scholarly journals Fundamental bound on the persistence and capacity of short-term memory stored as graded persistent activity

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Onur Ozan Koyluoglu ◽  
Yoni Pertzov ◽  
Sanjay Manohar ◽  
Masud Husain ◽  
Ila R Fiete
Keyword(s):  
Human Performance ◽  
Short Term Memory ◽  
Memory Performance ◽  
Persistent Activity ◽  
Short Term ◽  
Noisy Channels ◽  
Storage Duration ◽  
Term Memory ◽  
Activity Networks ◽  
The Brain

It is widely believed that persistent neural activity underlies short-term memory. Yet, as we show, the degradation of information stored directly in such networks behaves differently from human short-term memory performance. We build a more general framework where memory is viewed as a problem of passing information through noisy channels whose degradation characteristics resemble those of persistent activity networks. If the brain first encoded the information appropriately before passing the information into such networks, the information can be stored substantially more faithfully. Within this framework, we derive a fundamental lower-bound on recall precision, which declines with storage duration and number of stored items. We show that human performance, though inconsistent with models involving direct (uncoded) storage in persistent activity networks, can be well-fit by the theoretical bound. This finding is consistent with the view that if the brain stores information in patterns of persistent activity, it might use codes that minimize the effects of noise, motivating the search for such codes in the brain.

scholarly journals A Diverse Range of Factors Affect the Nature of Neural Representations Underlying Short-Term Memory

2018 ◽  
Author(s):  
A. Emin Orhan ◽  
Wei Ji Ma
Keyword(s):  
Neural Circuits ◽  
Short Term Memory ◽  
Persistent Activity ◽  
Short Term ◽  
Diverse Range ◽  
Term Memory ◽  
Temporal Complexity ◽  
Wide Range ◽  
Activity Models ◽  
The Brain

AbstractSequential and persistent activity models are two prominent models of short-term memory in neural circuits. In persistent activity models, memories are represented in persistent or nearly persistent activity patterns across a population of neurons, whereas in sequential models, memories are represented dynamically by a sequential pattern of activity across the population. Experimental evidence for both types of model in the brain has been reported previously. However, it has been unclear under what conditions these two qualitatively different types of solutions emerge in neural circuits. Here, we address this question by training recurrent neural networks on several short-term memory tasks under a wide range of circuit and task manipulations. We show that sequential and nearly persistent solutions are both part of a spectrum that emerges naturally in trained networks under different conditions. Fixed delay durations, tasks with higher temporal complexity, strong network coupling, motion-related dynamic inputs and prior training in a different task favor more sequential solutions, whereas variable delay durations, tasks with low temporal complexity, weak network coupling and symmetric Hebbian short-term synaptic plasticity favor more persistent solutions. Our results help clarify some seemingly contradictory experimental results on the existence of sequential vs. persistent activity based memory mechanisms in the brain.

scholarly journals Crossmodal Semantic Congruence Interacts with Object Contextual Consistency in Complex Visual Scenes to Enhance Short-Term Memory Performance

2021 ◽  
Vol 11 (9) ◽  
pp. 1206
Author(s):  
Erika Almadori ◽  
Serena Mastroberardino ◽  
Fabiano Botta ◽  
Riccardo Brunetti ◽  
Juan Lupiáñez ◽  
...  
Keyword(s):  
Short Term Memory ◽  
Memory Performance ◽  
Visual Stimuli ◽  
Spatial Position ◽  
Visual Scene ◽  
Facilitatory Effect ◽  
Short Term ◽  
Term Memory ◽  
Visual Scenes ◽  
Semantic Congruence

Object sounds can enhance the attentional selection and perceptual processing of semantically-related visual stimuli. However, it is currently unknown whether crossmodal semantic congruence also affects the post-perceptual stages of information processing, such as short-term memory (STM), and whether this effect is modulated by the object consistency with the background visual scene. In two experiments, participants viewed everyday visual scenes for 500 ms while listening to an object sound, which could either be semantically related to the object that served as the STM target at retrieval or not. This defined crossmodal semantically cued vs. uncued targets. The target was either in- or out-of-context with respect to the background visual scene. After a maintenance period of 2000 ms, the target was presented in isolation against a neutral background, in either the same or different spatial position as in the original scene. The participants judged the same vs. different position of the object and then provided a confidence judgment concerning the certainty of their response. The results revealed greater accuracy when judging the spatial position of targets paired with a semantically congruent object sound at encoding. This crossmodal facilitatory effect was modulated by whether the target object was in- or out-of-context with respect to the background scene, with out-of-context targets reducing the facilitatory effect of object sounds. Overall, these findings suggest that the presence of the object sound at encoding facilitated the selection and processing of the semantically related visual stimuli, but this effect depends on the semantic configuration of the visual scene.

