Biology subjects

Kwok, S. C.

Publications and source records attributed to Kwok, S. C..

At least 19 recordsLinked to original sources

bioRxiv2026

Perceptual similarity representations beyond the sensory cortex

It is commonly thought that information supporting conscious perception is primarily represented in sensory cortices, whereas association cortex encodes more abstract, task-dependent information. However, this impression may partly stem from difficulties in experimentally assessing the functions of association areas characterized by mixed selectivity and complex spatial topography. Here, we combined repetition-suppression (RS) and multi-voxel pattern analysis (MVPA) to extract richer information from human fMRI. With this approach, we asked whether association regions represent the perceptual similarity structure among color stimuli, although this perceptual similarity information was task-irrelevant in the experiment. Our analysis revealed such representations beyond the visual cortex, in lateral prefrontal, and parietal regions. We further demonstrated an electrophysiological complement to the fMRI findings by applying the same approach to local field potentials recorded in the macaque dorsomedial parietal cortex. Our findings suggest that higher-order areas beyond the visual cortex may play a key role in subjective color perception.

neuroscience↗

bioRxiv2026

Context-dependent functional diversity of dorsomedial posterior parietal neurons revealed by single-unit fMRI mapping during naturalistic viewing

The dorsomedial posterior parietal cortex (dmPPC) plays an important role in episodic processing by integrating sensory, cognitive, and motor information across distributed brain systems. However, how individual dmPPC neurons participate in large-scale functional organization during naturalistic experience remains poorly understood. To address this question, we combined single-unit electrophysiology and awake fMRI in separate cohorts of rhesus macaques viewing identical naturalistic video stimuli. Using single-unit fMRI mapping, we generated whole-brain neuron-BOLD functional maps by correlating individual neuronal activity with voxel-wise fMRI signals across the brain. We found that neuron-BOLD functional maps exhibited strong context-dependent organization, with neurons recorded during the same video context showing substantially greater similarity than neurons recorded during different video conditions. Compared with neuronal spiking activity or critical fMRI frames alone, neuron-BOLD functional maps more robustly capture contextual structure. Despite this shared large-scale organization, neighboring neurons recorded simultaneously from the same electrode often displayed markedly distinct whole-brain association patterns, revealing substantial local functional heterogeneity within the dmPPC. In addition, distributed cortical and medial temporal regions exhibited highly context-dependent neuron-BOLD association patterns during naturalistic viewing. Together, these findings demonstrate that dmPPC neurons participate in dynamic and heterogeneous large-scale functional organization during naturalistic episodic processing. More broadly, this study establishes single-unit fMRI mapping as a framework for linking single-neuron activity to distributed whole-brain dynamics across contextual conditions. Significance StatementUsing single-unit fMRI mapping, this study examined how individual dorsomedial posterior parietal cortex (dmPPC) neurons relate to large-scale brain activity during naturalistic video viewing in macaque monkeys. We found that neuron-BOLD functional maps exhibit strong context-dependent organization and capture contextual structure more robustly than neuronal spiking activity or fMRI frames alone. Despite this shared organization, neighboring dmPPC neurons often displayed markedly distinct whole-brain association patterns, revealing substantial local functional heterogeneity. These findings provide insight into how local neuronal populations participate in distributed cortical organization during naturalistic episodic processing.

neuroscience↗

bioRxiv2026

Using Light to Establish Habits in Laboratory Mice

Background and aimsPerseverative behaviours are commonly assessed using operant paradigms in which rodents work for drugs or food under physiological deprivation, limiting translational relevance to some behavioural addictions. Here we validated an operant paradigm in which the acquired behaviour is driven neither by physiological needs nor hedonic responses. MethodsMice were trained to lever-press for green light. Exp.1 used a within-subjects design to examine lever discrimination and whether responding could be "satiated" by light preexposure. Exp.2 examined instrumental contingency using a between-subjects design, with light delivery equated between contingent and non-contingent groups. Exp.3 replaced green light with dim red light producing less retinal photoreceptor excitation but comparable heat to assess non-photic cues. Exp.4 examined whether green light could affect food seeking different motivational states. ResultsIn Exp.1, green light supported lever discrimination. Among high responders, the satiation effect was modest (<15% reduction) and did not deter lever pressing. In Exp.2, instrumental contingency promoted response acquisition whereas random light delivery did not. In Exp.3, dim red light failed to sustain behaviour, producing [~]50% response decrement. In Exp.4, light potentiated food seeking under ad libitum feeding. Discussion and conclusionsResponse-contingent light serves as a reward to establish operant responding, which cannot be explained by alerting effects or thermal cues. Our study bridges the gap between animal models and findings from humans that coloured light may exacerbate smartphone use and that light therapy may reshape reward circuits in individuals with Internet gaming disorder symptoms [Li et al. (2026) Advanced Science 13:e14044].

