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1. Using functional connectivity models to characterize relationships between working and episodic memory

   https://doi.org/10.1002/brb3.2105  

   Stark, Gigi F. ; Avery, Emily W. ; Rosenberg, Monica D. ; Greene, Abigail S. ; Gao, Siyuan ; Scheinost, Dustin ; Todd Constable, R. ; Chun, Marvin M. ; Yoo, Kwangsun ( June 2021 , Brain and Behavior)

   Working memory is a critical cognitive ability that affects our daily functioning and relates to many cognitive processes and clinical conditions. Episodic memory is vital because it enables individuals to form and maintain their self‐identities. Our study analyzes the extent to which whole‐brain functional connectivity observed during completion of anN‐back memory task, a common measure of working memory, can predict both working memory and episodic memory.

   We used connectome‐based predictive models (CPMs) to predict 502 Human Connectome Project (HCP) participants' in‐scanner 2‐back memory test scores and out‐of‐scanner working memory test (List Sorting) and episodic memory test (Picture Sequence and Penn Word) scores based on functional magnetic resonance imaging (fMRI) data collected both during rest andN‐back task performance. We also analyzed the functional brain connections that contributed to prediction for each of these models.

   Functional connectivity observed duringN‐back task performance predicted out‐of‐scanner List Sorting scores and to a lesser extent out‐of‐scanner Picture Sequence scores, but did not predict out‐of‐scanner Penn Word scores. Additionally, the functional connections predicting 2‐back scores overlapped to a greater degree with those predicting List Sorting scores than with those predicting Picture Sequence or Penn Word scores. Functional connections with the insula, including connections between insular and parietal regions, predicted scores across the 2‐back, List Sorting, and Picture Sequence tasks.

   Our findings validate functional connectivity observed during theN‐back task as a measure of working memory, which generalizes to predict episodic memory to a lesser extent. By building on our understanding of the predictive power ofN‐back task functional connectivity, this work enhances our knowledge of relationships between working memory and episodic memory.

    

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2. 7-Tesla evidence for columnar and rostral–caudal organization of the human periaqueductal gray response in the absence of threat: a working memory study.

   https://doi.org/10.1523/JNEUROSCI.1757-23.2024  

   Fischbach, Alexandra K. ; Satpute, Ajay B. ; Quigley, Karen ; Kragel, Philip A. ; Chen, Danlei ; Bianciardi, Marta ; Wald, Larry ; Wager, Tor D. ; Choi, Ji-Kyung ; Zhang, Jiahe ; et al ( April 2024 , The Journal of Neuroscience)

   The periaqueductal gray (PAG) is a small midbrain structure that surrounds the cerebral aqueduct, regulates brain–body communication, and is often studied for its role in “fight-or-flight” and “freezing” responses to threat. We used ultra-high field 7-Tesla fMRI to resolve the PAG in humans and distinguish it from the cerebral aqueduct, examining its in vivo function in humans during a working memory task (N = 87). Both mild and moderate cognitive demand elicited spatially similar patterns of whole brain BOLD response, and moderate cognitive demand elicited widespread BOLD increases above baseline in the brainstem. Notably, these brainstem increases were not significantly greater than those in the mild demand condition, suggesting that a subthreshold brainstem BOLD increase occurred for mild cognitive demand as well. PAG response was group-aligned and examined with subject-specific masks. In PAG, both mild and moderate demand elicited a well-defined response in ventrolateral PAG (vlPAG), a region thought to be functionally related to anticipated painful threat in humans and non-human animals—yet, the present task posed only the most minimal (if any) “threat”, with the cognitive tasks used being approximately equivalent to remembering a phone number. These findings suggest that the PAG may play a more general role in visceromotor regulation, even in the absence of threat.

   Significance statementThe periaqueductal gray (PAG) is thought to control survival-related behavior, and is typically studied using experiments that manipulate threat. Others have proposed that the PAG plays a more general role in bodily regulation, but studies examining PAG function outside of threat-based experimental contexts are rare. We used high-resolution fMRI to examine PAG response in humans during a working memory task, which involves minimal threat. Moderate cognitive demands elicited a well-defined response in ventrolateral PAG, a functional subregion thought to coordinate a “freezing” response to threat. A task where threat is minimal elicited a clear fMRI response in one of the most well-known survival circuits in the brain, which suggests the PAG supports a more general function in brain­–body coordination.

