scholarly journals Temporal Chunking as a Mechanism for Unsupervised Learning of Task-Sets

2019 ◽  
Author(s):  
Flora Bouchacourt ◽  
Stefano Palminteri ◽  
Etienne Koechlin ◽  
Srdjan Ostojic
Keyword(s):  
Reaction Times ◽  
Neural Correlates ◽  
Behavioral Performance ◽  
Bold Signal ◽  
Improve Performance ◽  
Task Set ◽  
Neural Data ◽  
Stimulus Response ◽  
Task Sets ◽  
And Task

AbstractDepending 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 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.

scholarly journals Temporal chunking as a mechanism for unsupervised learning of task-sets

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Flora Bouchacourt ◽  
Stefano Palminteri ◽  
Etienne Koechlin ◽  
Srdjan Ostojic
Keyword(s):  
Reaction Times ◽  
Neural Correlates ◽  
Behavioral Performance ◽  
Bold Signal ◽  
Improve Performance ◽  
Task Set ◽  
Neural Data ◽  
Stimulus Response ◽  
Task Sets ◽  
And Task

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.

scholarly journals No-go trials in task switching: effects on the task-set and task-space level

2021 ◽  
Author(s):  
Juliane Scheil ◽  
Thomas Kleinsorge
Keyword(s):  
Task Switching ◽  
The Other ◽  
Specific Task ◽  
Task Space ◽  
Response Level ◽  
Task Set ◽  
Common Marker ◽  
Task Sets ◽  
And Task

AbstractA common marker for inhibition processes in task switching are n − 2 repetition costs. The present study aimed at elucidating effects of no-go trials on n − 2 repetition costs. In contrast to the previous studies, no-go trials were associated with only one of the three tasks in the present two experiments. High n − 2 repetition costs occurred if the no-go task had to be executed in trial n − 2, irrespective of whether a response had to be withheld or not. In contrast, no n − 2 repetition costs were visible if the other two tasks were relevant in n − 2. Whereas this n − 2 effect was unaffected by whether participants could reliably exclude a no-go trial or not, effects of no-gos in trial n were determined by this knowledge. The results differ from effects of no-go trials that are not bound to a specific task. It is assumed that the present no-go variation exerted its effect not on the response level, but on the level of task sets, resulting in enhanced salience of the no-go task that leads to higher activation and, as a consequence, to stronger inhibition. The dissociation of the effects on no-gos in trials n − 2 and n as a function of foreknowledge suggests that the balance between activation and inhibition is shifted not only for single trials and tasks, but for the whole task space.

scholarly journals Spontaneous task structure formation results in a cost to incidental memory of task stimuli

2018 ◽  
Author(s):  
Christina Bejjani ◽  
Tobias Egner
Keyword(s):  
Structure Formation ◽  
Structure Learning ◽  
Learning Task ◽  
Underlying Structure ◽  
Task Structure ◽  
Cognitive Demands ◽  
Task Set ◽  
Stimulus Response ◽  
Attention To Task ◽  
Task Sets

Humans are characterized by their ability to leverage rules for classifying and linking stimuli to context-appropriate actions. Previous studies have shown that when humans learn stimulus-response associations for two-dimensional stimuli, they implicitly form and generalize hierarchical rule structures (task-sets). However, the cognitive processes underlying structure formation are poorly understood. Across four experiments, we manipulated how trial-unique images mapped onto responses to bias spontaneous task-set formation and investigated structure learning through the lens of incidental stimulus encoding. Participants performed a learning task designed to either promote task-set formation (by “motor-clustering” possible stimulus-action rules), or to discourage it (by using arbitrary category-response mappings). We adjudicated between two hypotheses: Structure learning may promote attention to task stimuli, thus resulting in better subsequent memory. Alternatively, building task-sets might impose cognitive demands (for instance, on working memory) that divert attention away from stimulus encoding. While the clustering manipulation affected task-set formation, there were also substantial individual differences. Importantly, structure learning incurred a cost: spontaneous task-set formation was associated with diminished stimulus encoding. Thus, spontaneous hierarchical task-set formation appears to involve cognitive demands that divert attention away from encoding of task stimuli during structure learning.

scholarly journals Neural signatures of vigilance decrements predict behavioural errors before they occur