animal behavior and cognition↗

bioRxiv2024

Fornix and Uncinate Fasciculus Support Metacognition-Driven Cognitive Offloading

People often use external tools to offload cognitive demands associated with remembering future intentions. While previous research has established a causal role of metacognition in cognitive offloading, the neural mechanisms supporting this metacognitive control process remain unclear. To address this, we conducted a study with 34 participants using diffusion tensor imaging (DTI) to examine how white matter connectivity supports metacognition-driven cognitive offloading. Behaviorally, we replicated prior findings showing that under-confidence in internal memory predicts a bias toward using external reminders. At the neural level, we used diffusion tensor imaging to quantify fractional anisotropy (FA), a measure of microstructural integrity in white matter. We found the microstructural integrity of the superior longitudinal fasciculus (SLF) and cingulum bundle (CB) negatively predicted deviations from the optimal use of reminders. The microstructural integrity of the fornix negatively predicted participants confidence in performing the task when restricted to internal memory. Our findings reveal the microstructural organization of these fronto-temporal-parietal white-matter tracts are related to metacognition driven cognitive offloading. We discuss several aspects of metacognition driven cognitive offloading from a white matter microstructural perspective.

neuroscience↗

bioRxiv2024

Disentangling Mnemonic Metacognition from Confidence by Communication between the Precuneus and Hippocampus

Metacognition, the ability to introspectively monitor ones own performance, remains an area with poorly understood neural mechanisms, particularly regarding the intercommunication among various brain regions. Recent studies have identified the precuneus as a key region in mnemonic metacognitive tasks, while the hippocampus is recognized for its role in memory function. This study aimed to investigate the role of the precuneus and hippocampus in mnemonic metacognition by utilizing intracranial electrode recordings from patients with intractable epilepsy to analyze the correlational dynamics between these regions. Our findings revealed that high gamma activity serve as a key feature in both the precuneus and hippocampus for confidence judgment. Based on signal detection theory (SDT), we discovered that high gamma activity in the precuneus is significantly linked to type 2 sensitivity (meta-d), while hippocampal high gamma activity was primarily linked to type 1 sensitivity (d). Additionally, the correlation between high gamma activity in the hippocampus and precuneus was exclusively related to type 2 sensitivity (meta-d). Temporal analysis indicated that the hippocampus is initially engaged for the memory process, followed by its joint engagement together with the precuneus for confidence generation. These findings elucidate the distinct electrophysiological roles of the hippocampus and precuneus in mnemonic metacognition, providing deeper insights into the neural mechanisms underlying this cognitive process.

neuroscience↗

bioRxiv2023

Neural signatures for temporal-order memory in the medial posterior parietal cortex

Episodic memory involves encoding and remembering the order of events experienced over time. Previous work examining the mechanisms of temporal-order memories has focused on the hippocampus and prefrontal cortices but has largely ignored the memory ensembles in the medial posterior parietal cortex (mPPC). Combining in vivo multi-unit electrophysiology and a temporal-order judgment task with cinematic material in the macaque, we find that mPPC neuronal activity reflects temporal context both during encoding and recall. During learning, mPPC neuronal ensembles encode the temporal information as well as contextual information embedded in the videos, whereas at retrieval these neurons fire in synchrony prior to memory-guided decisions. Moreover, the similarity between encoding and retrieval correlates with the animals performance. A control experiment further ruled out eye saccades, fixation, and scan path for their confounding roles in the neural results. Together, these data suggest that neurons in mPPC track the passage of time and contextual changes, thereby orchestrating for successful temporal-order memories at retrieval. SIGNIFICANCERemembering the temporal order of events is a vital function of the brain. This study provides the first evidence for the retrieval of temporal order of episodes at both single neuron and ensemble levels in the primate parietal cortex. The studys key breakthrough is the revelation that ensembles of time perceptive neurons, acting as "temporal context cells", can encode a spectrum of time constants and contexts for the experienced past and subsequently utilize this temporal record to discriminate the chronological order of past experiences. These results enhance theoretical frameworks for how encoded temporal past is maintained and reconstructed during memory retrieval.

