Is conscious awareness needed for all working memory processes?

Stein and colleagues argue there is no yet conclusive evidence for nonconscious working memory (WM) and that is critical to probe WM while ensuring null sensitivity to memory cues. While this stringent approach reduces the likelihood of nonconscious signaling for WM, we discuss existing work meeting this null sensitivity criteria, and, related work on nonconscious cognition in keeping with WM/awareness dissociations on the basis of a functional operational definition of WM. Further, because it is likely that WM is a nonunitary functional construct and visual awareness a gradual phenomenon, we propose that delineating the neural mechanisms for distinct WM types across different levels of awareness may prove the most fruitful approach for understanding the interplay between WM and consciousness

Investigating via Transcranial Magnetic Stimulation (TMS) the interaction between Visual Short Term Memory (VSTM) and mental imagery in the Early Visual Cortex (EVC).

Visual mental imagery and visual short term memory are often assumed to play similiar roles. There are many evidence showing that they both involve visual cortical neurons which encode incoming sensory information. On the cognitive level it has been explained in terms of the visual cache, which is nvolved in the maintenance of visual short term memory and imagery content. Even though menatl imagery and visual short term memroy may share cogntive resources, they are nevertheless two distinct psychological processes that can be dissociated behaviorally. In this study, we wanted to see if those two processes diverges in early visual cortex. To be able to do it, we used transcranial magnetic stimualtion as a probe of visual cortical activation state. Experiment consists of three diffrent blocks: VSTM alone, mental imagery alone and concurrent VSTM and imagery. The concurrent condition was carried out to understand how imagery and VSTM might interact when they are engaged simultaneously

Interaction between visual perception and mental representations of imagery and memory in the early visual areas

The relationship between mental representations based on external visual percepts (i.e., information held in short-term memory or via mental imagery) and the encoding of visual input remains unsettled. What stimulates this debate is the share of overlapping neural resources between visual short-term memory (VSTM), mental imagery and visual perception in the realm of the early visual cortex (EVC). This overlap raises a number of questions: how do the internal memory and imagery representations affect the perception of incoming visual information? What happens to imagery and VSTM abilities when cognitive resources need to be shared with the encoding of visual input? In short: how do visual memory/imagery and visual perception interact? This work addressed these questions by the use of behavioral paradigms coupled with transcranial magnetic stimulation (TMS) in situations where the encoding of the visual percept (measured via the tilt after effect (TAE) magnitude) happens either simultaneously or subsequently to holding information in VSTM/imagery. Therefore, when VSTM and the encoding of external input occurred concurrently, VSTM maintenance was found to inhibit visual encoding, reflected as a reduction of the TAE. Using TMS, it was shown that this inhibition takes place at the level of EVC. This reduction was found when the VSTM content matched the visual input, and when they were incongruent. However, when the encoding of external input occurred after VSTM maintenance phase had ended, VSTM maintenance was found to facilitate the former when the VSTM content matched the visual input. The subjective strength and the contrast of VSTM and mental imagery content (as reported by participants) affect visual detection of a briefly presented masked target. The reported visual contrast was positively associated with reporting target presence for both VSTM and mental imagery, in other words, inducing a more liberal bias. However, a differential effect was found for the subjective strength of the representations. Whereas the subjective VSTM strength was positively associated with the visual detection of the target, the opposite effect was observed for imagery. Finally, TMS applied at the EVC revealed a partial dissociation in the neural basis of VSTM and mental imagery by inducing delayed responses for the former selectively. Thus, while VSTM and mental imagery share neural resources, their neural mechanisms are partly dissociable at the level of early visual cortex.Many items constitute the visual environment. However, only those of relevance are maintained in mind. Once retained, the information will be kept active in the brain for a certain time. Therefore, the question that arises is, would this information, held in mind, have any simultaneous or subsequent effect on a real-time visual perception. This Work addressed this question by using simple tasks during which people where asked to memorize or imagine some shapes and subsequently or simultaneously perceive objects. Within the task, a non-invasive stimulation technique, known by transcranial magnetic stimulation (TMS), was applied. Therefore, participants received few magnetic pulses on their skull while performing the task. The results show that when information is held in mind while perceiving objects, the precision of the visual perception is reduced. This reduction is observed regardless of whether the percept is identical to that of the information held in mind. However, this is not the case when visual perception happens only after ceasing to hold information in mind. In this situation, a reduction of the precision of visual perception was found only when both information previously held in mind and the perceived to-be object were non-identical. The opposite pattern of results was observed when both were identical. Additionally, the processes of imaging and memorizing objects were found to have different effects on subsequent visual perception. Thus, whereas the subjective memory strength was positively associated with the visual detection of objects, the opposite effect was observed for imagery. Also TMS added to this discrepancy by affecting the speed of memory and imagery processes differently

Is there evidence for non-conscious processing in working memory?

