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Selected Publications

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Luo, Xu, Zheng, Okazawa (2025) Nat Comm

Limitation of switching sensory information flow in flexible perceptual decision making

Luo T, Xu M, Zheng Z, Okazawa G

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Immediately after switching a task rule, human behavioral performance degrades (switch cost). We identified that there is a brief reduction in the efficiency of processing sensory evidence, which recovers a few hundred milliseconds after stimulus presentation. This could be a bottleneck of decision-making circuits in adjusting sensory readout.

Zhang et al. (2025) bioRxiv

Object categorization based on abstract concepts by monkeys, humans, and vision models

Zhang H, Zheng Z, Hu J, Wang Q, Xu M, Zhou Z, Li Z, Okazawa G​

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We found macaque monkeys can rapidly learn to classify natural images based on abstract object concepts such as animate vs. inanimate, natural vs. artificial, mammal vs. non-mammal. We trained monkeys to perform a battery of classification tasks and compared their performance with that of humans and vision models.

Okazawa & Kiani (2023) Annu Rev Physiol

Neural mechanisms that make perceptual decisions flexible

Okazawa G, Kiani R.

 

In this review, we summarize the current understanding of neural mechanisms underlying flexible, context dependent perceptual decision making. We propose to clarify what forms of flexibility different tasks are testing. Physiological findings have indicated that diverse brain areas reflect different forms of flexibility.

Okazawa et al. (2021) Cell

Representational geometry of perceptual decisions in the monkey parietal cortex.

Okazawa G, Hatch CE, Mancoo A, Machens CK, Kiani R.

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Past study considered that average firing rate of neural activity in the parietal cortex represents evidence for perceptual decisions. We found that this is not the case in face categorization tasks and revealed that evidence is instead encoded along a non-linear task-dependent manifold in neural state space.

Okazawa et al. (2018) Nat Comm

Psychophysical reverse correlation reflects both sensory and decision-making processes

Okazawa G, Sha L, Purcell BA, Kiani R

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Psychophysical reverse correlation has been extensively used to reveal sensory filters or properties of decision-making process. Through modeling and psychophysics, we show that many parameters in both sensory and decision-making processes affect psychophysical kernel and thus we should be very careful when interpreting its results. A model-based approach is recommended. 

Okazawa, Tajima, Komatsu (2015) PNAS

Image statistics underlying natural texture selectivity of neurons in macaque V4

Okazawa G, Tajima S, Komatsu H

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A mid-level visual area, V4, responds to complex visual stimuli, but it was not clear what neurons were responding to. We show single V4 neurons respond to naturalistic textures and these responses could be explained as selectivity for higher-order image statistics.

Full publication list

​Preprint

  1. Zhang H, Zheng Z, Hu J, Wang Q, Xu M, Zhou Z, Li Z, Okazawa G​ (2025) Object categorization based on abstract concepts by monkeys, humans, and vision models bioRxiv https://www.biorxiv.org/content/10.1101/2025.04.02.646407v1

  2. Zheng Z, Hu J, Okazawa G (2024) Spatiotemporal evidence accumulation through saccadic sampling for object recognition. bioRxiv https://www.biorxiv.org/content/10.1101/2024.09.05.611201v1​

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Published​

  1. Luo T, Xu M, Zheng Z, Okazawa G (2025) Limitation of switching sensory information flow in flexible perceptual decision making.  Nature Communications 16:172 [pdf]

  2. Ogasa K, Yokoi A, Okazawa G, Nishigaki M, Hirashima M, Hagura N (2024) Decision uncertainty as a context for motor memory. Nature Human Behaviour doi: 10.1038/s41562-024-01911-x [pdf]​

  3. Okazawa G, Kiani R (2023) Neural mechanisms that make perceptual decisions flexible [review].  Annu Rev Physiol 85:191-215. [pdf]

  4. Okazawa G, Hatch CE, Mancoo A, Machens CK, Kiani R (2021) Representational geometry of perceptual decisions in the monkey parietal cortex. Cell 184:3748-3761 [pdf]

  5. Okazawa G, Sha L, Kiani R (2021) Linear integration of sensory evidence over space and time underlies face categorization. (2021) J Neuroscience 41(37):7876-7893 [pdf]

  6. Waskom ML, Okazawa G, Kiani R (2019) Designing and Interpreting Psychophysical Investigations of Cognition [review]. (2019) Neuron104(1):100-112 [pdf]

  7. Okazawa G, Sha L, Purcell BA, Kiani R (2018) Psychophysical reverse correlation reflects both sensory and decision-making processes. Nature Communications 9:3479 [pdf]

    • Code is available.

  8. ​Okazawa G, Tajima S, Komatsu H (2016) Gradual development of visual texture-selective properties between macaque areas V2 and V4. Cerebral Cortex 27(10):4867-4880 [pdf]

  9. Okazawa G, Tajima S, Komatsu H (2015) Image statistics underlying natural texture selectivity of neurons in macaque V4. Proc Natl Acad Sci, USA 112 (4) E351-E360 [pdf]

    • See also commentary by C. Ziemba and J. Freeman

    • You can download ~10,000 texture dataset created for this study here.

