Figures and data
Experimental approaches to study the NCC.
In the contrastive approach (left), the visibility of stimuli is manipulated across trials such that they are either perceived (“conscious trials”) or not perceived (“unconscious trials”). Two of the most popular paradigms to manipulate visibility, near-threshold presentation of stimuli and backward masking, are depicted. In report tasks, participants perform button presses or saccadic eye movements to report whether they perceived the stimulus or not. In no-report tasks, attentional manipulations, stimulus intensity or automatic oculomotor or pupillary responses (e.g., optokinetic nystagmus, pupil dilation) are used to infer if the stimulus was perceived or not. Neural signals that correlate with consciousness should differ across trials that are classified as conscious and unconscious. In the supraliminal approach (right), full contrast stimuli are presented and are assumed to always be consciously perceived. Trials are compared across conditions that differ in the characteristics of the stimuli, such as presentation duration (discussed below).
Different types of implants used for intracranial recordings in humans.
ECoG strips or grids are typically placed under the dura mater (purple implant); Deep-brain stimulation (DBS) electrodes are typically used to record and stimulate subcortical regions (green implant); Microelectrode arrays are positioned on the cortex (yellow implant); sEEG depth electrodes are inserted in the brain across cortical and subcortical structures (blue implant). Hybrid models can record single-unit activity with either tetrodes (red) or microwires protruding from the electrode.
Summary of ECOG and sEEG studies using the contrastive approach to study visual NCCs in humans.
Summary of key results of intracranial studies of perceptual consciousness.
A. Broadband activity in response to seen vs. unseen face stimuli in the prefrontal cortex follows a bimodal distribution, leading the authors to speculate that early responses may be associated with perceptual consciousness. Panel adapted from Fang et al. (2024b) (CC BY-NC 4.0). B. In the ventral visual cortex including the face fusiform area, HGA increases track face stimulus detection in immediate and delayed report experiments, and stimulus intensity in a no-report experiment. Panel adapted from Stockart et al. (2025) (CC BY-NC-ND 4.0). C. A thalamic awareness potential is observed in response to seen, but not unseen, face stimuli. Panel adapted from Kronemer et al. (2022) (CC BY 4.0). D. Medial and intralaminar thalamic nuclei respond more to perceived face stimuli than ventral nuclei (left panel) and drive activity in the prefrontal cortex as shown by phase-amplitude coupling (PAC; right panel). Adapted from Fang et al. (2025). E. Multivariate decoding in the occipital and ventral-temporal cortices, but not the parietal and prefrontal cortices, tracks stimulus duration. Panel adapted from Vishne et al., 2023 (CC BY 4.0). F. Stimulus category can be decoded for the entire duration of the stimulus in the posterior cortex but not in the prefrontal cortex, while stimulus orientation decoding does not track the duration of the stimulus in either region of interest. Panel adapted from Cogitate Consortium et al. (2025) (CC BY 4.0).
© Fang et al. Figure 3A is reproduced from Fang et al. (2024b) (published under a CC BY-NC 4.0 license). Further reproduction must adhere to the terms of this license.
© Stockart et al. Figure 3B is reproduced from Stockart et al. (2025) (published under a CC BY-NC-ND 4.0 license). Further reproduction must adhere to the terms of this license.
Summary of ECOG and sEEG studies using the contrastive approach to study non-visual NCC in humans.
Summary of studies using the contrastive approach to study single-neuron NCC in humans.
