Neural correlates of perceptual consciousness from within: a narrative review of human intracranial research Despite many years of research, the quest to identify neural correlates of perceptual consciousness (NCC) remains unresolved. One major obstacle lies in methodological limitations: most studies rely on non-invasive neural measures with limited spatial or temporal resolution making it difficult to disentangle proper NCCs from concurrent cognitive processes. Additionally, the relatively low sensitivity of non-invasive neural measures limits the interpretation of null findings in studies targeting proper NCCs. In this review, we discuss how human intracranial recordings can advance the search for NCCs, by offering high spatiotemporal resolution, improved signal sensitivity, and broad cortical and subcortical coverage. We review studies that have examined NCCs at the level of single neurons and populations of neurons, and evaluate their implications on the debates between cognitive and sensory theories of consciousness. Finally, we highlight the limits of current intracranial human recordings and propose future directions based on emerging technologies and novel experimental paradigms.
Neural responses to sensorimotor conflict in an embodied agency task The Sense of Agency (SoA), the subjective experience that ‘I am in control of my actions’, has been proposed to involve both early implicit sensorimotor processes (feeling of agency) and later explicit higher–level processes (judgment of agency). Even though SoA is fundamental to our interactions with the external world and to our construct of the self, its underlying neural mechanism remains elusive. In this pre-registered EEG study, we used time-frequency analysis and Multivariate Pattern Analysis (MVPA) to investigate the neural characteristics of sensorimotor conflicts within an agency paradigm. Using an established embodied virtual reality paradigm, we modulated visual feedback to examine neural responses to conflicts between predicted and perceived sensory feedback. Participants moved their finger while viewing a virtual hand that either mimicked their movement, differed anatomically (identical movement, different finger), or spatially (identical finger, angular shift), and then rated their SoA while brain activity was recorded. In accordance with our pre-registered hypothesis, visuomotor conflicts, which were associated with robust decreases in self-attribution, were linked to increased alpha-band power, and exploratory analyses further revealed increased theta-band power. We show that trials containing a sensorimotor alteration could be reliably decoded from unaltered trials with up to 68% accuracy starting around 200 msec after movement onset. Cross-decoding further revealed shared neural patterns across anatomical and spatial manipulations, emerging around 500 msec post-movement. Together, our results indicate a temporal progression from early, condition-specific sensorimotor responses to a later domain-general component, consistent with the two-step model of agency.
Separable and integrated pleasantness coding for appetitive and aversive odors across olfactory and ventral prefrontal cortices Odor pleasantness is a key driver of approach and avoidance behaviors, raising the question of how pleasantness is represented in olfactory brain areas. To address this question, here we analyzed an existing dataset consisting of perceptual and fMRI responses to 160 odors from three individual participants. We find that piriform cortex, amygdala, orbitofrontal cortex, and ventromedial prefrontal cortex encode the pleasantness of appetitive and aversive odors. However, whereas these pleasantness representations are separable for appetitive and aversive odors in piriform cortex and amygdala, ventral prefrontal cortex (especially area 11) combines information from appetitive and aversive odors and forms a continuous representation of odor salience. These results suggest that distinct pleasantness codes for appetitive and aversive odors in olfactory cortices are integrated into a continuous representation in ventral prefrontal cortices.
Interoception, alexithymia, and motor congruency: Psychological drivers of body ownership in virtual reality Alexithymia, a personality trait marked by difficulty in identifying and describing emotions, is associated with differences in interoception – the ability to perceive and interpret internal bodily signals. Interoception plays a key role in forming a coherent sense of self and contributes to body ownership, the feeling that one’s body belongs to oneself. This study explored how interoception and alexithymia influence body ownership in immersive virtual reality, particularly under conditions of motor cue congruency. Findings revealed a negative relationship between alexithymia and interoception, and a positive effect of motor synchrony on body ownership. Interoceptive accuracy (assessed via the heartbeat counting task) showed a trend-level positive association with body ownership when virtual and physical movements were aligned. Given the modest sample size (N = 26) and reliance on a single cardiac interoceptive measure, findings should be considered preliminary and warrant replication in larger, multi-method studies.
Dendritic Inhibition Terminates Plateau Potentials in CA1 Pyramidal Neurons In CA1 pyramidal neurons (CA1-PYRs), plateau potentials control synaptic plasticity and the emergence of place cell identity. Here, we show that dendritic inhibition terminates plateaus in an all-or-none manner in CA1-PYRs recorded in acute hippocampal slices from mice of either sex. Plateaus were initially resistant to inhibition but became increasingly susceptible to termination as they progressed. Two subtypes of dendrite-targeting oriens-lacunosum moleculare (OLM) interneurons, accessed in transgenic mice based on the expression of the genes Ndnf or Chrna2 (OLMNdnf and OLMα2, respectively), could terminate plateau potentials. OLMNdnf generated slower postsynaptic currents that terminated plateaus more effectively than OLMα2. Voltage-gated Ca2+ channels (VGCCs) were necessary for plateaus, which were prolonged by blocking small-conductance Ca2+–activated K+ channels (SK). A single-compartment model with these two conductances recapitulated core experimental findings and provided a mechanistic explanation for terminations. Plateaus arose from VGCCs maintained in the active state by sustained Ca2+ influx, a positive feedback loop that was quasi-balanced by ISK. Inhibition terminated plateaus by driving the membrane potential below a dynamic threshold to deactivate VGCCs and end the positive feedback loop. Similar all-or-none termination dynamics were observed for plateaus evoked under cholinergic modulation. Lastly, two-photon Ca2+ imaging showed that plateaus evoke large dendritic Ca2+ transients that were graded by terminations. Overall, our results demonstrate how the feedback inhibitory circuit interacts with intrinsic cellular mechanisms to regulate plateau potentials and shape dendritic Ca2+ signals in CA1-PYRs.
