Why is cognitive effort experienced as costly? A widespread observation is that people avoid mentally effortful courses of action, and much recent work examining cognitive effort has explained subjective effort evaluation – and, consequently, preferences – in economic terms, which assumes that the expenditure of cognitive effort is experienced as costly. However, this economic perspective is largely tacit about the source of these costs. Here, we review recent theoretical treatments of effort costs, which take vastly different perspectives (information-theoretic, psychological, and biological) to explain how the subjective experience of cognitive effort arises from controlled information processing, exploring their predictions concerning the simple observation that people experience tasks with high (versus low) working memory demands as costly. Finally, we identify open questions that might help bridge across these accounts.
A demographic theory of similarity-biased social learning We develop a demographic theory of similarity-biased social learning that formalizes our understanding of when and why individuals should preferentially copy others that look or act like them. We build an evolutionary model in which individuals can either learn on their own or copy others from a demonstrator pool that contains varying proportions of in-group and out-group members, and where group tags can be more or less informative about local knowledge. We find that where social learning becomes common, selection favors copying biases that track the direction of informational advantage—toward the group that tends to be better adapted to local conditions, including an antisimilarity bias when tags are negatively associated with local correctness (as may be the case for some immigrant communities). We also find conditions in which a similarity bias can stabilize social learning when such learners are already common, but not when they are rare, with implications for the role of group identities in cultural evolution. We discuss implications for understanding parochialism as risk aversion, majority–minority dynamics, the sociology of immigration, and the lasting impacts of colonialism.
Early correlates of visual awareness are affected by self-related information Self-related cues, most notably one’s own face, are highly salient and confer processing advantages at both conscious and unconscious levels. Whether such self-related information and stimulus salience modulate the earliest electroencephalography (EEG) correlate of visual awareness, the visual awareness negativity (VAN), remains unknown. In this study, we examined whether self-related information influences the amplitude, latency, and topography of the VAN. Thirty-six participants performed a backward masking task while an EEG was recorded as viewing either their own or a familiar face under masked and unmasked conditions. VAN was computed for each identity by subtracting unaware from aware face-specific trials. Results showed that VAN amplitude was greater during self-face perception, specifically over the right hemisphere. Moreover, VAN was larger at parieto-occipital than at occipital electrodes. These findings indicate that stimulus salience related to self-information directly impacts the earliest neural correlates of visual awareness. Such an effect may reflect enhanced perceptual or attentional mechanisms triggered by self-related content. This suggests either that early awareness correlates are embedded within perceptual and attentional dynamics that shape conscious access, or that the VAN does not constitute a purely content-independent correlate of consciousness.
Foraging models explain human exploration in uncertain tasks Different fields have fundamentally different models of how decisions are made. Psychology and neuroscience tend to assume that decisions are made by calculating and comparing the values of all options. In ethology, conversely, decisions tend to be binary regardless of the number of options: Decision-makers calculate the value of continuing to exploit some option and explore only when this value drops below a threshold. Because these fields use incompatible methods, it remains unclear which view better describes human decision-making. We find that humans use compare-to-threshold computations even in classic compare-alternative tasks. Because the reinforcement-learning models typically used in the cognitive and brain sciences depend on compare-alternative computations, we also develop a compare-to-threshold foraging model. Compared to previous models, the foraging model better fits participant behavior, predicts the tendency to repeat choices, and predicts held-out participants that were almost impossible under traditional compare-alternative models. These results suggest that humans use compare-to-threshold computations in more environments than were previously known.
Representations of Subsecond Duration-Based Timing by Complex Spike Synchrony in Cerebellar Purkinje Neurons The cerebellum contributes to associative motor learning and sensorimotor coordination in part by tracking subsecond time intervals between behaviorally relevant events, raising the question of how duration, or absolute time, is encoded. Here, we investigated whether information about duration is present in Purkinje cell complex spikes during repetitive sensory stimuli. Crus I Purkinje cells expressing the fast calcium indicator GCaMP8f were imaged at high speed (250 fps), allowing detection of complex spike-associated calcium signals from hundreds of Purkinje cell dendrites simultaneously, with 4 ms temporal resolution, in awake head-fixed mice of both sexes. Air puffs were applied to the whisker pad in stimulus trains that varied in the mean and variance of interstimulus intervals (ISIs, 100–900 ms). In responsive cells, the mean probability of complex spike firing increased approximately fivefold ∼35 ms post-puff, primarily owing to well-timed spiking after the stimulus rather than an increase in spike rate. The maximal response probability, and in some cells also the response latency, varied linearly with ISI. The values of both variables were consistent for each ISI, regardless of the attributes of the stimulus train, suggesting that they carried information about absolute, rather than relative, durations between stimulus pairs. Because each puff evoked only one or zero complex spikes per Purkinje cell, the dependence of spike probability on ISI emerged as a trial-by-trial dependence of the degree of synchronous firing on ISI, suggesting that subsecond absolute timing of somatosensory signals may be represented by complex spike synchrony across populations of Purkinje cells.
