Bondanelli G, Ostojic S (2020) Coding with transient trajectories in recurrent neural networks. PLoS Comput Biol, 16(2): e1007655. https://doi.org/10.1371/journal.pcbi.1007655

Résumé :
Following a stimulus, the neural response typically strongly varies in time and across neurons before settling to a steady-state. While classical population coding theory disregards the temporal dimension, recent works have argued that trajectories of transient activity can be particularly informative about stimulus identity and may form the basis of computations through dynamics. Yet the dynamical mechanisms needed to generate a population code based on transient trajectories have not been fully elucidated. Here we examine transient coding in a broad class of high-dimensional linear networks of recurrently connected units. We start by reviewing a well-known result that leads to a distinction between two classes of networks: networks in which all inputs lead to weak, decaying transients, and networks in which specific inputs elicit amplified transient responses and are mapped onto output states during the dynamics. Theses two classes are simply distinguished based on the spectrum of the symmetric part of the connectivity matrix. For the second class of networks, which is a sub-class of non-normal networks, we provide a procedure to identify transiently amplified inputs and the corresponding readouts. We first apply these results to standard randomly-connected and two-population networks. We then build minimal, low-rank networks that robustly implement trajectories mapping a specific input onto a specific orthogonal output state. Finally, we demonstrate that the capacity of the obtained networks increases proportionally with their size.

Carbajal, J., L. Chartofylaka, M. Hamilton, A.-C. Fiévet & S. Peperkamp (2020). Compensation for phonological assimilation in bilingual children. Language Learning and Development, 16, 141-160.

Résumé :
We investigate bilingual children’s perception of assimilations, i.e. phonological rules by which a consonant at a word edge adopts a phonological feature of a neighboring consonant. For instance, English has place assimilation (e.g., green is pronounced with a final [m] in green pen), while French has voicing assimilation (e.g., sac is pronounced with a final [g] in sac vert ‘green bag’). Previous research has shown that French and English monolingual toddlers compensate for the assimilation rule of their language, correctly recovering the intended words, but not for a rule that does not exist in their language. Using a word recognition videogame with French sentences, we show that French-English bilingual 6-year-olds’ perform exactly like French monolinguals of the same age: they compensate for voicing but not for place assimilation. Thus, despite their dual language input they have acquired French voicing assimilation and show

Flora Bouchacourt, Stefano Palminteri, Etienne Koechlin, Srdjan Ostojic (2020), Temporal chunking as a mechanism for unsupervised learning of task-sets, eLife, 2020;9:e50469, 10.7554/eLife.50469

Résumé :
Depending on environmental demands, humans can learn and exploit multiple concurrent sets of stimulus-response associations. Mechanisms underlying the learning of such task-sets remain unknown. Here we investigate the hypothesis that task-set learning relies on unsupervised chunking of stimulus-response associations that occur in temporal proximity. We examine behavioral and neural data from a task-set learning experiment using a network model. We first show that task-set learning can be achieved provided the timescale of chunking is slower than the timescale of stimulus-response learning. Fitting the model to behavioral data on a subject-by-subject basis confirmed this expectation and led to specific predictions linking chunking and task-set retrieval that were borne out by behavioral performance and reaction times. Comparing the model activity with BOLD signal allowed us to identify neural correlates of task-set retrieval in a functional network involving ventral and dorsal prefrontal cortex, with the dorsal system preferentially engaged when retrievals are used to improve performance.

de Vignemont, F. (2020). What Phenomenal Contrast for Bodily Ownership?, Journal of the American Philosophical Association, 117-137. doi:10.1017/apa.2019.34

Résumé :
In a 1962 article, ‘On Sensations of Position’, G. E. M. Anscombe claimed that we do not feel our legs crossed; we simply know that they are that way. What about the sense of bodily ownership? Do we directly know that this body is our own, or do we know it because we feel this body that way? One may claim, for instance, that we are we aware that this is our own body thanks to our bodily experiences that ascribe the property of myness to the body that they represent. Here I approach this issue from the perspective of the debate on the admissible content of perception, appealing to the method of phenomenal contrast. After rejecting the myness hypothesis, I criticize alternative accounts of the contrast in somatosensory, cognitive, and agentive terms. I conclude that the phenomenology of ownership consists in the affective awareness of the unique significance of the body for survival.