Dorsal CA1 projections to nucleus accumbens and lateral septum differentially regulate social and locomotor behavior Beyond its established role in spatial and episodic memory, the dorsal hippocampus also shapes motivated behavior by routing contextual information to downstream targets. Dorsal CA1 (dCA1) projects to the nucleus accumbens (NAc) and lateral septum (LS); here, we show that these pathways regulate distinct behaviors. We mapped and selectively manipulated these circuits in mice using projection-specific viral tracing, intersectional labeling, and terminal optogenetics. Activating dCA1-to-NAc terminals selectively increased social interaction without altering locomotion or novel-object exploration, consistent with a role in social motivation rather than generalized exploration. In contrast, the dCA1-to-LS pathway bidirectionally regulated locomotion, with activation increasing movement and inhibition decreasing locomotion without specifically influencing social behavior. Intersectional labeling also identified a small population of dCA1 neurons that projects to both targets. Together, these findings suggest that distinct dCA1 output pathways can differentially regulate social interaction and locomotor state, providing a circuit-level view of how hippocampal contextual signals are routed to subcortical regions.
Stress disrupts hippocampal integration of overlapping events and memory inference in humans Integrating related events in memory is essential for building knowledge that extends beyond direct observation and enables flexible inference. Here, we show that acute stress impairs inference by both reducing the degree to which past memories are reactivated during new learning and leading to their differentiation, rather than integration, in hippocampus. Adults learned A-B associations on day 1 and underwent a stress or control manipulation before learning overlapping B-C associations on day 2, with A-C inference tested thereafter. We demonstrate that stress reduces hippocampal reactivation of A elements during B-C learning, and lower reactivation was directly correlated with impaired A-C inference. Representational similarity analysis revealed that stress increases neural dissimilarity between overlapping A and C elements in the hippocampus, indicating pattern differentiation and a representation as discrete events. Our findings demonstrate that acute stress hampers a key memory integration mechanism, with broad implications for educational, legal, and clinical settings.
Post-traumatic stress disorder Post-traumatic stress disorder (PTSD) is a maladaptive and debilitating psychiatric disorder that develops after exposure to a severe traumatic event. PTSD is characterized by intrusive re-experiencing of traumatic memories, avoidance of trauma reminders, negative alterations in cognition and mood, and changes in arousal and reactivity. PTSD is prevalent, with tens of millions of patients in the USA alone affected. The lifetime prevalence worldwide is estimated to be about 4–6%, but it can occur in up to 25–30% of people who experience severe psychological trauma, such as combat veterans, refugees and assault victims. PTSD is highly comorbid with major depressive disorder, anxiety disorders and substance use disorders, and it is a leading cause of suicide. PTSD also increases the risk of multiple medical problems including cardiovascular and metabolic disorders. We review the epidemiology and diagnostic aspects of PTSD in adults, the mechanistic and neurobiological understanding of the syndrome from neural circuitry to genetic mechanism as well as medication, psychotherapy and other trauma-informed treatment approaches to PTSD and trauma-related syndromes.
Second-Language Learning Facilitates Non-Adjacent Dependency Learning: Effects Moderated by Specific Language Statistical learning allows language learners to implicitly track regularities in input. Prior studies have suggested that second language (L2) learning affects statistical learning, but the nature of this relationship remains unclear. Does L2 learning broadly enhance sensitivity to statistical structure, selectively tune learners to patterns emphasized in the learned language, or both? We tested English-speaking adults enrolled in introductory Mandarin or Spanish courses, along with English monolingual controls, on two statistical learning tasks: a tonal word segmentation task and a non-adjacent dependency (NAD) learning task. Participants completed both tasks at the beginning of instruction and again after two academic terms. All groups performed above chance in the tonal task, but none showed significant improvement over time, including Mandarin learners. In contrast, only Spanish learners demonstrated increased sensitivity to NADs over time. These findings suggest that statistical learning is not uniformly boosted by L2 experience. Instead, L2 exposure may selectively tune learners’ sensitivity to relational patterns that are emphasized in their linguistic experience. More broadly, the results highlight how the structure of linguistic experience can shape statistical learning mechanisms.