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Visual evoked potentials (VEPs) can provide important diagnostic information regarding the functional integrity of the visual system. This document updates the ISCEV standard for clinical VEP testing and supersedes the 2009 standard. The main changes in this revision are the acknowledgment that pattern stimuli can be produced using a variety of technologies with an emphasis on the need for manufacturers to ensure that there is no luminance change during pattern reversal or pattern onset/offset. The document is also edited to bring the VEP standard into closer harmony with other ISCEV standards. The ISCEV standard VEP is based on a subset of stimulus and recording conditions that provide core clinical information and can be performed by most clinical electrophysiology laboratories throughout the world. These are: (1) Pattern-reversal VEPs elicited by checkerboard stimuli with large 1 degree (°) and small 0.25° checks. (2) Pattern onset/offset VEPs elicited by checkerboard stimuli with large 1° and small 0.25° checks. (3) Flash VEPs elicited by a flash (brief luminance increment) which subtends a visual field of at least 20°. The ISCEV standard VEP protocols are defined for a single recording channel with a midline occipital active electrode. These protocols are intended for assessment of the eye and/or optic nerves anterior to the optic chiasm. Extended, multi-channel protocols are required to evaluate postchiasmal lesions.

•Stimulus-driven theories hold that all salient stimuli capture attention.•goal-driven theories posit that salient but irrelevant stimuli can be inhibited.•despite absent behavioral costs, pop-out distractors captured attention initially.•attention to distractors is withdrawn at a later stage, while it is sustained for targets.•marking stimulus positions speeds up neural processing and improves performance. There is much debate about the neural mechanisms that achieve suppression of salient distracting stimuli during visual search. The proactive suppression hypothesis asserts that if exposed to the same distractors repeatedly, these stimuli are actively inhibited before attention can be shifted to them. A contrasting proposal holds that attention is initially captured by salient distractors but is subsequently withdrawn. By concurrently measuring stimulus-driven and intrinsic brain potentials in 36 healthy human participants, we obtained converging evidence against early proactive suppression of distracting input. Salient distractors triggered negative event-related potentials (N1pc/N2pc), enhanced the steady-state visual evoked potential (SSVEP) relative to non-salient (filler) stimuli, and suppressed contralateral relative to ipsilateral alpha-band amplitudes—three electrophysiological measure associated with the allocation of attention—even though these distractors did not interfere with behavioral responses to the search targets. Furthermore, these measures indicated that both stimulus-driven and goal-driven allocations of attention occurred in conjunction with one another, with the goal-driven effect enhancing and prolonging the stimulus-driven effect. These results provide a new perspective on the traditional dichotomy between bottom-up and top-down attentional allocation. Control experiments revealed that continuous marking of the locations at which the search display items were presented resulted in a dramatic and unexpected conversion of the target-elicited N2pc into a shorter-latency N1pc in association with faster reaction times to the targets.

•Specific visual and acoustic features are often associated during perception.•One example is the pitch of a tone and the size of a visual object.•We used EEG to study the cerebral origin of such associations.•Steady-state visual evoked potentials suggest an origin near primary visual cortex.•Our results support a low-level account for crossmodal associations. Crossmodal correspondences describe our tendency to associate sensory features from different modalities with each other, such as the pitch of a sound with the size of a visual object. While such crossmodal correspondences (or associations) are described in many behavioural studies their neurophysiological correlates remain unclear. Under the current working model of multisensory perception both a low- and a high-level account seem plausible. That is, the neurophysiological processes shaping these associations could commence in low-level sensory regions, or may predominantly emerge in high-level association regions of semantic and object identification networks. We exploited steady-state visual evoked potentials (SSVEP) to directly probe this question, focusing on the associations between pitch and the visual features of size, hue or chromatic saturation. We found that SSVEPs over occipital regions are sensitive to the congruency between pitch and size, and a source analysis pointed to an origin around primary visual cortices. We speculate that this signature of the pitch-size association in low-level visual cortices reflects the successful pairing of congruent visual and acoustic object properties and may contribute to establishing causal relations between multisensory objects. Besides this, our study also provides a paradigm can be exploited to study other crossmodal associations involving visual stimuli in the future.

