The Neurobiology of Emotional Stress: Individual Variability and Interpersonal Dynamics

While "stress" is a topic that is commonly used in everyday life and is widely known to have profound implications for health, the field has been limited by methodological and ethical difficulties in testing its effects in humans. This talk will address different components of LSEC's research on the neurobiology of human emotional stress, bridging the gap from the scanner to the "real-world, " understanding why some individuals seem to function better under stress while others fall apart, and uncovering whether "second-hand stress" is literally and biologically contagious.

Training and Transfer of Executive Functions: The Case of Interference Resolution

Functional brain imaging evidence for overlapping sites of activation in prefrontal cortex across cognitive tasks suggests such tasks may share common executive components. We tested this hypothesis by measuring behavioral interactions between memory tasks presumed to require interference resolution, which is a putative executive control process that mediates selection from competing representations. Under different training regimens we found either negative or positive transfer from working memory to semantic memory and episodic memory. We infer that “far transfer” results from decreasing or increasing the efficiency of the interference resolution process, which is shared across memory domains. Therefore, this aspect of executive control is plastic and adaptive, and its efficiency can be altered by training.

Neurogenocomputomics

The nascent field of neuroeconomics applies cognitive neuroscience approaches -- primarily electrophysiology and functional neuroimaging -- toward understanding the basis of simple economic decisions. Here I make the case that genetic analysis can provide a complementary window into the computations of, and individual differences within, neural circuits underlying these choices. Candidate genes are selected to test predictions from neural models about the separable roles of dopamine in striatum and frontal cortex in reinforcement-based decision making. Across two quite different tasks, polymorphisms within striatal genes predict participants' tendencies to probabilistically integrate positive and negative outcomes of their decisions, whereas a prefrontal gene predicts rapid trial-by-trial adaptation and exploration as individuals search for the best strategy to maximize returns. Quantitative fits to participants' choices reveal that genetic contributions to decision making can be understood in terms of modulation of independent parameters of a reinforcement learning system.

Resolving Uncertainty: Priming as a Window onto the Prefrontal Executive System

Cognitive control is required when uncertainty arises due to representational conflict or ineffective bottom-up retrieval. In this talk, I will first review extant data that indicate that distinct subregions within human ventrolateral prefrontal cortex mediate competition-laden selection and the controlled retrieval of conceptual knowledge. I will then discuss new fMRI and EEG studies that exploit learning (priming) at distinct levels of representation––stimulus, stimulus-decision associations, and stimulus-response associations––to gain leverage on the prefrontal executive system. These new data indicate that controlled retrieval and selection are two levels of a multi-level prefrontal executive system that map stimuli to action.

Cognition without control: When a little frontal lobe goes a long way

The prefrontal cortex is crucial for the ability to regulate thought and control behavior. In humans, the development of the cerebral cortex is characterized by an extended period of maturation during which young children exhibit marked deficits in cognitive control. In this talk, I will contend that prolonged prefrontal immaturity is, on balance, advantageous and that the positive consequences of this developmental trajectory outweigh the negative. In particular, I will argue that cognitive control impedes convention learning, and that the delay in prefrontal maturation is a necessary adaptation for human learning of social and linguistic conventions. I will conclude with a discussion of recent observations that are relevant to this claim in a wide-range of research areas, including creativity, sleep, autism spectrum disorders, and the Flynn effect.

Multiple brain circuits for decision-making

To survive in changeable circumstances, we have to make appropriate decisions on our behavior. For the purpose, the brain should recognize reward information from objects in the circumstances. Recent experimental and theoretical studies have suggested that primates, including human beings, have two brain processes to calculate reward values of objects. One is the process coding a specific reward value of a stimulus or event dependent on direct experience (e.g. classical conditioning and TD learning). The other enables us to predict reward based on the internal model of given circumstances without direct experience (e.g. categorization and inference). To clarify neuronal correlates of the multiple processes on reward prediction, we have executed three experiments. 1) Human fMRI imaging during random-dot discrimination with asymmetric reward condition. 2) Single unit recording from the monkey dopamine neuron in the random-dot discrimination task with asymmetric reward schedule. 3) Simultaneous single unit recording from the monkey caudate and lateral prefrontal cortex in the reward inference task. Results suggest that the nigro-striatal network works for the model-free reward prediction and the prefrontal network contributes to the model-based reward prediction.

Attention and Memory at Retrieval

The role of attention during memory retrieval will be explored in behavioural and functional neuroimaging experiments in typical people and people with brain damage. The focus will be on the role of parietal cortex during memory retrieval. I will present an Attention to Memory (AtoM) model that distinguishes between the superior and inferior parietal contributions to memory retrieval which may help account for some behavioural evidence.