Nonconscious information can be identified as task-relevant but not prioritized in working memory

Two critical features of working memory are the identification and appropriate use of task-relevant information while avoiding distraction. Here, in 3 experiments, we explored if these features can be achieved also for nonconscious stimuli. Participants performed a delayed match-to-sample task in which task relevance of 2 competing stimuli was indicated by a cue, and continuous flash suppression was used to manipulate the conscious/nonconscious visual experience. Experiment 1 revealed better-than-chance performance with nonconscious stimuli, demonstrating goal-directed use of nonconscious task-relevant information. Experiment 2 demonstrated that the cue that defined task relevance must be conscious to allow such goal-directed use. In Experiment 3, multi-voxel pattern analyses of brain activity revealed that only the target was prioritized and maintained during conscious trials. Conversely, during nonconscious trials, both target and distractor were maintained. However, decoding of task relevance during the probe/test phase demonstrated identification of both target and distractor information. These results show that identification of task-relevant information can operate also on nonconscious material. However, they do not support the prioritization of nonconscious task-relevant information, thus suggesting a mismatch in the attentional mechanisms involved during conscious and nonconscious working memory.

Humans, fish, spiders and bees inherited working memory and attention from their last common ancestor

All brain processes that generate behaviour, apart from reflexes, operate with information that is in an "activated" state. This activated information, which is known as working memory (WM), is generated by the effect of attentional processes on incoming information or information previously stored in short-term or long-term memory (STM or LTM). Information in WM tends to remain the focus of attention; and WM, attention and STM together enable information to be available to mental processes and the behaviours that follow on from them. WM and attention underpin all flexible mental processes, such as solving problems, making choices, preparing for opportunities or threats that could be nearby, or simply finding the way home. Neither WM nor attention are necessarily conscious, and both may have evolved long before consciousness. WM and attention, with similar properties, are possessed by humans, archerfish, and other vertebrates; jumping spiders, honey bees, and other arthropods; and members of other clades, whose last common ancestor (LCA) is believed to have lived more than 600 million years ago. It has been reported that very similar genes control the development of vertebrate and arthropod brains, and were likely inherited from their LCA. Genes that control brain development are conserved because brains generate adaptive behaviour. However, the neural processes that generate behaviour operate with the activated information in WM, so WM and attention must have existed prior to the evolution of brains. It is proposed that WM and attention are widespread amongst animal species because they are phylogenetically conserved mechanisms that are essential to all mental processing, and were inherited from the LCA of vertebrates, arthropods, and some other animal clades.

Neuroscientific Evidence for Processing Without Awareness

The extent to which we are affected by perceptual input of which we are unaware is widely debated. By measuring neural responses to sensory stimulation, neuroscientific data could complement behavioral results with valuable evidence. Here we review neuroscientific findings of processing of high-level information, as well as interactions with attention and memory. Although the results are mixed, we find initial support for processing object categories and words, possibly to the semantic level, as well as emotional expressions. Robust neural evidence for face individuation and integration of sentences or scenes is lacking. Attention affects the processing of stimuli that are not consciously perceived, and such stimuli may exogenously but not endogenously capture attention when relevant, and be maintained in memory over time. Sources of inconsistency in the literature include variability in control for awareness as well as individual differences, calling for future studies that adopt stricter measures of awareness and probe multiple processes within subjects.

The Essential Role of Executive Attention in Unconscious Visuomotor Priming

Many reports have emphasized that unconscious processing demands attention. However, some studies were unable to observe a modulation of attentional load in subliminal visual processing. We proposed that the paradoxical phenomena could be explained based on whether the mental workload task was involved in central executive processes. In two experiments, by combining a masked shape discrimination task with an N-back task, executive attention availability for masked visuomotor processing decreased as the N-back task demand increased. We observed that unconscious visuomotor priming diminished with increasing executive attention load in Experiment 2; however, this pattern did not occur in Experiment 1. Further analysis verified that in Experiment 1, the role of the central executive in unconscious visuomotor priming was eliminated by the accuracy-speed trade-off since the higher load spatial N-back tasks with larger memory set sizes, compared with higher load verbal N-bask tasks, were quite difficult for the subjects to manage. Therefore, our results demonstrated that central executive load modulates unconscious visuomotor priming and that this modulation can be weakened by task difficulty. Collectively, by emphasizing the essential role of executive attention in subliminal visuomotor priming, the present work provides a powerful interpretation of prior debates and develops extant attention capacity limitations from the realm of consciousness to that of unconsciousness.