The International Society for Clinical Electrophysiology of Vision (ISCEV) standard for visual evoked potentials (VEPs) describes a minimum procedure for clinical VEP testing and encourages more extensive testing. This ISCEV extended protocol is an extension to the VEP standard. It describes procedures for recording multiple VEPs to a range of sizes of pattern stimuli to establish the VEP spatial frequency limit (threshold) and for relating this limit to visual acuity.

Encoding of a sensory stimulus is believed to be the first step in perceptual decision making. Previous research has shown that electrical signals recorded from the human brain track evidence accumulation during perceptual decision making (Gold and Shadlen, 2007; O’Connell et al., 2012; Philiastides et al., 2014). In this study we directly tested the hypothesis that the latency of the N200 recorded by EEG (a negative peak occurring between 150 and 275 ms after stimulus presentation in human participants) reflects the visual encoding time (VET) required for completion of figure-ground segregation before evidence accumulation. We show that N200 latencies vary across individuals, are modulated by external visual noise, and increase response time by x milliseconds when they increase by x milliseconds, reflecting a linear regression slope of 1. Simulations of cognitive decision-making theory show that variation in human response times not related to evidence accumulation (non-decision time; NDT), including VET, are tracked by the fastest response times. Evidence that VET is tracked by N200 latencies was found by fitting a linear model between trial-averaged N200 latencies and the 10th percentiles of response times, a model-independent estimate of NDT. Fitting a novel neuro-cognitive model of decision making also yielded a slope of 1 between N200 latency and model-estimated NDT in multiple visual noise conditions, indicating that N200 latencies track the completion of visual encoding and the onset of evidence accumulation. The N200 waveforms were localized to the cortical surface at distributed temporal and extrastriate locations, consistent with a distributed network engaged in figure-ground segregation of the target stimulus. •Visual evoked potentials around 200 ms track the onset of evidence accumulation.•These potentials (N200 peaks) are thought to reflect figure-ground segregation.•N200 peaks track response times with a slope of 1 across visual noise conditions.•N200 peaks track non-decision times (NDT) estimated by cognitive models.•These potentials were localized at distributed extrastriate cortical locations.

•Intermodulation frequency components (IMs) can be induced by the binocular synoptic vision paradigm, the dichoptic vision paradigm, and the cross-sensory paradigm.•The location of IMs appears to be associated with the stimulation type and the level of neural integration.•IMs exhibit a role in representing information integration in studies of global perception and binocular rivalry.•IMs can be used in clinical neuroscience to characterize defects in neural integration functions.•IMs can provide information gain for brain-computer interface systems. The steady-state visual evoked potentials (SSVEPs), evoked by dual-frequency or multi-frequency stimulation, likely contains intermodulation frequency components (IMs). Visual IMs are products of nonlinear integration of neural signals and can be evoked by various paradigms that induce neural interaction. IMs have demonstrated many interesting and important characteristics in cognitive psychology, clinical neuroscience, brain–computer interface and other fields, and possess substantial research potential. In this paper, we first review the definition of IMs and summarize the stimulation paradigms capable of inducing them, along with the possible neural origins of IMs. Subsequently, we describe the characteristics and derived applications of IMs in previous studies, and then introduced three signal processing methods favored by researchers to enhance the signal-to-noise ratio of IMs. Finally, we summarize the characteristics of IMs, and propose several potential future research directions related to IMs.