neuroscience↗

bioRxiv2023

Sustained hippocampal theta-oscillations reflect experience-dependent learning in bidirectional temporal-order memory retrieval

Navigating within our neighborhood, learning a set of concepts, or memorizing a story, requires remembering the relationship between individual items that are presented sequentially. Theta activity in the mammalian hippocampus has been related to the encoding and recall of relational structures embedding episodic memories. However, how theta oscillations are involved in retrieving temporal order information in opposing directionality (forward vs backward) has not been characterized. Here, using intracranial recordings from 10 human epileptic patients of both genders with hippocampal electrodes, we tested the patients with a temporal order memory task in which they learned the spatial relationship among individual items arranged along a circular track and were tested on both forward-cued and backward-cued retrieval conditions. We found that sustained high-power oscillatory events in the hippocampal theta (2-8 Hz) band, as quantified by Pepisode rate, were higher for the backward conditions during the later stage but not in the earlier stage. The theta Pepisode results are consistent with the behavioral memory performance. In contrast, we observed a stronger effect of forward than backward retrieval for the gamma (30-70 Hz) Pepisode rate irrespective of stages. Our results revealed differential roles of theta vs. gamma oscillations in the retrieval of temporal order and how theta oscillations are specifically implicated in the learning process for efficient retrieval of temporal order memories under opposing directionality. Significance statementWhile the hippocampus is critical to link events into unitary episodes, the effect of repeated experiences, or learning, on these processes is not entirely clear. We discovered that hippocampal theta oscillation in humans is modulated by repeated experiences, which in turn increases the efficacy of backward-cued memory retrieval of temporal order. This study revealed an important physiological signature characterizing the role of experiences and learning in bidirectional temporal memory retrieval. Journal sectionBehavioral/Cognitive

neuroscience↗

bioRxiv2022

Mixed selectivity coding of content-temporal detail by dorsomedial posterior parietal neurons

The dorsomedial posterior parietal cortex is part of a higher-cognition network implicated in elaborate processes underpinning memory formation, recollection, episodes reconstruction, and temporal information processing. Neural coding for complex episodic processing is however under-documented. Here we revealed a set of neural codes of neuroethogram in the primate parietal cortex. Analyzing neural responses in macaque dmPPC to naturalistic videos, we discovered several groups of neurons that are sensitive to different categories of ethogram-items and to low-level sensory features, and saccadic eye movement. We also discovered that the processing of category and feature information by these neurons is sustained by accumulation of temporal information over a long timescale up to 30 s, corroborating its reported long temporal receptive windows. We performed an additional behavioral experiment and found that saccade-related activities could not account for the mixed neuronal responses elicited by the video stimuli. We further observed monkeys scan-paths and gaze consistency are modulated by video content. Taken altogether, these neural findings explain how dorsomedial PPC weaves fabrics of ongoing experiences together in real-time. The high dimensionality of neural representations should motivate us to shift the focus of attention from pure selectivity neurons to mixed selectivity neurons, especially in increasingly complex naturalistic task designs. HIGHLIGHTSO_LINeural codes for "neuroethogram" in macaque dorsomedial parietal cortex C_LIO_LIParietal neural codes exhibit mixed selectivity of event features C_LIO_LIDorsomedial PPC neurons support a long temporal receptive window for episodes C_LIO_LISaccadic movement could not explain away mixed neuronal responses C_LIO_LIConsistency in scan-path and gaze shown across viewing repetitions C_LI

neuroscience↗

bioRxiv2022

Theta oscillations in the human hippocampus normalize the information content of episodic memory

