An interview with Asst. Prof. Ali Ghazizadeh on ‘Common coding of expected value and value uncertainty memories in the prefrontal cortex and basal ganglia output’

This content is part of the Research in Practice in Neuroscience series of interviews with scientists, focusing on how their research work can have impact on medical practice. Click here to follow 'Research in Practice in Neuroscience' - for free - on Researcher for more great interviews.

Can you tell us about who you are, where you work and what you're currently working on? 

I'm Ali Ghazizadeh. I'm an assistant professor in the Electrical Engineering Department at the Sharif University of Technology in Tehran, Iran. I'm also heading the School of Cognitive Sciences at the Institute for Research in Fundamental Sciences IPM. My main research focus in the past 10 to 15 years has been on the neural mechanisms involved in value learning and memory. We address these questions across the species mainly using humans and non-human primates, various techniques such as electrophysiology, fMRI, and psychophysics, along with computational and mathematical modelling, the current focus of my group is to understand the neural mechanism that orients people's attention toward valuable visual objects. We want to understand how the learning and storage of so many valuable objects are orchestrated across the primate brain.

Could you tell us a bit more about your paper, and why this topic is so important?

This paper is a continuation of a large cohort of studies aimed at understanding object value learning and memory in cortical and subcortical areas in which I started to become involved when I was a research fellow at the Laboratory of sensory-motor research at the National Institutes of Health USA, working in the lab of Dr. Okihide Hikosaka. This whole research was propelled by the behavioral observation that non-human primates can learn the values of hundreds of nonsensical objects, and more importantly, that such learning affects their attention to objects for many months or even years in the future. Thus, we've uncovered a high capacity and stable form of visual memory. My colleagues and I have found the neural signatures of this phenomenon, mainly using electrophysiology within basal ganglia and substantia nigra. Now taking advantage of the coverage of fMRI, I looked for the neural correlates of the value memory across the brain and found several cortical and subcortical nodes to be involved in this form of memory, with differences in their memory longevity. This result was published in PNAS in 2018 and revealed that in addition to the basal ganglia few cortical areas, the prefrontal cortex can be activated by value memory. The natural question was then to know the relationship between this prefrontal cortical node and the basal ganglia activity for storage and expression of value memory, could it be that object value arises in one of these areas and then relate to the other or object value signals stored and expressed in a distributed format across cortex and basal ganglia. The findings of our most recent paper, published in Science Advances in 2021 seem to support that the distributed storage of information activity in both prefrontal and substantia nigra were similarly affected by greater changes in reward, and by reward uncertainty. Interestingly, the strength of activity in both regions predicted the attentional bias to valuable objects long after reward training. Finally, a curious finding was that the responses in the substantia nigra could be constructed from a certain combination of responses in the prefrontal cortex in ways that are consistent with the well-known basal ganglia direct and indirect pathways.

Could you discuss the connection between your research and medical practice, and how your work will have an impact on therapies or treatments in the future?

There is a very robust link between long-term object value memory and value-driven attention to what is known as cue-induced craving, which affects a variety of maladaptive behaviors such as food and drug addiction in humans. Our results show neural mechanisms for the stability of value-based memory and the conditions that create resistance to extinction and its neural substrates. These neural substrates can become the targets for behavioral, pharmaceutical, or electromagnetic manipulations to help affect an individual, say by reducing the rate of relapse. There are some published reports on the possible benefits of inactivating or over-activating certain cortical areas using transcranial electric or magnetic stimulation in humans for dealing with addiction and obesity. We think that our finding can help with honing methodologies to help these individuals.

Where could your work lead you next? what's the dream outcome here for you?

Our results show that the value memory for objects is accessed within the first 100 milliseconds of seeing objects. When these objects become valuable, they become very powerful in automatically controlling your attention. We know that a lot of physiological behavior then follows from initial attention to objects. Daniel Kahneman, the Nobel laureate refers to such rapid processes that bias thought and actions as, system one, in contrast to the more deliberate and slower, system two. I believe the ultimate goal of this research is to be able to understand how these two-systems control attention and interact with each other and what are their neural dynamics. At the heart of this goal is a better understanding of the phenomena of attention itself, even at the philosophical level, since it's probably true that if you understand and control your attention, then everything else will be under your control.

You can read and discover Asst. Prof. Ali Ghazizadeh’s research here.

Common coding of expected value and value uncertainty memories in the prefrontal cortex and basal ganglia output is published in American Association for the Advancement of Science

Photo Credits: Research Gate

Disclaimer: This is a transcript of a video conversation. You can listen to the recording on Researcher.