    • Code to compute the minimum texture statistics to fit V4 data.

  10. Namima T, Yasuda M, Banno T, Okazawa G, Komatsu H (2014) Effects of luminance contrast on the color selectivity of neurons in the macaque area v4 and inferior temporal cortex. J Neuroscience 34(45):14934-47 [pdf]

  11. Goda N, Tachibana A, Okazawa G, Komatsu H (2014) Representation of the material properties of objects in the visual cortex of nonhuman primates. J Neuroscience 34(7):2660-73 [pdf]

  12. Koida K, Yokoi I, Okazawa G, Mikami A, Widayati KA, Miyachi S, Komatsu H (2013) Color vision test for dichromatic and trichromatic macaque monkeys. J Vision 13(13):1, 1-15 [pdf]

  13. Okazawa G, Komatsu H  (2013) Image Statistics for Golden Appearance of a Painting by a Japanese Edo-era Artist Jakuchu Ito. (2013) In Lecture Notes in Computer Science, Computational Color Imaging (Ed. Tominaga S et. al) 7786:68-79, Springer

  14. Komatsu H, Nishio A, Okazawa G, Goda N (2013) ‘Yellow’ or ‘Gold’?: Neural Processing of Gloss Information [review]. (2013)  In Lecture Notes in Computer Science, Computational Color Imaging (Ed. Tominaga S et. al) 7786:1-12, Springer

  15. Okazawa G, Funahashi S (2013) Short-Term Memory of the Amplitude of Body Rotation in Orienting Behavior of African Clawed Frog (Xenopus laevis). ISRN Zoology 2013(ID734040):1-9

  16. Okazawa G, Goda N, Komatsu H (2012) Selective responses to specular surfaces in the macaque visual cortex revealed by fMRI. NeuroImage 63(3):1321-33 [pdf]

  17. Okazawa G, Koida K, Komatsu H (2011) Categorical properties of the color term "GOLD".  J Vision 11(8):4, 1-19 [pdf]

Abstracts

  1. Wu J*, Luo T*, Okazawa G (2024) Graded encoding of task context and its generalization in prefrontal cortex during face categorization. Society for Neuroscience 2024 Meeting (Chicago, USA) (* equal contribution)

  2. Zhang H, Zheng Z, Hu J, Wang Q, Xu M, Li Z, Okazawa G (2024) Rapid learning of visual categorization of abstract object concepts by macaque monkeys. Society for Neuroscience 2024 Meeting (Chicago, USA)

  3. Okazawa G, Kiani R (2024) Inferotemporal neurons represent decision formation during face categorization. Society for Neuroscience 2024 Meeting (Chicago, USA)

  4. Wu J*, Luo T*, Okazawa G (2024) Graded encoding and generalization of task context for perceptual tasks in prefrontal cortex. The 17th Annual Meeting of Chinese Neuroscience Society (Suzhou, China) (* equal contribution)

  5. Hu J, Xu M, Li Z, Okazawa G (2024) Linking neural responses in area V4 and perceptual reports through neurofeedback training of macaque monkeys. The 17th Annual Meeting of Chinese Neuroscience Society (Suzhou, China)

  6. Zhang H, Zheng Z, Hu J, Wang Q, Xu M, Li Z, Okazawa G (2024) Monkeys rapidly learn visual object categorization based on abstract concepts. The 17th Annual Meeting of Chinese Neuroscience Society (Suzhou, China)

  7. Zhang H, Zheng Z, Hu J, Wang Q, Li Z, Xu M, Okazawa G (2024) Novel binary categorization task to study high-level visual object classification in macaque monkeys. Cognitive Computational Neuroscience (CCN) 2024 (Boston, USA) [abstract]

  8. Luo T, Zheng Z, Xu M, Okazawa G (2024) Limited efficiency in switching relevant sensory dimensions during flexible perceptual decision making. The 48th Annual Meeting of the Japan Neuroscience Society (Fukuoka, Japan)

  9. Luo T, Zheng Z, Xu M, Okazawa G (2023) Reduced sensory processing efficiency after switching relevant sensory dimensions in flexible perceptual decision making. Society for Neuroscience 2023 Meeting (Washington DC, USA)

  10. Zheng Z, Hu J, Okazawa G (2023) Spatiotemporal integration of sensory evidence during saccadic sampling for face and object categorization. Society for Neuroscience 2023 Meeting (Washington DC, USA)

  11. Zhang Y, Shen X, Okazawa G, Min B (2023) Elucidating the circuit mechanism underlying task-dependent representational geometry of perceptual decisions. Society for Neuroscience 2023 Meeting (Washington DC, USA)

  12. Zheng Z, Hu J, Okazawa G (2023) Global spatiotemporal integration of sensory evidence during saccadic sampling in face categorization. The 16th Annual Meeting of Chinese Neuroscience Society (Zhuhai, China)

