Streams of conscious visual experience

Abstract

Consciousness, a cornerstone of human cognition, is believed to arise from complex neural interactions. Traditional views have focused on localized fronto-parietal networks or broader inter-regional dynamics. In our study, we leverage advanced fMRI techniques, including the novel Functionnectome framework, to unravel the intricate relationship between brain circuits and functional activity shaping visual consciousness. Our findings underscore the importance of the superior longitudinal fasciculus within the fronto-parietal fibers, linking conscious perception with spatial neglect. Additionally, our data reveal the critical contribution of the temporo-parietal fibers and the splenium of the corpus callosum in connecting visual information with conscious representation and their verbalization. Central to these networks is the thalamus, posited as a conductor in synchronizing these interactive processes. Contrasting traditional fMRI analyses with the Functionnectome approach, our results emphasize the important explanatory power of interactive mechanisms over localized activations for visual consciousness. This research paves the way for a comprehensive understanding of consciousness, highlighting the complex network of neural connections that lead to awareness.

Fig. 1. Results maps obtained in the conjunction analysis for the seen > unseen contrast for the classical and Functionnectome approaches.

a Results for the classical analysis approach. b Results for the Functionnectome approach. Maps are corrected at a cluster-defining threshold of Z > 2.3 and a cluster threshold of P < 0.05. N = 3 independent experiments, including 18, 18, and 20 participants, respectively. While results from the classical approach replicate brain regions often found in neuroimaging literature, the Functionnectome expands those results to demonstrate the involvement of white matter tracts. Z maps of the results can be found in https://neurovault.org/collections/15553/. ATR anterior thalamic radiation, CC corpus callosum, IPS inferior parietal sulcus, ITS inferior temporal sulcus, PSA posterior segment of the arcuate fasciculus, SLF2 second branch of the superior longitudinal fasciculus.

Fig. 2. Histogram of z values for the conjunction maps and proposed model of visual conscious access circuit based on the results.

a Distribution of z values for each brain voxel of the conjunction maps calculated using the classical (blue color; N = 216,289 independent voxels) and the Functionnectome (red color; N = 220,157 independent voxels). The dataset to generate the graph can be found at https://osf.io/gb2nh/. b Graphical representation of the anatomical connections between relevant nodes of the proposed conscious access circuit. Yellow arrows represent the posterior segment of the arcuate fasciculus; red arrows represent the splenium of the corpus callosum; blue arrows represent the second branch of the superior longitudinal fasciculus; green arrows represent the anterior thalamic radiation. FEF frontal eye field, IPS inferior parietal sulcus, VLTc ventro lateral temporal cortex.

Fig. 3. Sequence of events in a given trial of each task.

Attention was manipulated with the presentation of a tone, a peripheral cue, or a Stroop task, for the alerting, orienting and executive attention tasks, respectively. The target was a near-threshold Gabor stimulus, perceived ~50% of the time. Participants had to identify the orientation of the lines of the Gabor, and report whether or not they consciously detected its appearance in one of the markers. Note that for the orienting task, the conscious report was made by indicating if the target was seen or unseen, without reporting target location. For the executive attention task, the Stroop word was presented concurrently to the appearance of the target, and the response to the orientation of the target’s lines was not requested. For a detailed figure of each paradigm, please refer to the original publications^–.