2020 ◽  
Author(s):  
Hamid Karimi-Rouzbahani ◽  
Alexandra Woolgar ◽  
Anina N. Rich
Keyword(s):  
Reaction Times ◽  
Neural Correlates ◽  
Neural Representation ◽  
Neural Data ◽  
Active Condition ◽  
Behavioural Performance ◽  
Target Monitoring ◽  
The Brain ◽  
Insight Into ◽  
Over Time

AbstractThere are many monitoring environments, such as railway control, in which lapses of attention can have tragic consequences. Problematically, sustained monitoring for rare targets is difficult, with more misses and longer reaction times over time. What changes in the brain underpin these “vigilance decrements”? We designed a multiple-object monitoring (MOM) paradigm to examine how the neural representation of information varied with target frequency and time performing the task. Behavioural performance decreased over time for the rare target (monitoring) condition, but not for a frequent target (active) condition. This was mirrored in the neural results: there was weaker coding of critical information during monitoring versus active conditions. We developed new analyses that can predict behavioural errors from the neural data more than a second before they occurred. This paves the way for pre-empting behavioural errors due to lapses in attention and provides new insight into the neural correlates of vigilance decrements.

scholarly journals EEG Decoding Reveals the Temporal Dynamics and Functional Relevance of Goal-Relevant Representations

2017 ◽  
Author(s):  
Jason Hubbard ◽  
Atsushi Kikumoto ◽  
Ulrich Mayr
Keyword(s):  
Temporal Dynamics ◽  
Dynamic Properties ◽  
Strong Predictor ◽  
Early Period ◽  
High Temporal Resolution ◽  
Task Set ◽  
Stimulus Response ◽  
Functional Relevance ◽  
Electrophysiological Signal ◽  
Task Sets

AbstractModels of action control assume that abstract task-set settings regulate lower-level stimulus/response representations. Yet, we know little about the functional and dynamic properties of task-set representations in humans. Using a cued task-switching paradigm, we show that information about task sets and lower-level stimulus/response aspects can be extracted through decoding analyses from the scalp electrophysiological signal (EEG) on the single-trial level and with high temporal resolution. Task-sets are active throughout the entire processing cascade and trial-to-trial variations in task-set strength emerges as a remarkably strong predictor of variability in performance, both within and between individuals. Also, taskset strength is related to stimulus representation strength at an early period and to the strength of response representations at a later period, consistent with the notion that task-sets coordinate successive, lower-level representations in a concurrent manner. These results demonstrate a powerful approach towards uncovering stages of information processing and their relative importance for performance.

scholarly journals Effects of ketamine on brain function during metacognition of episodic memory

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Mirko Lehmann ◽  
Claudia Neumann ◽  
Sven Wasserthal ◽  
Johannes Schultz ◽  
Achilles Delis ◽  
...  
Keyword(s):  
Episodic Memory ◽  
Parietal Lobe ◽  
Memory Task ◽  
Reaction Times ◽  
Neural Correlates ◽  
Double Blind ◽  
Lingual Gyrus ◽  
States Of Consciousness ◽  
Fmri Study ◽  
Confidence Ratings

Abstract Only little research has been conducted on the pharmacological underpinnings of metacognition. Here, we tested the modulatory effects of a single intravenous dose (100 ng/ml) of the N-methyl-D-aspartate-glutamate-receptor antagonist ketamine, a compound known to induce altered states of consciousness, on metacognition and its neural correlates. Fifty-three young, healthy adults completed two study phases of an episodic memory task involving both encoding and retrieval in a double-blind, placebo-controlled fMRI study. Trial-by-trial confidence ratings were collected during retrieval. Effects on the subjective state of consciousness were assessed using the 5D-ASC questionnaire. Confirming that the drug elicited a psychedelic state, there were effects of ketamine on all 5D-ASC scales. Acute ketamine administration during retrieval had deleterious effects on metacognitive sensitivity (meta-d′) and led to larger metacognitive bias, with retrieval performance (d′) and reaction times remaining unaffected. However, there was no ketamine effect on metacognitive efficiency (meta-d′/d′). Measures of the BOLD signal revealed that ketamine compared to placebo elicited higher activation of posterior cortical brain areas, including superior and inferior parietal lobe, calcarine gyrus, and lingual gyrus, albeit not specific to metacognitive confidence ratings. Ketamine administered during encoding did not significantly affect performance or brain activation. Overall, our findings suggest that ketamine impacts metacognition, leading to significantly larger metacognitive bias and deterioration of metacognitive sensitivity as well as unspecific activation increases in posterior hot zone areas of the neural correlates of consciousness.