Working Memory can be conceived as a mental workspace holding and manipulating a limited amount of recently acquired information for a limited time. Some theories assume that it is tightly coupled with Consciousness (e.g., Baars & Franklin, 2003), commonly defined in experimental studies as the ability to report the content of perception or of memory. Other theories posit that working memory includes cognitive processes of which participants are not conscious (e.g., Soto et al., 2011; Logie, 2016), and can be activated without conscious intention (Hassin et al., 2009). Here, I describe experimental work designed to investigate the possible implicit activation of working memory without awareness. Importantly, participants were not only unaware of the stimuli that might be held in working memory, but also unaware that such stimuli were being presented at all. They were asked to guess which one of four cards presented on the screen was the winning one; one card was subliminally primed before a retention interval (which could vary between 500, 1000, 2000 and 5000 ms). The winner, on each trial, was chosen from amongst four blue cards, one of which had been primed, without awareness, by a card of a different colour (red or green) using Continuous Flash Suppression or Backward Masking. Bayesian and classical analyses from nine experiments mostly support the null hypothesis, thus indicating that working memory was not engaged in performing this task. Two conceptual replications and four exact replications of the original study by Soto et al. (2011), also failed in reproducing the original results. In conclusion, this collection of fifteen experiments encompassing different manipulations shows the absence of non-conscious WM retention, questioning the generalisability of previous studies showing non-conscious WM

