Cognition seminars

Animals possess the ability to effortlessly and precisely time their actions even though information received from the world is often ambiguous and is inadvertently transformed as it passes through the nervous system. With such uncertainty pervading through our nervous systems, we could expect that much of human and animal behavior relies on inference that incorporates an important additional source of information, prior knowledge of the environment. These concepts have long been studied under the framework of Bayesian inference with substantial corroboration over the last decade that human time perception is consistent with such models. We, however, know little about the neural mechanisms that enable Bayesian signatures to emerge in temporal perception. I will present our work on three facets of this problem, how Bayesian estimates are encoded in neural populations, how these estimates are used to generate time intervals, and how prior knowledge for these tasks is acquired and optimized by neural circuits. We trained monkeys to perform an interval reproduction task and found their behavior to be consistent with Bayesian inference. Using insights from electrophysiology and in silico models, we propose a mechanism by which cortical populations encode Bayesian estimates and utilize them to generate time intervals. Thereafter, I will present a circuit model for how temporal priors can be acquired by cerebellar machinery leading to estimates consistent with Bayesian theory. Based on electrophysiology and anatomy experiments in rodents, I will provide some support for this model. Overall, these findings attempt to bridge insights from normative frameworks of Bayesian inference with potential neural implementations for the acquisition, estimation, and production of timing behaviors.

There is a long-standing tension between the notion that the hippocampal formation is essentially a spatial mapping system, and the notion that it plays an essential role in the establishment of episodic memory and the consolidation of such memory into structured knowledge about the world. One theory that resolves this tension is the notion that the hippocampus generates rather arbitrary 'index' codes that serve initially to link attributes of episodic memories that are stored in widely dispersed and only weakly connected neocortical modules. I will show how an essentially 'spatial' coding mechanism, with some tweaks, provides an ideal indexing system and discuss the neural coding strategies that the hippocampus apparently uses to overcome some biological constraints affecting the possibility of shipping the index code out widely to the neocortex. Finally, I will present new data suggesting that the hippocampal index code is indeed transferred to layer II-III of the neocortex.

External cues imbued with significance can enhance the motivational state of an organism, trigger related memories and influence future planning and goal directed behavior. At the same time, internal thought and imaginings can moderate and counteract the impact of external motivational cues. The neural underpinnings of imagination have been largely opaque, due to the inherent inaccessibility of mental actions. The talk will describe studies utilizing imagination and tracking how its neural correlates bidirectionally interact with external motivational cues. Stimulus-response associative learning is only one form of memory organization. A more comprehensive and efficient organizational principal is the cognitive map. In the last part of the talk we will examine this concept in the case of abstract memories and social space. Social encounters provide opportunities to become intimate or estranged from others and to gain or lose power over them. The locations of others on the axes of power and affiliation can serve as reference points for our own position in the social space. Research is beginning to uncover the spatial-like neural representation of these social coordinates. We will discuss recent and growing evidence on utilizing the principals of the cognitive map across multiple domains, providing a systematic way of organizing memories to navigate life.

Visual attention refers to a set of processes allowing selection of relevant and filtering out of irrelevant information in the visual environment. A large amount of research on visual attention has involved visual search paradigms, where observers are asked to report whether a single target is present or absent. However, recent studies have revealed that these classic single-target visual search tasks only provide a snapshot of how attention is allocated in the visual environment, and that multitarget visual foraging tasks may capture the dynamics visual attention more accurately. In visual foraging, observers are asked to select multiple instances of multiple target types, as fast as they can. A critical question in foraging research concerns the factors driving the next target selection. Most likely, this would require two steps: (1) identifying a set of candidates for the next selection, and (2) selecting the best option among these candidates. After having briefly described the advantage of visual foraging over visual search, I will review recent visual foraging studies testing the influence of several manipulations (e.g., target crypticity, number of items, selection modality) on foraging behaviour. Overall, these studies revealed that the next target selection during visual foraging is determined by the competition between three factors: target value, target proximity, and priming of features. I will explain how the analysis of individual differences in foraging behaviour can provide important information, with the idea that individuals show by-default internal biases toward value, proximity and priming that determine their search strategy and behaviour.

In this seminar, I will present new methods in magnetic resonance spectroscopy (MRS) we’ve been working on in the lab. The talk will be divided into two parts. In the first, I will talk about neurochemical changes we observe in glutamate and GABA during various paradigms, including simple motors tasks and reinforcement learning. In the second part, I’ll present a new approach to MRS that focuses on measuring the relaxation times (T1, T2) of metabolites, which reflect changes to specific cellular microenvironments. I will explain why these can be exciting markers for studying several in-vivo pathologies, and also present some preliminary data from a cohort of mild cognitive impairment (MCI) patients, showing changes that correlate to cognitive decline.

Neocortical-hippocampal interactions during off-line periods such as slow-wave sleep are implicated in memory processing. In particular, recent memory traces are replayed in hippocampus during some sharp-wave ripple (SWR) events, and these replay events are positively correlated with neocortical memory trace reactivation. A prevalent model is that SWR arise ‘spontaneously’ in CA3 and propagate recent memory ‘indices’ outward to the neocortex to enable memory consolidation there; however, the spatiotemporal distribution of neocortical activation relative to SWR is incompletely understood. We used wide-field optical imaging to study voltage and glutamate release transients in dorsal neocortex in relation to CA1 multiunit activity (MUA) and SWR of sleeping and urethane anesthetized mice. Modulation of voltage and glutamate release signals in relation to SWRs varied across superficial neocortical regions, and it was largest in posteromedial regions surrounding retrosplenial cortex (RSC), which receives strong hippocampal output connections. Activity tended to spread sequentially from more medial towards more lateral regions. Contrary to the unidirectional hypothesis, activation exhibited a continuum of timing relative to SWRs, varying from neocortex leading to neocortex lagging the SWRs (± ~250 msec). The timing continuum was correlated with the skewness of peri-SWR hippocampal MUA and with a tendency for some SWR to occur in clusters. Thus, contrary to the model in which SWRs arise spontaneously in hippocampus, neocortical activation often precedes SWRs and may thus constitute a trigger event in which neocortical information seeds associative reactivation of hippocampal ‘indices’.

