonstrated between the half-field and the constituent quadrant VEP distributions. These results indicate that C. I and C. II have spatially separate sources. Assuming a simple dipolar model based on the known retinotopic organization of the striate cortex, it is shown that the measured distributions are compatible with the hypothesis that component C. I, but not C. II, originates in striate cortex, from surface negative cortical activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00233371
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  • 3
    Electronic Resource
    Electronic Resource
    Evoked potential evidence for differences in binocularity between striate and prestriate regions of human visual cortex (1979)
    Springer
    Experimental brain research 36 (1979), S. 375-380 
    Details
    ISSN: 1432-1106
    Keywords: Binocularity ; Interocular transfer ; Visual evoked potentials
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary For two components of the visual evoked potential elicited by the onset of a stationary pattern the degree of interocular transfer of the attenuation caused by prior exposure to a similar pattern was measured. The results show almost complete interocular transfer for component CII, thought to originate in prestriate cortex, but only partial transfer of CI, thought to be of striate cortical origin. This suggests that in man, as in monkey, monocularly driven neurones are more common in striate than in prestriate cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00238918
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  • 4
    Electronic Resource
    Electronic Resource
    Cortical Source Locations of Pattern-related Visual Evoked Potentials recorded from the Human Scalp (1971)
    [s.l.] : Nature Publishing Group
    Nature 229 (1971), S. 502-504 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Although there have been a few reports of changes in the waveform of VEPs obtained by flash stimulation of different regions of the (homogeneous) visual field4'5, there is increasing evidence that retinal location has a profound influence on both waveform and spatial distribution of various ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/229502a0
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  • 5
    Electronic Resource
    Electronic Resource
    The vertex-positive scalp potential evoked by faces and by objects (1992)
    Springer
    Experimental brain research 91 (1992), S. 340-350 
    Details
    ISSN: 1432-1106
    Keywords: Visual evoked potentials ; Face stimuli ; Object stimuli ; Response consistency ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of stimulus form on the scalp-recorded “vertex positive peak” (VPP) evoked by images of faces (Jeffreys 1989a) was studied in seven subjects. In separate experiments, we recorded the responses to 2D images of: (1) many different depictions of human faces; (2) the heads of several different species; (3) many familiar non-face objects; and (4) stimuli where the configuration of objects were modified to produce an “illusory” or “non-contextual” subjective impression of a face. The results showed that every facial representation, including the “illusory” stimuli, and most of the non-face objects, evoked a VPP of corresponding form and scalp distribution. The object-evoked VPPs, however, were always smaller and usually later than those evoked by the faces. VPPs of longer latency but often comparable amplitude were also recorded for impoverished compared to well-defined facial representations; and for most non-human compared to human faces. Very consistent responses were recorded to repeated presentations of the same stimulus for the same subject, but there was considerable variation in latency as well as amplitude (but not form) of the VPP evoked under identical experimental conditions for different subjects. These response properties of the VPP, suggest that its underlying physiological generators are sensitive to basic configurai properties of the visual stimulus; and also that face- and object-related information are processed in the same brain area(s), although not necessarily by the same physiological mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231668
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  • 6
    Electronic Resource
    Electronic Resource
    Evoked potential evidence for human brain mechanisms that respond to single, fixated faces (1992)
    Springer
    Experimental brain research 91 (1992), S. 351-362 
    Details
    ISSN: 1432-1106
    Keywords: Visual evoked potentials ; Face stimuli ; Fixation position ; Stimulus size ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary The influence of visual fixation position and stimulus size on the scalp-recorded “vertex positive peak” (VPP) evoked by images of faces was studied in three subjects. Responses were recorded, in turn, for line-drawn, frontal-view faces of approximately 8, 4, 2, and 1 deg length, fixated at the centre (bridge of the nose), and at points 1,2, 3, and 4 deg to the left and right, and above and below, centre. The results showed that central fixation produced VPPs of similar, maximal amplitude for all face sizes. By comparison, “on-face” eccentric viewing yielded attenuated and delayed responses, and the degree of response attenuation as a function of eccentricity was directly related to the face size, with similar amplitude responses being evoked for corresponding fixation locations on each face. Very small or no VPPs were recorded for most “off-face” fixations. Similar results were observed for profile faces, except that the maximal VPP was recorded for fixations near the eyes and not in the centre of the head, and almost identical VPPs were evoked by a centrally fixated face presented with and without an adjacent face or object. These response properties, which correspond to the subjective perception of the facial stimuli, suggest that the VPP reflects brain mechanisms optimized to respond to single, fixated faces, irrespective both of facial image size and of the presence of neighbouring figures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00231669
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  • 7
    Electronic Resource
    Electronic Resource
    Evoked potential evidence of adaptation to spatial Fourier components in human vision (1978)
    [s.l.] : Nature Publishing Group
    Nature 274 (1978), S. 156-158 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The transient visual evoked potential (VHP) elicited by the onset of a briefly presented pattern and recorded using electrodes attached to the scalp over the occipital lobe, has three major components occurring within 200ms after stimulus onset6. We are concerned here with the initial component ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/274156a0
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    Paper (German National Licenses)
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  • 8
    Electronic Resource
    Electronic Resource
    A face-responsive potential recorded from the human scalp (1989)
    Springer
    Experimental brain research 78 (1989), S. 193-202 
    Details
    ISSN: 1432-1106
    Keywords: Evoked potentials ; Face responses ; Temporal cortex ; Human
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary Evoked potentials were recorded to the separate tachistoscopic presentation of a variety of faces and other simple and complex visual stimuli. A positive potential of 150–200 ms peak latency which responds preferentially, but not exclusively, to faces was identified in 8 out of 9 subjects. This potential, best recorded from midline central and parietal electrodes, was evoked by all face stimuli, including photographs, outline drawings, and fragmentary figures. Changes in stimulus size and other parameters which do not affect the clarity of the face, generally had little effect on the peak amplitude. Stimulus changes such as face inversion, reversing the contrast polarity of photographic images, and selectively removing particular facial features, produced a marked increase in latency but often only slight attenuation of this peak. These response properties correspond well with those reported for face-related single cells in the temporal cortex of the rhesus monkey. The scalp distribution of this face-responsive peak also appears consistent with bilateral sources in the temporal cortex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00230699
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