Visual Memory Representations Research Articles

How do people build up visual memory representations from sensory evidence? Revisiting two classic models of choice

In many decision tasks, we have a set of alternative choices and are faced with the problem of how to use our latent beliefs and preferences about each alternative to make a single choice. Cognitive and decision models typically presume that beliefs and preferences are distilled to a scalar latent strength for each alternative, but it is also critical to model how people use these latent strengths to choose a single alternative. Most models follow one of two traditions to establish this link. Modern psychophysics and memory researchers make use of signal detection theory, assuming that latent strengths are perturbed by noise, and the highest resulting signal is selected. By contrast, many modern decision theoretic modeling and machine learning approaches use the softmax function (which is based on Luce’s choice axiom; Luce, 1959) to give some weight to non-maximal-strength alternatives. Despite the prominence of these two theories of choice, current approaches rarely address the connection between them, and the choice of one or the other appears more motivated by the tradition in the relevant literature than by theoretical or empirical reasons to prefer one theory to the other. The goal of the current work is to revisit this topic by elucidating which of these two models provides a better characterization of latent processes in m-alternative decision tasks, with a particular focus on memory tasks. In a set of visual memory experiments, we show that, within the same experimental design, the softmax parameter β varies across m-alternatives, whereas the parameter d′ of the signal-detection model is stable. Together, our findings indicate that replacing softmax with signal-detection link models would yield more generalizable predictions across changes in task structure. More ambitiously, the invariance of signal detection model parameters across different tasks suggests that the parametric assumptions of these models may be more than just a mathematical convenience, but reflect something real about human decision-making.

Uncovering the dynamics of visual memory representations over time

Uncovering the dynamics of visual memory representations over time

Repetition enhances the effects of activated long-term memory.

Recent research indicates that visual long-term memory (vLTM) representations directly interface with perception and guide attention. This may be accomplished through a state known as activated LTM, however, little is known about the nature of activated LTM. Is it possible to enhance the attentional effects of these activated representations? And furthermore, is activated LTM discrete (i.e., a representation is either active or not active, but only active representations interact with perception) or continuous (i.e., there are different levels within the active state that all interact with perception)? To answer these questions, in the present study, we measured intrusion effects during a modified Sternberg task. Participants saw two lists of three complex visual objects, were cued that only one list was relevant for the current trial (the other list was, thus, irrelevant), and then their memory for the cued list was probed. Critically, half of the trials contained repeat objects (shown 10 times each), and half of the trials contained non-repeat objects (shown only once each). Results indicated that repetition enhanced activated LTM, as the intrusion effect (i.e., longer reaction times to irrelevant list objects than novel objects) was larger for repeat trials compared with non-repeat trials. These initial findings provide preliminary support that LTM activation is continuous, as the intrusion effect was not the same size for repeat and non-repeat trials. We conclude that researchers should repeat stimuli to increase the size of their effects and enhance how LTM representations interact with perception.

Semantic interference mechanisms on long-term visual memory and their eye-movement signatures in mild cognitive impairment.

Long-term visual memory representations, measured by recognition performance, degrade as a function of semantic interference, and their strength is related to eye-movement responses. Even though clinical research has examined interference mechanisms in pathological cognitive aging and explored the diagnostic potential of eye-movements in this context, little is known about their interaction in long-term visual memory. An eye-tracking study compared a Mild Cognitive Impaired group with healthy adults. Participants watched a stream of 129 naturalistic images from different semantic categories, presented at different frequencies (1, 6, 12, 24) to induce semantic interference (SI), then asked in a 2-Alternative Forced Choice paradigm to verbally recognize the scene they remembered (old/novel). Recognition accuracy of both groups was negatively impacted by SI, especially in healthy adults. A wider distribution of overt attention across the scene predicted better recognition, especially by the Mild Cognitive Impaired (MCI) participants, although these fixation patterns were influenced by SI. MCI compensated the detrimental effect of SI by focusing overt attention during encoding and so accruing distinctive details of the scene. During recognition, MCI participants widened overt attention to boost retrieval. Independently of the group: (a) the re-instatement of fixations indicated a more successful recall and increased as a function of SI; and (b) attending visually salient regions negatively impacted on recognition accuracy, although the reliance on such regions grew as SI increased. Effects of SI on long-term memory were reduced in MCI participants. They used different oculomotor strategies compared to healthy adults to compensate for its detrimental effects. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

Attention can operate on object representations in visual sensory memory.

