bioRxiv Subject Collection: Neuroscience's Journal
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Thursday, February 13th, 2025
| Time |
Event |
| 8:18a |
A common algorithm for confidence judgements across visual, auditory and audio-visual decisions
Most studies investigating the computational basis of decision confidence have focused on simple visual perceptual tasks, leaving open questions about how confidence is formed in decisions involving other sensory modalities or those requiring the integration of information across modalities. To address these gaps, we used computational modelling to analyse confidence judgements in perceptual decisions involving visual, auditory, and audio-visual stimuli. Drawing on research into visual confidence, we adapted models from the literature to evaluate their fit to our data, comparing three popular classes: unscaled evidence strength, scaled evidence strength, and Bayesian models. Our results show that the scaled evidence strength models consistently outperformed the other model classes across all tasks and could also be used to predict behaviour in the audio-visual task from the unidimensional auditory and visual model fits. These findings suggest that confidence judgements across different perceptual decisions rely on a shared algorithm that dynamically accounts for both sensory uncertainty and evidence strength, without the computation of posterior probabilities. Additionally, we investigated the algorithms used for multidimensional (audio-visual) confidence judgements specifically, showing that participants integrated both the visual and auditory dimensions of the stimulus, rather than relying solely on the most informative modality, and used a modality-independent measure of sensory uncertainty to adjust their confidence. Overall, our findings provide evidence for a common algorithm underlying confidence judgements across modalities and demonstrate the broad applicability of the scaled evidence strength algorithm, even in tasks requiring the integration of distinct sensory information. | | 3:31p |
Context-dependent hierarchical categorization of human faces: Behavioral and EEG/MEG evidence
Social categorization of faces provides a key cognitive basis of human behavior and may occur along various dimensions of facial attributes. The present study investigated a potential hierarchical structure of social categorization of faces based on a superordinate (Species) versus a subordinate (Race) level of abstraction of facial attributes. We recorded behavioral performances in a face classification task and found faster responses to the same set of Asian faces when presented alternately with dog faces (a species context) relative to Black faces (a race context). In addition, using a repetition suppression (RS) paradigm, we recorded electroencephalography (EEG) and magnetoencephalography (MEG) signals to Asian faces in the species and race contexts, respectively. Our analyses of the RS effects on EEG/MEG signals to Asian faces revealed that dynamic neural encoding of similarity of Asian faces occurred in the right fusiform gyrus at 140-200 ms and in the left temporoparietal junction at 317-413 ms after stimulus onset in the species context but only in the left temporoparietal junction at 317-413 ms in the race context. These behavioral and EEG/MEG findings unravel the neurocognitive mechanisms of context-dependent social categorization of faces by highlighting its hierarchically organized structure based on different levels of facial attributes. | | 3:31p |
Fast-timescale hippocampal processes bridge between slowly unfurling neocortical states during memory search
Prior behavioral work showed that event structure plays a key role in our ability to mentally search through memories of continuous naturalistic experience. We hypothesized that, neurally, this memory search process involves a division of labor between slowly unfurling neocortical states representing event knowledge and fast hippocampal-neocortical communication that supports retrieval of new information at transitions between events. To test this, we tracked slow neural state-patterns in a sample of ten patients undergoing intracranial electroencephalography as they viewed a movie and then searched their memories in a structured naturalistic interview. As patients answered questions ("after X, when does Y happen next?"), state-patterns from movie-viewing were reinstated in neocortex; during memory-search, states unfurled in a forward direction. Moments of state-transition were marked by low-frequency power decreases in cortex and preceded by power decreases in hippocampus that correlated with reinstatement. Connectivity-analysis revealed information-flow from hippocampus to cortex underpinning state-transitions. Together, these results support our hypothesis that fast hippocampal processes bridge between slow neocortical states during memory search. | | 3:31p |
Developing an anatomically valid segmentation protocol for anterior regions of the medial temporal lobe for neurodegenerative diseases
Abstract: Background: The anterior portion of the medial temporal lobe (MTL) is one of the first regions targeted by pathology in sporadic Alzheimer's disease (AD) and Limbic-predominant Age-related TDP-43 Encephalopathy (LATE) indicating a potential for metrics from this region to serve as imaging biomarkers. Leveraging a unique post-mortem dataset of histology and magnetic resonance imaging (MRI) scans we aimed to 1) develop an anatomically valid segmentation protocol for anterior entorhinal cortex (ERC), Brodmann Area (BA) 35, and BA36 for in vivo 3 tesla (T) MRI and 2) incorporate this protocol in an automated approach. Methods: We included 20 cases (61-97 years old, 50% females) with and without neurodegenerative diseases (11 vs. 9 cases) to ensure generalizability of the developed protocol. Digitized MTL Nissl-stained coronal histology sections from these cases were annotated and registered to same-subject post-mortem MRI. The protocol was developed by determining the location of histological borders of the MTL cortices in relation to anatomical landmarks. Subsequently the