Subjective visual perception: from local processing to emergent phenomena of brain activity

Abstract

The combination of electrophysiological recordings with ambiguous visual stimulation made possible the detection of neurons that represent the content of subjective visual perception and perceptual suppression in multiple cortical and subcortical brain regions. These neuronal populations, commonly referred to as the neural correlates of consciousness, are more likely to be found in the temporal and prefrontal cortices as well as the pulvinar, indicating that the content of perceptual awareness is represented with higher fidelity in higher-order association areas of the cortical and thalamic hierarchy, reflecting the outcome of competitive interactions between conflicting sensory information resolved in earlier stages. However, despite the significant insights into conscious perception gained through monitoring the activities of single neurons and small, local populations, the immense functional complexity of the brain arising from correlations in the activity of its constituent parts suggests that local, microscopic activity could only partially reveal the mechanisms involved in perceptual awareness. Rather, the dynamics of functional connectivity patterns on a mesoscopic and macroscopic level could be critical for conscious perception. Understanding these emergent spatio-temporal patterns could be informative not only for the stability of subjective perception but also for spontaneous perceptual transitions suggested to depend either on the dynamics of antagonistic ensembles or on global intrinsic activity fluctuations that may act upon explicit neural representations of sensory stimuli and induce perceptual reorganization. Here, we review the most recent results from local activity recordings and discuss the potential role of effective, correlated interactions during perceptual awareness.

Intracranial markers of conscious face perception in humans

“…In the last couple of decades, the relationships between brain activity and the contents of perceptual consciousness have been investigated using a variety of experimental techniques operating at different spatial and temporal scales, from single-unit, multi-unit and local field potential recordings in monkeys (Logothetis and Schall, 1989; Leopold and Logothetis, 1996; Wilke et al, 2006; Maier et al, 2007; Wilke et al, 2009), to non-invasive neuroimaging techniques such as EEG, MEG and fMRI in humans (e.g., (Tong et al, 1998; Grill-Spector et al, 2000; Dehaene et al, 2001; van Aalderen-Smeets et al, 2006; Liu et al, 2012; Schurger et al, 2015)) (see (Rees et al, 2002; Tononi and Koch, 2008; Dehaene and Changeux, 2011; Boly et al, 2013; Panagiotaropoulos et al, 2014) for reviews).…”

Perceptual awareness and its neural basis: bridging experimental and theoretical paradigms

“…The approach of Varela and collaborators has stressed coherent oscillatory patterns in the thalamo-cortical system in the gamma range (see also [32,55,85]). This view has been supported by the compelling findings of electroencephalographic patterns related to subjective awareness of visual stimuli [84].…”

“…Some of the contributed articles with a neuroscientific focus emphasize (visual) cortical systems (pathways), with a revised functional perspective [14], whereas others, with a neurodynamic emphasis [25,32], also refer to interactions between visual cortex and the thalamus, with special reference to the pulvinar, a collection of higher order associative thalamic nuclei, of which the functional importance for perceptual awareness and attention is increasingly recognized.…”

“…It comprises contributions focused on advances about more 'classical' aspects of perceptual awareness, such as visual masking [14], binocular rivalry [29,32], the roles of attention [25,38] and conscious access, such as inattentional blindness and attentional blink [25], and others stressing new interesting directions to explore, such as the cyclic (discrete) nature of perception in vision versus audition [56], multisensory awareness [92] and the role of internal body representations for enabling subjectivity in perceptual experiences [93]. Visual search findings and theories are also considered [25].…”

Pain Perception Within Consciousness

“…For example, if a conscious patient with a fully functioning nervous system undergoes an operation without a general anesthetic, the stimulation sent to the brain at the commencement of the operation would result in pain because of the existence of a stimulus (the incision) causing a sensation (a biochemical impulse generated at the nerve endings or pain receptors on the skin)that travels from the incision to the cerebrum (Hartwigsen et al, 2010;Panagiotaropoulos et al, 2014) where it is interpreted and perceived, resulting in a conscious emotional reaction. If this same patient undergoes the same surgery under general anesthesia, painful sensation of the operation would still travel to the cerebrum but the brain's ability to perceive the stimulus and subsequently to experience pain would be eliminated because the patient is in unconscious state regardless of the cause of unconsciousness, either an anesthetic, or hypoxia or ischemia to the brain.…”