Coding of featural information in visual working memory in 2.5-year-old toddlers.
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ABSTRACT:
SUBMITTER: Cheng C
PROVIDER: S-EPMC8297794 | biostudies-literature |
REPOSITORIES: biostudies-literature
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Project description:Working memory (WM) enables the maintenance and manipulation of information relevant to behavioral goals. Variability in WM ability is strongly correlated with IQ [1], and WM function is impaired in many neurological and psychiatric disorders [2, 3], suggesting that this system is a core component of higher cognition. WM storage is thought to be mediated by patterns of activity in neural populations selective for specific properties (e.g., color, orientation, location, and motion direction) of memoranda [4-13]. Accordingly, many models propose that differences in the amplitude of these population responses should be related to differences in memory performance [14, 15]. Here, we used functional magnetic resonance imaging and an image reconstruction technique based on a spatial encoding model [16] to visualize and quantify population-level memory representations supported by multivoxel patterns of activation within regions of occipital, parietal and frontal cortex while participants precisely remembered the location(s) of zero, one, or two small stimuli. We successfully reconstructed images containing representations of the remembered-but not forgotten-locations within regions of occipital, parietal, and frontal cortex using delay-period activation patterns. Critically, the amplitude of representations of remembered locations and behavioral performance both decreased with increasing memory load. These results suggest that differences in visual WM performance between memory load conditions are mediated by changes in the fidelity of large-scale population response profiles distributed across multiple areas of human cortex.
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Project description:We characterized the population-level neural coding of ensemble representations in visual working memory from human electroencephalography. Ensemble representations provide a unique opportunity to investigate structured representations of working memory because the visual system encodes high-order summary statistics as well as noisy sensory inputs in a hierarchical manner. Here, we consistently observe stable coding of simple features as well as the ensemble mean in frontocentral electrodes, which even correlated with behavioral indices of the ensemble across individuals. In occipitoparietal electrodes, however, we find that remembered features are dynamically coded over time, whereas neural coding of the ensemble mean is absent in the old/new judgment task. In contrast, both dynamic and stable coding are found in the continuous estimation task. Our findings suggest that the prefrontal cortex holds behaviorally relevant abstract representations while visual representations in posterior and visual areas are modulated by the task demands.
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Project description:How is working memory for different visual categories supported in the brain? Do the same principles of cortical specialization that govern the initial processing and encoding of visual stimuli also apply to their short-term maintenance? We investigated these questions with a delayed discrimination paradigm for faces, bodies, flowers, and scenes and applied both univariate and multivariate analyses to functional magnetic resonance imaging (fMRI) data. Activity during encoding followed the well-known specialization in posterior areas. During the delay interval, activity shifted to frontal and parietal regions but was not specialized for category. Conversely, activity in visual areas returned to baseline during that interval but showed some evidence of category specialization on multivariate pattern analysis (MVPA). We conclude that principles of cortical activation differ between encoding and maintenance of visual material. Whereas perceptual processes rely on specialized regions in occipitotemporal cortex, maintenance involves the activation of a frontoparietal network that seems to require little specialization at the category level. We also confirm previous findings that MVPA can extract information from fMRI signals in the absence of suprathreshold activation and that such signals from visual areas can reflect the material stored in memory.
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Project description:Working memory involves the short-term maintenance of information and is critical in many tasks. The neural circuit dynamics underlying working memory remain poorly understood, with different aspects of prefrontal cortical (PFC) responses explained by different putative mechanisms. By mathematical analysis, numerical simulations, and using recordings from monkey PFC, we investigate a critical but hitherto ignored aspect of working memory dynamics: information loading. We find that, contrary to common assumptions, optimal loading of information into working memory involves inputs that are largely orthogonal, rather than similar, to the late delay activities observed during memory maintenance, naturally leading to the widely observed phenomenon of dynamic coding in PFC. Using a theoretically principled metric, we show that PFC exhibits the hallmarks of optimal information loading. We also find that optimal information loading emerges as a general dynamical strategy in task-optimized recurrent neural networks. Our theory unifies previous, seemingly conflicting theories of memory maintenance based on attractor or purely sequential dynamics and reveals a normative principle underlying dynamic coding.
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Project description:The classic mapping of distinct aspects of working memory (WM) to mutually exclusive brain areas is at odds with the distributed processing mechanisms proposed by contemporary network science theory. Here, we use machine-learning to determine how aspects of WM are dynamically coded in the human brain. Using cross-validation across independent fMRI studies, we demonstrate that stimulus domains (spatial, number and fractal) and WM processes (encode, maintain, probe) are classifiable with high accuracy from the patterns of network activity and connectivity that they evoke. This is the case even when focusing on 'multiple demands' brain regions, which are active across all WM conditions. Contrary to early neuropsychological perspectives, these aspects of WM do not map exclusively to brain areas or processing streams; however, the mappings from that literature form salient features within the corresponding multivariate connectivity patterns. Furthermore, connectivity patterns provide the most precise basis for classification and become fine-tuned as maintenance load increases. These results accord with a network-coding mechanism, where the same brain regions support diverse WM demands by adopting different connectivity states.
