PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 11518457

Adaptation dynamics in pattern-reversal visual evoked potentials.

S P Heinrich·M Bach
View original source ↗Export metadata ↓

Abstract

Recording a VEP usually involves prolonged repetitions of the stimulus, but the influence of adaptation is rarely discussed in this context. Two experiments were performed. In Experiment 1 the time course of the response amplitude during steady-state stimulation was assessed. During the first seconds of stimulation we found an increase in amplitude, followed by a continuous exponential decline. This confirmed earlier results. There is considerable inter-subject variability concerning all aspects of the time course in our 19 subjects. Experiment 2 used two types of transient pattern reversal stimuli: one regular stimulus as used in standard clinical applications and one with a pause in between each reversal. N1 and P1 amplitudes did not show significant differential effects. N2 amplitude was reduced by 73% in the standard condition whereas P1 peak time increased slightly but significantly (3.2 ms).

Explore related subjects

Adaptation, OcularAdultCerebral CortexEvoked Potentials, VisualHumansVisual PathwaysJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

S P Heinrich, M Bach. 2001. Adaptation dynamics in pattern-reversal visual evoked potentials.. https://doi.org/10.1023/a%3A1017509717071

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2002

Refractive compensation to optical defocus depends on the temporal profile of luminance modulation of the environment.

The refractive state of hatchling chicks rapidly compensates to applied optical defocus through alteration in eye growth. The mechanism is capable of sensing whether the plane of focus lies in front of or behind the photoreceptors, however, its nature and site of action within the retina are unknown. We attempted to create an imbalance in the adaptation of the retinal ON and OFF mechanisms previously implicated in refractive control through pharmacological interventions, by rearing chicks from 4 to 9 days of age with a monocular +10 D, 0 D or -10 D lens, in an environment illuminated by a moving or stationary plaid of luminance gradients. When the plaid moved in one direction a local Fast-ON sawtooth luminance modulation was produced, while plaid motion in the other direction resulted in a Fast-OFF sawtooth modulation. Significantly reduced refractive compensation accompanied +10 D lens/Fast-OFF and -10 D lens/Fast-ON rearing, but not for the other conditions. Thus the refractive compensation mechanism depends on the nature of the temporal contrast of the environment, suggesting a relationship between the sign of defocus and the state of adaptation of the retinal ON and OFF subsystems.

Adaptation, Ocular↗
PubMed2002

Colour and luminance interactions in the visual perception of motion.

We sought to determine the extent to which red-green, colour-opponent mechanisms in the human visual system play a role in the perception of drifting luminance-modulated targets. Contrast sensitivity for the directional discrimination of drifting luminance-modulated (yellow-black) test sinusoids was measured following adaptation to isoluminant red-green sinusoids drifting in either the same or opposite direction. When the test and adapt stimuli drifted in the same direction, large sensitivity losses were evident at all test temporal frequencies employed (1-16 Hz). The magnitude of the loss was independent of temporal frequency. When adapt and test stimuli drifted in opposing directions, large sensitivity losses were evident at lower temporal frequencies (1-4 Hz) and declined with increasing temporal frequency. Control studies showed that this temporal-frequency-dependent effect could not reflect the activity of achromatic units. Our results provide evidence that chromatic mechanisms contribute to the perception of luminance-modulated motion targets drifting at speeds of up to at least 32 degrees s(-1). We argue that such mechanisms most probably lie within a parvocellular-dominated cortical visual pathway, sensitive to both chromatic and luminance modulation, but only weakly selective for the direction of stimulus motion.

Adaptation, Ocular↗
PubMed2002

Light induction of a vertebrate clock gene involves signaling through blue-light receptors and MAP kinases.

The signaling pathways that couple light photoreception to entrainment of the circadian clock have yet to be deciphered. Two prominent groups of candidates for the circadian photoreceptors are opsins (e.g., melanopsin) and blue-light photoreceptors (e.g., cryptochromes). We have previously showed that the zebrafish is an ideal model organism in which to study circadian regulation and light response in peripheral tissues. Here, we used the light-responsive zebrafish cell line Z3 to dissect the response of the clock gene zPer2 to light. We show that the MAPK (mitogen-activated protein kinase) pathway is essential for this response, although other signaling pathways may also play a role. Moreover, action spectrum analyses of zPer2 transcriptional response to monochromatic light demonstrate the involvement of a blue-light photoreceptor. The Cry1b and Cry3 cryptochromes constitute attractive candidates as photoreceptors in this setting. Our results establish a link between blue-light photoreceptors, probably cryptochromes, and the MAPK pathway to elicit light-induced transcriptional activation of clock genes.

Adaptation, Ocular↗