Color Memory Research Articles

Cortico-hippocampal network connections support the multidimensional quality of episodic memory.

Episodic memories reflect a bound representation of multimodal features that can be reinstated with varying precision. Yet little is known about how brain networks involved in memory, including the hippocampus and posterior-medial (PM) and anterior-temporal (AT) systems, interact to support the quality and content of recollection. Participants learned color, spatial, and emotion associations of objects, later reconstructing the visual features using a continuous color spectrum and 360-degree panorama scenes. Behaviorally, dependencies in memory were observed for the gist but not precision of event associations. Supporting this integration, hippocampus, AT, and PM regions showed increased connectivity and reduced modularity during retrieval compared to encoding. These inter-network connections tracked a multidimensional, objective measure of memory quality. Moreover, distinct patterns of connectivity tracked item color and spatial memory precision. These findings demonstrate how hippocampal-cortical connections reconfigure during episodic retrieval, and how such dynamic interactions might flexibly support the multidimensional quality of remembered events.

Memory-based attentional biases survive spatial suppression driven by selection history

ABSTRACTInformation in visual working memory that is only prospectively relevant can nevertheless guide attention towards memory matching visual input. Previous studies demonstrated that such memory-based attentional biases can be modulated by top-down processing strategies. Here we examined whether attentional capture by memory matching distractors is also modulated by more implicit biases stemming from selection history. Observers performed a visual search task while holding a colour in memory for a subsequent task. Crucially, a coloured distractor in the search display not only matched the memory content half of the time, it also appeared on one location more often than on all other locations. Consistent with statistical learning having a strong impact on attentional priorities, attentional capture by the distractor was attenuated at high probability distractor locations. The additional slowing by memory matching distractors, however, was the same at suppressed and non-suppressed locations. We interpret this finding as evidence that memory-based feature biases are independent from learned spatial biases.

Can short-term memory be trained?

Is the capacity of short-term memory fixed, or does it improve with practice? It is already known that training on complex working memory tasks is more likely to transfer to untrained tasks with similar properties, but this approach has not been extended to the more basic short-term memory system responsible for verbal serial recall. Here we investigated this with adaptive training algorithms widely applied in working memory training. Serial recall of visually presented digits was found to improve over the course of 20 training sessions, but this improvement did not extend to recall of either spoken digits or visually presented letters. In contrast, training on a nonserial visual short-term memory color change detection task did transfer to a line orientation change detection task. We suggest that training only generates substantial transfer when the unfamiliar demands of the training activities require the development of novel routines that can then be applied to untrained versions of the same paradigm (Gathercole, Dunning, Holmes, & Norris, 2019). In contrast, serial recall of digits is fully supported by the existing verbal short-term memory system and does not require the development of new routines.

A Novel Test of Pure Irrelevance-Induced Blindness

Load theory claims that bottom-up attention is possible under conditions of low perceptual load but not high perceptual load. At variance with this claim, a recent one-trial study showed that under low load, with only two colors in the display – a ring and a disk –, an instruction to process only one of the two stimuli led to better memory performance for the color of the relevant than of the irrelevant stimulus. Control experiments showed that if instructed to pay attention to both objects, participants were able to memorize both colors. Thus, stimulus irrelevance diminished the likelihood of memory for a color stimulus under low perceptual-load conditions. Yet, we noted less than optimal design features in that prior study: a lack of more implicit priming measures of memory or attention and an interval between color stimulus presentation and memory test that probably exceeded 500 ms. We took care of these problems in the current one-trial study by improving the retrieval displays while leaving the encoding displays as in the original study and found that the results only partly replicated prior findings. In particular, there was no evidence of irrelevance-induced blindness under conditions in which a ring was designated as relevant, surrounding an irrelevant disk. However, a continuously cumulative meta-analysis across past and present experiments showed that our results do not refute the irrelevance-induced effects entirely. We conclude with recommendations for future tests of load theory.

Distributed plasticity in ant visual pathways following colour learning.