Numerous studies have shown that attention can be allocated to various types of objects, such as low-level objects developed by perceptual organization and high-level objects developed by semantic associations. However, little is known about whether attention can also be affected solely by object representations in the brain, after the disappearance of physical objects. Here, we used a modified double-rectangle paradigm to investigate how attention is affected by object representation in visual sensory memory when the physical objects disappear for a short period of time before the target onset. By manipulating the interstimulus interval (ISI) between the offset of the objects and the onset of the target, an object-based attention effect, with shorter reaction times (RTs) for within-object relative to between-object conditions, was observed in the short-ISI (within 500 ms in Experiments 1a, 1b, 2, and 3) conditions while disappearing in the long-ISI (800 ms in Experiment 4) conditions. This result demonstrated that the mere presence of object representation in visual sensory memory, or the sensory memory-maintained object, can serve as an object unit that attention can operate on. This provides evidence for the relationship between object-based attention and visual sensory memory: object representation in visual sensory memory could affect attentional allocation, or attention can operate on a sensory memory-maintained object.

Investigation of the relationship between visual feature binding in short- and long-term memory in healthy aging.

Binding visual features into coherent object representations is essential both in short- and long-term memory. However, the relationship between feature binding processes at different memory delays remains unexplored. Here, we addressed this question by using the Mnemonic Similarity Task and a delayed-estimation working memory task on a large sample of older adults. The results revealed that higher propensity to misbind object features in working memory is associated with lower lure discrimination performance in the mnemonic similarity task, suggesting that shared feature binding processes underlie the formation of coherent short- and long-term visual object memory representations.

Masks are memorable: ERP evidence on visual short-term memory and individuation in object substitution masking

ABSTRACT Object substitution masking (OSM) involves reduced perceptibility by a briefly lingering mask despite no spatial target-mask overlap. Two primary accounts for this phenomenon posit differences in object representation in visual short-term memory (VSTM). In the object substitution account a single representation resides in VSTM: a lone mask when attention is not focused on the target, and a lone target+mask when attention is focused on the target. The object updating account assumes individualization, with mask-alone and target+mask representations concurrently present in VSTM in correct delayed-offset OSM trials. We explored object individuation in OSM, focusing on the quantity of representations in VSTM in two OSM tasks with low (Easy Search) and high (Difficult Search) attentional demands, using event-related potentials (ERPs). Individuation was indicated in correct trials, with ERPs showing greater negativity in the sustained posterior contralateral negativity (SPCN) component for delayed compared to co-terminating offset conditions, consistent with greater VSTM load in delayed-offset. This effect, indicating target+mask and mask-alone as distinct memory representations, was found in Easy Search only. Additionally, no SPCN difference was found between correct and incorrect delayed trials in Difficult Search. We discuss our results in the context of individuation and perceptual load in OSM.

Real-World Objects Are Represented in Visual Long-Term Memory Both as Unbound Features and as Bound Objects.

Real-World Objects Are Represented in Visual Long-Term Memory Both as Unbound Features and as Bound Objects.

Quantifying aphantasia through drawing: Those without visual imagery show deficits in object but not spatial memory

Congenital aphantasia is a recently characterized variation of experience defined by the inability to form voluntary visual imagery, in individuals who are otherwise high performing. Because of this specific deficit to visual imagery, individuals with aphantasia serve as an ideal group for probing the nature of representations in visual memory, particularly the interplay of object, spatial, and symbolic information. Here, we conducted a large-scale online study of aphantasia and revealed a dissociation in object and spatial content in their memory representations. Sixty-one individuals with aphantasia and matched controls with typical imagery studied real-world scene images, and were asked to draw them from memory, and then later copy them during a matched perceptual condition. Drawings were objectively quantified by 2,795 online scorers for object and spatial details. Aphantasic participants recalled significantly fewer objects than controls, with less color in their drawings, and an increased reliance on verbal scaffolding. However, aphantasic participants showed high spatial accuracy equivalent to controls, and made significantly fewer memory errors. These differences between groups only manifested during recall, with no differences between groups during the matched perceptual condition. This object-specific memory impairment in individuals with aphantasia provides evidence for separate systems in memory that support object versus spatial information. The study also provides an important experimental validation for the existence of aphantasia as a variation in human imagery experience.