The principles governing the formation of episodic memories from the continuous stream of sensory stimuli are not fully understood. Theoretical models of the hippocampus propose that the representational format of episodic memories comprise oscillations in the theta frequency band (2-8 Hz) that set the time boundaries in which discrete events are bound encoded in the gamma frequency range (>30 Hz). We investigated this temporal segmentation and binding process by analyzing the intracranial EEG (iEEG) of surgically implanted epileptic patients performing a virtual-navigation task. We found a positive correlation between sensory information density encountered by the subject and hippocampal theta-frequency, suggesting that the human hippocampus normalizes the information content of episodic memories relative to the density of sensory information. This interpretation is further supported by the observation that as a marker of mnemonic encoding, i.e. the amount of persistent gamma events, directly correlates with sensory information density, gamma-frequency power and the phase relation between theta and gamma oscillations remain constant. Using a theoretical model of the hippocampus, we build a model that analogously displays a similar normalization of gamma episodes per theta cycle relative to information density by accounting for the physiological signatures of theta-gamma coding through combining fast and slow inhibitory feedback. We propose that this intrinsic normalization mechanism optimizes the trade-off between the discretization and compression of continuous experience relative to the limited capacity of episodic memory. SummaryWe move in continuous time and space, yet we can encode and recall discrete episodes from our past experiences. The neural mechanism behind this discretization is not fully understood. It has been previously observed that rodent locomotion modulates ongoing hippocampal theta rhythms. Thus, raising the question of whether these slow rhythms bind events together during a single oscillatory cycle relative to the movement speed or overall information density. We quantified the effects of increasing locomotion and sensory information in modulating theta oscillations during virtual navigation with intracranial hippocampal activity from human epileptic patients.. We observed hippocampal theta waves increased with higher speed and higher sensory demands, thereby maintaining constant information per oscillatory cycle. These results highlight the role of hippocampal theta oscillations in discretizing ongoing experience relative to the available information and explain how episodic memory integrates a fixed number of items per oscillatory theta cycle irrespective of richness of the external world.

neuroscience↗

bioRxiv2021

Temporal-sensitive prefrontal involvement in associating confidence with task performance illustrates metacognitive introspection in Old World monkeys (Macaca mulatta)

Metacognition refers to the ability to be aware of ones own cognition. Ample evidence indicates that metacognition in the human primate is highly dissociable from cognition, specialized across domains, and subserved by distinct neural substrates. However, these aspects remain relatively understudied in macaque monkeys. In the present study, we investigated the functionality of macaque metacognition by combining a confidence proxy, hierarchical Bayesian meta-d' computational modelling, and a single-pulse transcranial magnetic stimulation technique. We found that Brodmann area 46d (BA46d) played a critical role in supporting metacognition independent of task performance; we also found that the critical role of this region in meta-calculation was time-sensitive. Additionally, we report that macaque metacognition is highly domain-specific with respect to memory and perception decisions. These findings carry implications for our understanding of metacognitive introspection within the primate lineage.

neuroscience↗

bioRxiv2021

Distinct generation of subjective vividness and confidence during naturalistic memory retrieval in angular gyrus

Our subjective experience of remembering guides and monitors the reconstruction of past and simulation of the future, which enables us to identify mistakes and adjust our behavior accordingly. However, it remains incompletely understood what underlies the process of subjective mnemonic experience. Here, we combined behavior, repetitive transcranial magnetic stimulation (rTMS), and functional neuroimaging to probe whether vividness and confidence are generated differently during retrieval. We found that preretrieval rTMS targeting the left angular gyrus (AnG) selectively attenuated the vividness efficiency compared to control stimulation while keeping metacognitive efficiency and objective memory accuracy unaffected. Using trial-wise data, we showed that AnG stimulation altered the mediating role of vividness in confidence in the accuracy of memory judgment. Moreover, resting-state functional connectivity of hippocampus and AnG was specifically associated with vividness efficiency, but not metacognitive efficiency across individuals. Together, these results identify the causal involvement of AnG in gauging the vividness, but not the confidence, of memory, thereby suggesting a differentiation account of conscious assessment of memory by functionally and anatomically dissociating the monitoring of vividness from confidence.

neuroscience↗

bioRxiv2020

A meta-analysis on uncertainty monitoring in four non-primate animal species: Pigeons, rats, large-billed crows, and bees

Humans have the metacognitive capacity to be aware of what they do and do not know. While uncertainty monitoring has long been regarded as uniquely human, researchers in search of the polygenetic root of this ability have gathered evidence that primate species possess functional features parallel to humans. However, there were no systematic studies that quantitively take into account of extant data for these non-primate animals. Through a meta-analysis, we collected published data reported in 11 articles from 55 individual non-primate animals spanning over four species on the "opt-out" paradigm, the most prevailing paradigms used to test nonhuman animals uncertainty monitoring. We used chosen-forced advantage and opt-out rate to quantify animals performance results for computing the aggregated effect size for this literature. We found that these four NPA species process a significantly positive effect size for both scores and identified the moderators that have contributed to the inconsistencies across these studies. Implications for theories on metacognition are discussed.

animal behavior and cognition↗

bioRxiv2020

Diffusion property and functional connectivity of superior longitudinal fasciculus underpin human metacognition

