scholarly journals A neural model of working memory

2017 ◽  
Author(s):  
Sanjay G Manohar ◽  
Nahid Zokaei ◽  
Sean J Fallon ◽  
Tim Vogels ◽  
Masud Husain
Keyword(s):  
Working Memory ◽  
Neural Model ◽  
Memory Item ◽  
Common Mechanism ◽  
Attention And Memory ◽  
Persistent Activity ◽  
Neural Firing ◽  
Diverse Range ◽  
Dual Functional ◽  
Better Than

SummaryWorking memory, the ability to keep recently encountered information available for immediate processing, has been proposed to rely on two mechanisms that appear difficult to reconcile: selfsustained neural firing, or the opposite—activity-silent synaptic traces. Here we show that both phenomena can co-exist within a unified system in which neurons hold information in both activity and synapses. Rapid plasticity in flexibly-coding neurons allows features to be bound together into objects, with an important emergent property being the focus of attention. One memory item is held by persistent activity in an attended or “focused” state, and is thus remembered better than other items. Other, previously attended items can remain in memory but in the background, encoded in activity-silent synaptic traces. This dual functional architecture provides a unified common mechanism accounting for a diverse range of perplexing attention and memory effects that have been hitherto difficult to explain in a single theoretical framework.

Retrospective prioritization of multiple items during working memory storage

2019 ◽  
Author(s):  
Ashley DiPuma ◽  
Kelly Rivera ◽  
Edward Ester
Keyword(s):  
Working Memory ◽  
Memory Performance ◽  
Memory Item ◽  
Neutral Condition ◽  
Memory Storage ◽  
Single Item ◽  
Incorrect Item ◽  
Memory Precision ◽  
Neutral Conditions ◽  
Directing Attention

Working memory (WM) performance can be improved by an informative cue presented during storage. This effect, termed a retro-cue benefit, can be used to explore mechanisms of attentional prioritization in WM. Directing attention to a single item stored in memory is known to increase memory precision while decreasing the likelihood of incorrect item reports and random guesses, but it is unclear whether similar benefits manifest when participants direct attention to multiple items stored in memory. We tested this possibility by quantifying memory performance when participants were cued to prioritize one or two items stored in working memory. Consistent with prior work, cueing participants to prioritize a single memory item yielded higher recall precision, fewer swap errors, and fewer guesses relative to a neutral cue condition. Conversely, cueing participants to prioritize two memory items yielded fewer swap errors relative to a neutral condition, but no differences in recall precision or guess rates. Although swap rates were less likely during the cue-two vs. neutral conditions, planned comparisons revealed that when participants made swap errors during cue-two trials they were far more likely to confuse two prioritized stimuli than they were to confuse a prioritized stimulus vs. a non-prioritized stimulus. Our results suggest that it is possible to prioritize multiple items stored in memory, with the caveat that doing so may increase the probability of confusing prioritized items.

scholarly journals Prefrontal and Parietal Attractor Networks Mediate Working Memory Judgments

2020 ◽  
Author(s):  
Sihai Li ◽  
Christos Constantinidis ◽  
Xue-Lian Qi
Keyword(s):  
Working Memory ◽  
Prefrontal Cortex ◽  
Dorsolateral Prefrontal Cortex ◽  
Critical Role ◽  
Memory Task ◽  
Delayed Response ◽  
Persistent Activity ◽  
Neural Basis ◽  
Brain Areas ◽  
Dorsolateral Prefrontal

ABSTRACTThe dorsolateral prefrontal cortex plays a critical role in spatial working memory and its activity predicts behavioral responses in delayed response tasks. Here we addressed whether this predictive ability extends to categorical judgments based on information retained in working memory, and is present in other brain areas. We trained monkeys in a novel, Match-Stay, Nonmatch-Go task, which required them to observe two stimuli presented in sequence with an intervening delay period between them. If the two stimuli were different, the monkeys had to saccade to the location of the second stimulus; if they were the same, they held fixation. Neurophysiological recordings were performed in areas 8a and 46 of the dlPFC and 7a and lateral intraparietal cortex (LIP) of the PPC. We hypothesized that random drifts causing the peak activity of the network to move away from the first stimulus location and towards the location of the second stimulus would result in categorical errors. Indeed, for both areas, when the first stimulus appeared in a neuron’s preferred location, the neuron showed significantly higher firing rates in correct than in error trials. When the first stimulus appeared at a nonpreferred location and the second stimulus at a preferred, activity in error trials was higher than in correct. The results indicate that the activity of both dlPFC and PPC neurons is predictive of categorical judgments of information maintained in working memory, and the magnitude of neuronal firing rate deviations is revealing of the contents of working memory as it determines performance.SIGNIFICANCE STATEMENTThe neural basis of working memory and the areas mediating this function is a topic of controversy. Persistent activity in the prefrontal cortex has traditionally been thought to be the neural correlate of working memory, however recent studies have proposed alternative mechanisms and brain areas. Here we show that persistent activity in both the dorsolateral prefrontal cortex and posterior parietal cortex predicts behavior in a working memory task that requires a categorical judgement. Our results offer support to the idea that a network of neurons in both areas act as an attractor network that maintains information in working memory, which informs behavior.