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Project description:Attention turns looking, into seeing. Yet, little developmental research has examined the interface of attention and visual working memory (VWM), where what is seen is maintained for use in ongoing visual tasks. Using the task-evoked pupil response - a sensitive, real-time, involuntary measure of focused attention that has been shown to correlate with VWM performance in adults and older children - we examined the relationship between focused attention and VWM in 13-month-olds. We used a Delayed Match Retrieval paradigm, to test infants' VWM for object-location bindings - what went where - while recording anticipatory gaze responses and pupil dilation. We found that infants with greater focused attention during memory encoding showed significantly better memory performance. As well, trials that ended in a correct response had significantly greater pupil response during memory encoding than incorrect trials. Taken together, this shows that pupillometry can be used as a measure of focused attention in infants, and a means to identify those individuals, or moments, where cognitive effort is maximized.
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Project description:We investigated whether the representations of different objects are maintained independently in working memory or interact with each other. Observers were shown two sequentially presented orientations and required to reproduce each orientation after a delay. The sequential presentation minimized perceptual interactions so that we could isolate interactions between memory representations per se. We found that similar orientations were repelled from each other whereas dissimilar orientations were attracted to each other. In addition, when one of the items was given greater attentional priority by means of a cue, the representation of the high-priority item was not influenced very much by the orientation of the low-priority item, but the representation of the low-priority item was strongly influenced by the orientation of the high-priority item. This indicates that attention modulates the interactions between working memory representations. In addition, errors in the reported orientations of the two objects were positively correlated under some conditions, suggesting that representations of distinct objects may become grouped together in memory. Together, these results demonstrate that working-memory representations are not independent but instead interact with each other in a manner that depends on attentional priority.
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Project description:Behavioral evidence from the young suggests spatial cues that orient attention toward task-relevant items in visual working memory (VWM) enhance memory capacity. Whether older adults can also use retrospective cues ("retro-cues") to enhance VWM capacity is unknown. In the current event-related potential (ERP) study, young and old adults performed a VWM task in which spatially informative retro-cues were presented during maintenance. Young but not older adults' VWM capacity benefited from retro-cueing. The contralateral delay activity (CDA) ERP index of VWM maintenance was attenuated after the retro-cue, which effectively reduced the impact of memory load. CDA amplitudes were reduced prior to retro-cue onset in the old only. Despite a preserved ability to delete items from VWM, older adults may be less able to use retrospective attention to enhance memory capacity when expectancy of impending spatial cues disrupts effective VWM maintenance.
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Project description:AimThis study tested sex differences in the association between hippocampal volume and working memory of a national sample of 9-10-year-old children in the US. As the hippocampus is functionally lateralized (especially in task-related activities), we explored the results for the right and the left hippocampus.MethodsThis is a cross-sectional study using the Adolescent Brain Cognitive Development (ABCD) Study data. This analysis included baseline ABCD data (n = 10,093) of children between ages 9 and 10 years. The predictor variable was right and left hippocampal volume measured by structural magnetic resonance imaging (sMRI). The primary outcome, list sorting working memory, was measured using the NIH toolbox measure. Sex was the moderator. Age, race, ethnicity, household income, parental education, and family structure were the covariates.ResultsIn the overall sample, larger right (b = 0.0013; p < 0.001) and left (b = 0.0013; p < 0.001) hippocampal volumes were associated with higher children's working memory. Sex had statistically significant interactions with the right (b = -0.0018; p = 0.001) and left (b = -0.0012; p = 0.022) hippocampal volumes on children's working memory. These interactions indicated stronger positive associations between right and left hippocampal volume and working memory for females compared to males.ConclusionWhile right and left hippocampal volumes are determinants of children's list sorting working memory, these effects seem to be more salient for female than male children. Research is needed on the role of socialization, sex hormones, and brain functional connectivity as potential mechanisms that may explain the observed sex differences in the role of hippocampal volume as a correlate of working memory.
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Project description:Visual working memory capacity is extremely limited and appears to be relatively immune to practice effects or the use of explicit strategies. The recent discovery that visual working memory tasks, like verbal working memory tasks, are subject to proactive interference, coupled with the fact that typical visual working memory tasks are particularly conducive to proactive interference, suggests that visual working memory capacity may be systematically under-estimated.Working memory capacity was probed behaviorally in adult humans both in laboratory settings and via the Internet. Several experiments show that although the effect of proactive interference on visual working memory is significant and can last over several trials, it only changes the capacity estimate by about 15%.This study further confirms the sharp limitations on visual working memory capacity, both in absolute terms and relative to verbal working memory. It is suggested that future research take these limitations into account in understanding differences across a variety of tasks between human adults, prelinguistic infants and nonlinguistic animals.
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