Wednesday, December 4th, 2024

Time	Event
11:33a	The respiratory phase modulates task-related neural representations of visual stimuli We investigate how respiration influences cognition by examining the interaction between respiratory phase and task-related brain activity during two visual categorization tasks. While prior research shows that cognitive performance varies along the respiratory cycle, the underlying neurophysiological mechanisms remain poorly understood. Though some studies have shown that large-scale neural activity reflecting changes in the excitation-inhibition balance is co-modulated with the respiratory cycle, it remains unclear whether respiration directly shapes the quality by which task-relevant sensory information is encoded. We address this gap by applying single-trial multivariate analyses to EEG data obtained in humans, allowing us to track how respiration modulates the sensory evidence in this neurophysiological signal. Confirming previous studies, our data show that participants performance varies with the respiratory phase prior and during a trial. Importantly, they also suggest that respiration directly influences the sensory evidence carried by parieto-occipital processes emerging around 300 to 200 ms prior to participants responses. Hence, respiration and sensory-cognitive processes are not only highly intertwined but respiration directly facilitates the representation of behaviourally-relevant signals in the brain. (Comment on this)
11:33a	Beyond stimulus onset: Ongoing fixations within an object do not re-evoke category representations during free-viewing. Human visual perception in natural conditions involves multiple fixations within single objects. While traditional studies focus on transient neural responses to initial stimuli, this study investigates how object-category representations evolve across sequential fixations on an object. Using electroencephalography (EEG) and eye-tracking, we analyzed fixation-related potentials (FRPs) and applied multivariate pattern analysis (MVPA) to decode neural representations of faces and watches during prolonged viewing. Results revealed robust category-selective responses, including the N170 component, at stimulus onset, with sustained representations persisting throughout object presentation. Temporal signal deconvolution showed that subsequent fixations did not re-evoke the N170 but elicited transient occipital responses, likely reflecting low-level differences. These findings underscore the dynamic interplay between transient and sustained neural processes during naturalistic vision and highlight the importance of disentangling overlapping neural signals during free viewing. (Comment on this)
11:33a	Emotional content effects the precision of visual working memory ObjectivesOur working memory (WM) is susceptible to errors influenced by various sources. Recent research has illuminated the intricate relationship between emotional valence and working memory performance. This study aims to comprehensively investigate memory recall biases across different emotional categories. MethodTo explore this relationship, we designed and implemented a delayed-reproduction facial emotion n-back task. Participants were tasked with recalling the emotional valence of target faces across various n-back conditions, selecting their responses from a continuum of 19 morphed faces ranging from sad to happy. ResultsOur findings indicate that participants generally exhibit a negativity bias, struggling more with happy faces. Interestingly, they also perceive happy faces as less happy and sad faces as less sad, suggesting both positive and negative reappraisal in their emotional valence perception. This underscores the complex interplay between emotional valence and cognitive performance. Notably, recall of neutral images remained stable and was unaffected by preceding emotional contexts. ConclusionThese findings demonstrate that emotional content in working memory significantly impacts errors during WM tasks, with more emotionally charged faces leading to a greater drift toward the lower valence axis. This highlights the need for further exploration of how emotional factors influence cognitive processes in working memory. (Comment on this)
11:33a	The sparse driver system for in vivo single-cell labeling and manipulation in Drosophila In this protocol, we introduce a sparse driver system for cell-type specific single-cell labeling and manipulation in Drosophila, enabling complete and simultaneous expression of multiple transgenes in the same cells. The system precisely controls expression probability and sparsity via mutant FRT sites with reduced recombination efficiency and tunable FLP levels adjusted by heat-shock durations. We demonstrate that this generalizable toolkit enables tunable sparsity, multi-color staining, single-cell trans-synaptic tracing, single-cell manipulation, and in vivo analysis of cell-autonomous gene function. For details on the use and execution of this protocol, please refer to Xu et al. 2024. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=193 SRC="FIGDIR/small/626507v1_ufig1.gif" ALT="Figure 1"> View larger version (77K): org.highwire.dtl.DTLVardef@1a53b9org.highwire.dtl.DTLVardef@6eaa3aorg.highwire.dtl.DTLVardef@169cb2forg.highwire.dtl.DTLVardef@9aafb3_HPS_FORMAT_FIGEXP M_FIG C_FIG (Comment on this)