Metacognition as the capacity of monitoring ones own cognition operates across domains. Here, we addressed whether metacognition in different cognitive domains rely on common or distinct neural substrates with combined diffusion tensor imaging (DTI) and functional magnetic resonance imaging (fMRI) techniques. After acquiring DTI and resting-state fMRI data, we asked participants to perform a temporal-order memory task and a perceptual discrimination task, followed by trial-specific confidence judgments. DTI analysis revealed that the structural integrity (indexed by fractional anisotropy) in the anterior portion of right superior longitudinal fasciculus (SLF) was associated with both perceptual and mnemonic metacognitive abilities. Using perturbed mnemonic metacognitive scores produced by inhibiting the precuneus using TMS, the mnemonic metacognition scores did not correlate with individuals SLF structural integrity anymore, revealing the relevance of this tract in memory metacognition. In order to further verify the involvement of several cortical regions connected by SLF, we took the TMS-targeted precuneus region as a seed in a functional connectivity analysis and found the functional connectivity between precuneus and two SLF-connected regions (inferior parietal cortex and precentral gyrus) differentially mediated mnemonic but not perceptual metacognition performance. These results illustrate the importance of SLF and a putative white-matter grey-matter circuitry that supports human metacognition.

neuroscience↗

bioRxiv2020

Behavioral evidence for memory replay of video episodes in macaque monkeys

Humans recall the past by replaying fragments of events temporally. Here, we demonstrate a similar effect in macaques. We trained six rhesus monkeys with a temporal-order judgement (TOJ) task and collected 5000 TOJ trials. In each trial, they watched a naturalistic video of about 10 s comprising two across-context clips, and after a 2-s delay, performed TOJ between two frames from the video. The monkeys apply a non-linear forward, time-compressed replay mechanism during the temporal-order judgement. In contrast with humans, such compression of replay is however not sophisticated enough to allow them to skip over irrelevant information by compressing the encoded video globally. We also reveal that the monkeys detect event contextual boundaries and such detection facilitates recall by an increased rate of information accumulation. Demonstration of a time-compressed, forward replay like pattern in the macaque monkeys provides insights into the evolution of episodic memory in our lineage. Impact StatementMacaque monkeys temporally compress past experiences and use a forward-replay mechanism during judgment of temporal-order between episodes.

neuroscience↗

bioRxiv2018

Individual susceptibility to TMS affirms the precuneual role in meta-memory upon recollection

BackgroundA recent virtual-lesion study using inhibitory repetitive transcranial magnetic stimulation (rTMS) confirmed the causal behavioral relevance of the precuneus in the evaluation of ones own memory performance (aka mnemonic metacognition).\n\nObjectiveThis studys goal is to elucidate how these TMS-induced neuromodulatory effects might relate to the neural correlates and be modulated by individual anatomical profiles in relation to meta-memory.\n\nMethodsIn a within-subjects design, we assessed the impact of 20-min rTMS over the precuneus, compared to the vertex, across three magnetic resonance imaging (MRI) neuro-profiles on 18 healthy subjects during a memory versus a perceptual task.\n\nResultsTask-based functional MRI revealed that BOLD signal magnitude in the precuneus is associated with variation in individual meta-memory efficiency, and such correlation diminished significantly following TMS targeted at the precuneus. Moreover, individuals with higher resting-state functional connectivity (rs-fcMRI) between the precuneus and the hippocampus, or smaller grey matter volume in the stimulated precuneal region exhibit considerably higher vulnerability to the TMS effect. These effects were not observed in the perceptual domain.\n\nConclusionWe provide compelling evidence in outlining a possible circuit encompassing the precuneus and its mnemonic midbrain neighbor the hippocampus at the service of realizing our meta-awareness during memory recollection of episodic details.\n\nHighlightsO_LITMS on precuneus reduces meta-memory ability during memory retrieval.\nC_LIO_LITMS disrupts the correlation between BOLD activity and meta-memory ability.\nC_LIO_LITMS effect is modulated by rs-fcMRI between precuneus and hippocampus.\nC_LIO_LIIndividuals with greater precuneal grey matter volume more immune to TMS effect.\nC_LI

neuroscience↗

bioRxiv2018

Mnemonic introspection in macaques is dependent on dorsolateral prefrontal but not orbitofrontal cortex