  13. Luo T, Zheng Z, Xu M, Okazawa G (2022) Modulation of decision-making processes after switching task rule during face categorization. The 15th Annual Meeting of Chinese Neuroscience Society (Suzhou, China)

  14. Okazawa G, Hatch CE, Mancoo A, Machens CK, Kiani R (2021) What do distinct parietal neural responses for face and motion discrimination tasks reveal about the mechanisms of the decision-making process?  Vision Science Society (VSS) 2021 (online)

  15. Okazawa G, Hatch CE, Mancoo A, Machens CK, Kiani R (2021) The geometry of the representation of decision variable and stimulus difficulty in the parietal cortex. COSYNE 2021 (online)

  16. Okazawa G, Hatch CE, Mancoo A, Machens CK, Kiani R (2020) The geometry of the representation of decision variable and stimulus difficulty in the macaque parietal cortex. The 43th Annual Meeting of the Japan Neuroscience Society (Kobe, Japan)

  17. Okazawa G, Kiani R (2019). Distinct representations of decision variable and task difficulty in the monkey lateral intraparietal cortex. Society for Neuroscience 49th Annual Meeting (Chicago, USA)

  18. Okazawa G, Kiani R (2019). Task difficulty has a distinct representation from the decision variable in the monkey parietal cortex. Ninth International Workshop Statistical Analysis of Neuronal Data (SAND9) (Pittsburgh, PA).

  19. Okazawa G, Kiani R (2018). Representation of the dynamics of decision-making process in the lateral intraparietal cortex during face discrimination. Society for Neuroscience 48th Annual Meeting (San Diego, USA).

  20. Okazawa G, Sha L, Kiani R (2017). Psychophysical reverse correlation reflects both sensory filters and the decision-making process [refereed]. COSYNE 2017 (Salt lake city, USA).

  21. Okazawa G, Sha L, Kiani R (2016) Face discrimination under uncertainty depends on linear integration of visual features over space and time. Society for Neuroscience 46th Annual Meeting (San Diego, USA).

  22. Okazawa G, Tajima S, Komatsu H (2015) Comparison of natural texture selectivity and underlying image-statistics representation between macaque V2 and V4. The 38th Annual Meeting of the Japan Neuroscience Society (Kobe, Japan).

  23. Okazawa G, Tajima S, Komatsu H (2014) Image statistics explaining natural texture selectivity in macaque V4. The 37th Annual Meeting of the Japan Neuroscience Society (Yokohama, Japan).

  24. Okazawa G, Tajima S, Komatsu H (2013) Natural texture selectivity of macaque V4 neurons examined by adaptive sampling.  Society for Neuroscience 43rd Annual Meeting (San Diego, USA).

  25. Okazawa G, Tajima S, Komatsu H (2013) Image features determining texture selectivity of macaque V4 neurons revealed by adaptive sampling. The 36th Annual Meeting of the Japan Neuroscience Society (Kyoto, Japan).

  26. Okazawa G, Komatsu H (2013) Image statistics for golden appearance of a painting by a Japanese edo-era artist Jakuchu Ito [refereed]. The forth computational color imaging workshop (CCIW 2013) (Chiba, Japan).

  27. Okazawa G, Goda N, Komatsu H (2012) Localizing regions activated by surface gloss in macaque visual cortex by fMRI.  8th Asia-Pacific Conference on Vision (Incheon, Korea).

  28. Okazawa G, Goda N, Komatsu H (2011) Cortical regions activated by surface gloss in the macaque visual cortex localized using fMRI.  Society for Neuroscience 41st Annual Meeting (Washington DC., USA).

Invited talk

2024/10   Yanqi Youth Forum for Brain Science Frontiers, Shanghai, China

2024/9     CHAIN seminar, Hokkaido University, Hokkaido, Japan

2024/9     34th Annual Meeting of the Japanese Neural Network Society, Hokkaido, Japan

​2023/6     Zhejiang University, Hanzhou, China
2023/3     The 8th CiNet Conference ”Beyond Motor Control: Bridging the gap between action and perception”, Osaka, Japan
2023/2     The 4th Conference on New Technology of Primate Neuroscience, Tokyo, Japan
2022/12    The 52nd NIPS International Symposium on “Frontiers in Primate Systems Neuroscience”, Okazaki, Japan
2022/10    Neuron@noon seminar, CNIR, SungKyunKwan University, Korea
2022/9     The 25th Vision Science Forum, Okazaki, Japan
2021/9      Barccsyn Webinar, Barcelona, Spain
2021/9      The 15th Motor Control Meeting, The Japanese Society for Motor Control, Japan
2020/8     Center for Information and Neural Networks, Osaka, Japan
2018/12     University of Washington, Seattle, WA
2018/12     Columbia University, New York, NY
2018/7       RIKEN Center for Brain Science, Wako, Japan
2018/3       Center for Information and Neural Networks, Osaka, Japan
2018/3       Tamagawa University, Tokyo, Japan
2018/3       RIKEN Center for Brain Science, Wako, Japan 
 

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