Colour processing at early stages of visual pathways is a topic of intensive study both in vertebrate and invertebrate species. However, it is still unclear how colour learning and memory formation affects an insect brain in the peripheral processing stages and high-order integration centres, and whether associative colour experiences are reflected in plasticity of underlying neuronal circuits. To address this issue, we used Camponotus blandus ants as their proven colour learning and memory capabilities, precisely controllable age and experience, and already known central visual pathways offer unique access to analyse plasticity in neuronal circuits for colour vision in a miniature brain. The potential involvement of distinct neuropils-optic lobes (OLs), mushroom body (MB) input (collar) and output (vertical lobe), anterior optic tubercle (AOTU) and central complex (CX)-in associative colour experiences was assessed by quantification of volumetric and synaptic changes (MB collar) directly after colour conditioning and, 3 days later, after the establishment of long-term memory (LTM). To account for potential effects of non-associative light exposure, we compared neuronal changes in the brain of colour-naive foragers with those of foragers that had been exposed to light in a non-associative way. The results clearly show that the OLs, AOTU, and CX respond with plastic changes after colour learning and LTM formation. This suggests a complex neuronal network for colour learning and memory formation involving multiple brain levels. Such a colour-processing network probably represents an efficient design promoting fast and accurate behavioural decisions during orientation and navigation.

The subjective metric of remembered colors: A Fisher-information analysis of the geometry of human chromatic memory.

In order to explore the metric structure of the space of remembered colors, a computer game was designed, where players with normal color vision had to store a color in memory, and later retrieve it by selecting the best match out of a continuum of alternatives. All tested subjects exhibited evidence of focal colors in their mnemonic strategy. We found no concluding evidence that the focal colors of different players tended to cluster around universal prototypes. Based on the Fisher metric, for each subject we defined a notion of distance in color space that captured the accuracy with which similar colors where discriminated or confounded when stored and retrieved from memory. The notions of distance obtained for different players were remarkably similar. Finally, for each player, we constructed a new color scale, in which colors are memorized and retrieved with uniform accuracy.

Working Memory Has Better Fidelity Than Long-Term Memory: The Fidelity Constraint Is Not a General Property of Memory After All

How detailed are long-term-memory representations compared with working memory representations? Recent research has found an equal fidelity bound for both memory systems, suggesting a novel general constraint on memory. Here, we assessed the replicability of this discovery. Participants (total N = 72) were presented with colored real-life objects and were asked to recall the colors using a continuous color wheel. Deviations from study colors were modeled to generate two estimates of color memory: the variability of remembered colors—fidelity—and the probability of forgetting the color. Estimating model parameters using both maximum-likelihood estimation and Bayesian hierarchical modeling, we found that working memory had better fidelity than long-term memory (Experiments 1 and 2). Furthermore, within each system, fidelity worsened as a function of time-correlated mechanisms (Experiments 2 and 3). We conclude that fidelity is subject to decline across and within memory systems. Thus, the justification for a general fidelity constraint in memory does not seem to be valid.

Color Quality and Memory Color Assessment

Color Quality and Memory Color Assessment

Investigating Chromatic Adaptation via Memory Colour Matching Method on a Display

An experiment was carried out to investigate the incomplete chromatic adaptation on a self-luminous display using memory colour matching method. The goal was to distinguish between the chromatic adaptation and simultaneous colour contrast and develop models to predict each effect. Five adapting fields derived from a pilot visual matching experiment corresponding to four CCTs (2856K, 4500K, 6500K, 9000K) and fourteen familiar objects were studied. Twenty normal colour vision observers participated in the experiment. In total, 1400 matches were accumulated. Seventy corresponding pairs were obtained. The dataset was also conducted to test various CATs and to verify the D function in CAT02. The results showed that the chromatic adaptation for self-luminous display is more incomplete than that in the real scene, but the trend between CCT and degree of adaptation is consistent with our previous study.

A novel low colored and transparent shape memory copolyimide and its durability in space thermal cycling environments

Recently, shape memory polymers (SMPs) with high optical transmittance have been paid great attentions to endow the flexible optoelectronics with shape memory functions. Herein, a low colored and transparent shape memory copolyimide (SMcoPI) is obtained by suppressing the charge transfer complex interactions. The optical transmittance of the synthesized SMcoPI film could reach at ∼86% at the wavelength of 450 nm, far higher than the nearly zero optical transmittance of yellow and brown Kapton H. The better optical transparency could be attributed to the loose molecular chain arrangements induced by the meta-substituted groups and flexible ether linkages. The glass transition temperature (Tg) range of the synthesized SMcoPI films is from 179 °C to 220 °C, which is higher than that of reported optically transparent SMPs. The effective decomposition temperature at the weight loss of 5 wt% is 517 °C, showing excellent thermal stability. The SMcoPI also demonstrated good shape memory behaviors with high shape recovery ratio (Rr, >96%) and shape fixity ratio (Rf, >97%). In addition, the SMcoPI could maintain high optical transmittance, good thermostability and excellent shape memory behaviors after the ground-stimulated space thermal cycling test for 250 h. The synthesized SMcoPI has application potentials in high temperature areas or optoelectronic devices.