Unconscious Visual Working Memory: A critical review and Bayesian meta-analysis

The relationship between consciousness and working memory (WM) has been recently debated both at the theoretical and methodological levels (Persuh et al., 2018; Velichkovsky, 2017). While there is behavioral and neural evidence that argues for the existence of unconscious WM, several methodological concerns have been raised, rendering this issue highly controversial. To address the robustness of the previous findings, here we adopt a meta-analytic approach to estimate the effect size and heterogeneity of the previously reported unconscious WM results, also including unpublished results. We used meta-regression to isolate relevant experimental variables, in particular, consciousness manipulation and the WM paradigm to identify the source of the heterogeneity in the reported effect size of the unconscious WM. Our meta-analysis supports the existence of the unconscious WM effect and critically reveals several experimental variables that contribute to relevant heterogeneity. Our analysis clarifies several theoretical and methodological issues. We recommend that future studies explicitly operationalize the definition of consciousness, standardize the methodology and systematically explore the role of critical variables for the unconscious WM effect.

Unconscious priming shares a common resource pool with the manipulation subsystem

Background

Working memory can be subdivided into two relatively independent subordinate systems, the maintenance subsystem and the manipulation subsystem. Although the two subsystems are quite heterogeneous, research thus far has not adequately distinguished the resource pools of the two subsystems. Additionally, previous research on the relationship between working memory and unconscious priming is paradoxical. Different subsystems leading to different effects on unconscious priming might be the reason for the paradoxical research. Therefore, the current article aimed to distinguish the resource pools among two working-memory subsystems and to investigate the relationship between the two subsystems and unconscious priming.

Methods

To address these issues, a maintenance dual-task and a manipulation dual-task program were developed. Each participant had to separately perform the two dual tasks in a balanced order. In each dual task, participants first completed a masked priming task accompanied by working-memory load. As a control, participants completed a prime identification test to confirm that the processing of the masked prime was at the unconscious level. The maintenance dual task comprised sandwich masking trials accompanied by Sternberg trials, while the manipulation dual task comprised sandwich masking trials accompanied by N-back trials.

Results

The results of the prime identification test indicated that the participants could not consciously perceive the masked prime of both dual tasks. The results of the working-memory task of both dual tasks indicated that the load manipulation was successful for both dual tasks. Most importantly, the results of the masking task of both dual tasks showed that an increase in working-memory load decreased the magnitude of unconscious priming in the manipulation dual task, whereas an increase in working-memory load did not decrease unconscious priming in the maintenance dual task. These observations demonstrate that the manipulation subsystem, rather than the maintenance subsystem, interferes with unconscious priming. Together with previous research, we propose a two-pool attention resource model to explain the modulation of working memory on unconscious priming by dissociating the executive resource pool of the manipulation system from the retention resource pool of the maintenance system. Thus, the current work confirms and extends the extant literature about the dependence of unconscious processing on attention resources by suggesting that unconscious priming shares a common resource pool with the manipulation subsystem.

Larger capacity for unconscious versus conscious episodic memory

Episodic memory is the memory for experienced events. A peak competence of episodic memory is the mental combination of events to infer commonalities. Inferring commonalities may proceed with and without consciousness of events. Yet what distinguishes conscious from unconscious inference? This question inspired nine experiments that featured strongly and weakly masked cartoon clips presented for unconscious and conscious inference. Each clip featured a scene with a visually impenetrable hiding place. Five animals crossed the scene one-by-one consecutively. One animal trajectory represented one event. The animals moved through the hiding place, where they might linger or not. The participants' task was to observe the animals' entrances and exits to maintain a mental record of which animals hid simultaneously. We manipulated information load to explore capacity limits. Memory of inferences was tested immediately, 3.5 or 6 min following encoding. The participants retrieved inferences well when encoding was conscious. When encoding was unconscious, the participants needed to respond intuitively. Only habitually intuitive decision makers exhibited a significant delayed retrieval of inferences drawn unconsciously. Their unconscious retrieval performance did not drop significantly with increasing information load, while conscious retrieval performance dropped significantly. A working memory network, including hippocampus, was activated during both conscious and unconscious inference and correlated with retrieval success. An episodic retrieval network, including hippocampus, was activated during both conscious and unconscious retrieval of inferences and correlated with retrieval success. Only conscious encoding/retrieval recruited additional brain regions outside these networks. Hence, levels of consciousness influenced the memories' behavioral impact, memory capacity, and the neural representational code.