Di Liberto GM, Pelofi C, Bianco R, Patel P, Mehta AD, Herrero JL, de Cheveigné A, Shamma S, Mesgarani N. (2020), Cortical encoding of melodic expectations in human temporal cortex, Elife, 3;9. pii: e51784. doi: 10.7554/eLife.51784.

Résumé :
Humans engagement in music rests on underlying elements such as the listeners’ cultural background and interest in music. These factors modulate how listeners anticipate musical events, a process inducing instantaneous neural responses as the music confronts these expectations. Measuring such neural correlates would represent a direct window into high-level brain processing. Here we recorded cortical signals as participants listened to Bach melodies. We assessed the relative contributions of acoustic versus melodic components of the music to the neural signal. Melodic features included information on pitch progressions and their tempo, which were extracted from a predictive model of musical structure based on Markov chains. We related the music to brain activity with temporal response functions demonstrating, for the first time, distinct cortical encoding of pitch and note-onset expectations during naturalistic music listening. This encoding was most pronounced at response latencies up to 350 ms, and in both planum temporale and Heschl’s gyrus.

Doris Pischedda, Stefano Palminteri and Giorgio Coricelli (2020) The effect of counterfactual information on outcome value coding in medial prefrontal and cingulate cortex: from an absolute to a relative neural code. Journal of Neuroscience, JN-RM-1712-19; DOI: 10.1523/JNEUROSCI.1712-19.2020

Résumé :
Adaptive coding of stimuli in visual cortex is well documented in perception, where it supports efficient encoding over a broad range of possible percepts. Recently, a similar neural mechanism has been reported also in value-based decision, where it allows optimal encoding of vast ranges of values in PFC: neuronal response to value depends on the choice context (relative coding), rather than being invariant across contexts (absolute coding). Additionally, value learning is sensitive to the amount of feedback information: providing complete feedback (both obtained and forgone outcomes) instead of partial feedback (only obtained outcome) improves learning. However, it is unclear whether relative coding occurs in all PFC regions and how it is affected by feedback information. We systematically investigated univariate and multivariate feedback encoding in various PFC regions and compared three modes of neural coding: absolute, partially-adaptive and fully-adaptive.

Twenty-eight human participants (both sexes) performed a learning task while undergoing fMRI scanning. On each trial, they chose between two symbols associated with a certain outcome. Then, the decision outcome was revealed. Notably, in half of the trials participants received partial feedback, while in the other half they got complete feedback. We used univariate and multivariate analysis to explore value encoding in different feedback conditions.

We found that both obtained and forgone outcomes were encoded in mPFC, but with opposite sign in ventral and dorsal subdivisions. Moreover, we showed that increasing feedback information induced a switch from absolute to relative coding. Our results suggest that complete feedback information promotes context-dependent outcome encoding.

Sacha Yesilaltay, Hugo Mercier (2020), Relevance Is Socially Rewarded, But Not at the Price of Accuracy, Evolutionary Psychology, 1-7, 10.1177/1474704920912640

Abstract
Selecting good sources of information is a critical skill to navigate our highly social world. To evaluate the epistemic reputation of potential sources, the main criterion should be the relevance of the information they provide us. In two online experiments (N = 801), we found that receivers are more thankful toward, deem more competent, and are more likely to request information in the future from sources of more relevant messages—if they know the message to be accurate or deem it plausible. To prevent sources from presenting information as more relevant than it is in order to improve their reputation, receivers lower the reputation of sources sending messages that are more relevant-if-true, if they know the message to be inaccurate. Our research sheds light on the reputational trade-offs involved in choosing what information to communicate and helps explain transmission patterns such as rumors diffusion.

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