Corrigendum to "Clear evidence for item limits in visual working memory" [Cogn. Psychol. 97 (2017) 79-97].
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ABSTRACT:
SUBMITTER: Adam KCS
PROVIDER: S-EPMC6688620 | biostudies-literature | 2018 Dec
REPOSITORIES: biostudies-literature
Publications
Corrigendum to "Clear evidence for item limits in visual working memory" [Cogn. Psychol. 97 (2017) 79-97].
Adam Kirsten C S KCS Vogel Edward K EK Awh Edward E
Cognitive psychology 20181103
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Project description:There is a consensus that visual working memory (WM) resources are sharply limited, but debate persists regarding the simple question of whether there is a limit to the total number of items that can be stored concurrently. Zhang and Luck (2008) advanced this debate with an analytic procedure that provided strong evidence for random guessing responses, but their findings can also be described by models that deny guessing while asserting a high prevalence of low precision memories. Here, we used a whole report memory procedure in which subjects reported all items in each trial and indicated whether they were guessing with each response. Critically, this procedure allowed us to measure memory performance for all items in each trial. When subjects were asked to remember 6 items, the response error distributions for about 3 out of the 6 items were best fit by a parameter-free guessing model (i.e. a uniform distribution). In addition, subjects' self-reports of guessing precisely tracked the guessing rate estimated with a mixture model. Control experiments determined that guessing behavior was not due to output interference, and that there was still a high prevalence of guessing when subjects were instructed not to guess. Our novel approach yielded evidence that guesses, not low-precision representations, best explain limitations in working memory. These guesses also corroborate a capacity-limited working memory system - we found evidence that subjects are able to report non-zero information for only 3-4 items. Thus, WM capacity is constrained by an item limit that precludes the storage of more than 3-4 individuated feature values.
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Project description:I propose that the capacity of working memory places a specific limit on the maintenance of temporary bindings. Two experiments support this binding hypothesis: Participants remembered word lists of varying length. When tested on a randomly selected word, their error rates increased with the length of the list, reflecting a limited capacity for short-term maintenance. This increase in errors was predominantly due to binding errors: People confused the correct word with other words of the current memory list, but very rarely with words not in the list. The frequencies of response choices were analyzed through two measurement models - one based on the assumption of discrete memory states, one on the assumption of continuous memory strength - that capture memory for items and for bindings in separate parameters. Increasing memory set size impaired binding memory but not item memory, supporting the binding hypothesis.
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Project description:Chronic innate immune activation in the central nervous system (CNS) significantly contributes to neurodegeneration in progressive multiple sclerosis (MS). Using multiple EAE models, we explored the potential of the innate immune sensor NLRX1 to protect neurons in the anterior visual pathway from inflammatory neurodegeneration. To do this, we assessed retinal ganglion cell (RGC) density and optic nerve axonal degeneration, gliosis, and T-cell infiltration in Nlrx1-/- and wild-type (WT) EAE mice. Our results indicate that Nlrx1-/- mice exhibit significantly increased RGC loss and axonal injury compared to WT mice in both active immunization EAE and spontaneous opticospinal encephalomyelitis models. Adoptive transfer experiments, in which wild type T cells were transferred into lymphocyte-deficient Rag-/- mice to minimize the effects of Nlrx1 knockout on peripheral lymphocyte priming, revealed more severe microgliosis and astrogliosis in the optic nerve of Nlrx1-/-Rag-/- mice compared to Rag-/- mice, suggesting a regulatory role of NLRX1 in innate immune compartments. Transcriptome analysis in primary astrocytes demonstrated that NLRX1 negatively regulates TLR-mediated NF-κB activation. The novel pharmacologic NLRX1 activator LABP-66 decreased LPS-mediated gene expression of inflammatory cytokines and chemokines in mixed glial cultures. Moreover, treating EAE mice with oral LABP-66 after the onset of paralysis resulted in less anterior visual pathway neurodegeneration compared to vehicle. These data suggest that a pharmacologic NLRX1 activators attenuates glial immune activation and has the potential to limit inflammatory neurodegeneration in diseases, such as MS, where chronic CNS-compartmentalized inflammation may drive neurodegenerative pathology. This study highlights that NLRX1 could serve as a promising target for neuroprotection in progressive MS and other neurodegenerative diseases where chronic compartmentalized innate immune activation and neuroinflammation play a role.
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Project description:Recent findings indicate that the hippocampus supports not only long-term memory encoding but also plays a role in working memory (WM) maintenance of multiple items; however, the neural mechanism underlying multi-item maintenance is still unclear. Theoretical work suggests that multiple items are being maintained by neural assemblies synchronized in the gamma frequency range (25-100 Hz) that are locked to consecutive phase ranges of oscillatory activity in the theta frequency range (4-8 Hz). Indeed, cross-frequency coupling of the amplitude of high-frequency activity to the phase of slower oscillations has been described both in animals and in humans, but has never been linked to a theoretical model of a cognitive process. Here we used intracranial EEG recordings in human epilepsy patients to test pivotal predictions from theoretical work. First, we show that simultaneous maintenance of multiple items in WM is accompanied by cross-frequency coupling of oscillatory activity in the hippocampus, which is recruited during multi-item WM. Second, maintenance of an increasing number of items is associated with modulation of beta/gamma amplitude with theta band activity of lower frequency, consistent with the idea that longer cycles are required for an increased number of representations by gamma cycles. This effect cannot be explained by a difference in theta or beta/gamma power. Third, we describe how the precision of cross-frequency coupling predicts individual WM performance. These data support the idea that working memory in humans depends on a neural code using phase information.
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