Conscious perception in patients with prefrontal damage.

We are conscious and verbally report some of the information reaching our senses, although a big amount of information is processed unconsciously. There is no agreement about the neural correlates of consciousness, with low-level theories proposing that neural processing on primary sensory brain regions is the most important neural correlate of consciousness, while high-level theories propose that activity within the fronto-parietal network is the key component of conscious processing (Block, 2009). Contrary to the proposal of high-level theories, patients with prefrontal lobe damage do not present clinical symptoms associated to consciousness deficits. In the present study, we explored the conscious perception of near-threshold stimuli in a group of patients with right prefrontal damage and a group of matched healthy controls. Results demonstrated that perceptual contrast to perceive the near-threshold targets was related to damage to the right dorsolateral prefrontal cortex, and with reduced integrity of the ventral branch of the right superior longitudinal fascicule (SLF III). These results suggest a causal role of the prefrontal lobe in conscious processing.

Neural modulations of interference control over conscious perception.

The relation between attention and consciousness is a highly debated topic in Cognitive Neuroscience. Although there is an agreement about their relationship at the functional level, there is still no consensus about how these two cognitive processes interact at the neural level. According to the gateway hypothesis (Posner, 1994), attention filters the information accessing to consciousness, resulting in both neural and functional modulations. Contrary to this idea, the cumulative influence hypothesis (Tallon-Baudry, 2012) proposes that both attention and consciousness independently impact decision processes about the perception of stimuli. Accordingly, we could observe an interaction between attention and consciousness at the behavioral level, but not at the neural level. Previous studies have shown that alerting and orienting networks of attention modulate participants' ability to verbally report near-threshold visual stimuli both at behavioral and neural levels, supporting the gateway hypothesis over the cumulative influence hypothesis. The impact of the executive control network of attention on conscious perception, however, has only been explored behaviorally (Colás et al., 2017). In the present study, we employed high-density encephalography to investigate the neural basis of the interaction between executive attention and conscious perception. We presented a classical Stroop task concurrently with a detection task of near-threshold stimuli. In two separate sessions, we manipulated the proportion of congruent and incongruent Stroop stimuli. We found that the Stroop-evoked N2 potential (usually associated to conflict detection and localized in the anterior cingulate cortex) was modulated by both conflict detection and conscious perception processes. These results suggest that the relation between executive control and conscious perception lies in frontal lobe regions associated to conflict detection, supporting the gateway hypothesis over the cumulative influence hypothesis.

Interference Control Modulations Over Conscious Perception.

The relation between attention and consciousness has been a controversial topic over the last decade. Although there seems to be an agreement on their distinction at the functional level, no consensus has been reached about attentional processes being or not necessary for conscious perception. Previous studies have explored the relation of alerting and orienting systems of attention and conscious perception, but the impact of the anterior executive attention system on conscious access remains unexplored. In the present study, we investigated the behavioral interaction between executive attention and conscious perception, testing control mechanisms both at stimulus-level representation and after error commission. We presented a classical Stroop task, manipulating the proportion of congruent and incongruent trials, and analyzed the effect of reactive and proactive control on the conscious perception of near-threshold stimuli. Reactive control elicited under high proportion congruent conditions influenced participants' decision criterion, whereas proactive control elicited under low proportion congruent conditions was ineffective in modulating conscious perception. In addition, error commission affected both perceptual sensitivity to detect near-threshold information and response criterion. These results suggest that reactivation of task goals through reactive control strategies in conflict situations impacts decision stages of conscious processing, whereas interference control elicited by error commission impacts both perceptual sensitivity and decision stages of conscious processing. We discuss the implications of our results for the gateway hypothesis about attention and consciousness, as they showed that interference control (both at stimulus-level representation and after error commission) can modulate the conscious access of near-threshold stimuli.