PhD Project 10
Modelling and mapping generalization and knowledge acquisition in the hippocampal-prefrontal-thalamic circuit
While the hippocampus is implicated in forming specific memories, recent proposals argue that nuclei in anterior thalamus process memory attributes en route from the medial prefrontal cortex to the hippocampus and determine their generalization. By integrating computational modelling, high-field functional MRI and multivariate data analyses we will track the emergence of knowledge representations within this neural circuit. This project will expand our understanding of how the brain assigns conceptual meaning to novel information, with implications for research on semantics and semantic memory.
The project is an interdisciplinary approach to the study of conceptual memory which involves different methodologies and different fields of inquiry; namely experimental psychology, cognitive neuroscience and computational modelling.
The unprecedented and innovative aspect is the possibility to look closely at the representations that emerge in specific brain areas (brain networks) associated with the processing of mnemonic and linguistic structures.
A novel fMRI paradigm was developed to simultaneously track how concepts at multiple hierarchical levels of abstraction are learned and represented in brain. The experimental paradigm focuses on rule learning as an instantiation of concept learning. The accumulation of conceptual knowledge over time and the trial-to-trial rate of change in knowledge were estimated for each level of abstraction from behaviour. The resulting parameters were used to inform the neuroimaging analyses.
fMRI analyses revealed a specific engagement of the striatum, mPFC and hippocampus in hierarchical as compared to non-hierarchical concept-learning with differential roles in accumulating and updating hierarchical knowledge. PPI analyses furthermore showed different performance-dependent connectivity patterns of these regions. Additionally, representational similarity analysis of a post-learning stimulus presentation block revealed the representation of a hierarchical category structure in the lateral middle frontal gyrus.
The results have been presented as a poster at the 2016 SfN Meeting. Currently a manuscript is being prepared to be submitted for publication.
A second fMRI study which probes the neural representation of multidimensional conceptual space, was developed and currently fMRI data is collected.