Orienting Attention to Short-Term Memory Representations via Sensory Modality and Semantic Category Retro-Cues.

There is growing interest in characterizing the neural mechanisms underlying the interactions between attention and memory. Current theories posit that reflective attention to memory representations generally involves a fronto-parietal attentional control network. The present study aimed to test this idea by manipulating how a particular short-term memory (STM) representation is accessed, that is, based on its input sensory modality or semantic category, during functional magnetic resonance imaging (fMRI). Human participants performed a novel variant of the retro-cue paradigm, in which they were presented with both auditory and visual non-verbal stimuli followed by Modality, Semantic, or Uninformative retro-cues. Modality and, to a lesser extent, Semantic retro-cues facilitated response time relative to Uninformative retro-cues. The univariate and multivariate pattern analyses (MVPAs) of fMRI time-series revealed three key findings. First, the posterior parietal cortex (PPC), including portions of the intraparietal sulcus (IPS) and ventral angular gyrus (AG), had activation patterns that spatially overlapped for both modality-based and semantic-based reflective attention. Second, considering both the univariate and multivariate analyses, Semantic retro-cues were associated with a left-lateralized fronto-parietal network. Finally, the experimental design enabled us to examine how dividing attention cross-modally within STM modulates the brain regions involved in reflective attention. This analysis revealed that univariate activation within bilateral portions of the PPC increased when participants simultaneously attended both auditory and visual memory representations. Therefore, prefrontal and parietal regions are flexibly recruited during reflective attention, depending on the representational feature used to selectively access STM representations.

Influence of outstanding object memories on gist representation in visual long-term memory

Influence of outstanding object memories on gist representation in visual long-term memory

Generating reliable visual long-term memory representations for free: Incidental learning during natural behavior

Generating reliable visual long-term memory representations for free: Incidental learning during natural behavior

Relational Interactions between Visual Memory Representations Increase with Maintenance Duration

Relational Interactions between Visual Memory Representations Increase with Maintenance Duration

Central tendency representation and exemplar matching in visual short-term memory.

I address a recent extension of the generalized context model (GCM), a model which excludes prototypes, to the visual short-term memory (VSTM) literature, which is currently deluged with prototype effects. The paper includes a brief review whose aim is to discuss the background and key findings suggesting that prototypes have an obligatory influence on visual short-term memory responses in the same VSTM task that the GCM's random walk extension, EBRW, was extended to account for: Sternberg scanning. I present a new model that incorporates such "central tendency representations" in memory, as well as several other regularities of the literature, and compare its prediction and postdictions to those of the GCM on some unpublished Sternberg scanning data. The GCM cannot account for the pattern in those data without post hoc modifications but the pattern is predicted nicely by the central tendency representation model. Although the new model is certainly wrong, the review and modeling exercise suggest a reconsideration of prototype models may be warranted, at least in the VSTM literature.

Training Enhances Fidelity of Color Representations in Visual Long-Term Memory

Visual perception can be affected by training mental representations. However, it remains unclear if training procedures can also affect the quality of mental representations. To investigate if training enhances the fidelity of mental representations retrieved from visual long-term memory (VLTM), we used a task including object-color associations with a continuous response-space. We tested 15 participants in a training group and 15 participants in a control group. Training consisted of six training runs executed on 3 consecutive days. Before and after training, we assessed accessibility and fidelity of mental representations in VLTM and of single objects in visual short-term memory (VSTM). Not only accessibility to mental representation but also their fidelity increased across training and transferred to novel object-color associations in VLTM and VSTM after training. At the end of the training, fidelity of VLTM representations were virtually identical to fidelity of VSTM representations. We conclude that training object-color associations does not only improve the accessibility of VLTM representations, but also their fidelity based on perceptual plasticity of the visual system.

