Dr. Ali Ghazizadeh



Acquired Object Salience: Neural Substrates and Behavioral Consequences


Our interactions with objects are often guided by past experiences with them or the lack thereof. Previously, we have demonstrated that rewarding or aversive outcome associations as well as mere perceptual exposures (familiarity vs novelty) biases gaze toward objects with effects that last for many months.  For reward association, this gaze bias was shown to support efficient visual search. However, the neural substrates of experience dependent object salience remain poorly understood. Importantly, it is not known to what degree the coding of different dimensions of salience such as value, punishment and novelty are distributed across areas that control gaze. Here I will first review some of our recent studies that show cortical and subcortical areas involved acquired salience in nonhuman primates. I will then show results suggesting that the value and value uncertainty is learned and represented in parallel in prefrontal cortex (PFC) and basal ganglia. Both regions also similarly code punishment related object salience. However, novelty and recency salience seem to be preferentially encoded in PFC. Furthermore, behavioral and neural analysis as well as multi-alternative drift-diffusion modelling suggests that efficient search is likely to be accompanied by processing area enlargement for valuable objects.  Finally, I will describe some preliminary results on learning and long-term memory of value-based object salience in humans.

Brief Bio

Ghazizadeh Lab investigates the neural correlates of learning and memory especially within cortex and basal ganglia. Recent focus is on ecological dimensions of acquired object salience including value, uncertainty, aversiveness and novelty. Techniques used include electrophysiology, psychophysics and fMRI in non-human primates and in humans. Dr. Ghazizadeh is currently a faculty of electrical engineering department in Sharif University of Technology (SUT) and adjunct faculty of school of cognitive science in IPM. Prior to that he was a research fellow at the laboratory of sensorimotor research (LSR) in NIH from 2011-2017. He has received his MSc and PhD degree in neuroscience from Johns Hopkins university and the joint program in UCSF and UC Berkeley, respectively and his BSc degree in electrical engineering from SUT.