Application specific extension of the MCRI: Memory colors and preferred colors of reddish meat products

AbstractThis article explores the possibility of extending the memory color rendition index (MCRI) for specific applications. The memory colors and preferred colors of three types of meat products (ham sausage, chicken breast and raw hamburger) have been derived in a psychophysical rating experiment. The rating data have been modeled by modified bivariate Gaussian functions from which similarity functions have been derived. These functions, which predict the degree of similarity with respect to the memory color or preferred color of the meat products, have been used to evaluate the color quality of four commercially available meat lighting lamps. It was found that predicted color quality depends on the illuminance level, indicating that illuminance level is a potentially important aspect of color rendition evaluation, one that is not taken into account by most color rendition indices.

Does visual working memory adapt to the nature of anticipated interference?

Visual working memory (VWM) is an important memory buffer to briefly store visual information for ongoing tasks. Evidence shows that VWM representations can be protected against interfering input during the maintenance period. In this study, we investigated whether the protection of VWM representations is selective with regards to the anticipated nature of the interference, or whether VWM automatically protects all information in the wake of interference. In two experiments, participants were required to memorize both the color and the orientation of grating pattern for a memory test at the end of a delay period. During the delay period, either an additional color or an additional orientation memory task was presented. Which type of interfering task (color or orientation) would be presented was predictable with 80% likelihood. The results showed that memory for orientation survived orientation interference better when orientation interference was expected than when color interference was expected. Likewise, memory for color survived color interference better when color interference was expected than when orientation interference was expected. We conclude that visual working memory protection is adaptive in that it selectively shields the feature for which it expects the strongest interference.

Blue is in the Eye of the Beholder: A Cross-Linguistic Study on Color Perception and Memory.

The linguistic relativity hypothesis states that the language one speaks affects how one thinks. Color categorization across languages has often been studied in order to examine the hypothesis. However, those studies often rely on uniform color stimuli or focus on one aspect of cognition. In experiment one, we examined how Russian- and English-speaking participants rated the color of blue/grey eyes perceptually and from memory. Russian-speakers are more likely to describe such eyes as grey, whereas English-speakers are more likely to describe them as blue. Participants were randomly assigned to one of three conditions. In the first condition (perception), participants saw the color scale and an eye picture simultaneously and then chose the color that best matched the picture. In the second condition (memory), participants matched the color of an eye to the color scale from memory. The third condition (label) was similar to the second, except participants labeled the eye orally before matching the color from memory. A Bayesian analysis showed that Russian-speakers rated the eyes greyer than did English-speakers in the memory and label conditions, but not perception conditions. In experiment two, we examined how short-term linguistic memory traces are related to color memory. Overall, results find nuanced support for the linguistic relativity hypothesis: language affects color memory more than color perception.

Tailoring exciton and excimer emission in an exfoliated ultrathin 2D metal-organic framework

Two-dimensional (2D) metal–organic frameworks have exhibited a range of fascinating attributes, of interest to numerous fields. Here, a calcium-based metal-organic framework with a 2D layered structure has been designed. Dual emissions relating to intralayer excimers and interlayer trapped excitons are produced, showing excitation-dependent shifting tendency, characteristic of a low dimensional semiconductor nature. Furthermore, the layer stacking by weak van der Waals forces among dynamically coordinated DMF molecules enables exfoliation and morphology transformation, which can be achieved by ultrasound in different ratios of DMF/H2O solvents, or grinding under appropriate humidity conditions, leading to nano samples including ultrathin nanosheets with single or few coordination layers. The cutting down of layer numbers engenders suppression of interlayer exciton-related emission, resulting in modulation of the overall emitting color and optical memory states. This provides a rare prototypical model with switchable dual-channel emissions based on 2D-MOFs, in which the interlayer excitation channel can be reversibly tuned on/off by top-down exfoliation and morphology transformation.

Colour envisioned: concepts of colour in the blind and sighted

ABSTRACTImagine you were born completely blind, what would your understanding of colour be? Here we address this question, which hitherto has had no substantive answer. We asked samples of congenitally blind, adventitiously blind, and normally sighted (trichromatic) adults to rate the dissimilarities of pairs of colour terms. We then used multidimensional scaling to generate perceptual maps based on these dissimilarity ratings. The resulting maps were strikingly similar across groups. All groups were able to organize both basic and descriptive colour terms into a pattern resembling the trichromatic colour space, with only minor differences between the maps generated by the congenitally blind group and those generated by the adventitiously blind and sighted groups. These results suggest that the semantic associates of colour can exert a profound influence on how the blind understand colour terms and relationships. Furthermore, they also suggest that colour memory is well preserved in the adventitiously blind, despite prolonged blindness.

