Visual presentation of appetitive and negative cues triggers fast responses in the human brain. Here we assessed functional MRI (fMRI) responses to food, cocaine, and neutral cues presented at a subliminal (“unconscious”, 33 ms) and supraliminal (“conscious”, 750 and 3000 ms) level in healthy, cocaine naïve volunteers. Because there is evidence of circadian variability in reward sensitivity, our second aim was to assess diurnal variability in the brain’s reactivity to cues. Sixteen participants completed two randomly ordered fMRI sessions (once 9-11 AM and another 5–7 PM). in which food, cocaine, and neutral cues were presented for 33, 750 and 3000 ms. Participants rated food cues as positive and “wanted” (more so in evenings than mornings), and cocaine cues as negative (no diurnal differences). fMRI showed occipital cortex activation for food>neutral, cocaine>neutral and cocaine>food; dorsolateral prefrontal cortex for cocaine>neutral and cocaine>food, and midbrain for cocaine>food (all p_FWE < 0.05). When comparing unconscious (33 ms) > conscious (750 and 3000 ms) presentations, we observed significant differences for cocaine>neutral and cocaine>food in occipital cortex, for cocaine>neutral in the insula/temporal lobe, and for food>neutral in the middle temporal gyrus (p_FWE < 0.05). No diurnal differences for brain activations were observed. We interpret these findings to suggest that negative items (e.g., cocaine) might be perceived at a faster speed than positive ones (e.g., food), although we cannot rule out that the higher saliency of cocaine cues, which would be novel to non-drug using individuals, contributed to the faster speed of detection.

视觉上的食欲和消极暗示会触发人脑快速反应。在这里，我们评估了健康，可卡因初次接受者的潜意识水平（“无意识”，33 ms）和and上水平（“意识”，750和3000 ms）对食物，可卡因和中性提示的功能性MRI（fMRI）反应。因为有证据表明奖励敏感度存在昼夜节律变化，所以我们的第二个目标是评估大脑对线索反应的昼夜变化。16名参与者完成了两次随机排序的功能磁共振成像会议（一次上午9时11分，另一个下午5时7分）。其中出现了食物，可卡因和中性线索持续了33、750和3000毫秒。参加者对食物提示的评价为积极和“想要”（晚上比早晨更多），可卡因提示为负面（没有昼夜差异）。功能磁共振成像显示食物的枕叶皮层活化> 中性，可卡因>中性和可卡因>食物；可卡因>中性和可卡因>食物的背外侧前额叶皮层，可卡因>食物的中脑（所有p_FWE  <0.05）。当比较无意识（33 ms）>有意识（750和3000 ms）的表现时，我们观察到枕叶皮层中可卡因>中性和可卡因>食物，岛叶/颞叶中可卡因>中性以及食物>中性时的显着差异。颞中回（p _FWE  <0.05）。没有观察到大脑激活的昼夜差异。尽管我们不能排除可卡因提示的显着性较高，但对于非吸烟者而言，这是新颖的，因此我们解释这些发现表明，阴性物品（例如可卡因）的感知速度可能比阳性物品（例如食物）的感知速度更快。使用个人药物，有助于加快检测速度。