Learning of across- and within-task contingencies modulates partial-repetition costs in dual-tasking

2021 ◽  
Author(s):  
Lasse Pelzer ◽  
Christoph Naefgen ◽  
Robert Gaschler ◽  
Hilde Haider
Keyword(s):  
Dual Task ◽  
Discrimination Task ◽  
Experimental Approach ◽  
Feature Binding ◽  
Dual Tasking ◽  
Single Task ◽  
Task Set ◽  
Task Processing ◽  
Tone Discrimination ◽  
Task Sets

AbstractDual-task costs might result from confusions on the task-set level as both tasks are not represented as distinct task-sets, but rather being integrated into a single task-set. This suggests that events in the two tasks are stored and retrieved together as an integrated memory episode. In a series of three experiments, we tested for such integrated task processing and whether it can be modulated by regularities between the stimuli of the two tasks (across-task contingencies) or by sequential regularities within one of the tasks (within-task contingencies). Building on the experimental approach of feature binding in action control, we tested whether the participants in a dual-tasking experiment will show partial-repetition costs: they should be slower when only the stimulus in one of the two tasks is repeated from Trial n − 1 to Trial n than when the stimuli in both tasks repeat. In all three experiments, the participants processed a visual-manual and an auditory-vocal tone-discrimination task which were always presented concurrently. In Experiment 1, we show that retrieval of Trial n − 1 episodes is stable across practice if the stimulus material is drawn randomly. Across-task contingencies (Experiment 2) and sequential regularities within a task (Experiment 3) can compete with n − 1-based retrieval leading to a reduction of partial-repetition costs with practice. Overall the results suggest that participants do not separate the processing of the two tasks, yet, within-task contingencies might reduce integrated task processing.

scholarly journals The effect of high-frequency rTMS of the left dorsolateral prefrontal cortex on the resolution of response, semantic and task conflict in the colour-word Stroop task

2021 ◽  
Author(s):  
Benjamin A. Parris ◽  
Michael G. Wadsley ◽  
Gizem Arabaci ◽  
Nabil Hasshim ◽  
Maria Augustinova ◽  
...  
Keyword(s):  
Prefrontal Cortex ◽  
Task Performance ◽  
Stroop Task ◽  
Word Reading ◽  
Reaction Times ◽  
Task Conflict ◽  
General Effect ◽  
Task Set ◽  
Left Dlpfc ◽  
Dorsolateral Prefrontal

AbstractPrevious work investigating the effect of rTMS of left Dorso-Lateral Prefrontal Cortex (DLPFC) on Stroop task performance reports no changes to the Stroop effect but reduced reaction times on both congruent and incongruent trials relative to sham stimulation; an effect attributed to an enhanced attentional (or task) set for colour classification. The present study tested this account by investigating whether, relative to vertex stimulation, rTMS of the left DLPFC modifies task conflict, a form of conflict that arises when task sets for colour classification and word reading compete, given that this particular type of conflict would be reduced by an enhanced task set for colour classification. Furthermore, the present study included measures of other forms of conflict present in the Stroop task (response and semantic conflict), the potential effects on which would have been hidden in previous studies employing only incongruent and congruent stimuli. Our data showed that left DLPFC stimulation had no effect on the magnitude of task conflict, nor did it affect response, semantic or overall conflict (where the null is supported by sensitive Bayes Factors in most cases). However, consistent with previous research left DLPFC stimulation had the general effect of reducing reaction times. We, therefore, show for the first time that relative to real vertex stimulation left DLPFC stimulation does not modify Stroop interference. Alternative accounts of the role of the left DLPFC in Stroop task performance in which it either modifies response thresholds or facilitates responding by keeping the correct response keys active in working memory are discussed.

Sign in / Sign up

Export Citation Format

Share Document