scholarly journals Reorganization of the connectivity between elementary functions as a common mechanism of phenomenal consciousness and working memory: from functions to strategies

2018 ◽  
Vol 373 (1755) ◽  
pp. 20170346 ◽  
Author(s):  
Jesper Mogensen ◽  
Morten Overgaard
Keyword(s):  
Working Memory ◽  
Phenomenal Consciousness ◽  
Situational Factors ◽  
Surface Phenomenon ◽  
Common Mechanism ◽  
Elementary Functions ◽  
Connectionist Networks ◽  
Cognitive Access ◽  
Present Context ◽  
Neural Correlate Of Consciousness

In the present communication, phenomenal consciousness, access consciousness and the closely related concept of working memory are presented in the context of a neurocognitive model—the REF (reorganization of elementary functions) framework. The REF framework is based on connectionist networks within which the ‘units’ are advanced processing modules called elementary functions (EFs). In this framework, the focus is on dynamically changeable ‘strategies’—based on reorganizations of the connectivity between EFs—rather than on the more traditional ‘cognitive functions’. The background for the REF framework and especially how the neural correlate of consciousness is understood within these models is summarized. According to the REF framework, phenomenal consciousness cannot ‘overflow’ availability of information for action. Phenomenal consciousness may, however, overflow working memory because working memory in the present context is seen as a surface phenomenon reflecting underlying dynamic strategies—influenced by both experience and situational factors. This article is part of the theme issue ‘Perceptual consciousness and cognitive access'.

scholarly journals Working Memory: Delay Activity, Yes! Persistent Activity? Maybe Not

2018 ◽  
Vol 38 (32) ◽  
pp. 7013-7019 ◽  
Author(s):  
Mikael Lundqvist ◽  
Pawel Herman ◽  
Earl K. Miller
Keyword(s):  
Working Memory ◽  
Persistent Activity

Nonlinear integration of multispectral information: Human colour vision analogues to sensory integration in rattlesnake

2012 ◽  
Vol 25 (0) ◽  
pp. 179
Author(s):  
Vincent A. Billock ◽  
Brian H. Tsou
Keyword(s):  
Spectral Sensitivity ◽  
Information Integration ◽  
Sensory Integration ◽  
Colour Vision ◽  
Neural Model ◽  
Neural Firing ◽  
Visual Responses ◽  
Neural Synchronization ◽  
Synchronization Mechanism ◽  
Integration Problems

Information integration occurs at every sensory scale and although distinctions are made for integration between and within senses, integration at intermediate scales may exploit familiar mechanisms. Here, we explore this idea by applying a sensory integration mechanism to some poorly understood multispectral integration problems in human colour vision. Billock and Tsou (IMRF, 2011) used a binding-like neural synchronization mechanism to model intensity-dependent (inverse) enhancement of visual responses by auditory stimulation in cat. The same model also applies to mutual enhancement of visual and infrared responses in rattlesnake, suggesting that a similar mechanism could model integration of spectral information in human colour vision. For example, chromatic brightness is thought to be a vector-like nonlinear combination of luminance and chromatic channels; its neural correlate is unknown. We model its spectral sensitivity by pairwise excitatory synchronization between luminance (broadband) neurons and cortically rectified L+M- and S+M-L- LGN neurons. Similarly, the yellow lobe of the yellow-blue opponent channel is known to be a nonlinearly enhanced combination of long- and medium-wavelength-sensitive inputs, but no sensible neural model for this interaction has been advanced. We model the spectral sensitivity of ‘yellowness’ using excitatory synchronization between cortically rectified L+M+S- and M+L- LGN units. The inputs for both simulations were macaque neural firing rate data (DeValois et al., 1966). Fascinatingly, in both cases, multispectral integration in human colour vision was well modeled using the rattlesnake/cat neural synchronization equations without any use of fitting parameters. This is the first application of sensory integration concepts to human colour vision transformations.

scholarly journals Tracking stimulus representation across a 2-back visual working memory task

2020 ◽  
Vol 7 (8) ◽  
pp. 190228 ◽  
Author(s):  
Quan Wan ◽  
Ying Cai ◽  
Jason Samaha ◽  
Bradley R. Postle
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
Memory Task ◽  
Memory Item ◽  
Neural Representation ◽  
Stimulus Representation ◽  
Representational Format ◽  
The Status ◽  
Memory Content ◽  
Default Assumption

How does the neural representation of visual working memory content vary with behavioural priority? To address this, we recorded electroencephalography (EEG) while subjects performed a continuous-performance 2-back working memory task with oriented-grating stimuli. We tracked the transition of the neural representation of an item ( n ) from its initial encoding, to the status of ‘unprioritized memory item' (UMI), and back to ‘prioritized memory item', with multivariate inverted encoding modelling. Results showed that the representational format was remapped from its initially encoded format into a distinctive ‘opposite' representational format when it became a UMI and then mapped back into its initial format when subsequently prioritized in anticipation of its comparison with item n + 2. Thus, contrary to the default assumption that the activity representing an item in working memory might simply get weaker when it is deprioritized, it may be that a process of priority-based remapping helps to protect remembered information when it is not in the focus of attention.

