Cerebral cortex最新文献

Initiated by a long stay of Valérie Doyère in the laboratory of Joseph LeDoux, a Franco-American collaborative group was formed around the topic of emotion and time perception in a comparative perspective between humans and non-human animals. Here, we discuss results from our studies on the mechanisms underlying time distortion under 2 conditions, timing of a threatening stimulus and timing of a neutral stimulus in the context of fear, with insights from neurodevelopment. Although the type of temporal distortion depends on the experimental situations, in both humans and rodents a high-arousal emotion automatically triggers acceleration of an "internal clock" system, an effect that may rely on the early maturing amygdala. Our studies, particularly in humans, also point to the role of attention and self-awareness in regulating the effect of fear on timing, relying on the prefrontal cortex, a late maturing structure. Thus, in line with LeDoux, while the amygdala may process all characteristics of events (including time) necessary to quickly trigger appropriate survival behaviors, some type of time distortions may rely on higher-order processing, some specific to humans. The extent of the network underlying threat-related time distortions remains to be explored, with species comparisons being a promising means of investigation.

Functional magnetic resonance imaging studies typically rely on between-person analyses. To examine individual differences in functional connectivity, we used Group Iterative Multiple Model Estimation and its subgrouping function to analyze functional magnetic resonance imaging data of 54 participants who were suppressing imagined future threat. A two-stage random-effects meta-analytic approach was employed to examine individual differences. In addition to generalizable connections between brain regions, we identified individual differences in personalized models suggesting different pathways through which individuals suppress future threat. Two subgroups with distinct connectivity patterns emerged: One subgroup (n = 29; 53.70%), characterized by an additional lagged connection from the right to the left posterior cingulate cortex, exhibited comparatively higher anxiety and less brain connectivity, whereas the other subgroup (n = 25; 46.30%), showing an additional connection from the left posterior cingulate cortex to the ventromedial prefrontal cortex, was associated with lower anxiety levels and greater connectivity. This study points to individual differences in functional connectivity during emotion regulation.

Studying subjective experience is hard. We believe that pain is not identical to nociception, nor pleasure a computational reward signal, nor fear the activation of "threat circuitry". Unfortunately, introspective self-reports offer our best bet for accessing subjective experience, but many still believe that introspection is "unreliable" and "unverifiable". But which of introspection's faults do we find most damning? Is it that introspection provides imperfect access to brain processes (e.g. perception, memory)? That subjective experience is not objectively verifiable? That it is hard to isolate from non-subjective processing capacity? Here, I argue none of these prevents us from building a meaningful, impactful psychophysical research program that treats subjective experience as a valid empirical target through precisely characterizing relationships among environmental variables, brain processes and behavior, and self-reported phenomenology. Following recent similar calls by Peters (Towards characterizing the canonical computations generating phenomenal experience. 2022. Neurosci Biobehav Rev: 142, 104903), Kammerer and Frankish (What forms could introspective systems take? A research programme. 2023. J Conscious Stud 30:13-48), and Fleming (Metacognitive psychophysics in humans, animals, and AI. 2023. J Conscious Stud 30:113-128), "introspective psychophysics" thus treats introspection's apparent faults as features, not bugs-just as the noise and distortions linking environment to behavior inspired Fechner's psychophysics over 150 years ago. This next generation of psychophysics will establish a powerful tool for building and testing precise explanatory models of phenomenology across many dimensions-urgency, emotion, clarity, vividness, confidence, and more.

Adolescence has been characterized by risk taking and fearlessness. Yet, the emergence of anxiety disorders that are associated with fear peaks during this developmental period. Moreover, adolescents show heightened sensitivity to stress relative to children and adults. To address inconsistencies between the common characterization of adolescents as fearless and the evidence of heightened anxiety and stress during this time, we build upon foundational discoveries of threat-related circuitry and behavior in adult rodents by Joseph LeDoux and colleagues. Specifically, the conservation of this circuitry across species has provided opportunities for identifying mechanisms underlying threat responses that we have extended to developing humans and rodents. We elucidate situations in which adolescents show heightened threat responses and others where they appear fearless and link them to developmental changes of threat circuitry during this period. We discuss the potential adaptiveness of these threat responses for survival of the individual and species but also the potential risks for anxiety and stress. We end by offering potential new ways in which behavioral treatments for youth with anxiety and stress-related disorders may be optimized to target the developing vs developed brain.

