Spatial and Temporal Dynamics of Cortical Object Processing
About
The information carried by different spatial frequency (SF) has long been recognized to represent in a coarse-to-fine sequence. The visual system uses the combination of global and local features, which are carried by low SF (LSF) and high SF (HSF) respectively, to facilitate the processing of the upcoming stimulus. To understand the mechanistic role of SF processing in temporal dynamics of category representation, we examined neural responses of the inferior temporal (IT) cortex of macaque monkeys viewing SF filtered face and non-face stimuli with two different exposure times (fast trials: 20ms and slow trials: 200ms). The stimuli were six faces and three inanimate objects and each of which had been filtered in five frequency ranges (band-pass SF filter). In addition, for all the stimuli, corresponding phase-scrambled images were generated. All stimuli were equalized to have same luminance and contrast.
Goals
We directly addressed spatiotemporal dynamics of object and face representation by investigating how the network of IT neurons processes distinct SF over time. We applied a combination of encoding and decoding methods to the single and population of recoded neural data to explore the role of SF coding properties in IT category representation. Consistent with the coarse-to-fine nature of perception, we found an earlier representation of LSF in IT population compared with HSF. Furthermore, our results showed a systematic category representation difference over SFs in fast and slow trials, while the category information was similar for unfiltered stimuli in both fast and slow trials. These observations suggest a direct link between SF processing and evolution of category information over time. Together, these results provide evidence for the existence of an effective interaction between SF coding and category representation in IT cortex.
Researchers
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Mohammad-Reza Abolghasemi Dehaqani
abolghasemi@ipm.ir
Ehsan Rezayat
rezayat [at] ipm [dot] ir
Farideh Shakerian
f.shakerian[at]ipm[dot]ir
Ramin Toosi
r.toosi[at]ut[dot]ac[dot]ir
Behnam Karami
behnam079[at]gmail[dot]com
Roxana Koushki
frx71.koushki[at]gmail[dot]com
Collaborators
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Abdol-Hossein Vahabie
vahabi [at] ipm [dot] ir
Mohammad Ali Akhaee
Akhaee[at]ut[dot]ac[dot]ir
Achievements and Future works
We have shown that repeated reward experience enables primates to efficiently locate good objects when searching for reward [5]. Besides, our recent results have implicated temporal-prefrontal circuitry along with functionally connected subcortical regions in the implicit and high-capacity memory for long-term retention of object values (1). In another study, we showed that the primate prefrontal cortex represents both flexible short-term and stable long-term high-capacity memories, which could prioritize valuable objects far into the future [2]. Currently, we are investigating the neural mechanism of value-driven visual search in non-human primates and also the neural networks of value memory in humans. Additionally, we are investigating common and dissociable neural mechanism for novelty [4], aversiveness and risk with respect to reward [3]. These findings will shed light on the neural basis of long-term value-based memories with implications for maladaptive behaviors such as drug addiction and obesity.
Selected Publications
[1] Ghazizadeh et al, PNAS, 2018 [2] Ghazizadeh et al, Current Biology 2018 [3] Ghazizadeh et al, Frontiers Neuroscience, 2016 [4] Ghazizadeh et al, Biorxiv, 2019 [5] Ghazizadeh et al, Journal of Vision, 2016 [6] Daneshi et al, Scientific Reports, 2019 [7] Ghazizadeh et al, J Neurophys, 2010 [8] Ataei et al, Int Conf Sampling Theory, 2019
Collaborators
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Laboratory of sensorimotor research, National Institutes of Health Motor control lab, Johns Hopkins University Laboratoire de Neurosciences Cognitives, Marseille University of Melbourne, Australia
Project Name
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Date: January 2020
Client: Lines
Category: Branding
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Date: January 2020
Client: Southwest
Category: Website Design
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