Self-Corrected Reaching in a Three-Location Delayed-Response Search Task

1998 ◽  
Vol 9 (1) ◽  
pp. 66-70 ◽  
Author(s):  
J. Steven Reznick ◽  
J. J. Fueser ◽  
Michelle Bosquet
Keyword(s):  
Working Memory ◽  
Spatial Orientation ◽  
Search Task ◽  
Chance Level ◽  
Delayed Response ◽  
Age Group ◽  
Cause Of Error ◽  
Better Than

Infants watched an experimenter hide a toy in one of three wells and then attempted to retrieve it after a brief delay. Seven-month-olds performed at chance. Nine-month-olds reached correctly on 43% of trials, which is significantly better than chance. After an incorrect reach, infants were allowed to choose between the two remaining locations. Seven-month-olds responded at a chance level on their second reach, but 9-month-olds chose correctly more often than would be expected by chance despite a 10- to 20-s delay between hiding and search. One cause of error on the initial reach was a profound bias toward the center well. In Experiment 2, the wells were covered simultaneously, and the infant's spatial orientation was disrupted during the delay; this procedure eliminated the centripetal bias. Nine-month-olds still responded correctly more often than would be expected by chance on their second reach. These findings suggest that 9-month-olds sometimes have a more durable working memory for location than is generally reported for that age group.

scholarly journals Early Top–Down Control of Visual Processing Predicts Working Memory Performance

2010 ◽  
Vol 22 (6) ◽  
pp. 1224-1234 ◽  
Author(s):  
Aaron M. Rutman ◽  
Wesley C. Clapp ◽  
James Z. Chadick ◽  
Adam Gazzaley
Keyword(s):  
Working Memory ◽  
Selective Attention ◽  
Visual Processing ◽  
Temporal Dynamics ◽  
Memory Performance ◽  
Event Related Potential ◽  
Natural Scenes ◽  
Attention And Memory ◽  
Top Down ◽  
Sensory Neural

Selective attention confers a behavioral benefit on both perceptual and working memory (WM) performance, often attributed to top–down modulation of sensory neural processing. However, the direct relationship between early activity modulation in sensory cortices during selective encoding and subsequent WM performance has not been established. To explore the influence of selective attention on WM recognition, we used electroencephalography to study the temporal dynamics of top–down modulation in a selective, delayed-recognition paradigm. Participants were presented with overlapped, “double-exposed” images of faces and natural scenes, and were instructed to either remember the face or the scene while simultaneously ignoring the other stimulus. Here, we present evidence that the degree to which participants modulate the early P100 (97–129 msec) event-related potential during selective stimulus encoding significantly correlates with their subsequent WM recognition. These results contribute to our evolving understanding of the mechanistic overlap between attention and memory.

The functional neuroanatomy of schizophrenic subsyndromes

2003 ◽  
Vol 33 (6) ◽  
pp. 1007-1018 ◽  
Author(s):  
G. D. HONEY ◽  
T. SHARMA ◽  
J. SUCKLING ◽  
V. GIAMPIETRO ◽  
W. SONI ◽  
...  
Keyword(s):  
Working Memory ◽  
Factor Analysis ◽  
Rating Scale ◽  
Premotor Cortex ◽  
Cognitive Activity ◽  
Memory Task ◽  
Verbal Working Memory ◽  
Functional Neuroanatomy ◽  
Diverse Range ◽  
Negatively Associated

Background. There is considerable variability between patients in their expression of the diverse range of symptoms encompassed by the syndrome of schizophrenia, which may modulate functional activation to cognitive processing.Method. Here we investigate associations between schizophrenic subsyndrome scores, identified by factor analysis, and experimentally controlled brain activation. Five factors were defined by rotated principal components analysis of PANSS rating scale measurements in 100 patients with schizophrenia. A subsample of 30 patients and a group of 27 comparison subjects were studied using functional magnetic resonance imaging (fMRI) during the performance of two periodically designed cognitive activation experiments: verbal working memory and psychomotor sequencing.Results. Factor analysis replicated the five dimensions consistently reported. Within the patient group, power of activation by working memory was negatively associated with global symptom severity in left lingual and temporo-parietal cortices; negatively associated with positive subsyndrome scores in left inferior frontal and superior temporal cortices and basal ganglia; and positively associated with negative subsyndrome scores in lateral and medial premotor cortex. No relationship was observed between subsyndrome scores and functional activation during the motor task. Between-group comparisons demonstrated reduced power of response to the working memory task by patients in bilateral dorsolateral prefrontal and left pre- and post-central cortices.Conclusions. In this study we observed task-specific modulation of functional response associated with symptom expression in schizophrenia. Our findings are compatible with previous empirical findings and theoretical conceptualization of human brain function, in terms of capacity constraints on activation in the face of competing demands from pathological and task-related cognitive activity.

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