Neuronal Discharges and Gamma Oscillations Explicitly Reflect Visual Consciousness in the Lateral Prefrontal Cortex

Abstract

Neuronal discharges in the primate temporal lobe, but not in the striate and extrastriate cortex, reliably reflect stimulus awareness. However, it is not clear whether visual consciousness should be uniquely localized in the temporal association cortex. Here we used binocular flash suppression to investigate whether visual awareness is also explicitly reflected in feature-selective neural activity of the macaque lateral prefrontal cortex (LPFC), a cortical area reciprocally connected to the temporal lobe. We show that neuronal discharges in the majority of single units and recording sites in the LPFC follow the phenomenal perception of a preferred stimulus. Furthermore, visual awareness is reliably reflected in the power modulation of high-frequency (>50 Hz) local field potentials in sites where spiking activity is found to be perceptually modulated. Our results suggest that the activity of neuronal populations in at least two association cortical areas represents the content of conscious visual perception.

What is consciousness, and could machines have it?

“…As a result, the same physical stimulus can lead to distinct subjective percepts. This example illustrates a prefrontal neuron sensitive to faces and unresponsive to checkers, whose firing shoots up in tight association with the sudden onset of subjective face perception (31). (Bottom) During masking, a flashed image, if brief enough and followed by a longer "mask, " can remain subjectively invisible.…”

“…For instance, rivaling pictures or ambiguous words are perceived in an all-or-none manner; at any given time, we subjectively perceive only a single interpretation out of many possible ones [even though the others continue to be processed unconsciously (31,32)]. The serial operation of consciousness is attested by phenomena such as the attentional blink and the psychological refractory period, in which conscious access to a first item A prevents or delays the perception of a second competing item B (9,27,30,(33)(34)(35).…”

“…Nonhuman primates exhibit similar visual illusions (31,32), attentional blink (42), and central capacity limits (43) as human subjects. The prefrontal cortex appears to act as a central information sharing device and serial bottleneck in both human and nonhuman primates (43).…”

A Common Mechanism for Perceptual Reversals in Motion-Induced Blindness, the Troxler Effect, and Perceptual Filling-In

“…Illusory disappearances are an especially interesting class of multistable images as they can occur during natural viewing without any overt manipulation to the stimulus, and thus offer a unique tool for studying visual awareness (Libedinsky & Livingstone, 2011;Panagiotaropoulos et al, 2012). To better understand what underlies the nature of illusory disappearances, the present study explored three specific phenomena: MIB, the TE, and PFI.…”

“…By understanding the nature of how such multistable percepts alternate, it is possible to gain insight into the underlying mechanisms of perception and cognition. Studying the pattern of reversals between competing multistable percepts provides a tangible means to uncover the mechanisms of inhibition, adaptation, and attention that shape the content of human consciousness and have featured prominently in cognitive neuroscience in the last two decades or so (e.g., Blake, 2001;Chong & Blake, 2006;Leopold & Logothetis, 1999;Meng & Tong, 2004;Panagiotaropoulos, Deco, Kapoor, & Logothetis, 2012;Panagiotaropoulos, Kapoor, Logothetis, & Deco, 2013;Parkkonen, Andersson, Ha¨ma¨la¨inen, & Hari, 2008;Srinivasan, Russell, Edelman, & Tononi, 1999;Tong, Meng, & Blake, 2006). Moreover, perceptual alternations have contributed to clarifying the link between visual awareness and oscillatory brain activity (Matsuzaki, Juha´sz, & Asano, 2012;Sokoliuk & VanRullen, 2013) which is thought to be responsible for the temporal structure of conscious perception (Jensen, Bonnefond, & VanRullen, 2012).…”