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Eysel, U. T.; Burandt, U. (1984): Fluorescent tube light evokes flicker responses in visual neurons. In: Visionresearch, Jg. 24, H. 9, S. 943–948.Abstract Single neurons in the cat visual system respond distinctly to the temporal

information present in light from fluorescent tubes driven by 50 or 60 Hz alternatingcurrent. Despite the resulting flicker frequencies of 100 or 120 Hz all retinal andmost thalamic neurons show strong phase locking of the neuronal responses to themodulation of fluorescent tube light. Some retinal ganglion cells have not yetreached their critical flicker fusion frequency under such conditions. Though usuallybeyond perception, the frequency and depth of modulation of artificial light thusmight well play a role in biological light effects.

Schlagwörter Animals; Cats; Evoked Potentials, Visual; Flicker Fusionphysiology; GeniculateBodiesphysiology; Light; Lighting; Optic Nervephysiology; Photometry;Retinaphysiology; Retinal Ganglion Cellsphysiology

Frascella, J.; Lehmkuhle, S. (1984): An electrophysiological assessment of X and Y cells as pattern and flickerdetectors in the dorsal lateral geniculate nucleus of the cat. In: Experimental brain research. ExperimentelleHirnforschung. Expérimentation cérébrale, Jg. 55, H. 1, S. 117–126.Abstract We tested the hypothesis that geniculate X cells are the neural substrate of

psychophysically identified pattern channels and that geniculate Y cells are theneural substrate of psychophysically identified flicker channels. The hypothesis wastested by measuring the relative sensitivity of isolated X and Y cells in the dorsallateral geniculate nucleus of the cat to counterphase and on-off gratingpresentations. The fundamental and second harmonic responses of X and Y cells tosinusoidal counterphase and on-off temporal modulation were measured at anumber of spatial frequencies using two contrasts, 0.1 and 0.4. The fundamentalresponses of both X and Y cells to sinusoidal counterphase were greater relative toon-off responses. The second harmonic responses of Y cells to counterphase werelarger at high spatial frequencies. Contrast sensitivity also was measured. At allspatial frequencies, both X and Y cells were slightly more sensitive to counterphasethan to on-off presentations. Since flicker sensitivity in humans is twice as high forcounterphase as for on-off presentations across all spatial frequencies, whereaspattern sensitivity is equal for the two presentations, we conclude that X and Y cellsdo not subserve uniquely pattern and flicker sensitivity, respectively. Thisconclusion is based on the result that differences between X and Y cells tocounterphase and on-off presentations were inconsistent with the differencesobserved for pattern and flicker sensitivity. We suggest then that a spatial/temporaldichotomy does not seem to accurately characterize the functional roles of X and Ycells.

Schlagwörter Animals; Brain Mapping; Cats; Evoked Potentials, Visual; Flicker Fusionphysiology;Form Perceptionphysiology; Geniculate Bodiescytology; Neuronsclassification;Pattern Recognition, Visualphysiology; Retinaphysiology; Sensory Thresholds;Synaptic Transmission

Magnussen, S.; Spillmann, L.; Stürzel, F.; Werner, J. S. (2001): Filling-in of the foveal blue scotoma. In: Visionresearch, Jg. 41, H. 23, S. 2961–2967.Abstract The blue-blindness (tritanopia) of the human foveola normally goes unnoticed but

can be directly visualized by having observers view a flickering, monochromatic,short-wavelength field. The blue scotoma appears as a tiny dark spot in centralvision, the visibility of which depends upon the wavelength of the field and thetemporal frequency of modulation. Comparisons of fading times as a function offlicker frequency for the blue scotoma, foveal afterimages and optically stabilizedimages indicate a common time course, consistent with the hypothesis thatperceptual filling-in of the foveal blue scotoma reflects the operation of neuralprocesses similar to those involved in fading and regeneration of stabilized images.