11:33a	Temporal Lobe Epilepsy is dominated by Region Specific Interictal Cortical Inhibition Epilepsy is typically characterized by excessive neuronal excitability, manifesting as seizures and interictal epileptiform discharges (IEDs) in the EEG. However, the dynamics of excitation and inhibition (E/I balance) remain poorly understood. Here, we leverage the aperiodic exponent of the EEG power spectrum--a marker indicative of synaptic inhibition--to investigate shifts in E/I balance during antiseizure medication (ASM) tapering in patients with mesial temporal lobe epilepsy (TLE). We analyzed EEG data from 28 TLE patients and 25 controls with non-epileptic episodes (NEE) undergoing presurgical video EEG monitoring. Unexpectedly, TLE patients showed a localized increase in the aperiodic exponent in the ipsilesional temporal lobe during ASM tapering, absent in controls. This inhibition increase correlated with seizure latency and predicted seizure occurrence. Intracranial recordings from 10 TLE patients revealed higher aperiodic exponents in the lateral temporal cortex compared to the hippocampus, suggesting stronger inhibition in the lateral cortex. Notably, hippocampal IEDs triggered transient inhibitory responses in the lateral cortex, accompanied by increased high-frequency activity and disrupted hippocampus-to-lateral connectivity. These findings suggest that TLE likely involves complex inhibitory mechanisms beyond the epileptic focus in the interictal period, with neocortical inhibition potentially containing epileptic activity, and offers a new tool to map epileptic brain regions. (Comment on this)
2:15p	An investigation of the effects of α and β-frequency neural entrainment using tACS on phase-aligned TMS-evoked corticospinal excitability Deep brain stimulation [DBS] is an effective treatment for many brain disorders (e.g., Parkinsons disease), has a favourable adverse effect profile, and can be particularly effective for individuals with treatment resistant symptoms. DBS is, however, inaccessible for most individuals, is extremely expensive, and is not considered suitable for children and adolescents. For these reasons, non-invasive alternatives to DBS, such as transcranial magnetic stimulation [TMS], are increasingly being sought to treat brain health conditions. Unfortunately, current TMS approaches exhibit large intra- and inter-subject variability in their efficacy, which limits their use clinically. One likely reason for this is that TMS is invariably delivered without reference to ongoing brain activity (i.e., open loop). We propose that the efficacy of stimulation might be improved, and the variability of its effects reduced, if stimulation could be synchronised with ongoing brain activity. To investigate this, we used transcranial alternating current stimulation (tACS) to induce entrainment of brain activity at two frequencies (=10 Hz and {beta}=20 Hz), and we delivered single pulse TMS that was temporally aligned with the phase of each tACS oscillation. To investigate the effects of tACS-phase-aligned TMS we measured motor-evoked potentials (MEPs). Our findings confirm that for -tACS and {beta}-tACS both corticospinal excitability and inter-trial variability varied as a function of tACS phase. Importantly, however, the tACS phase angle that produced maximum TMS-evoked excitability was different for -tACS and {beta}-tACS; coinciding with the negative peak (trough) for -tACS and the positive peak (peak) for {beta}-tACS. These findings confirm that aligning non-invasive brain stimulation to ongoing brain activity may increase the efficacy of TMS and reduce the variability of its effects. However, our results illustrate that the optimal phase of the tACS cycle at which to deliver TMS may vary for different tACS frequencies. (Comment on this)
