Saba Farbodkia

Queen's University at Kingston, Centre for Neuroscience Studies, Graduate Student

Bahai Institute for Higher Education, Biology, Teacher Assistant

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I was graduated from the Master's program of Neuroscience at BIHE, an institute developed in response to the persecution of Baha'is ( a religious minority in Iran) by the Islamic government of Iran.

I am aiming to pursue my education in neuroscience, because it is the field that I feel a deep enthusiasm to work in. My general view in life is that everyone is the source of a lot of potentials that if educated well, can be used to grow the society's potentials. This is the way I have chosen to grow my potentials, although I think this way can be modified in future to meet the more immediate requirements of the society.
Supervisors: Suliann Ben Hamed and Martin Pare
Phone: 613 770 4243

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Readout of the intrinsic and extrinsic properties of a stimulus from un-experienced neuronal activities: towards cognitive neuroprostheses.

by guilhem ibos and Saba Farbodkia

While sensory and motor systems have attracted most of the research effort in the field neuropros... more While sensory and motor systems have attracted most of the research effort in the field neuroprosthetics, little attention has been devoted to higher order cortical processes. Here, we propose a first step in the direction of applying neural decoding to the study and manipulation of visuospatial attention, an endogenous process at the interface between sensory and motor functions. To this aim, we investigate whether the offline activity of a population of non-human primate frontal eye field neurons (FEF) in response to an endogenous cue can be readout on a trial by trial basis to provide a precise description of the cue's attributes, namely, its location and identity, but also the allocation of attention following its interpretation. Using a linear decoder, we reach up to 86% correct predictions for the different decoded variables, including the spatial allocation of endogenous attention. We show that the decoding performance drops on incorrect trials, indicating that cue encoding participates to the animal's behavioral performance. Last, we show that the temporal resolution of the decoding influences readout performance. These results are a strong indication of the feasibility of the readout of endogenous variables by standard decoding algorithms, on a suboptimal dataset. However, its validity remains to be proved in a real-time situation.

How noise correlation impact population code in superior colliculus: an information theoretic approach

We previously showed that superior colliculus (SC) visuomovement neurons recorded while monkeys p... more We previously showed that superior colliculus (SC) visuomovement neurons recorded while monkeys perform visual search tasks have discriminating ability that exceeds the monkey's discriminating ability, suggesting that there is substantial noise added to this neuronal population [1]. We recently began to investigate the latter issue with modeling. First, we examined the effect of noise correlation as a limiting factor on the population's overall discrimination ability. To do so, we simulated a population of singly recorded neurons while manipulating noise correlation within the range of our estimates made from simultaneously recorded pairs of neurons with overlapping receptive fields. Positive noise correlation did decrease the performance of our simulated neuronal population. Based on these results, we sought to further investigate the effect of noise correlation on the discriminating ability of simultaneously recorded pairs of neurons.

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How noise correlations impact the amount of information in superior colliculus: the analysis of a population with shared receptive fields

Superior colliculus (SC) visuomovement neurons recorded while monkeys perform two versions of vis... more Superior colliculus (SC) visuomovement neurons recorded while monkeys perform two versions of visual search task with different difficulty levels have discriminating ability that exceeds the monkey’s discriminating ability [1]. This suggests that there is substantial noise added to this neuronal population. We investigated the effect of noise correlation as a possible limiting factor on the population’s overall discrimination ability. We simultaneously recorded from pairs of neurons during the simpler version of the task, and quantified the noise correlations for each pair. As expected noise correlations were mostly positive for pairs that shared the same receptive field (average= 0.14), and they mostly had the same sign as the signal correlations. Theoretically, this should reduce the amount of information that the pairs carry about the stimulus. The dependence of noise correlations on the stimuli (0.14 for target, 0.13 for distracters) was not statistically significant (p= 0.7); therefore, we didn’t expect that information be significantly added to most of pairs. We investigated the overall impact of noise correlations on the amount of information that each pair carried, by and quantifying the amount of information that the pair carried, when the noise correlations were ignored. The impacts were negligible for each pair. However, it is possible that at the level of population, the impact be different from what we observed for the pairs, due to accumulation of small amounts of correlation. To completely rule out the possibility of limiting effects of noise correlations on growth of information in the population, we investigated if the impacts would be similar in a larger population. We simulated a population of neurons with their responses sharing the basic discharge properties of our recorded neurons during each version of the task, and incorporated randomly assigned noise correlations drawn from a normal distribution with its mean and standard deviation taken from what we had obtained from the simultaneously recorded neurons. Our results so far show that at least for the simpler version of the task, where the signal-to-noise ratio is generally higher, the noise correlations do not have a significant effect, even when the population size grows large enough to saturate the mutual information between the signal and neural responses to its maximum possible amount. Therefore, it can be suggested that noise correlations do not play an important role in limiting the amount of information in a population of SC neurons during a feature visual search task.

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Readout of the intrinsic and extrinsic properties of stimuli from unexperienced neuronal activities

While sensory and motor systems have attracted most of the research effort in Brain-Computer Inte... more While sensory and motor systems have attracted most of the research effort in Brain-Computer Interfaces (BCI), little attention has been devoted to higher order cortical processes . Here, we propose to apply BCIs to the study and manipulation of visuospatial attention, an endogenous process at the interface between sensory and motor functions. As a first step to this aim, we investigate whether the activity of a population of frontal eye field neurons (FEF) in response to an endogenous cue can be readout on a trial by trial basis to provide a precise description of the cue's attributes, namely, its location and identity, but also the allocation of attention following its interpretation. Using the procedure described in Ben Hamed et al. [2, 3], we reach over 78% correct predictions for all decoded variables, including the spatial allocation of endogenous attention. We show that the decoding performance drops on incorrect trials, indicating that cue encoding participates to the animal's behavioral performance. Last, we show that the temporal resolution of the decoding influences readout performance. These results are a strong indication of the feasibility of the readout of endogenous variables by standard decoding algorithms, on a suboptimal dataset. Its validity remains to be proved in a real-time situation.

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Readout of the intrinsic and extrinsic properties of a stimulus from un-experienced neuronal activities: towards cognitive neuroprostheses.

by guilhem ibos and Saba Farbodkia

How noise correlation impact population code in superior colliculus: an information theoretic approach

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How noise correlations impact the amount of information in superior colliculus: the analysis of a population with shared receptive fields

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Readout of the intrinsic and extrinsic properties of stimuli from unexperienced neuronal activities

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Saba Farbodkia

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