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1. Switching between External and Internal Attention in Hippocampal Networks

   https://doi.org/10.1523/JNEUROSCI.0029-23.2023  

   Poskanzer, Craig; Aly, Mariam (August 2023, The Journal of Neuroscience)

   Everyday experience requires processing external signals from the world around us and internal information retrieved from memory. To do both, the brain must fluctuate between states that are optimized for external versus internal attention. Here, we focus on the hippocampus as a region that may serve at the interface between these forms of attention and ask how it switches between prioritizing sensory signals from the external world versus internal signals related to memories and thoughts. Pharmacological, computational, and animal studies have identified input from the cholinergic basal forebrain as important for biasing the hippocampus toward processing external information, whereas complementary research suggests the dorsal attention network (DAN) may aid in allocating attentional resources toward accessing internal information. We therefore tested the hypothesis that the basal forebrain and DAN drive the hippocampus toward external and internal attention, respectively. We used data from 29 human participants (17 female) who completed two attention tasks during fMRI. One task (memory-guided) required proportionally more internal attention, and proportionally less external attention, than the other (explicitly instructed). We discovered that background functional connectivity between the basal forebrain and hippocampus was stronger during the explicitly instructed versus memory-guided task. In contrast, DAN–hippocampus background connectivity was stronger during the memory-guided versus explicitly instructed task. Finally, the strength of DAN–hippocampus background connectivity was correlated with performance on the memory-guided but not explicitly instructed task. Together, these results provide evidence that the basal forebrain and DAN may modulate the hippocampus to switch between external and internal attention. SIGNIFICANCE STATEMENTHow does the brain balance the need to pay attention to internal thoughts and external sensations? We focused on the human hippocampus, a region that may serve at the interface between internal and external attention, and asked how its functional connectivity varies based on attentional states. The hippocampus was more strongly coupled with the cholinergic basal forebrain when attentional states were guided by the external world rather than retrieved memories. This pattern flipped for functional connectivity between the hippocampus and dorsal attention network, which was higher for attention tasks that were guided by memory rather than external cues. Together, these findings show that distinct networks in the brain may modulate the hippocampus to switch between external and internal attention. 

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2. Spectral signature and behavioral consequence of spontaneous shifts of pupil-linked arousal in human

   https://doi.org/10.7554/eLife.68265  

   Podvalny, Ella; King, Leana E; He, Biyu J (August 2021, eLife)

   Arousal levels perpetually rise and fall spontaneously. How markers of arousal—pupil size and frequency content of brain activity—relate to each other and influence behavior in humans is poorly understood. We simultaneously monitored magnetoencephalography and pupil in healthy volunteers at rest and during a visual perceptual decision-making task. Spontaneously varying pupil size correlates with power of brain activity in most frequency bands across large-scale resting state cortical networks. Pupil size recorded at prestimulus baseline correlates with subsequent shifts in detection bias ( c ) and sensitivity ( d ’). When dissociated from pupil-linked state, prestimulus spectral power of resting state networks still predicts perceptual behavior. Fast spontaneous pupil constriction and dilation correlate with large-scale brain activity as well but not perceptual behavior. Our results illuminate the relation between central and peripheral arousal markers and their respective roles in human perceptual decision-making. 

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3. Neural dynamics encoding risky choices during deliberation reveal separate choice subspaces

   https://doi.org/10.1016/j.pneurobio.2025.102776  

   Peters, Logan M; Roadarmel, Alec; Overton, Jacqueline A; Stickle, Matthew P; Kong, Zhaodon; Saez, Ignacio; Moxon, Karen Anne (July 2025, Progress in Neurobiology)

