Publications of Matthieu Koroma
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See detailEye movement responses to caloric vestibular irrigations reveal the contribution of voluntary processes to autonomic reflexes
Koroma, Matthieu ULiege; Delcamp, Clément; Mortaheb, Sepehr ULiege et al

Scientific conference (2021, May 28)

Can autonomic reflexes inform us about higher-order cognitive processes ? To address this issue, we studied habituation (a form of non-associative learning) of the slow, uncontrolled eye movement response ... [more ▼]

Can autonomic reflexes inform us about higher-order cognitive processes ? To address this issue, we studied habituation (a form of non-associative learning) of the slow, uncontrolled eye movement response (nystagmus) following repetitive caloric (warm water) vestibular irrigation. After a 30s irrigation trial (total trials=6), participants (n=26) either kept their gaze fixated, or let their gaze free, testing voluntary adaptations of the nystagmus response measured with electrooculography (EOG). Participants also reported the intensity of the vertigo that they experienced after each irrigation. We found that the amplitude of the nystagmus response decreased over repetitive irrigations, revealing a clear habituation (repeated measures ANOVA with participants as random factor, F(5)=-18.8, p<0.001). We further showed that the amplitude of nystagmus is reduced after the gaze fixation condition compared to the freely moving gaze (interaction between irrigation and fixation, F(5,1)=5.1, p=0.025). Finally, by relying on a model comparison approach, we demonstrate that the oculomotor response holds partial information on the decrease of the vertigo experienced over successive irrigations, suggesting a bi-directional interaction between central and autonomic processes (Likelihood-ratio chi-squared test between mixed-models predicting vertigo response and including or excluding the duration of nystagmus, 𝜒2(12)=11.96, p=0.013). These findings suggest that reflexes carry partial information about voluntary processes. From the interoceptive active inference framework, these results might be relevant for evidencing signs of sentience when this cannot be communicated overtly. [less ▲]

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See detailSleepers Selectively Suppress Informative Inputs during Rapid Eye Movements.
Koroma, Matthieu ULiege; Lacaux, Célia; Andrillon, Thomas et al

in Current biology : CB (2020), 30(12), 2411-24173

Sleep leads to a disconnection from the external world. Even when sleepers regain consciousness during rapid eye movement (REM) sleep, little, if any, external information is incorporated into dream ... [more ▼]

Sleep leads to a disconnection from the external world. Even when sleepers regain consciousness during rapid eye movement (REM) sleep, little, if any, external information is incorporated into dream content [1-3]. While gating mechanisms might be at play to avoid interference on dreaming activity [4], a total disconnection from an ever-changing environment may prevent the sleeper from promptly responding to informative events (e.g., threat signals). In fact, a whole range of neural responses to external events turns out to be preserved during REM sleep [5-9]. Thus, it remains unclear whether external inputs are either processed or, conversely, gated during REM sleep. One way to resolve this issue is to consider the specific impact of eye movements (EMs) characterizing REM sleep. EMs are a reliable predictor of reporting a dream upon awakening [10, 11], and their absence is associated with a lower arousal threshold to external stimuli [12]. We thus hypothesized that the presence of EMs would selectively prevent the processing of informative stimuli, whereas periods of REM sleep devoid of EMs would be associated with the monitoring of external signals. By reconstructing speech in a multi-talker environment from electrophysiological responses, we show that informative speech is amplified over meaningless speech during REM sleep. Yet, at the precise timing of EMs, informative speech is, on the contrary, selectively suppressed. These results demonstrate the flexible amplification and suppression of sensory information during REM sleep and reveal the impact of EMs on the selective gating of informative stimuli during sleep. [less ▲]

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See detailSleepers track informative speech in a multitalker environment.
Legendre, Guillaume; Andrillon, Thomas; Koroma, Matthieu ULiege et al

in Nature Human Behaviour (2019), 3(3), 274-283

Sleep is a vital need, forcing us to spend a large portion of our life unable to interact with the external world. Current models interpret such extreme vulnerability as the price to pay for optimal ... [more ▼]

Sleep is a vital need, forcing us to spend a large portion of our life unable to interact with the external world. Current models interpret such extreme vulnerability as the price to pay for optimal learning. Sleep would limit external interferences on memory consolidation(1-3) and allow neural systems to reset through synaptic downscaling(4). Yet, the sleeping brain continues generating neural responses to external events(5,6), revealing the preservation of cognitive processes ranging from the recognition of familiar stimuli to the formation of new memory representations(7-15). Why would sleepers continue processing external events and yet remain unresponsive? Here we hypothesized that sleepers enter a 'standby mode' in which they continue tracking relevant signals, finely balancing the need to stay inward for memory consolidation with the ability to rapidly awake when necessary. Using electroencephalography to reconstruct competing streams in a multitalker environment(16), we demonstrate that the sleeping brain amplifies meaningful speech compared to irrelevant signals. However, the amplification of relevant stimuli was transient and vanished during deep sleep. The effect of sleep depth could be traced back to specific oscillations, with K-complexes promoting relevant information in light sleep, whereas slow waves actively suppress relevant signals in deep sleep. Thus, the selection of relevant stimuli continues to operate during sleep but is strongly modulated by specific brain rhythms. [less ▲]

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See detailRepresentation of retrieval confidence by single neurons in the human medial temporal lobe.
Rutishauser, Ueli; Ye, Shengxuan; Koroma, Matthieu ULiege et al

in Nature Neuroscience (2015), 18(7), 1041-50

Memory-based decisions are often accompanied by an assessment of choice certainty, but the mechanisms of such confidence judgments remain unknown. We studied the response of 1,065 individual neurons in ... [more ▼]

Memory-based decisions are often accompanied by an assessment of choice certainty, but the mechanisms of such confidence judgments remain unknown. We studied the response of 1,065 individual neurons in the human hippocampus and amygdala while neurosurgical patients made memory retrieval decisions together with a confidence judgment. Combining behavioral, neuronal and computational analysis, we identified a population of memory-selective (MS) neurons whose activity signaled stimulus familiarity and confidence, as assessed by subjective report. In contrast, the activity of visually selective (VS) neurons was not sensitive to memory strength. The groups further differed in response latency, tuning and extracellular waveforms. The information provided by MS neurons was sufficient for a race model to decide stimulus familiarity and retrieval confidence. Together, our results indicate a trial-by-trial relationship between a specific group of neurons and declared memory strength in humans. We suggest that VS and MS neurons are a substrate for declarative memories. [less ▲]

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