The HED Task Catalog is under development. IDs are not stable until formal release. Comments are welcome at github.com/hed-standard/hed-task/issues.

Visual Masking Task

HED task ID: hedtsk_visual_masking

Family: Perceptual judgment and psychophysics tasks

Also known as: Backward Masking, Metacontrast Masking, Pattern Masking

A brief target is rendered invisible or reduced in visibility by a preceding or following mask; variants include metacontrast, paracontrast, pattern, forward, backward, common-onset, and object-substitution masking.

Description

Participants attempt to detect or discriminate brief, near-threshold visual stimuli that are rendered difficult to see through low contrast, brief duration, or metacontrast masking (a spatially adjacent, temporally trailing mask that suppresses visibility of the target without overlapping it spatially). The key dependent variable is not only accuracy but the relationship between trial-by-trial detection success and prestimulus brain states — particularly the phase and power of ongoing alpha (~10 Hz) and theta (~7 Hz) oscillations recorded via EEG. This paradigm demonstrates that conscious visual perception is not a passive, deterministic process but is gated by rhythmic fluctuations in cortical excitability, supporting pulsed-inhibition and perceptual-sampling theories.

Inclusion test

An experiment is an instance of this task when its procedure matches, it manipulates at least one of the listed variables, and it records at least one of the listed measures.

Procedure

A brief target stimulus is rendered invisible or reduced in visibility by a temporally adjacent mask. Participants detect, identify, or discriminate the target.

Manipulation

Mask type (metacontrast, pattern, backward, forward, common-onset, object-substitution); SOA/ISA between target and mask; target-mask spatial relationship; mask energy.

Measurement

Target detection/identification accuracy or d-prime as a function of SOA (U-shaped or monotonic masking functions); subjective visibility ratings; priming effects from unseen targets.

Variations

Named versions that change what the participant experiences or does. The identifier of a variation is hedvar_<task>__<variation>.

Variation

Description

Justification

Standard Metacontrast Masking

hedvar_visual_masking__standard_metacontrast_masking

Target followed by annular mask at variable SOAs; measure detection/discrimination accuracy.

Canonical metacontrast: annular mask suppresses disc

Phosphene Detection at Threshold

hedvar_visual_masking__phosphene_detection_at_threshold

Near-threshold light flashes on uniform background; simplest version eliminating masking.

TMS-evoked phosphenes measured at perceptual threshold

TMS-Evoked Phosphene Detection

hedvar_visual_masking__tms_evoked_phosphene_detection

Transcranial magnetic stimulation to visual cortex at varying alpha phases; causal test of oscillatory gating.

Visual cortex stimulation produces phosphene; different masking mechanism

Object Substitution Masking

hedvar_visual_masking__object_substitution_masking

Four-dot mask surrounding target location; tests different masking mechanism than metacontrast.

Four-dot surround mask replaces object representation; different mechanism

Pattern Masking at Threshold

hedvar_visual_masking__pattern_masking_at_threshold

Random-dot or noise-pattern mask overlapping target spatially; distinguishes from metacontrast which is non-overlapping.

Pattern mask overlapping in space and time; different mask type

Continuous Flash Suppression Threshold

hedvar_visual_masking__continuous_flash_suppression_threshold

Mondrian-pattern masking to one eye while target presented to the other; binocular rivalry version.

Monocular suppression by rapidly alternating masks; binocular suppression paradigm

Rhythmic Entrainment + Detection

hedvar_visual_masking__rhythmic_entrainment_detection

Presenting rhythmic visual streams before the target to entrain alpha and test whether entrained phase modulates detection.

Rhythmic stimulation before target; tests oscillatory effects on detection

Masked Priming Variant

hedvar_visual_masking__masked_priming_variant

Masked stimuli serve as primes for subsequent visible targets; measures subliminal processing below the consciousness threshold.

Masked prime before target; tests subliminal priming via masking

Backward Masking with Attentional Manipulation

hedvar_visual_masking__backward_masking_with_attentional_manipulation

Combining masking with dual-task or attentional-blink paradigms to examine attention × consciousness interactions.

Attention directed during masking; tests attentional modulation of masking

Auditory Backward Masking

hedvar_visual_masking__auditory_backward_masking

Analogous paradigm in auditory modality; tone detection masked by noise burst at variable SOAs.

Auditory masking paradigm; different sensory modality

Cognitive processes

This task is designed to engage the following processes:

Key references

  • Mathewson, K. E., Gratton, G., Fabiani, M., Beck, D. M., & Ro, T. (2009). To see or not to see: Prestimulus alpha phase predicts visual awareness. Journal of Neuroscience, 29(9), 2725–2732. (DOI, PubMed)

  • Busch, N. A., Dubois, J., & VanRullen, R. (2009). The phase of ongoing EEG oscillations predicts visual perception. Journal of Neuroscience, 29(24), 7869–7876. (DOI, PubMed)

  • VanRullen, R., & Koch, C. (2003). Is perception discrete or continuous? Trends in Cognitive Sciences, 7(5), 207–213. (DOI, PubMed)

  • Del Cul, A., Baillet, S., & Dehaene, S. (2007). Brain dynamics underlying the nonlinear threshold for access to consciousness. PLoS Biology, 5(10), e260. (DOI, PubMed)

  • Dehaene, S., & Changeux, J. P. (2011). Experimental and theoretical approaches to conscious processing. Neuron, 70(2), 200–227. (DOI, PubMed)

  • Sergent, C., & Dehaene, S. (2004). Is consciousness a gradual phenomenon? Evidence for an all-or-none bifurcation during the attentional blink. Psychological Science, 15(11), 720–728. (DOI, PubMed)

Further references

  • VanRullen, R. (2016). Perceptual cycles. Trends in Cognitive Sciences, 20(10), 723–735. (DOI, PubMed)

  • Dugué, L., Marque, P., & VanRullen, R. (2011). The phase of ongoing oscillations mediates the causal relation between brain excitation and visual perception. Journal of Neuroscience, 31(33), 11889–11893. (DOI, PubMed)

  • Iemi, L., Busch, N. A., Laudini, A., Haegens, S., Samaha, J., Villringer, A., & Nikulin, V. V. (2019). Multiple mechanisms link prestimulus neural oscillations to sensory responses. eLife, 8, e43620. (DOI, PubMed)

  • Samaha, J., Iemi, L., Haegens, S., & Busch, N. A. (2020). Spontaneous brain oscillations and perceptual decision-making. Trends in Cognitive Sciences, 24(8), 639–653. (DOI, PubMed)

  • Mashour, G. A., Roelfsema, P., Changeux, J. P., & Dehaene, S. (2020). Conscious processing and the global neuronal workspace hypothesis. Neuron, 105(5), 776–798. (DOI, PubMed)

  • Dehaene, S., Lau, H., & Kouider, S. (2017). What is consciousness, and could machines have it? Science, 358(6362), 486–492. (DOI, PubMed)

  • Del Cul, A., Dehaene, S., Reyes, P., Bravo, E., & Slachevsky, A. (2009). Causal role of prefrontal cortex in the threshold for access to consciousness. Brain, 132(9), 2531–2540. (DOI, PubMed)

  • King, J. R., Pescetelli, N., & Dehaene, S. (2016). Brain mechanisms underlying the brief maintenance of seen and unseen sensory information. Neuron, 92(5), 1122–1134. (DOI, PubMed)