Biology subjects

Azadi, R.

Publications and source records attributed to Azadi, R..

3 recordsLinked to original sources

bioRxiv2022

Behavioral detectability of optogenetic stimulation of inferior temporal cortex varies with the size of concurrently viewed objects.

We have previously demonstrated that macaque monkeys can behaviorally detect a subtle optogenetic impulse delivered to their inferior temporal (IT) cortex. We have also shown that the ability to detect the cortical stimulation impulse varies depending on some characteristics of the visual images viewed at the time of brain stimulation, revealing the visual nature of the perceptual events induced by stimulation of the IT cortex. Here we systematically studied the effect of the size of viewed objects on behavioral detectability of optogenetic stimulation of the central IT cortex. Surprisingly, we found that behavioral detection of the same optogenetic impulse highly varies with the size of the viewed object images. Reduction of the object size in four steps from 8 to 1 degree of visual angle significantly decreased detection performance. These results show that identical stimulation impulses delivered to the same neural population induce variable perceptual events depending on the mere size of the objects viewed at the time of brain stimulation.

neuroscience↗

bioRxiv2022

Surgical procedure for implantation of Opto-Array in nonhuman primates

Optogenetics allows precise temporal control of neuronal activity in the brain. Engineered viral vectors are routinely used to transduce neurons with light-sensitive opsins. However, reliable virus injection and light delivery in animals with large brains, such as nonhuman primates, has proven challenging. The Opto-Array is a novel yet simple device that is used to deliver light to extended regions of surface cortex for high-throughput behavioral optogenetics in large brains. Here we present protocols for surgical delivery of virus and implantation of the Opto-Array in two separate surgeries in a rhesus monkeys inferior temporal cortex. As a proof of concept, we measured the behavioral performance of an animal detecting cortical optogenetic stimulations with different illumination power and duration using the Opto-Array. The animal was able to detect the optogenetic stimulation for all tested illumination powers and durations. A regression analysis also showed both power and duration of illumination significantly modulate the detectability of the optogenetic stimulation. The outcome of this approach is superior to the standard practice of injecting and recording through a chamber for large areas of surface cortex. Moreover, the chronic nature of the Opto-Array allows perturbation of neuronal activity of the same site across multiple sessions because it is highly stable, thus data can be pooled over months. The detailed surgical method presented here makes it possible to use optogenetics to modulate neuronal activity across large regions of surface cortex in the nonhuman primate brain.

neuroscience↗

bioRxiv2020

Chronically implantable LED arrays for behavioral optogenetics in primates.

Challenges in behavioral optogenetics in large brains demand development of a chronically implantable platform for light delivery. We have developed Opto-Array, a chronically implantable array of LEDs for high-throughput optogenetic perturbation in non-human primates. We tested the Opto-Array in the primary visual cortex of a macaque monkey, and demonstrated that optogenetic cortical silencing by the Opto-Array results in reliable retinotopic visual deficits on a luminance discrimination task.

neuroscience↗