The role of distractor strength in visual working memory

U posljednjih desetak godina, spoznaje o funkcioniranju vidnog radnog pamćenja (VRP) iz temelja su promijenjene pojavom modela resursa VRP-a. Pretpostavka ove skupine modela jest kako je VRP ograničen skup resursa koji se kontinuirano dijeli između svih podražaja koji se pamte, bez pretpostavke o postojanju limita u broju podražaja na koje se resursi mogu podijeliti. Porastom broja podražaja koji se pamti smanjuje se količina resursa pridana svakom podražaju, a samim time i reprezentacijska snaga svakog podražaja. Ova pretpostavka potvrđena je nalazima kako preciznost dosjećanja kontinuirano pada s porastom broja podražaja koji se pamti. Premda modeli resursa imaju jasne pretpostavke o ulozi količine resursa kojom je neki podražaj kodiran u preciznosti dosjećanja, otpornost snažnijih reprezentacija na perceptivne distraktore gotovo je neistraženo pitanje. Intuitivno, mogućnost zadržavanja zapamćenih informacija uslijed distraktora ovisi o snazi reprezentacija tih informacija, pri čemu će snažnije reprezentacije u manjoj mjeri biti narušene distraktorima. Druga važna odrednica otpornosti reprezentacija VRP-a na perceptivne distraktore je snaga samih distraktora. U ovom istraživanju željeli smo sustavno ispitati ulogu ova dva čimbenika - snage distraktora i snage reprezentacija u VRP-u - na preciznost dosjećanja u zadatku kontinuirane procjene u VRP-u. U eksperimentu 1 snaga reprezentacije manipulirana je variranjem broja podražaja koji se pamtio i dostupnim vremenom kodiranja. U eksperimentu 2a nakon kodiranja podražaja jednom je podražaju dan prioritet za dosjećanje. U eksperimentu 2b tijekom faze zadržavanja pažnja je privremeno usmjerena na jedan od zapamćenih podražaja s ciljem osvježavanja njegove reprezentacije. U posljednjem, eksperimentu 3, distraktori su prikazivani tijekom različitih faza obrade podražaja (kodiranja, zadržavanja, dosjećanja) uz pretpostavku kako je snaga reprezentacije najslabija prije no što kodiranje završi. Snaga perceptivnih distraktora u svim eksperimentima manipulirana je kao vrijeme prikaza distraktora i to na tri razine (bez distraktora, slabi distraktor, snažni distraktor). Rezultati su pokazali kako snaga reprezentacije ima važnu ulogu u zaštiti reprezentacije od distraktora. Dosjećanje podražaja kojima je pridano više resursa uslijed pamćenja manjeg broja podražaja i dužeg vremena kodiranja (eksperiment 1), koji su označeni kao prioritetni za dosjećanje (eksperiment 2a), koji su osvježeni tijekom faze zadržavanja (eksperiment 2b), te kojima faza kodiranja nije ometena (eksperiment 3), bilo je preciznije i uslijed prikaza distraktora. Uloga snage distraktora je potvrđena, no bila je kompleksna i ovisila je o na cinu na koji su reprezentacije osvježene. Model mješovitih distribucija koji pretpostavlja kako se dosjećanje može opisati točnim dosjećanjima, pogreškama zamjene, intruzijama i pogađanjem, dobro je pristajao podacima. Najkonzistentnije promjene uočene su u vjerojatnosti točnog dosjećanja. Važno, intruzije su se pokazale sastavnom vrstom pogrešaka u svim eksperimentima.Introduction Our environment is overloaded with visual information, with only a fraction of them necessary for an ongoing task. What determines the success of performing everyday tasks in such an environment? Visual working memory (VWM) is considered a vital component of most complex behaviours, but previous studies provided evidence of its susceptibility to irrelevant visual information, i.e. distractors. When is VWM impervious to distractors? VWM is best described as a highly limited resource that is flexibly shared among items in a visual scene. As the number of items increases, the amount of resources allocated to each item decreases, leading to a decline in strength (i.e. quality) of memory representations, and consequently to less precise recall of each item. This finding is consistent with a resource model of VWM and has been highlighted as a hallmark observation in VWM studies. An alternative view is provided by the influential "slot" model of VWM which claims that VWM is limited with a fixed maximum number of items that can be held in memory at one time. Moreover, according to this model, an item is either represented in its entirety in a memory slot or not stored at all. Strength of memory representation is therefore almost completely neglected in this type of model. However, investigation of the role of representation strength, besides the well known set size effect, has been limited even in studies motivated by the resource model. It is an intuitive prediction that memorandum strength should influence task performance. For example, our ability to maintain relevant information in the presence of distracting visual input should depend on the strength of memoranda, with stronger representations suffering less from irrelevant visual input. Here we thoroughly investigated the roles of strength of representations in VWM and distractor strength. Method To this end, we conducted four experiments (N = 64) in which we systematically manipulated the strength of VWM representations and the strength of distractors. We employed a delayedestimation task with continuous report, wherein subjects memorized colour stimuli. We manipulated strength of representation by: manipulating set size and encoding time (experiment 1), prioritizing one item for recall (experiment 2a), refreshing a representation of a single item during maintenance (experiment 2b), or interrupting memory phases before and after a stable representation was formed (experiment 3). After showing a memory array but before recalling one of the memorized items, irrelevant visual stimuli were shown. Simultaneously with memoranda strength, we manipulated distractor strength (no distractors, weak distractors, strong distractors). Results In all experiments we consistently found evidence that strength of memoranda serves a protective role against visual distractors. Regardless of the method used to manipulate memoranda strength, recall of stronger memoranda was less vulnerable to distractors. On the other hand, the effect of distractor strength showed a complex pattern which differed between experiments and depended on the manipulation of VWM representation strength. Next, we fit the data with a mixture model which assumes that the recall error distribution is a mixture of target recall, swap errors, intrusions, and guesses. This model captured the data well and showed better fit than the alternative normal + uniform model. When analyzing parameters of this model the most consistent manipulation dependent changes were observed on the target recall parameter. Intrusions were observed in all experiments. Interestingly, they depended more on VWM representation strength than on distractor strength. Conclusion This study revealed that strength of memoranda in VWM serves a protective role against visual distractors, making any addition of mechanisms of memoranda protection or distractor inhibition unnecessary. However, we showed that distractors, regardless of their strength, are able to penetrate VWM and lead to a decrease in recall precision. These findings are consistent with a resource conceptualisation of VWM where representational strength (i.e. the amount of allocated resources) plays a crucial role in ability to perform a task