Motion-onset visual evoked potentials (MO VEPs) are robust to dioptric blur when low contrast and low spatial frequency patterns are used for stimulation. To reveal mechanisms of MO VEPs robustness, we studied whether the resistance to defocus persists even when using a high-contrast checkerboard using digital defocus in the emmetropic eyes of 13 subjects (males 20–60 years). We compared the dominant components of MO VEPs to pattern-reversal VEPs (PR VEP), which are sensitive to the blur. For stimulation, we used checkerboard patterns with 15´ and 60´ checks. To defocus the checkerboard, we rendered it with a second-order Zernike polynomial ( Z 2 0 ) with an equivalent defocus of 0, 2, or 4 D. For PR VEP, the checkerboards were reversed in terms of their contrast. To evoke MO VEP, the checkerboard of 60´ checks moved for 200 ms with a speed of 5 or 10 deg/s in the cardinal directions. The MO VEP did not change in peak time (P ≥ 0.0747) or interpeak amplitude (P > 0.0772) with digital blur. In contrast, for PR VEP, the results showed a decrease in interpeak amplitude (P ≤ 6.65ˑ10-4) and an increase in peak time (P ≤ 0.0385). Thus, we demonstrated that MO VEPs evoked by checkerboard, structure containing high spatial content, can be robust to defocus.

Provided the significant overlap in features of autism spectrum disorder (ASD) and attention-deficit/hyperactivity disorder (ADHD), there is a critical need to identify transdiagnostic markers that could meaningfully stratify subgroups. The objective of this study was to compare the visual evoked potential (VEP) between 30 autistic children, 17 autistic children with co-occurring ADHD presentation (ASD + ADHD), and 21 neurotypical children (NTC). Electroencephalography was recorded while children passively viewed a pattern-reversal stimulus. Mean amplitude of the P1 event-related potential was extracted from a midline occipital channel and compared between groups. P1 mean amplitude was reduced in the ASD + ADHD group compared to the ASD and NTC groups, indicating a distinct pattern of brain activity in autistic children with co-occurring ADHD features.

Visual evoked potentials (VEPs) recorded by encephalography (EEG) allow us to study the neuronal activity non-invasively and in high temporal resolution. Traditionally, EEG analyses have relied on univariate group-level statistics and trial averaging to detect effects. However, recent advances in high-density EEG enable the investigation of brain responses at the single-subject and single-trial level. In this study, we combine ultra-high-density (uHD) EEG with cross-validated single-trial decoding to bridge both approaches, improving generalizability and reproducibility. Study participants were shown a diverse set of random images while 512 channels from the uHD system recorded their EEG over the occipital lobe. Image properties (contrast, hue, luminance, saturation and spatial frequency) were extracted for each stimuli and VEPs were used for decoding these properties in a cross-validated regression analysis. Additionally, the same data were spatially subsampled to investigate the impact of spatial resolution and electrode density on the decoding performance. Image properties could be decoded from single-trial VEPs, with contrast, saturation and spatial frequency providing the best decoding performances. Grand average decoding performance across all image properties and subjects yielded a Pearson’s r of 0.50 between predicted and actual image property score. Greater electrode density improves decoding performance compared to standard EEG as well as subsampled configurations. Image properties robustly modulate early components of the VEP. Importantly, these modulations are pronounced enough to allow for single-trial decoding. Our analyses highlight the importance of electrode density with improvements in decoding performance extending even below 10 mm of inter-electrode distance.

Genetically encoded optical neuromodulators create an opportunity for circuit-specific intervention in neurological diseases. One of the diseases most amenable to this approach is retinal degeneration, where the loss of photoreceptors leads to complete blindness. To restore photosensitivity, we genetically targeted a light-activated cation channel, channelrhodopsin-2, to second-order neurons, ON bipolar cells, of degenerated retinas in vivo in the Pde6b rd1 (also known as rd1 ) mouse model. In the absence of 'classical' photoreceptors, we found that ON bipolar cells that were engineered to be photosensitive induced light-evoked spiking activity in ganglion cells. The rescue of light sensitivity was selective to the ON circuits that would naturally respond to increases in brightness. Despite degeneration of the outer retina, our intervention restored transient responses and center-surround organization of ganglion cells. The resulting signals were relayed to the visual cortex and were sufficient for the animals to successfully perform optomotor behavioral tasks.