سخنرانی علمی آقای دکتر شاهین نصر پژوهشگر دانشکده پزشکی هاروارد با موضوع Application of FMRI in human visual perception در تاریخ 20 آبان ماه در تالار ابن سینا به صورت ویدیو کنفرانس زنده برگزار شد.

آقای دکتر شاهین نصر فارغ التصیل رشته مهندسی پزشکی از دانشکده پزشکی شهید بهشتی بوده و کارشناسی ارشد و دکترای خود را در دانشگاه علم وصنعت و پژوهشگاه IPM در رشته علوم اعصاب شناختی ادامه دادند. ایشان هم اکنون در دانشکده پزشکی هاروارد و بیمارستان عمومی ماساچوست در بوستون، ایالات متحده آمریکا، به عنوان هیئت علمی پژوهشی مشغول به کار هستند. 

چکیده سخنرانی ایشان به شرح زیر می باشد:

Applications of high-resolution functional magnetic resonance imaging in understanding human visual perception

Dr. Shahin Nasr,Assistant Professor, Harvard Medical School, Massachusetts General Hospital

Abstract

In human and non-human primates, sensory cortices consist of multiple areas in which neurons within similar functional roles are organized in cortical columns. These columns act like the building blocks in processing different stimulus features and are selectively connected to each other, forming relatively segregated processing streams within sensory cortices. For instance, in the visual cortex, cortical columns within magno- and parvo-cellular streams are involved in encoding stimulus color and depth, respectively. 

Up until recently, evidence for these fine-scale cortical structures were limited to reports based on using invasive techniques such as single cell recording and optical imaging in non-human primates and/or post-mortem histological approaches in humans and non-human primates.  However, with advances in neuroimaging techniques and by taking advantage of ultra-high field scanners, now it is possible to localize and study these mesoscopic neural structures in vivo non-invasively.

In the first part of this talk, I will review our recent findings based on high-resolution fMRI by using an ultra-high field (7T) scanner, in which my colleagues and I have provided one of the first in vivo evidences for these fine-scale structures in human striate and extrastriate visual areas, including ocular dominance columns in the primary visual area (V1) and color- and disparity-selective columns within extrastriate visual areas (V2-V4). I will also demonstrate the obstacles in localizing the same structures in lower field (e.g. 3T) scanners.

In the next part of this talk, I will clarify how multiple visual features such as stimulus contrast, spatial frequency, motion and hue (wavelength) are encoded within these fine-scale structures. I will also present evidences for heterogeneous representation of 3D space within stereo-selective columns distributed across dorsal and ventral portions of extrastriate visual areas and the potential impact of this heterogeneous representation on human visual perception. 

In the last part of this talk, I will highlight the clinical significance of our findings by presenting the preliminary evidence for impacts of amblyopia on organization of ocular dominance and stereo-selective columns in human visual system.