protocol was applied to 15 cases twice, with a 2-week interval, to assess intra-rater reliability with the Dice Similarity Index (DSI). Thereafter it was implemented in our in-house Automatic Segmentation of Hippocampal Subfields (ASHS)-T1 approach and evaluated with DSIs. Results: The anterior histological border distances of ERC, BA35 and BA36 were evaluated with respect to various anatomical landmarks and the distance relative to the beginning of the hippocampus was chosen. To formulate segmentation rules, we examined the histological sections for the location of borders in relationship to anatomical landmarks in the coronal sections. The DSI for the anterior MTL cortices for the intra-rater reliability was 0.85-0.88 and for the ASHS-T1 against the manual segmentation was 0.62-0.65. Discussion: We developed a reliable segmentation protocol and incorporated it in an automated approach. Given the vulnerability of the anterior MTL cortices to tau deposition in AD and LATE, the updated approach is expected to improve imaging biomarkers for these diseases. | | 7:47p |
Neuromodulation of the endbulb of Held synapse in the cochlear nucleus
Synapses vary greatly in synaptic strength and plasticity, even within the same circuitry or set of pre- and postsynaptic neurons. Neuromodulation is a candidate mechanism to explain some of this variability. Neuromodulators such as monoamines can differentially regulate presynaptic function as well as neuronal excitability. Variability is found also for the large calyceal synapses of the auditory pathway that are endowed with high synaptic vesicle (SV) release probability (Pvr) and large postsynaptic currents enabling reliable and temporally precise transmission of auditory information. Here we investigated whether the calyceal endbulb of Held synapse formed by auditory nerve fibers onto bushy cells (BCs) in the anteroventral cochlear nucleus (AVCN) is modulated by norepinephrine (NE) and serotonin (5-HT). Using electron microscopy (EM) of the cochlear nucleus we found evidence for putative monoaminergic varicosities in both ventral and dorsal divisions. Immunostaining for vesicular 5-HT and NE transporters revealed NE-containing and 5-HT-containing varicosities in the AVCN, juxtaposed to both endbulbs and BCs. Furthermore, we detected immunofluorescence for 5-HT1B, 5-HT4, 5-H7 receptors (R) and 2C-adrenergic receptors (AR) in BCs. We used voltage-clamp recordings from mouse BCs in order to uncover potential presynaptic effects of neuromodulation, which revealed an increase in frequency of miniature excitatory postsynaptic currents (mEPSCs) upon application of NE but not 5-HT. Evoked synaptic transmission was unaffected by the application of either NE or 5-HT. Likewise, while studying the biophysical properties of the BCs, we did not observe effects of NE or 5-HT on low-voltage-activated K+ (K+LVA) and hyperpolarization-activated mixed cation (HCN) channels during application. In summary, we report evidence for the presence of monoaminergic innervation in the cochlear nucleus and for subtle functional NE-neuromodulation at the endbulb of Held synapse. | | 7:47p |
Perception and neural representation of intermittent odor stimuli in mice
Odor cues in nature are sparse and highly fluctuating due to turbulent transport. To investigate how animals perceive these intermittent cues, we developed a behavioral task in which head-restrained mice made binary decisions based on the total number of discrete odor pulses presented stochastically over several seconds. Mice readily learned this task, and their performance was well-described by widely used decision models. Logistic regression of binary choices against the timing of odor pulses within the respiratory cycle revealed that mice placed higher perceptual weight to stimuli arriving during inhalation than exhalation, a phase dependency that strongly correlated with the magnitude of responses in olfactory sensory neurons. The population response of anterior piriform cortex (APCx) neurons to odor pulses was also modulated by respiration phase, although individual neurons displayed varying levels of phase-dependence. Single APCx neurons responded stochastically and transiently to odor pulses, leading to a representation that carries signatures of sensory evidence, but not its accumulation. Our study reveals that mice can integrate intermittent odor signals across dozens of breaths, but respiratory modulation of sensory inputs imposes limits on information acquisition that cortical circuits cannot overcome to improve behavior. | | 7:47p |
Cortical control of innate behavior from subcortical demonstration
Motor control in mammals is traditionally viewed as a hierarchy of descending spinal-targeting pathways, with frontal cortex at the top. Many redundant muscle patterns can solve a given task, and this high dimensionality allows flexibility but poses a problem for efficient learning. Although a feasible solution invokes subcortical innate motor patterns, or primitives, to reduce the dimensionality of the control problem, how cortex learns to utilize such primitives remains an open question. To address this, we studied cortical and subcortical interactions as head-fixed mice learned contextual control of innate hindlimb extension behavior. Naive mice performed reactive extensions to turn off a cold air stimulus within seconds and, using predictive cues, learned to avoid the stimulus altogether in tens of trials. Optogenetic inhibition of large areas of rostral cortex completely prevented avoidance behavior, but did not impair hindlimb extensions in reaction to the cold air stimulus. Remarkably, mice covertly learned to avoid the cold stimulus even without any prior experience of successful, cortically-mediated avoidance. These findings support a dynamic, heterarchical model in which the dominant locus of control can change, on the order of seconds, between cortical and subcortical brain areas. We propose that cortex can leverage periods when subcortex predominates as demonstrations, to learn parameterized control of innate behavioral primitives. |
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