Biology subjects

Keysers, C.

Publications and source records attributed to Keysers, C..

27 records · Page 2Linked to original sources

bioRxiv2019

Does higher sampling rate (Multiband + SENSE) benefit the detection of task correlated BOLD for cognitive neuroscience applications at 3T?

Multiband (MB) or Simultaneous multi-slice (SMS) acquisition schemes allow the acquisition of MRI signals from more than one spatial coordinate at a time. Commercial availability has brought this technique within the reach of many neuroscientists and psychologists. Most early evaluation of the performance of MB acquisition employed resting state fMRI or the most basic tasks. In this study, we tested whether the advantages of using MB acquisition schemes generalize to group analyses using a cognitive task more representative of typical cognitive neuroscience applications. Twenty-three subjects were scanned on a Philips 3T scanner using five sequences up to eight-fold acceleration with MB-factors 1 to 4, SENSE factors up to 2 and corresponding TRs of 2.45s down to 0.63s, while they viewed (i) movies showing complex actions with hand object interactions and (ii) control movies without hand object interaction. Using random effects group-level, voxel-wise analysis we found that all sequences were able to detect the basic action observation network known to be recruited by our task. The highest t-values were found for sequences with MB4 acceleration. For the MB1 sequence, a 50% bigger voxel volume was needed to reach comparable t-statistics. The group-level t-values for resting state networks (RSNs) were also highest for MB4 sequences. Here the MB1 sequence with larger voxel size did not perform comparable to the MB4 sequence. Altogether, we can thus recommend the use of MB4 (and SENSE 1.5 or 2) on a Philips scanner when aiming to perform group-level analyses using cognitive block design fMRI tasks and voxel sizes in the range of cortical thickness (e.g. 2.7mm isotropic). While results will not be dramatically changed by the use of multiband, our results suggest that MB will bring a moderate but significant benefit.

neuroscience↗

bioRxiv2019

Challenges in assessing voxel-wise single-subject level benefits of MB acceleration

Multiband (MB) acceleration of functional magnetic resonance imaging has become more widely available to neuroscientists. Here we compare MB factors of 1, 2 and 4 while participants view complex hand actions vs. simpler hand movements to localize the action observation network. While in a previous study, we show that MB4 shows moderate improvements in the group-level statistics, here we explore the impact it has on single subject statistics. We find that MB4 provides an increase in p values at the first level that is of medium effect size compared to MB1, providing moderate evidence across a number of voxels that MB4 indeed improves single subject statistics. This effect was localized mostly within regions that belong to the action observation network. In parallel, we find that Cohens d at the single subject level actually decreases using MB4 compared to MB1. Intriguingly, we find that subsampling MB4 sequences, by only considering every fourth acquired volume, also leads to increased Cohens d values, suggesting that the FAST algorithm we used to correct for temporal auto-correlation may over-penalize sequences with higher temporal autocorrelation, thereby underestimating the potential gains in single subject statistics offered by MB acceleration, and alternative methods should be explored. In summary, considering the moderate gains in statistical values observed both at the group level in our previous study and at the single subject level in this study, we believe that MB technology is now ripe for neuroscientists to start using MB4 acceleration for their studies, be it to accurately map activity in single subjects of interest (e.g. for presurgical planning or to explore rare patients) or for the purpose of group studies.

neuroscience↗

bioRxiv2019

Measuring shared responses across subjects using intersubject correlation

Our capacity to jointly represent information about the world underpins our social experience. By leveraging one individuals brain activity to model anothers, we can measure shared information across brains--even in dynamic, naturalistic scenarios where an explicit response model may be unobtainable. Introducing experimental manipulations allows us to measure, for example, shared responses between speakers and listeners, or between perception and recall. In this tutorial, we develop the logic of intersubject correlation (ISC) analysis and discuss the family of neuroscientific questions that stem from this approach. We also extend this logic to spatially distributed response patterns and functional network estimation. We provide a thorough and accessible treatment of methodological considerations specific to ISC analysis, and outline best practices.

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bioRxiv2018

Action perception recruits the cerebellum and is impaired in spinocerebellar ataxia patients

Our cerebellum has been proposed to generate prediction signals that may help us plan and execute our motor programs. However, to what extent our cerebellum is also actively involved in perceiving the action of others remains to be elucidated. Using fMRI, we show here that observing goal-directed hand actions of others bilaterally recruits cerebellar Lobules VI, VIIb and VIIIa. Moreover, whereas healthy subjects (n=31) were found to be able to discriminate subtle differences in the kinematics of observed limb movements of others, patients suffering from spinocerebellar ataxia type 6 (SCA6; n=21) were severely impaired in performing such tasks. Our data suggest that the human cerebellum is actively involved in perceiving the kinematics of the hand actions of others and that SCA6 patients deficits include a difficulty in perceiving the actions of other individuals. This finding alerts us to the fact that cerebellar disorders can alter social cognition. Given that impairments in social cognition have been reported to be one of the most debilitating consequences of neurological disorders, this finding may be relevant to improving the quality of life of patients and their families.