Holistic face perception is impaired in developmental prosopagnosia

Individuals with developmental prosopagnosia (DP) have severe difficulties recognising familiar faces. A current debate is whether these face recognition impairments derive from problems with face perception and in particular whether individuals with DP cannot utilize holistic representations of individual faces. To assess this hypothesis, we recorded event-related potentials (ERPs) during a sequential face identity matching task where successively presented pairs of upright faces were either identical or differed with respect to their internal features, their external features, or both. Participants with DP and age-matched controls reported on each trial whether the face pair was identical or different. To track the activation of cortical visual face memory representations, we measured N250r components over posterior face-selective regions. N250r components to full face repetitions were strongly attenuated for DPs as compared to control participants, indicating impaired face identity matching processes in DP. In the Control group, the N250r to full face repetitions was superadditive (i.e., larger than the sum of the two N250r components to partial repetitions of external or internal features). This demonstrates that holistic face representations were involved in identity matching processes. In the DP group, N250r components to full and partial identity repetitions were strictly additive, indicating that the identity matching of external and internal features operated in an entirely part-based fashion, without any involvement of holistic representations. In line with this conclusion, DPs also made a disproportionate number of errors on partial repetition trials, where they often failed to report a change of internal facial features. This suggests an atypical strategy for encoding external features as cues to identity in DP. These results provide direct electrophysiological and behavioural evidence for qualitative differences in the representation of face identity in the occipital-temporal face processing system in developmental prosopagnosia.

The lower bounds of massive memory: Investigating memory for object details after incidental encoding.

Visual long-term memory capacity appears massive and detailed when probed explicitly. In the real world, however, memories are usually built from chance encounters. Therefore, we investigated the capacity and detail of incidental memory in a novel encoding task, instructing participants to detect visually distorted objects among intact objects. In a subsequent surprise recognition memory test, lures of a novel category, another exemplar, the same object in a different state, or exactly the same object were presented. Lure recognition performance was above chance, suggesting that incidental encoding resulted in reliable memory formation. Critically, performance for state lures was worse than for exemplars, which was driven by a greater similarity of state as opposed to exemplar foils to the original objects. Our results indicate that incidentally generated visual long-term memory representations of isolated objects are more limited in detail than recently suggested.

Visual Memories Bypass Normalization

How distinct are visual memory representations from visual perception? Although evidence suggests that briefly remembered stimuli are represented within early visual cortices, the degree to which these memory traces resemble true visual representations remains something of a mystery. Here, we tested whether both visual memory and perception succumb to a seemingly ubiquitous neural computation: normalization. Observers were asked to remember the contrast of visual stimuli, which were pitted against each other to promote normalization either in perception or in visual memory. Our results revealed robust normalization between visual representations in perception, yet no signature of normalization occurring between working memory stores—neither between representations in memory nor between memory representations and visual inputs. These results provide unique insight into the nature of visual memory representations, illustrating that visual memory representations follow a different set of computational rules, bypassing normalization, a canonical visual computation.

Evidence for verbal memory enhancement with electrical brain stimulation in the lateral temporal cortex.

Direct electrical stimulation of the human brain can elicit sensory and motor perceptions as well as recall of memories. Stimulating higher order association areas of the lateral temporal cortex in particular was reported to activate visual and auditory memory representations of past experiences (Penfield and Perot, 1963). We hypothesized that this effect could be used to modulate memory processing. Recent attempts at memory enhancement in the human brain have been focused on the hippocampus and other mesial temporal lobe structures, with a few reports of memory improvement in small studies of individual brain regions. Here, we investigated the effect of stimulation in four brain regions known to support declarative memory: hippocampus, parahippocampal neocortex, prefrontal cortex and temporal cortex. Intracranial electrode recordings with stimulation were used to assess verbal memory performance in a group of 22 patients (nine males). We show enhanced performance with electrical stimulation in the lateral temporal cortex (paired t-test, P = 0.0067), but not in the other brain regions tested. This selective enhancement was observed both on the group level, and for two of the four individual subjects stimulated in the temporal cortex. This study shows that electrical stimulation in specific brain areas can enhance verbal memory performance in humans.awx373media15704855796001.

Anesthesia Medication Handling Needs a New Vision.

Anesthesia Medication Handling Needs a New Vision.