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■ JNS論文「線条皮質の損傷は慎重な意思決定およびサッカードの制御に影響を及ぼす」が出ました

Yoshida M. et.al., "Striate Cortical Lesions Affect Deliberate Decision and Control of Saccade: Implication for Blindsight" The Journal of Neuroscience, October 15, 2008 28(42):10517-10530
要はV1 lesionによって、サッカードの軌道は真っ直ぐになるし、サッカードの応答潜時は早くなる、だからV1 lesionによってvisionだけではなくてsaccade controlやdecisionまで影響を受けるのだ、という話です。
内部モデルとかdiffusion modelとかいろんなこと言ってます。いろいろコントロールデータも取ってます。本編のfigureが11個でsupplementaryにさらに7個。論文3本分のデータをつっこんであります。そのままだと一つの論文には一つのテーマという一般ルールから外れますんで、それらを全部合わせて、「visionだけでなくそれ以降のprocessing (decision makingやmotor control) も変わる」という一つのストーリーにしました。
いろいろ書いてありますが、わたしがいちばん言いたいことは、「V1 lesion後のvisionはnormal visionでのnear-threshold条件とは違う」ということでして、そのためのサッカードの解析です。その意味ではこの論文もblindsightの研究です。
Monkeys with unilateral lesions of the primary visual cortex (V1) can make saccades to visual stimuli in their contralateral ("affected") hemifield, but their sensitivity to luminance contrast is reduced. We examined whether the effects of V1 lesions were restricted to vision or included later stages of visual– oculomotor processing. Monkeys with unilateral V1 lesions were tested with a visually guided saccade task with stimuli in various spatial positions and of various luminance contrasts. Saccades to the stimuli in the affected hemifield were compared with those to the near-threshold stimuli in the normal hemifield so that the performances of localization were similar. Scatter in the end points of saccades to the affected hemifield was much larger than that of saccades to the near-threshold stimuli in the normal hemifield. Additional analysis revealed that this was because the initial directional error was not as sufficiently compensated as it was in the normal hemifield. The distribution of saccadic reaction times in the affected hemifield tended to be narrow. We modeled the distribution of saccadic reaction times by a modified diffusion model and obtained evidence that the decision threshold for initiation of saccades to the affected hemifield was lower than that for saccades to the normal hemifield. These results suggest that the geniculostriate pathway is crucial for on-line compensatory mechanisms of saccadic control and for decision processes. We propose that these results reflect deficits in deliberate control of visual–oculomotor processing after V1 lesions, which may parallel loss of visual awareness in human blindsight patients.

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