The human prefrontal cortex (PFC) has been associated more with meta-perceptual as opposed to meta-memory decisions from correlational neuroimaging investigations. Recently, metacognitive abilities have also been shown to be causally dependent upon anterior and dorsal PFC in non-human primate lesion studies. Two studies, utilizing post-decision wagering paradigms and reversible inactivation, challenged this meta-perceptual versus meta-memory notion and showed that dorsal and anterior prefrontal areas are associated with metamemory for experienced objects and awareness of ignorance respectively. Causal investigations are important but scarce; nothing is known, for example, about the causal contributions of prefrontal sub-regions to spatial metamemory. Here, we investigated the effects of dorsal versus ventral PFC lesions on two-alternative forced choice spatial discrimination tasks in male macaque monkeys. Importantly, we were rigorous in approach and applied three independent but complementary indices used to quantify individual animals metacognitive ability ("type II sensitivity") namely meta-d', d' measures, and Phi coefficient ({Phi}). Our results were consistent across indices: while neither lesions to superior dorsolateral PFC (sdlPFC) nor orbitofrontal cortex (OFC) impaired spatial recognition performance, only monkeys with sdlPFC lesions were impaired in meta-accuracy. Together with the observation that the same OFC lesioned monkeys were impaired in updating rule-value in a Wisconsin Card Sorting Test analog, we therefore document a functional double-dissociation between these two PFC regions. Out study presents important causal evidence that other dimensions, namely domain-specific processing (e.g., spatial versus non-spatial metamemory), also need considerations in understanding the functional specialization in the neural underpinnings of introspection. Significance StatementThis study demonstrates macaque monkeys meta-cognitive capability of introspecting its own memory success is causally dependent on intact superior dorsolateral prefrontal cortices (PFC) but not the orbitofrontal cortices. Combining neurosurgical techniques on monkeys and state-of-the-art measures of metacognition, we affirm a critical role of the PFC in supporting spatial meta-recognition memory and delineate functional specificity within PFC for distinct elements of metacognition.

neuroscience↗

bioRxiv2018

Time-dependent mnemonic vulnerability induced by new-learning

Reactivation renders consolidated memory labile again, and the ensuing temporary reconsolidation process is highly susceptible to mnemonic modification. Here, we show that memories in such an unstable state could be reprogrammed by sheer behavioral means, bypassing the need for pharmacological intervention. In two experiments using a \"face-location associationc\" paradigm in which participants experienced a \"Learning - New-learning - Final-test\" programme, we demonstrate that reactivated memory traces were robustly hampered when the new learning was strategically administered within a critical 20-minute time window. Using fMRI, we further advance our theoretical understanding that this lability can be mechanistically explained by the differential activation in the hippocampal-amygdala memory system implicated by the new-learning whereas the mnemonic intrusion caused by newly learned memories is efficaciously reconciled by the left inferior frontal gyrus. Our findings provide important implications for educational and clinical practices in devising effective strategies for memory integration.

neuroscience↗

bioRxiv2018

Causal evidence for mnemonic metacognition in human precuneus

Metacognition is the capacity to introspectively monitor and control ones own cognitive processes. Previous anatomical and functional neuroimaging findings implicated the important role of precuneus in metacognition processing, especially during mnemonic tasks. However, the issue of whether this medial parietal cortex is a domain-specific region that supports mnemonic metacognition remains controversial. Here, we focally disrupted this parietal area with repetitive transcranial magnetic stimulation in healthy participants of both sexes, seeking to ascertain its functional necessity for metacognition for memory versus perceptual decisions. Perturbing the precuneal activity impaired the metacognitive efficiency selectively in the memory judgment of temporal-order, but not in perceptual discrimination. Moreover, the correlation in individuals metacognitive efficiency between the domains disappeared when the precuneus was perturbed. Together with the previous finding that lesion to the anterior prefrontal cortex impairs perceptual but not mnemonic metacognition, we double dissociated the macro-anatomical underpinnings for the two kinds of metacognitive capacity in an interconnected network of brain regions.\n\nSIGNIFICANCE STATEMENTTheories on the neural basis of metacognition have thus far largely centered on the role of prefrontal cortex. Here we refined the theoretical framework through characterizing a unique precuneal involvement in mnemonic metacognition with a noninvasive but inferentially powerful method: transcranial magnetic stimulation. By quantifying meta-cognitive efficiency across two distinct domains (memory vs. perception) that are matched for stimulus characteristics, we reveal an instrumental - and highly selective - role of the precuneus in mnemonic metacognition. These causal evidence corroborate ample clinical reports that parietal lobe lesions often produce inaccurate self-reports of confidence in memory recollection and establish that the precuneus as a nexus for the introspective ability to evaluate the success of memory judgment in humans.

neuroscience↗