scholarly journals Stabilized supralinear network can give rise to bistable, oscillatory, and persistent activity

2018 ◽  
Vol 115 (13) ◽  
pp. 3464-3469 ◽  
Author(s):  
Nataliya Kraynyukova ◽  
Tatjana Tchumatchenko
Keyword(s):  
Working Memory ◽  
Sensory Integration ◽  
Memory Storage ◽  
Unified Theory ◽  
Rhythm Generation ◽  
Persistent Activity ◽  
Cortical Circuits ◽  
Cortical Function ◽  
Neuronal Mechanisms ◽  
Exactly Solvable

A hallmark of cortical circuits is their versatility. They can perform multiple fundamental computations such as normalization, memory storage, and rhythm generation. Yet it is far from clear how such versatility can be achieved in a single circuit, given that specialized models are often needed to replicate each computation. Here, we show that the stabilized supralinear network (SSN) model, which was originally proposed for sensory integration phenomena such as contrast invariance, normalization, and surround suppression, can give rise to dynamic cortical features of working memory, persistent activity, and rhythm generation. We study the SSN model analytically and uncover regimes where it can provide a substrate for working memory by supporting two stable steady states. Furthermore, we prove that the SSN model can sustain finite firing rates following input withdrawal and present an exact connectivity condition for such persistent activity. In addition, we show that the SSN model can undergo a supercritical Hopf bifurcation and generate global oscillations. Based on the SSN model, we outline the synaptic and neuronal mechanisms underlying computational versatility of cortical circuits. Our work shows that the SSN is an exactly solvable nonlinear recurrent neural network model that could pave the way for a unified theory of cortical function.

scholarly journals Persistent Activity during Working Memory from Front to Back

2021 ◽  
Author(s):  
Clayton E Curtis ◽  
Thomas C Sprague
Keyword(s):  
Working Memory ◽  
Neural Activity ◽  
Cognitive Abilities ◽  
Memory Storage ◽  
Past Century ◽  
Persistent Activity ◽  
Neuroscience Research ◽  
Early Visual Cortex ◽  
High Level

Working memory (WM) extends the duration over which information is available for processing. Given its importance in supporting a wide-array of high level cognitive abilities, uncovering the neural mechanisms that underlie WM has been a primary goal of neuroscience research over the past century. Here, we critically review what we consider the two major arcs of inquiry, with a specific focus on findings that were theoretically transformative. For the first arc, we briefly review classic studies that led to the canonical WM theory that cast the prefrontal cortex (PFC) as a central player utilizing persistent activity of neurons as a mechanism for memory storage. We then consider recent challenges to the theory regarding the role of persistent neural activity. The second arc, which evolved over the last decade, stemmed from sophisticated computational neuroimaging approaches enabling researchers to decode the contents of WM from the patterns of neural activity in many parts of the brain including early visual cortex. We summarize key findings from these studies, their implications for WM theory, and finally the challenges these findings pose. A comprehensive theory of WM will require a unification of these two arcs of research.

scholarly journals Persistent Activity During Working Memory From Front to Back

2021 ◽  
Vol 15 ◽  
Author(s):  
Clayton E. Curtis ◽  
Thomas C. Sprague
Keyword(s):  
Working Memory ◽  
Neural Activity ◽  
Cognitive Abilities ◽  
Memory Storage ◽  
Past Century ◽  
Persistent Activity ◽  
Neuroscience Research ◽  
Early Visual Cortex ◽  
High Level

Working memory (WM) extends the duration over which information is available for processing. Given its importance in supporting a wide-array of high level cognitive abilities, uncovering the neural mechanisms that underlie WM has been a primary goal of neuroscience research over the past century. Here, we critically review what we consider the two major “arcs” of inquiry, with a specific focus on findings that were theoretically transformative. For the first arc, we briefly review classic studies that led to the canonical WM theory that cast the prefrontal cortex (PFC) as a central player utilizing persistent activity of neurons as a mechanism for memory storage. We then consider recent challenges to the theory regarding the role of persistent neural activity. The second arc, which evolved over the last decade, stemmed from sophisticated computational neuroimaging approaches enabling researchers to decode the contents of WM from the patterns of neural activity in many parts of the brain including early visual cortex. We summarize key findings from these studies, their implications for WM theory, and finally the challenges these findings pose. Our goal in doing so is to identify barriers to developing a comprehensive theory of WM that will require a unification of these two “arcs” of research.