scholarly journals Visual short-term memory for 3D shapes reveals similar properties to simple 2D features

2019 ◽  
Author(s):  
Joel Robitaille ◽  
Stephen Emrich
Keyword(s):  
Short Term Memory ◽  
Memory Load ◽  
Memory Performance ◽  
Delayed Response ◽  
Short Term ◽  
Complex Objects ◽  
Term Memory ◽  
Visual Short Term Memory ◽  
2D And 3D ◽  
3D Shapes

In the past two decades, significant advances have been made to understand the psychophysical properties of visual short-term memory (VSTM). Most studies, however, make inferences based on memory for simple surface features of 2D shapes. Here, we examined the role of object complexity and dimensionality on the psychophysical properties of VSTM by comparing orientation memory for 2D lines and complex 3D objects in a delayed-response continuous report task, where memory load (Experiment 1) or axis of rotation (Experiment 2) was manipulated. In both experiments, our results demonstrate an overall cost of complexity that affected participants raw errors as well as their guess rate and response precision derived from mixture modelling. We also demonstrate that participants’ memory performance is correlated between stimulus types and that memory performance for both 2D and 3D shapes is better fit to the variable precision model of VSTM than to tested competing models. Interestingly, the ability to report complex objects is not consistent across axes of rotation. These results indicate that, despite the fact that VSTM shares similar properties for 2D and 3D shapes, VSTM is far from being a unitary process and is affected by stimulus properties such as complexity and dimensionality.

Spectral analysis of event-related EEG responses during short-term memory performance

1996 ◽  
Vol 9 (1) ◽  
pp. 21-30 ◽  
Author(s):  
M. Barry Sterman ◽  
David A. Kaiser ◽  
Bettina Veigel
Keyword(s):  
Spectral Analysis ◽  
Short Term Memory ◽  
Memory Performance ◽  
Short Term ◽  
Term Memory

scholarly journals Persistent Spatial Information in the FEF during Object-based Short-term Memory Does Not Contribute to Task Performance

2014 ◽  
Vol 26 (6) ◽  
pp. 1292-1299 ◽  
Author(s):  
Kelsey L. Clark ◽  
Behrad Noudoost ◽  
Tirin Moore
Keyword(s):  
Task Performance ◽  
Spatial Information ◽  
Short Term Memory ◽  
Spatial Working Memory ◽  
Memory Performance ◽  
Persistent Activity ◽  
Short Term ◽  
Object Based ◽  
Saccade Task

We previously reported the existence of a persistent spatial signal in the FEF during object-based STM. This persistent activity reflected the location at which the sample appeared, irrespective of the location of upcoming targets. We hypothesized that such a spatial signal could be used to maintain or enhance object-selective memory activity elsewhere in cortex, analogous to the role of a spatial signal during attention. Here, we inactivated a portion of the FEF with GABAa agonist muscimol to test whether the observed activity contributes to object memory performance. We found that, although RTs were slowed for saccades into the inactivated portion of retinotopic space, performance for samples appearing in that region was unimpaired. This contrasts with the devastating effects of the same FEF inactivation on purely spatial working memory, as assessed with the memory-guided saccade task. Thus, in a task in which a significant fraction of FEF neurons displayed persistent, sample location-based activity, disrupting this activity had no impact on task performance.