    

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3. The causal impact of objective numeracy on judgments: Improving numeracy via symbolic and non-symbolic approximate arithmetic training yields more consistent risk judgments

   https://doi.org/10.5964/jnc.6925  

   Chesney, Dana L. ; Shoots-Reinhard, Brittany ; Peters, Ellen ( January 2021 , Journal of Numerical Cognition)

   Park and Brannon (2013, https://doi.org/10.1177/0956797613482944) found that practicing non-symbolic approximate arithmetic increased performance on an objective numeracy task, specifically symbolic arithmetic. Manipulating objective numeracy would be useful for many researchers, particularly those who wish to investigate causal effects of objective numeracy on performance. Objective numeracy has been linked to performance in multiple areas, such as judgment-and-decision-making (JDM) competence, but most existing studies are correlational. Here, we expanded upon Park and Brannon’s method to experimentally manipulate objective numeracy and we investigated whether numeracy’s link with JDM performance was causal. Experimental participants drawn from a diverse internet sample trained on approximate-arithmetic tasks whereas active control participants trained on a spatial working-memory task. Numeracy training followed a 2 × 2 design: Experimental participants quickly estimated the sum of OR difference between presented numeric stimuli, using symbolic numbers (i.e., Arabic numbers) OR non-symbolic numeric stimuli (i.e., dot arrays). We partially replicated Park and Brannon’s findings: The numeracy training improved objective-numeracy performance more than control training, but this improvement was evidenced by performance on the Objective Numeracy Scale, not the symbolic arithmetic task. Subsequently, we found that experimental participants also perceived risks more consistently than active control participants, and this risk-consistency benefit was mediated by objective numeracy. These results provide the first known experimental evidence of a causal link between objective numeracy and the consistency of risk judgments. 

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4. Multitask brain network reconfiguration is inversely associated with human intelligence

   https://doi.org/10.1093/cercor/bhab473  

   Thiele, Jonas A. ; Faskowitz, Joshua ; Sporns, Olaf ; Hilger, Kirsten ( February 2022 , Cerebral Cortex)

   Intelligence describes the general cognitive ability level of a person. It is one of the most fundamental concepts in psychological science and is crucial for the effective adaption of behavior to varying environmental demands. Changing external task demands have been shown to induce reconfiguration of functional brain networks. However, whether neural reconfiguration between different tasks is associated with intelligence has not yet been investigated. We used functional magnetic resonance imaging data from 812 subjects to show that higher scores of general intelligence are related to less brain network reconfiguration between resting state and seven different task states as well as to network reconfiguration between tasks. This association holds for all functional brain networks except the motor system and replicates in two independent samples (n = 138 and n = 184). Our findings suggest that the intrinsic network architecture of individuals with higher intelligence scores is closer to the network architecture as required by various cognitive demands. Multitask brain network reconfiguration may, therefore, represent a neural reflection of the behavioral positive manifold – the essence of the concept of general intelligence. Finally, our results support neural efficiency theories of cognitive ability and reveal insights into human intelligence as an emergent property from a distributed multitask brain network.

    

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5. A tale of two lexica: Investigating computational pressures on word representation with neural networks

   https://doi.org/10.3389/frai.2023.1062230  

   Avcu, Enes ; Hwang, Michael ; Brown, Kevin Scott ; Gow, David W. ( March 2023 , Frontiers in Artificial Intelligence)

   Introduction The notion of a single localized store of word representations has become increasingly less plausible as evidence has accumulated for the widely distributed neural representation of wordform grounded in motor, perceptual, and conceptual processes. Here, we attempt to combine machine learning methods and neurobiological frameworks to propose a computational model of brain systems potentially responsible for wordform representation. We tested the hypothesis that the functional specialization of word representation in the brain is driven partly by computational optimization. This hypothesis directly addresses the unique problem of mapping sound and articulation vs. mapping sound and meaning. Results We found that artificial neural networks trained on the mapping between sound and articulation performed poorly in recognizing the mapping between sound and meaning and vice versa. Moreover, a network trained on both tasks simultaneously could not discover the features required for efficient mapping between sound and higher-level cognitive states compared to the other two models. Furthermore, these networks developed internal representations reflecting specialized task-optimized functions without explicit training. Discussion Together, these findings demonstrate that different task-directed representations lead to more focused responses and better performance of a machine or algorithm and, hypothetically, the brain. Thus, we imply that the functional specialization of word representation mirrors a computational optimization strategy given the nature of the tasks that the human brain faces. 

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