The Neuropharmacology of Implicit Learning

Two decades of pharmacologic research on the human capacity to implicitly acquire knowledge as well as cognitive skills and procedures have yielded surprisingly few conclusive insights. We review the empirical literature of the neuropharmacology of implicit learning. We evaluate the findings in the context of relevant computational models related to neurotransmittors such as dopamine, serotonin, acetylcholine and noradrenalin. These include models for reinforcement learning, sequence production, and categorization. We conclude, based on the reviewed literature, that one can predict improved implicit acquisition by moderately elevated dopamine levels and impaired implicit acquisition by moderately decreased dopamine levels. These effects are most prominent in the dorsal striatum. This is supported by a range of behavioral tasks in the empirical literature. Similar predictions can be made for serotonin, although there is yet a lack of support in the literature for serotonin involvement in classical implicit learning tasks. There is currently a lack of evidence for a role of the noradrenergic and cholinergic systems in implicit and related forms of learning. GABA modulators, including benzodiazepines, seem to affect implicit learning in a complex manner and further research is needed. Finally, we identify allosteric AMPA receptors modulators as a potentially interesting target for future investigation of the neuropharmacology of procedural and implicit learning

Supramodal sentence processing in the human brain: fMRI evidence for the influence of syntactic complexity in more than 200 participants

This study investigated two questions. One is: To what degree is sentence processing beyond single words independent of the input modality (speech vs. reading)? The second question is: Which parts of the network recruited by both modalities is sensitive to syntactic complexity? These questions were investigated by having more than 200 participants read or listen to well-formed sentences or series of unconnected words. A largely left-hemisphere frontotemporoparietal network was found to be supramodal in nature, i.e., independent of input modality. In addition, the left inferior frontal gyrus (LIFG) and the left posterior middle temporal gyrus (LpMTG) were most clearly associated with left-branching complexity. The left anterior temporal lobe (LaTL) showed the greatest sensitivity to sentences that differed in right-branching complexity. Moreover, activity in LIFG and LpMTG increased from sentence onset to end, in parallel with an increase of the left-branching complexity. While LIFG, bilateral anterior temporal lobe, posterior MTG, and left inferior parietal lobe (LIPL) all contribute to the supramodal unification processes, the results suggest that these regions differ in their respective contributions to syntactic complexity related processing. The consequences of these findings for neurobiological models of language processing are discussed

Supramodal Sentence Processing in the Human Brain: fMRI Evidence for the Influence of Syntactic Complexity in More Than 200 Participants

This study investigated two questions. One is: To what degree is sentence processing beyond single words independent of the input modality (speech vs. reading)? The second question is: Which parts of the network recruited by both modalities is sensitive to syntactic complexity? These questions were investigated by having more than 200 participants read or listen to well-formed sentences or series of unconnected words. A largely left-hemisphere frontotemporoparietal network was found to be supramodal in nature, i.e., independent of input modality. In addition, the left inferior frontal gyrus (LIFG) and the left posterior middle temporal gyrus (LpMTG) were most clearly associated with left-branching complexity. The left anterior temporal lobe showed the greatest sensitivity to sentences that differed in right-branching complexity. Moreover, activity in LIFG and LpMTG increased from sentence onset to end, in parallel with an increase of the left-branching complexity. While LIFG, bilateral anterior temporal lobe, posterior MTG, and left inferior parietal lobe all contribute to the supramodal unification processes, the results suggest that these regions differ in their respective contributions to syntactic complexity related processing. The consequences of these findings for neurobiological models of language processing are discussed

When did you stop speaking to yourself? Adolescent development of world knowledge-based audience design

The ability to adapt utterances to the world knowledge of one’s addressee is undeniably ubiquitous in human social cognition, but its development and association with other cognitive mechanisms during adolescence have not been studied. In an online production task, we measured the ability of children entering adolescence (ages 11-12) and adolescents (ages 15-16) to tailor referential expressions in accordance with the inferred world knowledge of their addressee – an ability we refer to as world knowledge-based audience design. A post-test survey showed that relevant theory of mind information was accessed upon prompting in both age groups, but the younger age group did not consistently utilize this information during online production, resulting in a significantly improved world knowledge-based audience design across age groups. We also investigated the reliance of world knowledge-based audience design on cognitive control functions. Cognitive control (as reflected by performance on the Wisconsin card sorting task) increased significantly with age, but did not explain the age-related increase in audience design performance. We thus provide evidence for an adolescent development of world knowledge-based audience design over and above development of theory of mind and cognitive control

When did you stop speaking to yourself? Age-related differences in adolescents’ world knowledge-based audience design

The ability to adapt utterances to the world knowledge of one’s addressee is undeniably ubiquitous in human social cognition, but its development and association with other cognitive mechanisms during adolescence have not been studied. In an online production task, we measured the ability of children entering adolescence (ages 11–12, M = 11.8, [Formula: see text]) and adolescents (ages 15–16, M = 15.9, [Formula: see text]) to tailor referential expressions in accordance with the inferred world knowledge of their addressee—an ability we refer to as world knowledge-based audience design (AD). A post-test survey showed that both age groups held similar assumptions about the addressees’ knowledge of referents, but the younger age group did not consistently adapt their utterances in accordance with these assumptions during online production, resulting in a significantly improved AD behaviour across age groups. We also investigated the reliance of AD on executive functions (EF). Executive functioning (as reflected by performance on the Wisconsin card sorting task) increased significantly with age, but did not explain the age-related increase in AD performance. We thus provide evidence in support of an adolescent development of world knowledge-based AD over and above development of EF

Testing for Audience Design: a short report

In this short report, we present the results from a novel test set-up, aiming to track the practice of Audience Design (AD) in the reference production of Swedish speaking 7 year olds. AD is the conduct of altering one's communicative signal with the receiver of the signal in mind, so that they can easily infer its intended meaning. The results show a distinctive group that does not adapt production in the same manner as in a practice trial prompt for a third party without shared frame of mind. While we controlled for the participant’s knowledge of the referential objects of the test, we did not control for the participants assumptions about the world knowledge of the different addresses, which might have altered the result

Adolescent development of world knowledge-based audience design

Data and scripts from the development of audience design (DAD) project. Test battery was conducted on children entering adolescence (11-12) and mid adolescents (15-16) and consisted of one referential communication (audience design) task and the Wisconsin card sorting task (WCST)

Investigating Conversational Dynamics in Human-Robot Interaction with fMRI

We investigated how verbal communication with a robot differs from talking to a human in terms of brain activity by analysing an open-source fMRI dataset. We focused on modeling conversational dynamics rather than conversation as a whole, by analysing fine-grained events, in particular turn initiation. The results indicate that turn initiation in a conversation with a human involves higher activation in auditory and visual cortex than turn initiation with a robot. Conversely, listening to the robot showed higher engagement of auditory cortex than listening to a human. We suggest that verbal and non-verbal turn-taking cues provided by the human agent engage more cognitive processing for picking up the turn. On the other hand, listening to a robot agent requires more processing than listening to a human. Both findings suggest that the accurate simulation of appropriate turn-taking cues and behaviors will help robots to establish more natural conversation dynamics and that the use of brain imaging can provide valuable objective measurements for assessing user states in human-robot interaction