With the Donders Inclusion Seminars, we celebrate diversity. Please join us on Apr. 21st 2021 at 15.00 (CET) as we next welcome Dr. Silvy Collin of Tilburg University on Crowdcast. Her seminar is entitled "Schemas and schema-mediated memory". To read the abstract and register for the event visit: https://www.crowdcast.io/e/donders-inclusion-3

When listening to music, we typically lock onto and move to a beat (1-6 Hz). Behavioral studies on such synchronization (Repp 2005) abound, yet the neural mechanisms remain poorly understood. Some models hypothesize an array of self-sustaining entrainable neural oscillators that resonate when forced with rhythmic stimuli (Large et al. 2010). In contrast, our formulation focuses on event time estimation and plasticity: a neuronal beat generator that adapts its intrinsic frequency and phase to match the extermal rhythm. The model quickly learns new rhythms, within a few cycles as found in human behavior. When the stimulus is removed the beat generator continues to produce the learned rhythm in accordance with a synchronization continuation task.

Interpretation of interval timing data generated from animal models is complicated by ostensible motivational effects which arise from the delay-to-reward imposed by interval timing tasks, as well as overlap between timed and non-timed responses. These factors become increasingly prevalent at longer intervals. To address these concerns, two adjustments to long interval timing tasks are proposed. First, subjects should be afforded with reinforced non-timing behaviors concurrent with timing. Second, subjects should initiate the onset of timed stimuli. Under these conditions, interference by extraneous behavior would be detected in the rate of concurrent non- timing behaviors, and changes in motivation would be detected in the rate at which timed stimuli are initiated. In a task with these characteristics, rats initiated a concurrent fixed-interval (FI) random-ratio (RR) schedule of reinforcement. This design facilitated response-initiated timing behavior, even at increasingly long delays. Pre-feeding manipulations revealed an effect on the number of initiated trials, but not on the timing peak function.

Pain is a major clinical problem affecting 1 in 5 people in the world. There are unresolved questions that urgently require answers to treat pain effectively, a crucial one being how the feeling of pain arises from brain activity. Computational models of pain consider how the brain processes noxious information and allow mapping neural circuits and networks to cognition and behaviour. To date, they have generally have assumed two largely independent processes: perceptual and/or predictive inference, typically modelled as an approximate Bayesian process, and action control, typically modelled as a reinforcement learning process. However, inference and control are intertwined in complex ways, challenging the clarity of this distinction. I will discuss how they may comprise a parallel hierarchical architecture that combines pain inference, information-seeking, and adaptive value-based control. Finally, I will discuss whether and how these learning processes might contribute to chronic pain.

Gravity is a constant in our lives. It provides an internalized reference to which all other perceptions are related. We can experimentally manipulate the relationship between physical gravity with other cues to the direction of “up” using virtual reality - with either HMDs or specially built tilting environments - to explore how gravity contributes to perceptual judgements. The effect of gravity can also be cancelled by running experiments on the International Space Station in low Earth orbit. Changing orientation relative to gravity - or even just perceived orientation – affects your perception of how far away things are (they appear closer when supine or prone). Cancelling gravity altogether has a similar effect. Changing orientation also affects how much visual motion is needed to perceive a particular travel distance (you need less when supine or prone). Adapting to zero gravity has the opposite effect (you need more). These results will be discussed in terms of their practical consequences and the multisensory processes involved, in particular the response to visual-vestibular conflict.

Mahzarin Banaji and her colleague coined the term “implicit bias” in the mid-1990s to refer to behavior that occurs without conscious awareness. Today, Professor Banaji is Cabot Professor of Social Ethics in the Department of Psychology at Harvard University, a member of the American Academy of Arts and Sciences, the National Academy of Sciences and has received numerous awards for her scientific contributions. The purpose of the seminar, Blindspot: Hidden Biases of Good People, is to reveal the surprising and even perplexing ways in which we make errors in assessing and evaluating others when we recruit and hire, onboard and promote, lead teams, undertake succession planning, and work on behalf of our clients or the public we serve. It is Professor Banaji’s belief that people intend well and that the inconsistency we see, between values and behavior, comes from a lack of awareness. But because implicit bias is pervasive, we must rely on scientific evidence to “outsmart” our minds. If we do so, we will be more likely to reach the life goals we have chosen for ourselves and to serve better the organizations for which we work.

The study of altered states of consciousness has long had the potential to provide important insight into the nature of consciousness. In recent years there has been a resurgence of research and public interest in atypical or altered states of consciousness. These have focused both on conditions in which consciousness is considered to be impaired due to brain trauma or enhanced in some way through mediation practices or ingestion of psychedelics. The talk will begin with a brief overview of recent scientific approaches to understanding these different types of altered consciousness. The remainder of the talk will focus on lab-based experiments conducted by myself and others looking at the effects of serotoninergic hallucinogens (i.e. psilocybin and LSD) on perceptual and cognitive function. Together this body of research provides important new insights for the scientific study of consciousness and an initial understanding of the neuropharmacological mechanisms underlying conscious experience.