Schlagwörter Afterimagephysiology; Flicker Fusion; Humans; Optic Diskphysiology; Perceptual

iLib08 - CitaviiLib08 - CitaviiLib08 - CitaviiLib08 - CitaviClosurephysiology

Regan, D.; Lee, B. B.: A comparison of the 40-Hz response in man, and the properties of macaque ganglioncells. In: Visual neuroscience, Jg. 10, H. 3, S. 439–445.Abstract Visually evoked field potentials in human subjects and single-cell responses from

retinal ganglion cells in the macaque monkey were compared in closely similarstimulus situations. The classical heterochromatic flicker photometry (HFP)technique was used to measure spectral sensitivity in man, both psychophysicallyand by recording the 40-Hz response, and to measure the spectral sensitivity ofmagnocellular (MC-) pathway cells of the macaque. The three measures gaveclosely similar spectral-sensitivity curves. Close agreement between the threemeasures was also found when the variable-modulation HFP technique was usedto measure spectral sensitivity. When the relative phase between red and greenlights was varied, the point of minimum subjective flicker for human observers wasclose to a sharp minimum found in the amplitude of the 40-Hz response in humanand was also close to a minimum in the response of MC-pathway neurons in themonkey. The human 40-Hz response saturated at between 10 and 30% modulationdepth, and so did the response of MC-pathway cells in the monkey. The 16-Hzresponse in human showed none of the above correlations with MC-pathwayproperties. On the other hand, parvocellular (PC-) pathway cells respondedvigorously to constant-luminance, chromatic modulation, at frequencies higher thancan be detected by human observers. The human 16-Hz response also was strongin that stimulus situation. In addition, the response of PC-pathway cells onincreasing modulation depth showed little saturation, and this behaviour wasparalleled by the human 16-Hz response.(ABSTRACT TRUNCATED AT 250WORDS)

Schlagwörter Animals; Evoked Potentials, Visualphysiology; Humans; Macaca; OccipitalLobephysiology; Photic Stimulation; Psychophysics; Retinal GanglionCellsphysiology; Sensory Thresholds; Visual Pathwaysphysiology; VisualPerceptionphysiology

Schieting, S.; Spillmann, L. (1987): Flicker adaptation in the peripheral retina. In: Vision research, Jg. 27, H. 2,S. 277–284.Abstract With strict fixation, a flickering light spot smaller than 3 deg presented to the

peripheral retina will rapidly appear to lose contrast and stop flickering within 35 s,before fading away completely. The time required for this adaptation to occurdecreases with: decreasing depth of modulation (97-9%); decreasing stimulusdiameter (2 deg-7 min arc); increasing retinal eccentricity (20-50 deg); andincreasing flicker frequency (1-7 Hz). Interestingly, the effect does not depend uponthe regularity of the flickering stimulus, and it occurs twice as fast for stimulipresented to the temporal retina as for stimuli presented to the nasal retina. Whenchanges in retinal eccentricity are compensated for by taking into account thecortical magnification factor, the time needed for perceived flicker to disappearremains constant at all eccentricities. With dichoptic stimulation interocular transferis about 35%, suggesting a cortical contribution to flicker adaptation. The resultsindicate that the visual system adapts rather easily to peripheral flickering stimuli.Similarities as well as differences to motion adaptation are discussed.

Schlagwörter Adaptation, Ocular; Fixation, Ocular; Humans; Motion Perceptionphysiology;Retinaphysiology; Vision, Ocularphysiology; Visual Cortexphysiology; VisualPerceptionphysiology

Seitz, Aaron R.; Nanez, Jose E.; Holloway, Steve R.; Watanabe, Takeo (2006): Perceptual learning of motionleads to faster flicker perception. In: PLoS ONE, Jg. 1, S. e28. Online verfügbar unterdoi:10.1371/journal.pone.0000028.Abstract Critical flicker fusion thresholds (CFFT) describe when quick amplitude modulations