   Human decision-making involves the coordinated activity of multiple brain areas, acting in concert, to enable humans to make choices. Most decisions are carried out under conditions of uncertainty, where the desired outcome may not be achieved if the wrong decision is made. In these cases, humans deliberate before making a choice. The neural dynamics underlying deliberation are unknown and intracranial recordings in clinical settings present a unique opportunity to record high temporal resolution electrophysiological data from many (hundreds) brain locations during behavior. Combined with dynamic systems modeling, these allow identification of latent brain states that describe the neural dynamics during decision-making, providing insight into these neural dynamics and computations. Results show that the neural dynamics underlying risky decisions, but not decisions without risk, converge to separate subspaces depending on the subject’s preferred choice and that the degree of overlap between these subspaces declines as choice approaches, suggesting a network level representation of evidence accumulation. These results bridge the gap between regression analyses and data driven models of latent states and suggest that during risky decisions, deliberation and evidence accumulation toward a final decision are represented by the same neural dynamics, providing novel insights into the neural computations underlying human choice. 

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4. Anchoring Functional Connectivity to Individual Sulcal Morphology Yields Insights in a Pediatric Study of Reasoning

   https://doi.org/10.1523/JNEUROSCI.0726-24.2025  

   Häkkinen, Suvi; Voorhies, Willa_I; Willbrand, Ethan_H; Tsai, Yi-Heng; Gagnant, Thomas; Yao, Jewelia_K; Weiner, Kevin_S; Bunge, Silvia_A (May 2025, The Journal of Neuroscience)

   A salient neuroanatomical feature of the human brain is its pronounced cortical folding, and there is mounting evidence that sulcal morphology is relevant to functional brain architecture and cognition. However, the relationships between sulcal anatomy, brain activity, and behavior are still poorly understood. We previously found that the depth of three small, shallow sulci in the lateral prefrontal cortex (LPFC) was linked to reasoning performance during development (Voorhies et al., 2021). These findings beg the question: What is the linking mechanism between sulcal morphology and cognition? Here, we investigated functional connectivity among sulci in LPFC and the lateral parietal cortex in participants drawn from the same sample as our previous study. We leveraged manual parcellations (21 sulci/hemisphere, 1,806 total) and functional magnetic resonance imaging data from a reasoning task from 43 participants aged 7–18 years (20 females). We conducted clustering and classification analyses of individual-level functional connectivity among sulci. Broadly, we found that (1) connectivity patterns of individual sulci could be differentiated and more accurately than cortical patches equated for size and shape; (2) sulcal connectivity did not consistently correspond with that of probabilistic labels or large-scale networks; (3) sulci clustered based on connectivity patterns, not dictated by spatial proximity; and (4) across individuals, greater depth was associated with higher network centrality for several sulci under investigation. These results illustrate how sulcal morphology can be functionally relevant and provide proof of concept that using sulci to define an individual coordinate space for functional connectomes is a promising future direction. 

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5. Intrinsic functional connectivity among memory networks does not predict individual differences in narrative recall

   https://doi.org/10.1162/imag_a_00169  

   Kurkela, Kyle; Ritchey, Maureen (May 2024, Imaging Neuroscience)

   Abstract Individuals differ greatly in their ability to remember the details of past events, yet little is known about the brain processes that explain such individual differences in a healthy young population. Previous research suggests that episodic memory relies on functional communication among ventral regions of the default mode network (“DMN-C”) that are strongly interconnected with the medial temporal lobes. In this study, we investigated whether the intrinsic functional connectivity of the DMN-C subnetwork is related to individual differences in memory ability, examining this relationship across 243 individuals (ages 18-50 years) from the openly available Cambridge Center for Aging and Neuroscience (Cam-CAN) dataset. We first estimated each participant’s whole-brain intrinsic functional brain connectivity by combining data from resting-state, movie-watching, and sensorimotor task scans to increase statistical power. We then examined whether intrinsic functional connectivity predicted performance on a narrative recall task. We found no evidence that functional connectivity of the DMN-C, with itself, with other related DMN subnetworks, or with the rest of the brain, was related to narrative recall. Exploratory connectome-based predictive modeling (CBPM) analyses of the entire connectome revealed a whole-brain multivariate pattern that predicted performance, although these changes were largely outside of known memory networks. These results add to emerging evidence suggesting that individual differences in memory cannot be easily explained by brain differences in areas typically associated with episodic memory function. 

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