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 Fear not! Anxiety biases attentional enhancement of threat without impairing working memory filtering

2019 ◽  
Author(s):  
Christine Salahub ◽  
Stephen Emrich
Keyword(s):  
Working Memory ◽  
Visual Working Memory ◽  
State Anxiety ◽  
Attentional Control ◽  
Event Related Potentials ◽  
Memory Storage ◽  
Attentional Biases ◽  
Related Potentials ◽  
Filtering Efficiency ◽  
Memory Resources

Individuals with anxiety have attentional biases toward threat-related distractors. This deficit in attentional control has been shown to impact visual working memory (VWM) filtering efficiency, as anxious individuals inappropriately store threatening distractors in VWM. It remains unclear, however, whether this mis-allocation of memory resources is due to inappropriate attentional enhancement of threatening distractors, or to a failure in suppression. Here, we used a systematically lateralized VWM task with fearful and neutral faces to examine event-related potentials related to attentional selection (N2pc), suppression (PD), and working memory maintenance (CDA). We found that state anxiety correlated with attentional enhancement of threat-related distractors, such that more anxious individuals had larger N2pc amplitudes toward fearful distractors than neutral distractors. However, there was no correlation between anxiety and memory storage of fearful distractors (CDA). These findings demonstrate that anxiety biases attention toward fearful distractors, but that this bias does not always guarantee increased memory storage of threat-related distractors.

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 Rhythmic Accessibility to Sequential Working Memory in a Theta Phase-Dependent Manner

2021 ◽  
Author(s):  
Takuya Ideriha ◽  
Junichi Ushiyama
Keyword(s):  
Working Memory ◽  
Memory Storage ◽  
Dependent Manner ◽  
Random Interval ◽  
Phase Coding ◽  
Short Period ◽  
Theta Phase ◽  
Sequential Information ◽  
The Impact ◽  
Theta Range

Working memory is active short-term memory storage that is easily accessible and underlies various activities, such as maintaining phone numbers in mind for a short period [1,2]. There is accumulating theoretical and physiological evidence that memorized items are represented rhythmically by neural oscillation in the theta range (4-7 Hz) [3,4]. However, the impact of this process on human behavior is yet to be examined. Here we show that simply memorizing sequential information affects a behavioral index (i.e., reaction time, RT) in a rhythmic manner. In the main experiment (Experiment 1), we measured RTs to a visual probe that appeared at one of two sequentially memorized locations after a random interval. Consequently, RTs to the first and second probes each fluctuated in the theta range as a function of the random interval, and the phases of the two theta fluctuations were not in phase or anti-phase, but shifted by approximately 270 degree. Interestingly, the 270 degree phase difference corresponded to the rhythm of "phase coding", where sequential information is represented on the specific phase of theta oscillation [5-7]. These relationships were not observed in tasks simply requiring attention (Experiment 2) or memorization (Experiment 3) of spatial locations without sequential order. In conclusion, the current results demonstrate that our behavior fluctuates when recalling memorized sequential items in the theta-range, suggesting that accessibility to sequential working memory is rhythmic rather than stable, possibly reflecting theta-phase coding.

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

scholarly journals Contralateral Delay Activity Tracks Fluctuations in Working Memory Performance

2018 ◽  
Vol 30 (9) ◽  
pp. 1229-1240 ◽  
Author(s):  
Kirsten C. S. Adam ◽  
Matthew K. Robison ◽  
Edward K. Vogel
Keyword(s):  
Working Memory ◽  
Individual Differences ◽  
Memory Load ◽  
Memory Performance ◽  
Memory Task ◽  
Memory Storage ◽  
Alpha Power ◽  
Working Memory Load ◽  
Contralateral Delay Activity ◽  
Trial Performance

Neural measures of working memory storage, such as the contralateral delay activity (CDA), are powerful tools in working memory research. CDA amplitude is sensitive to working memory load, reaches an asymptote at known behavioral limits, and predicts individual differences in capacity. An open question, however, is whether neural measures of load also track trial-by-trial fluctuations in performance. Here, we used a whole-report working memory task to test the relationship between CDA amplitude and working memory performance. If working memory failures are due to decision-based errors and retrieval failures, CDA amplitude would not differentiate good and poor performance trials when load is held constant. If failures arise during storage, then CDA amplitude should track both working memory load and trial-by-trial performance. As expected, CDA amplitude tracked load (Experiment 1), reaching an asymptote at three items. In Experiment 2, we tracked fluctuations in trial-by-trial performance. CDA amplitude was larger (more negative) for high-performance trials compared with low-performance trials, suggesting that fluctuations in performance were related to the successful storage of items. During working memory failures, participants oriented their attention to the correct side of the screen (lateralized P1) and maintained covert attention to the correct side during the delay period (lateralized alpha power suppression). Despite the preservation of attentional orienting, we found impairments consistent with an executive attention theory of individual differences in working memory capacity; fluctuations in executive control (indexed by pretrial frontal theta power) may be to blame for storage failures.

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