Ali Ghazizadeh
Learning and memory lab
Affiliation: Electrical engineering department, Sharif university of technology, neuroimaging group, school of cognitive science, IPM
Contact: alighazizadeh[at]ipm[dot]ir





Open positions: (send requests+ CV to the email above)
We seek highly motivated individuals with solid math or biology backgrounds to join the lab. Post-doctoral and student researchers should email their CV, 2-3 recommendation letters and a statement of research plans.
We also look for a motivated lab technician. Previous experience and willingness to work with animals, with electronics equipment and good programming skills are highly desirable.



Research Description

As the most complex system known to us, human brain, is thought to underly all of our perceptions, emotions and actions, it is the biological basis of what makes us "us". In my lab, we take a broad interest in understanding nervous system function. Current focus of the lab is in the areas of visual learning and memory, decision making, perception and motivation using human and nonhuman primates as model organisms. We use psychophysics, imaging and electrophysiology along with computational analysis and mathematical modeling to get at the principles that shape neural systems structure, function and their relation to behavior. Current active research themes include:

Object value learning and memory
We, primates, use vision as our primary sense to deal with many objects that surround us. Our lifelong experience with objects teaches us that some objects are more valuable than others (e.g. our favorite foods, people etc). Despite the primacy of this phenomenon little is known about the neural mechanism that learns and stores the object values in primate brain. Recent evidence shows that different structures are involved in different time-scales of value learning and memory and depending on the context.

Dimensions of object salience
There is evidence that previous experience with objects can change their intrinsic salience (i.e. how attention grabbing they are). We have investigated the influence of different experiential dimensions such as reward, risk, aversiveness and novelty in changing object salience (Ghazizadeh et al 2016). There are commonalities as well as differences between these dimensions in the way they modify salience. Little is known about the neural mechanism underlying these similarities and differences and their interaction with long-term memory. This is one of our active areas of research.

Value driven perceptual learning
It is long thought that guiding features in visual search are limited to objects physical properties such as color or orientation pop-out. However, it there is mounting evidence that high-level propoerties may also be very effective in driving efficient search (as seen in detecting faces for example). Our results (Ghazizadeh et al 2016) show that long-term association of reward value can also result in efficient search in ways that are similar to bottom-up influences (i.e. fast detection and high capacity). This goes against the long-held dogma in the field. We are investigating the neural mechanisms that can mediate the observed 'value pop-out'

Tools for neural analysis
We are interested in developing better methods for neuroscience data analysis and visualization. Previously we developed a deconvolution technique for parsing components of neural activity to closely spaced events (Ghazizadeh et al 2010). Currently, we are working on methods with applications in neural electrophysiology, EEG and fMRI.


Post docs:



1 Open position






PhD Students:



Sepideh Farmani
Ms. Farmani’s project involves addressing value mamory in humans using psyhophysics and fMRI imaging techniques
farmani[at]ipm[dot]ir



   


Researchers:



Soroush Meghdadi







Kiomarz Sharifi







Mohammad-amin Fakharian









Group website: ghazizadehlab.org



3 Selected Publications


[1] Ali Ghazizadeh, Simon Hong, Okihide Hikosaka, Prefrontal cortex represent value memory of objects for months, Curr Biology, 2018

[2] Ali Ghazizadeh, Whitney Griggs, David A. Leopold, Okihide Hikosaka, A long term high capacity memory system in temporal and prefrontal cortices for valuable objects, PNAS, 2018

[3] Hyoung F Kim, Ali Ghazizadeh, Okihide Hikosaka, Dopamine neurons encoding long-term memory of object value for visual oculomotor habit, Cell, 163(5):1165-75, 2015

[4] Ali Ghazizadeh, Frederic Ambroggi, Howard L. Fields, Prefrontal Cortex Mediates Extinction of Responding by a Dual Neural Mechanism in Accumbens Shell, Journal of Neuroscience 32: 726-723, 2012

[5] Ali Ghazizadeh, Howard L. Fields, Frederic Ambroggi, Isolating Event related Neuronal Responses by Deconvolution, J Neurophysiol 104: 1790-1802, 2010



















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