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Recent Publications

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Okazawa & Kiani (2023) Annu Rev Physiol

Neural mechanisms that make perceptual decisions flexible

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, Sha, & Kiani (2021) J Neurosci

Linear integration of sensory evidence over space and time underlies face categorization.

Okazawa G, Sha L, Kiani R.

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In simple perceptual tasks such as dot direction discrimination, the brain accumulates sensory evidence for decisions. How about more complex decisions such as face categorization? We found that face categorization could be explained as linear accumulation of evidence over space (facial features) and time.

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.

Publications: Publications

Full publication list

  • Neural mechanisms that make perceptual decisions flexible. (2023) Okazawa G, Kiani R. Annu Rev Physiol [pdf]

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

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

  • Designing and Interpreting Psychophysical Investigations of Cognition [review]. (2019)
    Waskom ML, Okazawa G, Kiani R Neuron 104(1):100-112 [pdf]

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

      • Code is available.

      • A summary is available in Japanese (in Neuroscience News published by the Japan Neuroscience Society)

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

  • Image statistics underlying natural texture selectivity of neurons in macaque V4. (2015)
    Okazawa G, Tajima S, Komatsu H Proceedings of the National Academy of Sciences, 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.

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

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

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

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

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

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

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

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

Publications: Text
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