of a light source become undetectable as the frequency of the modulation

iLib08 - CitaviiLib08 - CitaviiLib08 - CitaviiLib08 - Citaviincreases. The threshold at which CFF occurs has been shown to remain constantunder repeated testing. Additionally, CFF thresholds are correlated with variousmeasures of intelligence, and have been regarded by clinicians as a generalmeasure of cortical processing capacity. For these reasons, CFF is used as acognitive indicator in drug studies, as a measure of fatigue, and has beensuggested as a diagnostic measure for various brain diseases. Here we report thatCFFT increases dramatically in subjects who are trained with a motion-directionlearning procedure. Control tasks demonstrate that CFFT changes are tightlycoupled with improvements in discriminating the direction of motion stimuli, and arelikely related to plasticity in low-level visual areas that are specialized to processmotion signals. This plasticity is long-lasting and is retained for at least one yearafter training. Combined, these results show that CFFT relates to a specializedsensory process and bring into question that CFFT is a measure of high-level, orgeneral, processes.

Spekreijse, H.; van Norren, D.; van den Berg, T. J. (1971): Flicker responses in monkey lateral geniculatenucleus and human perception of flicker. In: Proceedings of the National Academy of Sciences of the UnitedStates of America, Jg. 68, H. 11, S. 2802–2805.Abstract An analysis was made of the impulse discharge patterns-evoked by sinusoidal

luminance modulation-of single cells in the lateral geniculate nucleus of themacaque monkey. The goal was to determine whether a correspondence could beobserved between flicker detection by human subjects in psychophysicalexperiments and electrophysiological measurements of discharge patterns of singlecells of the lateral geniculate nucleus. We found that the average dischargepatterns of single cells exhibited the following behavior when mean retinalillumination was changed: In the low-frequency region (less than about 10 Hz) theresponse strength (impulses/sec) is independent of the mean luminance, inaccordance with Weber's law; in the high-frequency region (above about 10 Hz) theresponse depends on the absolute modulation amplitude, in accordance with theFerry-Porter law. Therefore the main features of human critical flicker frequencydata are already present in the cellular (lateral geniculate nucleus) response of themacaque monkey. However, the steepness of high frequency fall-off in theresponse characteristics of these cells is much less than the corresponding fall-offin the human critical-flicker-frequency curves.

Schlagwörter Animals; Electrophysiology; Flicker Fusion; Geniculate Bodiesphysiology;Haplorhini; Humans; Macaca; Stereotaxic Techniques; Visual Perception

Thomas, C. G.; Menon, R. S. (1998): Amplitude response and stimulus presentation frequency response ofhuman primary visual cortex using BOLD EPI at 4 T. In: Magnetic resonance in medicine : official journal of theSociety of Magnetic Resonance in Medicine / Society of Magnetic Resonance in Medicine, Jg. 40, H. 2, S.203–209.Abstract Detailed measurement of the neural response to flicker frequency using functional

MRI (fMRI) were made. The fMRI signal peaks at a flicker frequency of 8 Hz inhuman V1, in agreement with previous positron emission tomography (PET) andfMRI experiments. The modulation amplitude of the hemodynamic response tovarying continuous periods of flicker stimulation was measured. The hemodynamicresponse was not observed to be modulated by neural modulation for periodsshorter than 6.7 s. The resemblance between the BOLD response to the stimuluspresentation frequency and the base-line power spectra at the same frequenciessuggests that the same underlying mechanism could be responsible for both curvesand that the base-line fMRI power spectrum is probably due to base-line electricalactivity in the brain. The integrals of the resting base-line power spectrum, thebackground power spectrum, the respiration component, and the cardiaccomponent were found to be linearly dependent on TE.

Schlagwörter Adult; Echo-Planar Imaginginstrumentation; Female; Flicker Fusionphysiology;Fourier Analysis; Humans; Image Processing, Computer-Assistedinstrumentation;

iLib08 - CitaviiLib08 - CitaviiLib08 - CitaviiLib08 - CitaviMagnetic Resonance Imaginginstrumentation; Male; SensoryThresholdsphysiology; Visual Cortexphysiology

Trehub, A. (1965): Spontaneous slow modulation of flicker-evoked response in human brain. In:Electroencephalography and clinical neurophysiology, Jg. 19, H. 2, S. 182–184.Schlagwörter Cerebral Cortexphysiology; Electroencephalography; Humans; Light