Joao BarbosaEcole Normale Supérieure de Paris | ENS
Joao Barbosa
PhD
About
23
Publications
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Introduction
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February 2013 - present
Publications
Publications (23)
Working memory (WM) is the ability to retain and manipulate information in mind, which allows mnemonic representations to flexibly guide behavior. Successful WM requires that objects' individual features are bound into cohesive representations, however the mechanisms supporting feature binding remain unclear. Binding errors (or swaps) provide a win...
Serial dependence, a behavioral phenomenon where information from previous trials biases current trial reports, is pervasive in working memory tasks. There is growing interest in its mechanisms, and recent work has shown that individuals with schizophrenia and anti-NMDA receptor (NMDAR) encephalitis exhibit reduced serial dependence in simple delay...
Brains can gracefully weed out irrelevant stimuli to guide behavior. This feat is believed to rely on a progressive selection of task-relevant stimuli across the cortical hierarchy, but the specific across-area interactions enabling stimulus selection are still unclear. Here, we propose that population gating, occurring within primary auditory cort...
Brains can gracefully weed out irrelevant stimuli to guide behavior. This feat is believed to rely on a progressive selection of task-relevant stimuli across the cortical hierarchy, but the specific across-area interactions enabling stimulus selection are still unclear. Here, we propose that population gating, occurring within A1 but controlled by...
In the last few decades, the field of neuroscience has witnessed major technological advances that have allowed researchers to measure and control neural activity with great detail. Yet, behavioral experiments in humans remain an essential approach to investigate the mysteries of the mind. Their relatively modest technological and economic requisit...
Artificial Neural Networks (ANNs) trained on specific cognitive tasks have re-emerged as a useful tool to study the brain. However, ANNs would better aid cognitive neuroscience if a given network could be easily trained on a wide range of tasks for which neural recordings are available. Moreover, unintentional divergent implementations of cognitive...
Persistently active neurons during mnemonic periods have been regarded as the mechanism underlying working memory maintenance. Alternatively, neuronal networks could instead store memories in fast synaptic changes, thus avoiding the biological cost of maintaining an active code through persistent neuronal firing. Such “activity-silent” codes have b...
Alterations in neuromodulation or synaptic transmission in biophysical attractor network models, as proposed by the dominant dopaminergic and glutamatergic theories of schizophrenia, successfully mimic working memory (WM) deficits in people with schizophrenia (PSZ). Yet, multiple, often opposing alterations in memory circuits can lead to the same b...
Working memory function is severely limited. One key limitation that constrains the ability to maintain multiple items in working memory simultaneously is so-called swap errors. These errors occur when an inaccurate response is in fact accurate relative to a non-target stimulus, reflecting the failure to maintain the appropriate association or “bin...
Working memory function is severely limited. One key limitation that constrains the ability to maintain multiple items in working memory simultaneously is so-called swap errors. These errors occur when an inaccurate response is in fact accurate relative to a non-target stimulus, reflecting the failure to maintain the appropriate association or 'bin...
Alterations in neuromodulation or synaptic transmission in biophysical attractor network models, as proposed by the dominant dopaminergic and glutamatergic theories of schizophrenia, successfully mimic working memory (WM) deficits in people with schizophrenia (PSZ). Yet, multiple, often opposing circuit mechanisms can lead to the same behavioral pa...
A hallmark of the ‘activity-silent’ working memory framework [1] is that memories stored silently in synaptic traces can be reactivated through non-specific stimuli [1–5]. Evidence supporting ‘activity-silent’ working memory has recently emerged from human electroencephalography (EEG) [6,7], in particular from ‘reactivations’ of unattended memories...
In the last few decades, the field of neuroscience has witnessed major technological advances that have allowed researchers to measure and control neural activity with great detail. Yet, behavioral experiments in humans remain an essential approach to investigate the mysteries of the mind. Their relatively modest technological and economic requisit...
A mechanistic understanding of core cognitive processes, such as working memory, is crucial to addressing psychiatric symptoms in brain disorders. We propose a combined psychophysical and biophysical account of two symptomatologically related diseases, both linked to hypofunctional NMDARs: schizophrenia and autoimmune anti-NMDAR encephalitis. We fi...
Persistent neuronal spiking has long been considered the mechanism underlying working memory, but recent proposals argue for alternative ‘activity-silent’ substrates. Using monkey and human electrophysiology data, we show here that attractor dynamics that control neural spiking during mnemonic periods interact with activity-silent mechanisms in the...
Serial dependence, how immediately preceding experiences bias our current estimations, has been described experimentally during delayed-estimation of many different visual features, with subjects tending to make estimates biased towards previous ones. It has been proposed that these attractive biases help perception stabilization in the face of cor...
We report markedly reduced working memory-related serial dependence with preserved memory accuracy in anti-NMDAR encephalitis and schizophrenia. We argue that NMDAR-related changes in cortical excitation, while quickly destabilizing persistent neural activity, cannot fully account for a reduction of memory-dependent biases. Rather, our modeling res...
Persistent neuronal spiking has long been considered the mechanism underlying working memory, but recent proposals argue for alternative, 'activity-silent' substrates for memory. Using monkey and human electrophysiology, we show here that attractor dynamics that control neural spiking during mnemonic periods interact with activity-silent mechanisms...
Serial dependence, how recent experiences bias our current estimations, has been described experimentally during delayed-estimation of many different visual features, with subjects tending to make estimates biased towards previous ones. It has been proposed that these attractive biases help perception stabilization in the face of correlated natural...
Working memory is the ability to maintain, in a ready-to-manipulate state, information that is no longer available for sensory processing. A classic way of studying visual working memory is to briefly show a visual cue at one of several possible locations and, after a short delay, to ask the subject to report where the cue was presented. Early neur...
The amount of information that can be retained in working-memory (WM) is limited. Limitations of WM capacity have been the subject of intense research, especially trying to specify algorithmic models for WM. Comparatively, neural circuit perspectives have barely been used to test WM limitations in behavioral experiments. Here, we used a neuronal mi...
Questions
Questions (2)
Hi folks,
I'm planing to run an experiment on Amazon Turks and one big limitation is that I can't be sure subjects are really fixating. My question is two-fold: a) how to work around it and b) how important is fixation
Task details (that might be irrelevant for the general question)
My task is a variation of a multi-item working memory that subjects have to report the color feature after a delay. On each trial, a set of colored circles appear on the screen. The stimuli are then removed and after a delay of 3s the subject has to report the color of one cued stimulus.
Fixation workaround
A way I thought to work around it was to have the fixation cross change color at random times. The subjects have to detect when that happens as fast as they can. Subjects with faster RT will get higher bonus that will multiply the reward for correct trials. The problem with this solution is that the task is of course more demanding and this will impair their working memory precision. I'm also not convinced this will actually work.
Finally, the second part of the question, would be about how important is fixation. Do you think for this experiment fixation is something I can't relax? Why do you think fixation is so important? I can see that fixation is a way to control the over attention allocation, but in any case subjects might be allocating covertly their attention to one stimulus more than to other. Fixation during delay, for example, shouldn't matter so much, right?
Thank you all in advance
Dear all,
How can one define visuo-spatial working memory capacity of subjects reporting a continuous value? Subjects are shown a set of stimuli and after a given delay, they have to report using a cursor where one of the stimulus was shown. I'm aware of this kind measure for discrete reports, but I guess those are not useful here.
Thank you in advance,
