Consciousness and the prefrontal parietal network: insights from attention, working memory, and chunking

Abstract

Consciousness has of late become a "hot topic" in neuroscience. Empirical work has centered on identifying potential neural correlates of consciousness (NCCs), with a converging view that the prefrontal parietal network (PPN) is closely associated with this process. Theoretical work has primarily sought to explain how informational properties of this cortical network could account for phenomenal properties of consciousness. However, both empirical and theoretical research has given less focus to the psychological features that may account for the NCCs. The PPN has also been heavily linked with cognitive processes, such as attention. We describe how this literature is under-appreciated in consciousness science, in part due to the increasingly entrenched assumption of a strong dissociation between attention and consciousness. We argue instead that there is more common ground between attention and consciousness than is usually emphasized: although objects can under certain circumstances be attended to in the absence of conscious access, attention as a content selection and boosting mechanism is an important and necessary aspect of consciousness. Like attention, working memory and executive control involve the interlinking of multiple mental objects and have also been closely associated with the PPN. We propose that this set of cognitive functions, in concert with attention, make up the core psychological components of consciousness. One related process, chunking, exploits logical or mnemonic redundancies in a dataset so that it can be recoded and a given task optimized. Chunking has been shown to activate PPN particularly robustly, even compared with other cognitively demanding tasks, such as working memory or mental arithmetic. It is therefore possible that chunking, as a tool to detect useful patterns within an integrated set of intensely processed (attended) information, has a central role to play in consciousness. Following on from this, we suggest that a key evolutionary purpose of consciousness may be to provide innovative solutions to complex or novel problems.

Keywords: attention; chunking; consciousness; parietal cortex; prefrontal cortex; theory; working memory.

Figure 1

Schematic illustration of possible relationships between attention and consciousness, with notable experimental examples. Note that although the lower example is taken by some as evidence for the independence of attention and consciousness, it is instead possible that in this and all other cases there is a strong positive correlation between attention and consciousness.

Figure 2

Adaptation of model of attention as formulated by Knudsen (2007) to incorporate consciousness. Bottom-up attention initially processes sensory input according to low level and biologically salient filters. This data is then compared with long-term memory representations, current goals, and other internal states, in order to assign weightings for an attentional competitive selection process. The result of this process leads to the strongest signals being favorably activated, with others inhibited. Those items gaining sufficient excitation will enter consciousness. Conscious contents, which are maintained in working memory in the model, can also be influenced by a recurrent loop with top-down attention biasing weightings for competitive selection. According to this model, it is possible for both top-down and bottom-up attention to occur for unconscious items (for instance by modulating expectations without the object of those expectations having sufficient strength in the subsequent competitive selection process to reach consciousness). However, conscious access for a given object is only possible following an attentional competitive selection process, which can be modulated by top-down and/or bottom-up weightings.