Charting the Diversity of Strategic Processes in Visuospatial Short-Term Memory

2020 ◽  
pp. 174569162095069
Author(s):  
Corentin Gonthier
Keyword(s):  
Short Term Memory ◽  
Memory Performance ◽  
Visuospatial Memory ◽  
Short Term ◽  
Term Memory ◽  
Multiple Strategies ◽  
Strategic Processes ◽  
Strategic Behaviors ◽  
Spatial Tasks ◽  
The Difference

Despite the abundant literature on visuospatial short-term memory, researchers have devoted little attention to strategic processes: What procedures do subjects implement to memorize visuospatial material? Evidence for various strategies exists, but it is spread across a variety of fields. This integrative review of the literature brings together scattered evidence to provide an overview of strategic processes in visuospatial memory tasks. The diversity of strategies and their proposed operating mechanisms are reviewed and discussed. The evidence leads to proposing seven broad strategic processes used in visuospatial short-term memory, each with multiple variants. Strategies can vary across individuals, but the same subjects also appear to use multiple strategies depending on the perceptual features of to-be-remembered displays. These results point to a view of visuospatial strategies as a functional library of facilitatory processes on which subjects can draw to support visuospatial short-term memory performance. Implications are discussed for the difference between visual and spatial tasks, for the appropriate measurement of strategic behaviors, and for the interpretation of performance in visuospatial memory tasks.

scholarly journals Hippocampal 2-Arachidonoyl Glycerol Signaling Regulates Time-of-Day- and Stress-Dependent Effects on Rat Short-Term Memory

2020 ◽  
Vol 21 (19) ◽  
pp. 7316
Author(s):  
Alessia Santori ◽  
Maria Morena ◽  
Matthew N. Hill ◽  
Patrizia Campolongo
Keyword(s):  
Recognition Memory ◽  
Short Term Memory ◽  
Memory Performance ◽  
High Stress ◽  
Time Of Day ◽  
Stress Conditions ◽  
Short Term ◽  
Term Memory ◽  
Stress Dependent ◽  
Arachidonoyl Glycerol

Background: Cannabinoids induce biphasic effects on memory depending on stress levels. We previously demonstrated that different stress intensities, experienced soon after encoding, impaired rat short-term recognition memory in a time-of-day-dependent manner, and that boosting endocannabinoid anandamide (AEA) levels restored memory performance. Here, we examined if two different stress intensities and time-of-day alter hippocampal endocannabinoid tone, and whether these changes modulate short-term memory. Methods: Male Sprague-Dawley rats were subjected to an object recognition task and exposed, at two different times of the day (i.e., morning or afternoon), to low or high stress conditions, immediately after encoding. Memory retention was assessed 1 hr later. Hippocampal AEA and 2-arachidonoyl glycerol (2-AG) content and the activity of their primary degrading enzymes, fatty acid amide hydrolase (FAAH) and monoacylglycerol lipase (MAGL), were measured soon after testing. Results: Consistent with our previous findings, low stress impaired 1-hr memory performance only in the morning, whereas exposure to high stress impaired memory independently of testing time. Stress exposure decreased AEA levels independently of memory alterations. Interestingly, exposure to high stress decreased 2-AG content and, accordingly, increased MAGL activity, selectively in the afternoon. Thus, to further evaluate 2-AG’s role in the modulation of short-term recognition memory, rats were given bilateral intra-hippocampal injections of the 2-AG hydrolysis inhibitor KML29 immediately after training, then subjected to low or high stress conditions and tested 1 hr later. Conclusions: KML29 abolished the time-of-day-dependent impairing effects of stress on short-term memory, ameliorating short-term recognition memory performance.

Language Influences on Verbal Short-Term Memory Performance in Down Syndrome

2004 ◽  
Vol 47 (6) ◽  
pp. 1334-1346 ◽  
Author(s):  
Jon Brock ◽  
Christopher Jarrold
Keyword(s):  
Down Syndrome ◽  
Short Term Memory ◽  
Memory Performance ◽  
Memory Task ◽  
Vocabulary Knowledge ◽  
Typically Developing ◽  
Typically Developing Children ◽  
Short Term ◽  
Language Abilities ◽  
Term Memory

Down syndrome is associated with severe deficits in language and verbal short-term memory, but the causal relationship between these deficits is unclear. The current study therefore investigated the influence of language abilities on verbal short-term memory performance in Down syndrome. Twenty-one individuals with Down syndrome and 29 younger typically developing children were tested on memory for words and nonwords using 2 immediate recognition tasks: an order memory task that was a relatively pure measure of verbal short-term memory and an item memory task that was more sensitive to language ability. Despite having superior vocabulary knowledge to the typically developing children, individuals with Down syndrome were impaired on both order and item tasks. This impairment was particularly marked on the item task, where individuals with Down syndrome showed an atypically large lexicality effect. These results are interpreted in terms of an underlying verbal short-term memory deficit in Down syndrome that is compounded by poor phonological discrimination abilities.

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