In visual search, the repetition of target and distractor colors enables both successful search and effective distractor handling. Nevertheless, the specific consequences of trial-to-trial feature repetition in different search contexts are poorly understood. Here, we investigated how feature repetition shapes the electrophysiological and behavioral correlates of target processing and distractor handling, testing theoretically informed predictions with single-trial mixed-effects modeling. In two experiments, the colors of a fixed-shape target and singleton distractor changed unpredictably across trials. Targets were color singletons in Experiment 1, allowing efficient search among pop-out items, but were not uniquely colored in Experiment 2, encouraging slower shape-feature search. Interference by the distractor occurred only in pop-out search but was reduced by repetition. This was paralleled by the contralateral electroencephalography (EEG) response: Following a search color change, the target-related N2pc was greatly reduced, and salient distractors elicited an N2pc followed by an enhanced PD. This biphasic response was absent in Experiment 2, where color was less useful to search. Overall, distractor positivities were not sensitive to feature repetition, suggesting that they are unrelated to preparatory suppression. Attention-related lateralization components are not universally elicited by target or distractor feature values but are driven specifically by expected features important to the search task.

There is considerable interest in understanding the developmental origins and health implications of individual differences in brain structure and function. In this pre-registered study we demonstrate that a hidden subgroup within the general population-people with synesthesia (e.g. who "hear" colors)-show a distinctive behavioral phenotype and wide-ranging differences in brain structure and function. We assess the performance of 13 different brain-based biomarkers (structural and functional MRI) for classifying synesthetes against general population samples, using machine learning models. The features in these models were derived from subject-specific parcellations of the cortex using the Human Connectome Project approach. All biomarkers performed above chance with intracortical myelin being a particularly strong predictor that has not been implicated in synesthesia before. Resting state data show widespread changes in the functional connectome (including less hub-based connectivity). These brain-based individual differences within the neurotypical population can be as large as those that differentiate neurotypical from clinical brain states.

What are the neural processes associated with perceptual awareness that are distinct from preconscious sensory encoding and postperceptual processes such as reporting an experience? Using electroencephalography and a no-report visual masking paradigm, we manipulated stimulus visibility by varying the time between stimuli and masks in linear steps (17, 33, 50, 67, and 83 ms). Awareness increased nonlinearly, with stimuli never seen at the two shortest intervals, always seen at the two longest, and 50% seen at the intermediate interval. Separate report and no-report conditions were used to isolate awareness from task performance. Our results revealed a neural signal closely linked to perceptual awareness, independent of the task: a fronto-central event-related potential that we refer to as the N2 (~250 to 300 ms). Earlier event-related potential signals reflected the linear manipulation of stimulus strength, while later signals like P3b and temporal generalization of decoding were tied to task performance, appearing only in the report condition. Taken together, these findings inform current debates regarding theories of consciousness and offer new avenues for exploring the neural mechanisms supporting conscious processing.

Mice communicate through high-frequency ultrasonic vocalizations, which are crucial for social interactions such as courtship and aggression. Although ultrasonic vocalization representation has been found in adult brain areas along the auditory pathway, including the auditory cortex, no evidence is available on the neuronal representation of ultrasonic vocalizations early in life. Using in vivo two-photon calcium imaging, we analyzed auditory cortex layer 2/3 neuronal responses to USVs, pure tones (4 to 90 kHz), and high-frequency modulated sweeps from postnatal day 12 (P12) to P21. We found that ACx neurons are tuned to respond to ultrasonic vocalization syllables as early as P12 to P13, with an increasing number of responsive cells as the mouse age. By P14, while pure tone responses showed a frequency preference, no syllable preference was observed. Additionally, at P14, USVs, pure tones, and modulated sweeps activate clusters of largely nonoverlapping responsive neurons. Finally, we show that while cell correlation decreases with increasing processing of peripheral auditory stimuli, neurons responding to the same stimulus maintain highly correlated spontaneous activity after circuits have attained mature organization, forming neuronal subnetworks sharing similar functional properties.

The levels-of-processing framework, proposing that deep encoding enhances retention, plays a crucial role in episodic memory research. Neuroimaging evidence highlights that increased activity of the left ventrolateral prefrontal cortex during deep encoding predicts subsequent memory success. However, cognitive mechanisms underlying this region's involvement in establishing and consolidating deep and shallow traces remain unclear. In this preregistered study, we investigated whether repetitive transcranial magnetic stimulation over the left ventrolateral prefrontal cortex versus the vertex differentially modulates the formation and maintenance of deep and shallow traces. Trains of 20 Hz online repetitive transcranial magnetic stimulation were delivered over the left ventrolateral prefrontal cortex or vertex during tasks involving pleasantness (deep) and alphabetical order (shallow) judgments of words. Following encoding, two recognition tests assessed immediate and 24-h delayed recognition of words. Compared to the vertex control, ventrolateral prefrontal stimulation selectively disrupted the formation of episodic memory under deep encoding conditions, evidenced by increased response time at encoding and reduced immediate recognition in the deep but not shallow condition. Notably, forgetting rates across the 24-h delay were similar for disrupted deep, intact deep, and shallow items, implying that the rate of trace decay is independent of the strength of trace formation. The constant trace decay indicates that distinct mechanisms are involved in establishing and maintaining episodic traces.