Strongly masked content retained in memory made accessible through repetition

A growing body of evidence indicates that information can be stored even in the absence of conscious awareness. Despite these findings, unconscious memory is still poorly understood with limited evidence for unconscious iconic memory storage. Here we show that strongly masked visual data can be stored and accumulate to elicit clear perception. We used a repetition method across a wide range of conditions (Experiment 1) and a more focused follow-up experiment with enhanced masking conditions (Experiment 2). Information was stored despite being masked, demonstrating that masking did not erase or overwrite memory traces but limited perception. We examined the temporal properties and found that stored information followed a gradual but rapid decay. Extraction of meaningful information was severely impaired after 300 ms, and most data was lost after 700 ms. Our findings are congruent with theories of consciousness that are based on an integration of subliminal information and support theoretical predictions based on the global workspace theory of consciousness, especially the existence of an implicit iconic memory buffer store.

How does the non-conscious become conscious?

In this My Word, Joseph LeDoux describes how his work as a graduate student got him interested in human consciousness. Although he has not studied this topic since 1970s, he never stopped thinking and writing about it during his four-decade career exploring how non-conscious processes involving the amygdala detect and respond to danger. Here, he tells us what is on his mind about consciousness these days.

Neuroscience of Object Relations in Health and Disorder: A Proposal for an Integrative Model

Recent advances in the neuroscience of episodic memory provide a framework to integrate object relations theory, a psychoanalytic model of mind development, with potential neural mechanisms. Object relations are primordial cognitive-affective units of the mind derived from survival- and safety-level experiences with caretakers during phase-sensitive periods of infancy and toddlerhood. Because these are learning experiences, their neural substrate likely involves memory, here affect-enhanced episodic memory. Inaugural object relations are encoded by the hippocampus-amygdala synaptic plasticity, and systems-consolidated by medial prefrontal cortex (mPFC). Self- and object-mental representations, extracted from these early experiences, are at first dichotomized by contradictory affects evoked by frustrating and rewarding interactions ("partial object relations"). Such affective dichotomization appears to be genetically hardwired the amygdala. Intrinsic propensity of mPFC to form schematic frameworks for episodic memories may pilot non-conscious integration of dichotomized mental representations in neonates and infants. With the emergence of working memory in toddlers, an activated self- and object-representation of a particular valence can be juxtaposed with its memorized opposites creating a balanced cognitive-affective frame (conscious "integration of object relations"). Specific events of object relations are forgotten but nevertheless profoundly influence the mental future of the individual, acting (i) as implicit schema-affect templates that regulate attentional priorities, relevance, and preferential assimilation of new information based on past experience, and (ii) as basic units of experience that are, under normal circumstances, integrated as attractors or "focal points" for interactive self-organization of functional brain networks that underlie the mind. A failure to achieve integrated object relations is predictive of poor adult emotional and social outcomes, including personality disorder. Cognitive, cellular-, and systems-neuroscience of episodic memory appear to support key postulates of object relations theory and help elucidate neural mechanisms of psychodynamic psychotherapy. Derived through the dual prism of psychoanalysis and neuroscience, the gained insights may offer new directions to enhance mental health and improve treatment of multiple forms of psychopathology.

The Dynamic-Processing Model of Working Memory

Recent shifts in the understanding of how the mind and brain retain information in working memory (WM) call for revision to traditional theories. Evidence of dynamic, “activity-silent,” short-term retention processes diverges from conventional models positing that information is always retained in WM by sustained neural activity in buffers. Such evidence comes from machine-learning methods that can decode patterns of brain activity and the simultaneous administration of transcranial magnetic stimulation (TMS) to causally manipulate brain activity in specific areas and time points. TMS can “ping” brain areas to both reactivate latent representations retained in WM and affect memory performance. On the basis of these findings, I argue for a supplement to sustained retention mechanisms. Brain-decoding methods also reveal that dynamic levels of representational codes are retained in WM, and these vary according to task context, from perceptual (sensory) codes in posterior areas to abstract, recoded representations distributed across frontoparietal regions. A dynamic-processing model of WM is advanced to account for the overall pattern of results.

Perceptual Representations and the Vividness of Stimulus-Triggered and Stimulus-Independent Experiences

In recent years, researchers from independent subfields have begun to engage with the idea that the same cortical regions that contribute to on-line perception are recruited during and underlie off-line activities such as information maintenance in working memory, mental imagery, hallucinations, dreaming, and mind wandering. Accumulating evidence suggests that in all of these cases the activity of posterior brain regions provides the contents of experiences. This article is intended to move one step further by exploring specific links between the vividness of experiences, which is a characteristic feature of consciousness regardless of its actual content, and certain properties of the content-specific neural-activity patterns. Investigating the mechanisms that underlie mental imagery and its relation to working memory and the processes responsible for mind wandering and its similarities to dreaming form two clusters of research that are in the forefront of the recent scientific study of mental phenomena, yet communication between these two clusters has been surprisingly sparse. Here our aim is to foster such information exchange by articulating a hypothesis about the fine-grained phenomenological structure determining subjective vividness and its possible neural basis that allows us to shed new light on these mental phenomena by bringing them under a common framework.

