熵函數偵測人類初級視覺系統處理可預測性之訊息傳遞

Abstract

可預測之視覺訊息會調節初級視覺區的神經活動，即便此視覺刺激尚未接觸到神經細胞的受域。這代表視覺訊息傳遞的機制是：從初級視覺區傳到下游的高等腦區，再將回饋訊息傳回初級視覺區；或是初級視覺區之間彼此的訊息交流。因此，我們假設人類的初級視覺區中，不同區域的神經細胞會有訊息的傳遞，且我們應該要能藉由高解析度磁振造影儀偵測到此訊息傳遞。一位受試者完成了密集的磁振造影視覺實驗，並請他判斷擴張圓與縮小圓的動態特徵，藉此模擬逐漸靠近或逐漸遠離的球。我們利用「時間推遲互信息」和「轉移熵」分析在中央視野與邊緣視野所對應的視覺腦區之間的訊息傳遞大小與方向。當受試者看到擴張圓時，我們偵測到三種訊息傳遞，然而在縮小圓時，以外到內的訊息為主。而此訊息傳遞，只有在左腦被偵測到。此外，當擴張圓被遮住時，我們在右腦偵測到雙向訊息；遮住的縮小圓下，卻沒偵測到任何訊息傳遞。整體而言，我們成功利用磁振造影儀偵測到人類初級視覺系統區中的訊息傳遞。

Predictable visual stimuli modulate neural responses in regions of primary visual cortex (V1) even though the stimuli do not fall within the receptive fields of the modulated regions. This suggests a neural mechanism that transfers sensory signals from V1 to downstream cortical processes and feeds back to other V1 processes or direct interaction between V1. We therefore hypothesize that information transfer between different groups of V1 neurons should be present within the human V1 system. We sought to detect this using in vivo high spatial and temporal resolution functional magnetic resonance imaging (fMRI) with multi-band acquisition. A single participant underwent extensive fMRI experiments involving judgments about expanding and shrinking visual disks, mimicking the visual stimulation of an approaching or distancing ball. We applied time-delayed mutual information (MI) and transfer entropy (TE) analysis to dissociate information transfer magnitudes and directions between V1 regions sensitive to central and peripheral retinotopic stimulation. Information transfer direction between central and peripheral V1 neurons was mixed during expanding disk perception but more from peripheral to central V1 for shrinking disks. This pattern was evident in the left but not the right hemisphere. In addition, information transfer for occluded expanding disks was bidirectional and in the right hemisphere, and no information transfer was detected for occluded shrinking disks. Overall, our findings suggest that information transfer in the human V1 system is detectable with fMRI.