Advances in neuroscience implicate reentrant signaling as the predominant form of communication between brain areas. This principle was used in a series of masking experiments that defy explanation by feed-forward theories. The masking occurs when a brief display of target plus mask is continued with the mask alone. Two masking processes were found: an early process affected by physical factors such as adapting luminance and a later process affected by attentional factors such as set size. This later process is called (...) masking by object substitution, because it occurs whenever there is a mismatch between the reentrant visual representation and the ongoing lower level activity. Iterative reentrant processing was formalized in a computational model that provides an excellent fit to the data. The model provides a more comprehensive account of all forms of visual masking than do the long-held feed-forward views based on inhibitory contour interactions. (shrink)

Using masking techniques combined with electrophysiological recordings is a promising way to study neural correlates of visual awareness, as shown in recent studies. Here I comment on the following puzzling aspects typical for this endeavour that have made obstacles for a potentially even more impressive progress. First, the continuing practice of confounds between objective stimulus variables and subjective dependent measures. Second, complexity of timing the emergence of subjective conscious percept which is partly due to complex interactivity between target and mask. (...) Third, the ambiguity of the concept of neural correlates of awareness. (shrink)

Over the past decade, many findings in cognitive about the contents of consciousness: we will not address neuroscience have resulted in the view that selective what might be called the ‘enabling factors’ for conscious- attention, working memory and cognitive control ness (e.g. appropriate neuromodulation from the brain- stem, etc.). involve competition between widely distributed rep-.

The currently leading cognitive theory of consciousness, Global Workspace Theory,1,2 postulates that the primary functions of consciousness include a global broadcast serving to recruit internal resources with which to deal with the current situation and to modulate several types of learning. In addition, conscious experiences present current conditions and problems to a "self" system, an executive interpreter that is identifiable with brain structures like the frontal lobes and precuneus.1Be it human, animal or artificial, an autonomous agent3 is said to be (...) functionally conscious if its control structure (mind) implements Global Workspace Theory and the LIDA Cognitive Cycle, which includes unconscious memory and control functions needed to integrate the conscious component of the system. We would therefore consider humans, many animals4 and even some virtual or robotic agents5,6 to be functionally conscious. Such entities may approach phenomenal consciousness, as found in human and other biological brains, as additional brain-like features are added.Here we argue that adding mechanisms to produce a stable, coherent perceptual field7 in a LIDA controlled mobile robot might provide a small but significant step toward phenomenal consciousness in machines.>8 We also propose that implementing several of the various notions of self in such a LIDA controlled robot may well prove another step toward phenomenal consciousness in machines. (shrink)

If successive, brief visual images are exposed for recognition or for psychophysical ratings, various effects and phenomena of fast dynamics of conscious perception such as mutual masking, metacontrast, proactive enhancement of contrast, proactive speed-up of the latency of subjective visual experience, the Fröhlich Effect, the Tandem Effect, attentional facilitation by visuospatial precuing, and some others have been found. The theory proposed to deal with these phenomena proceeds from the assumption that two types of brain processes are necessary in order to (...) consciously recognize visual stimuli: fast, specific processes of encoding that allocate and reactivate the stimulus representation which is based on the activity of selected cortical neurons and relatively slower processes of facilitation of the activity of this specific representation that are mediated by the excitatory modulation of the EPSPs of those selected cortical neurons by the ascending input from nonspecific thalamus. Theperceptual retouchconstruct is proposed in order to characterize and analyze the interaction of and . The neurophysiological characteristics of this bifunctional system of afference help to put forward several predictions that are found to be consistent with the empirical regularities of the above-described perceptual-attentional phenomena. These data form a body of converging evidence that is consistent with the predictions of the perceptual retouch approach. (shrink)

A recent theoretical emphasis on complex interactions within neural systems underlying consciousness has been accompanied by proposals for the quantitative characterization of these interactions. Here, we distinguish key aspects of consciousness that are amenable to quantitative measurement from those that are not. We carry out a formal analysis of the strengths and limitations of three quantitative measures of dynamical complexity in the neural systems underlying consciousness: neural complexity, information integration, and causal density. We find that no single measure fully captures (...) the multidimensional complexity of these systems and all have practical limitations. Our analysis suggests guidelines for the specification of alternative measures which, in combination, may improve the quantitative characterization of conscious neural systems. Given that some aspects of consciousness are likely to resist quantification altogether, we conclude that a satisfactory theory is likely to be one that combines both qualitative and quantitative elements. (shrink)

The development of the issue of binding as fundamental to neural dynamics has made possible recent advances in the modeling of difficult problems of perception and brain function. Among them is perceptual segmentation, invariant pattern recognition and one-shot learning. Also, longer-term conceptual developments that have led to this success are reviewed.