A hierarchical coordinate system for sequence memory in human entorhinal cortex The entorhinal cortex (EC) supports a coordinate system for spatial memories, organised in a hierarchy along the EC dorso-ventral axis. Recent theories suggest that a similar coordinate system could scaffold non-spatial memories. Here we show that an abstract hierarchical coordinate system supports arbitrary sequence memories in the human medial temporal lobe (MTL). In single-unit recordings from MTL, we find abstract, coordinate-like coding in a simple sequential memory task. In fMRI we find that abstract coordinate representations are arranged hierarchically along the entorhinal cortex, mirroring the anatomical gradient of grid cells in the rodent EC but now for non-spatial sequences. We replicate this finding in an independent cohort of participants. These data suggest that memories are scaffolded on a hierarchical coordinate system aligned to preserved anatomy across domains and species.
Hippocampal Reactivation Trades Episodic Detail for Semantic Gist in Human Memory Memory must balance preserving episode-specific details with extracting generalizable structure. Here, we test whether spontaneous hippocampal reactivation during postencoding rest actively transforms memories by strengthening semantic gist at the expense of episodic detail. Twenty-four participants encoded Deese–Roediger–McDermott word lists presented in male or female voices, creating orthogonal semantic (list theme) and episodic (voice source) information. Using high-resolution fMRI, we tracked list-specific reactivation in hippocampal subfields during a 90-sec delay period. Most consistently in CA1, reactivation frequency showed opposing relationships with subsequent memory: Greater reactivation predicted increased false recognition of semantic lures (gist extraction; dz = 0.52) and decreased accuracy for voice discrimination (source memory; dz = −0.65), yielding a large, bidirectional effect within CA1 (gist minus source, paired dz = 1.00). This bidirectional pattern was most prominent in anterior-to-mid hippocampus, consistent with its role in schematic processing. These findings reveal that hippocampal reactivation implements a computational trade-off, actively constructing abstract and generalizable representations while competitively weakening episode-specific details. This mechanism could explain how the brain rapidly extracts meaning from experience, with false memories emerging as a natural consequence of adaptive memory transformation rather than retrieval failure.
An Update on the Model of Connectivity of the Hippocampal Formation (I): The Perforant Pathway to the Dentate Gyrus The hippocampus participates in crucial functions such as memory consolidation, spatial processing and emotional regulation that require diverse input from multiple cortical areas that is funneled through the upper layers of the entorhinal cortex (EC), mostly from layer II to the dentate gyrus (DG). Traditional models of the hippocampal formation described 200,000 EC layer II neurons projecting to 1 million granule cells (GCs) in the rat, rendering low divergence (1:5), with each EC neuron establishing about 18,000 synapses with GCs and each GC receiving about 4000 synapses from EC neurons. In this manuscript, we update this model of connectivity incorporating new features described in the last three decades that include updated populations of EC layer II neurons obtained with design-based stereology, a revised definition of EC layer II based on molecular criteria and selecting reelin expressing neurons as the only layer II neurons projecting to the hippocampus. The updated model shows ~80,000 neurons from EC layer II projecting to the DG, ~45,000 from the medial entorhinal cortex (MEC) and ~35,000 from the lateral entorhinal cortex (LEC) with high divergence of 1:20 and 1:30. We also show that EC layer II neurons may establish ~90,000–115,000 synapses on GCs, while GCs receive about 8000 synapses from EC layer II neurons. We estimate a ~25% redundancy in the connectivity, so each EC neuron may contact ~68,000–86,000 GCs and each GC would be contacted by ~3000 neurons from MEC and 3000 from LEC. In addition, we quantitatively assess a potential projection of mossy cells to the middle molecular layer described in mice, which could have an impact on GC inhibition. Overall, we produced a detailed, complete, and updated quantitative model of EC projections to the DG that reveals a much more divergent and richer projection than previously described, with implications for functional models (e.g., pattern separation) and more widely for building realistic hippocampal models or establishing comparisons across species.