The Common Basis of Memory and Consciousness: Understanding the Brain as a Write-Read Head Interacting With an Omnipresent Background Field

The main goal of this article consists in addressing two fundamental issues of consciousness research and cognitive science, namely, the question of why declarative memory functions are inextricably linked with phenomenal awareness and the question of the physical basis of memory traces. The presented approach proposes that high-level cognitive processes involving consciousness employ a universal mechanism by means of which they access and modulate an omnipresent background field that is identified with the zero-point field (ZPF) specified by stochastic electrodynamics (SED), a branch of physics that deals with the universal principles underlying quantum systems. In addition to its known physical properties and memory capacities, the ZPF is hypothesized to be an immanently sentient medium. It is propounded that linking up to a particular field mode of the ZPF activates a particular phenomenal nuance, implying that the phase-locked coupling of a set of field modes, i.e., the formation of a so-called ZPF information state, constitutes an appropriate mechanism for the amalgamation of elementary shades of consciousness into a complex state of consciousness. Since quantum systems rest exactly on this mechanism, conscious memory processes in the brain are expected to differ from unconscious processes by the presence of the typical features of many-body quantum systems, particularly long-range coherence and attractor formation, which is supported by a huge body of empirical evidence. On this basis, the conceptual framework set out in this article paves the way for a new understanding of the brain as a write-read head interacting with the ZPF, leading to self-consistent interpretations of the neural correlates of memory formation and memory retrieval and explaining why these memory processes are closely intertwined with phenomenal awareness. In particular, the neural correlates suggest that the brain produces consciously perceived memory traces by writing sequences of information states into the ZPF and retrieves consciously experienced memory traces by reading sequences of information states from the ZPF. Using these theoretical foundations, altered states of consciousness and memory disorders can be traced back to impairments of the ZPF write-read mechanism. The mechanism should reveal itself through characteristic photon emissions, resulting in testable predictions.

Probing the limits of activity-silent non-conscious working memory

Two types of working memory (WM) have recently been proposed: (i) active WM, relying on sustained neural firing, and (ii) activity-silent WM, for which firing returns to baseline, yet memories may be retained by short-term synaptic changes. Activity-silent WM in particular might also underlie the recently discovered phenomenon of non-conscious WM, which permits even subliminal stimuli to be stored for several seconds. However, whether both states support identical forms of information processing is unknown. Theory predicts that activity-silent states are confined to passive storage and cannot operate on stored information. To determine whether an explicit reactivation is required before the manipulation of information in WM, we evaluated whether participants could mentally rotate brief visual stimuli of variable subjective visibility. Behaviorally, even for unseen targets, subjects reported the rotated location above chance after several seconds. As predicted, however, at the time of mental rotation, such blindsight performance was accompanied by (i) neural signatures of consciousness in the form of a sustained desynchronization in alpha/beta frequency and (ii) a reactivation of the memorized information as indicated by decodable representations of participants' guess and response. Our findings challenge the concept of genuine non-conscious "working" memory, argue that activity-silent states merely support passive short-term memory, and provide a cautionary note for purely behavioral studies of non-conscious information processing.

A Novel Framework for Unconscious Processing

Understanding the distinction between conscious and unconscious cognition remains a priority in psychology and neuroscience. A comprehensive neurocognitive account of conscious awareness will not be possible without a sound framework to isolate and understand unconscious information processing. Here, we provide a brain-based framework that allows the identification of unconscious processes, even with null effects on behaviour.

Working Memory and Consciousness: The Current State of Play

Working memory (WM), an important posit in cognitive science, allows one to temporarily store and manipulate information in the service of ongoing tasks. WM has been traditionally classified as an explicit memory system-that is, as operating on and maintaining only consciously perceived information. Recently, however, several studies have questioned this assumption, purporting to provide evidence for unconscious WM. In this article, we focus on visual working memory (VWM) and critically examine these studies as well as studies of unconscious perception that seem to provide indirect evidence for unconscious WM. Our analysis indicates that current evidence does not support an unconscious WM store, though we offer independent reasons to think that WM may operate on unconsciously perceived information.