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Title: Mechanisms for novel multidimensional choices in prefrontal cortex
Author: Bongioanni, Alessandro
ISNI:       0000 0004 8502 8992
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2018
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In this thesis the cognitive and neuro-computational bases of novel value-based decision-making in non-human primates are studied. Humans routinely perform choices among options that have not previously been experienced, using value expectations derived from their component attributes. Animal studies, however, are typically performed after extensive training ensuring familiarity with the task. Here we show how Rhesus macaques can readily perform value-guided choices among novel stimuli - if their components are known. An economic analysis of subjective biases is provided. Neuroimaging and causal techniques are then used to uncover a network centred in anterior medial frontal cortex (AMFC) underlying adaptive novel decisions. A first experiment, using fMRI with a binary decision task, reveals that orbitofrontal cortex is equally modulated by value in novel and familiar choices, but in contrast AMFC and dorsolateral prefrontal cortex (dlPFC) show a markedly different pattern of responses between conditions. A second experiment, using fMRI and single option trials, reveals how AMFC and dlPFC, but no other regions, encode representations of abstract value independent from its components (reward magnitude and probability), appearing across sessions with exposure to the novel options. Additionally, a pattern of hexagonal symmetry is found in AMFC activity, indicating a grid-like encoding of two-dimensional value space. Such a code provides a mechanistic explanation of how novel options' values may be computed. A last experiment confirms this by showing that transiently disrupting AMFC with focused transcranial ultrasound impairs the use of an integrated representation of value when novel decisions are made. Together, these experiments bridge neuroscientific studies in humans and monkeys and reveal a neural basis for novel decision-making that has not previously been investigated in either species.
Supervisor: Rushworth, Matthew Sponsor: Wellcome Trust ; Economic and Social Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: Value-based decision-making