Gray Bananas and a Red Letter A - From Synesthetic Sensation to Memory Colors.

Grapheme–color synesthesia is a condition in which objectively achromatic graphemes induce concurrent color experiences. While it was long thought that the colors emerge during perception, there is growing support for the view that colors are integral to synesthetes’ cognitive representations of graphemes. In this work, we review evidence for two opposing theories positing either a perceptual or cognitive origin of concurrent colors: the cross-activation theory and the conceptual-mediation model. The review covers results on inducer and concurrent color processing as well as findings concerning the brain structure and grapheme–color mappings in synesthetes and trained mappings in nonsynesthetes. The results support different aspects of both theories. Finally, we discuss how research on memory colors could provide a new perspective in the debate about the level of processing at which the synesthetic colors occur.

A Bayesian Model of the Memory Colour Effect.

According to the memory colour effect, the colour of a colour-diagnostic object is not perceived independently of the object itself. Instead, it has been shown through an achromatic adjustment method that colour-diagnostic objects still appear slightly in their typical colour, even when they are colourimetrically grey. Bayesian models provide a promising approach to capture the effect of prior knowledge on colour perception and to link these effects to more general effects of cue integration. Here, we model memory colour effects using prior knowledge about typical colours as priors for the grey adjustments in a Bayesian model. This simple model does not involve any fitting of free parameters. The Bayesian model roughly captured the magnitude of the measured memory colour effect for photographs of objects. To some extent, the model predicted observed differences in memory colour effects across objects. The model could not account for the differences in memory colour effects across different levels of realism in the object images. The Bayesian model provides a particularly simple account of memory colour effects, capturing some of the multiple sources of variation of these effects.

Color appearance rating of familiar real objects under immersive viewing conditions

AbstractWith the concept of memory colors being considered to play a crucial role for many imaging and lighting applications, the questions how people assess the color appearance of familiar objects and what kind of fundamental characteristics can be derived from these assessments have extensively been studied in the past. However, all of the previous studies, the authors of this article are aware of, lack in realistic viewing and adaptation conditions. In the attempt of overcoming these deficiencies, a new experiment investigating the impact of long‐term memory on the color appearance ratings of 12 familiar test objects was performed. The pooled observer data were modeled in CIECAM02 color space using bivariate Gaussian functions whose centroids define the corresponding memory color centers for each test object. Comparisons with previous results obtained by Smet et al. revealed no significant differences in the reported memory color centers, but showed distinct deviations in the covariance matrices defining the shape of the fitted distribution functions. It is supposed that this new set of functions will lead to significantly different results when being used for the construction of an updated memory‐based color quality metric.

Multiscale Daltonization in the Gradient Domain

Abstract We propose a daltonization method that enhances chromatic edges and contrast for color-deficient people by optimizing the gradient of an image. We rotate and scale the error gradient between the original and its simulation in the color space into the direction of optimal visibility that is orthogonal to both the main direction of information loss and the direction of lightness. Then, we reintegrate the daltonized image version from the modified gradient through an iterative diffusion process. Moreover, we include multiscaling to guarantee optimal daltonization on different scales of the image. Also, we provide an interface for data attachment modules designed to maintain naturalness of memory colors like neutral colors. We evaluate and compare our proposed method to other top-performing daltonization methods in behavioral and psychometric experiments. A visual-search experiment assessing performance of the attentional mechanism of the human visual system before and after daltonization measures the greatest improvement in accuracy for our proposed method compared to the original and all investigated daltonization methods. It also reveals optimal results for both natural and Ishihara images among both protan and deutan color-deficient observers. Furthermore, we can deduce from the results of a pairwise preference evaluation that our proposed method is preferred highest amongst all color-deficient people in total. Our proposed method is also ranked among the most preferred daltonization methods for both protan and deutan color-deficient observers individually.

Performance of different metrics proposed to CIE TC 1-91

The main aim of the article is to find out the performance of different metrics proposed to CIE TC 1-91. Currently, six different indexes have been proposed to CIE TC 1-91: Colour Quality Scale (CQS), Feeling of Contrast Index (FCI), Memory colour rendering index (MCRI), Preference of skin (PS), Relative gamut area index (RGAI) and Illuminating Engineering society Method for evaluating light source colour rendition (IES TM-30). The evaluation and analysis are based on previously conducted experiment in lighting booth. The analysis showed the area based metric FCI was good subjective preference indicator. The subjective preference was measured in terms of naturalness of objects, colourfulness of colour checker chart, and the visual appearance of the lit scene in the booth.