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bioRxiv2018

Perceiving Hesitation requires both the Motor and Mentalizing systems

The mentalizing network and the putative mirror neuron system (pMNS) are two important large scale brain networks for social cognition, with very little overlap between them. Evidence suggests however that the two networks can collaborate for understanding the state of mind of others on the basis of their body movements. Here using fMRI we find that when participants view hand actions to detect hesitations they activate both their mentalizing and pMNS networks and information is exchanged across these networks. In a follow-up experiment using repetitive TMS we find that disturbing activity in either network slows hesitation attribution. In contrast, watching the same actions to determine the size of the object being grasped only triggered activity in the pMNS network, and rTMS over the mentalizing network then no longer slowed reactions. When we see others actions, we recruit our own motor system. Our results suggest that for detecting a simple mental state like hesitation, this pre-processed motor information becomes a necessary input into a mentalizing network that is essential for associating deviations from a predicted motor program with a specific mental state.

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bioRxiv2018

Cingulate dependent social risk assessment in rats

Social transmission of distress has been conceived of as a one-way phenomenon in which an observer catches the emotions of another. Here we use a paradigm in which an observer rat witnesses another receive electro-shocks. Bayesian model comparison and Granger causality argue against this one-way vision in favor of bidirectional information transfer: how the observer reacts to the demonstrators distress influences the behavior of the demonstrator. Intriguingly, this was true to a similar extent across highly familiar and entirely unfamiliar rats. Injecting muscimol in the anterior cingulate of observers reduced freezing in the observers and in the demonstrators receiving the shocks. That rats share the distress of unfamiliar strains is at odds with evolutionary thinking that empathy should be biased towards close individuals. Using simulations, we support the complementary notion that distress transmission could be selected to more efficiently detect dangers in a group.

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bioRxiv2018

Emotional Mirrors in the Rat’s Anterior Cingulate Cortex

AbstractHow do the emotions of others affect us? The human anterior cingulate cortex (ACC) responds while experiencing pain in the self and witnessing pain in others, but underlying cellular mechanisms remain poorly understood. Here we show the ACC (area 24) contains neurons responding when a rat experiences pain and while witnessing another receive footshocks. Most of these do not respond to a fear conditioned tone (CS). Deactivating this region reduces freezing while witnessing footshocks to others but not while hearing the CS. A decoder trained on spike counts while witnessing footshocks can decode the animals own pain intensity when experiencing pain. Mirror-like neurons thus exist in ACC that encode the pain of others in a code shared with pain but not fear in the self.\n\nOne Sentence SummaryACC contains neurons responding selectively when a rat witnesses anothers pain and experiences pain in the self.

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bioRxiv2018

Representing Multiple Observed Actions in the Motor System

There is now converging evidence that others actions are represented in the motor system. However, social cognition requires us to represent not only the actions but also the interactions of others. To do so, it is imperative that the motor system can represent multiple observed actions. The current fMRI study investigated whether this is possible by measuring brain activity from 29 participants while they observed two right hands performing sign language gestures. Three key results were obtained. First, brain activity in the premotor and parietal motor cortex was stronger when two hands performed two different gestures than when one hand performed a single gesture. Second, both individual observed gestures could be decoded from brain activity in the same two regions. Third, observing two different gestures compared with two identical gestures activated brain areas related to motor conflict, and this activity was correlated with parietal motor activity. Together, these results show that the motor system is able to represent multiple observed actions, and as such reveal a potential mechanism by which third-party social encounters could be processed in the brain.

neuroscience↗

bioRxiv2018

Where and how our brain represents the temporal structure of observed action

Reacting faster to the behavior of others provides evolutionary advantages. Reacting to unpredictable events takes hundreds of milliseconds. Understanding where and how the brain represents what actions are likely to follow one another is therefore important. Everyday actions are predictable sequences of acts, yet neuroscientists focus on how brains responds to unexpected, individual motor acts. Using fMRI we show the brain encodes sequence-specific information in the motor system. Using EEG, we show visual responses were faster and smaller for predictable sequences that recruit the motor system. This study shifts the study of action observation from single acts to motor sequences, informs how we adapt to the actions of others and suggests the motor system may implement perceptual predictive coding.

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