2:15p	Temporal Configuration as a New Feature of Sound: Psychological and Neurophysiological Evidence, Cross-species Consistency and Underlying Neuronal Mechanisms Temporal integration is crucial for auditory perception, yet the mechanisms underlying its role are not fully elucidated. This study examines the perceptual discrimination of click trains with varied temporal configurations to determine if they can be perceived as distinct auditory objects, potentially introducing a novel dimension to sound perception. In humans, psychological experiments using a delayed match-to-sample task revealed that participants could distinctly discriminate between click trains with different temporal configurations, suggesting that temporal configuration significantly influences auditory perception. This was supported by electroencephalogram (EEG) recordings showing robust mismatch negativity (MMN) signals, indicating that the auditory system differentiates standard from deviant sounds based on their temporal characteristics. Parallel electrocorticography (ECoG) studies in rats demonstrated similar discriminatory abilities, suggesting a cross-species consistency. Neuronal recordings showed pronounced stimulus-specific adaptation (SSA) in the primary auditory cortex (A1) but minimal SSA in lower auditory areas such as the inferior colliculus (IC) and medial geniculate body (MGB), indicating that A1 uniquely integrates temporal features and discriminates complex temporal patterns. This research advances our understanding of how temporal configurations are processed in the auditory system and suggests a new feature of sound perception. (Comment on this)
2:46p	Individual differences in probabilistic learning and updating predictive representations in individuals with obsessive-compulsive tendencies Obsessive-compulsive (OC) tendencies involve intrusive thoughts and rigid, repetitive behaviours that also manifest at the subclinical level in the general population. The neurocognitive factors driving the development and persistence of the excessive presence of these tendencies remain highly elusive, though emerging theories emphasize the role of implicit information processing. Despite various empirical studies on distinct neurocognitive processes, the incidental retrieval of environmental structures in dynamic and noisy environments, such as probabilistic learning, has received relatively little attention. In this study, we aimed to unravel potential individual differences in implicit probabilistic learning and the updating of predictive representations related to OC tendencies in the general population. We conducted two independent online experiments (NStudy1 = 164, NStudy2 = 257) with young adults. Probabilistic learning was assessed using a reliable implicit visuomotor probabilistic learning task, which involved sequences with second-order non-adjacent dependencies. Our findings revealed that even among individuals displaying a broad spectrum of OC tendencies within a non-clinical population, implicit probabilistic learning remained remarkably robust. Furthermore, the results highlighted effective updating capabilities of predictive representations, which were not influenced by OC tendencies. These results offer new insights into individual differences in probabilistic learning and updating in relation to OC tendencies, contributing to theoretical, methodological, and practical approaches for understanding the maladaptive behavioural manifestations of OC disorder and subclinical tendencies. (Comment on this)
5:33p	Cortical dynamics in hand/forelimb S1 and M1 evoked by brief photostimulation of the mouses hand Spiking activity along synaptic circuits linking primary somatosensory (S1) and motor (M1) areas is fundamental for sensorimotor integration in cortex. Circuits along the ascending somatosensory pathway through mouse hand/forelimb S1 and M1 were recently described in detail (Yamawaki et al., 2021). Here, we characterize the peripherally evoked spiking dynamics in these two cortical areas in the same system. Brief (5 ms) optogenetic photostimulation of the hand generated short ([~]25 ms) barrages of activity first in S1 (onset latency 15 ms) then M1 (10 ms later). The estimated propagation speed was 20-fold faster from hand to S1 than from S1 to M1. Response amplitudes in M1 were strongly attenuated to approximately a third of those in S1. Responses were typically triphasic, with suppression and rebound following the initial peak. Parvalbumin (PV) inhibitory interneurons were involved in each phase, accounting for three-quarters of the initial spikes generated in S1, and their selective photostimulation sufficed to evoke suppression and rebound in both S1 and M1. Partial silencing of S1 by PV activation during hand stimulation reduced the M1 sensory responses. These results provide quantitative measures of spiking dynamics of cortical activity along the hand/forelimb-related transcortical loop; demonstrate a prominent and mechanistic role for PV neurons in each phase of the response; and, support a conceptual model in which somatosensory signals reach S1 via high-speed subcortical circuits to generate characteristic barrages of cortical activity, then reach M1 via densely polysynaptic corticocortical circuits to generate a similar but delayed and attenuated profile of activity. (Comment on this)

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