强迫性饮食与行为的生物学机制及治疗方法 | Dr. Casey Halpern

强迫性饮食与行为的生物学机制及治疗方法

摘要

宾夕法尼亚大学立体定向与功能神经外科主任 Casey Halpern 博士探讨了强迫性行为（包括暴食症、强迫症和成瘾）背后的神经科学。他的实验室致力于开发和应用工程化设备——尤其是deep brain stimulation（DBS，深部脑刺激）——以直接调节负责失控行为的大脑回路。本次对话涵盖了nucleus accumbens（伏隔核）的作用、当前治疗方法，以及一项开创性的人类首次试验：使用响应性 DBS 治疗强迫性饮食。

---

核心要点

• **nucleus accumbens（伏隔核）**是奖赏回路的核心枢纽，在反复接触高度适口食物、药物或其他强效奖赏后会发生失调——在动物模型中，这一过程最短仅需两周。
• **Binge eating disorder（暴食症）**是最常见的饮食障碍，估计影响3–5%的人口，且在肥胖人群中可能存在大量漏诊。
• 暴食症、强迫症和成瘾的共同特征是失控——在明知风险的情况下仍追求奖赏——Halpern 博士将其视为这些疾病共同的神经学本质。
• 响应性（间歇性）DBS——仅在检测到渴望信号时触发——似乎比持续刺激更有效、更持久；持续刺激会因大脑的稳态调节而随时间失效。
• 肥胖是一种表型，而非统一的诊断；约20%的肥胖患者具有暴食成分，但并非所有肥胖都由行为驱动。
• 高脂肪和高度精加工食物可在数周内劫持正常的伏隔核功能，使持续性强迫饮食行为更易发生。
• 提出了暴食症发展的”双重打击假说”：生物/遗传易感性与反复出现的环境压力源相结合。
• 神经性厌食症与肥胖相关强迫性过度饮食在神经层面可能更相似而非相异，两者均涉及由社会压力和大脑回路脆弱性驱动的强迫行为。
• DBS 治疗强迫症的有效率约为50%，即使有效的患者仍存在症状——这促使研究者探索更精准、更具疾病针对性的方法。
• 围绕肥胖和饮食障碍的社会污名会使结果更差，因为它引发羞耻感、阻碍患者寻求治疗，并强化紊乱行为的循环。

---

详细笔记

神经外科医生与其他脑科专家的区别

• 神经外科涵盖整个中枢和周围神经系统——肿瘤、动脉瘤、脊柱疾病以及功能性/运动障碍。
• 立体定向与功能神经外科是一个亚专科，专注于精准的、以生理学为导向的干预，而非纯粹的结构性手术。
• DBS 涉及将一根细绝缘导线植入目标脑区，并连接到皮下脉冲发生器（类似于心脏起搏器）。电刺激本身——而非导线的放置——才是治疗手段。
• 聚焦超声（经颅）是一种经 FDA 批准的非侵入性消融方法，目前已获批用于原发性震颤的治疗。

深部脑刺激的工作原理

• 在帕金森病中，DBS 靶向丘脑底核；震颤细胞的电活动被转换为音频，并与患者的震颤频率匹配——从而实现对电极放置位置正确性的实时确认。
• 患者在手术过程中通常保持清醒，以进行精确定位；刺激效果（如震颤缓解、情绪提升、发笑）可被实时观察到。
• 偶然发现：因震颤而接受 DBS 治疗的帕金森病患者有时报告抑郁、强迫症症状或赌博行为有所改善，这提示边缘-运动回路存在重叠。

强迫症：神经生物学与治疗

• 涉及的脑区：眶额皮质（OFC）、前额叶皮质、背侧纹状体（尾状核/壳核）以及腹侧纹状体（包括伏隔核）。
• 这些区域构成皮质-皮质下环路；在强迫症中，它们表现为失调，而非简单的功能低下或亢进。
• 强迫症存在于一个谱系中——从亚临床强迫倾向（在高成就人群中很常见）到严重的、难治性障碍。
• 治疗层级：
  1. SSRIs（一线药物治疗）
  2. 三环类抗抑郁药
  3. 暴露与反应预防（ERP）——被认为是最有效的非手术方案之一；部分由宾大的 Edna Foa 博士参与开发
  4. DBS 或囊切开术（消融）用于难治性病例
• 约30%的强迫症患者对药物和行为治疗的反应不充分。
• DBS 治疗强迫症的有效率约为50%；即使有效的患者仍存在症状，这凸显了改善靶向性的必要性。
• 囊切开术（对小脑区域进行热消融）可有效发挥作用，且几乎没有可检测到的副作用；某些区域似乎可以安全消融——其必要性被描述为类似于”阑尾”。

伏隔核与奖赏回路

• 伏隔核大小接近 1 厘米——比许多 DBS 靶点都大——且包含功能上不同的亚区。
• 它调控奖赏寻求行为；当其功能受到扰动时，会促进对奖赏的强迫性追求，即使面临负面后果（类似于大鼠即使遭受电击仍寻求食物）。
• 在暴露于60%高脂饮食的小鼠中，伏隔核功能在两周内发生改变——同时出现过度活跃和活跃度降低的区域——使持续性强迫饮食更易发生。
• 伏隔核中的渴望/预期信号似乎先于暴食行为出现，并可通过局部场电位（LFP）记录检测到。

暴食症：定义与神经生物学

• 患病率：普通人群的3–5%；肥胖人群中可能更高（肥胖影响约35%的美国人口）。
• 暴食的定义包含：（1）在短时间内吃下异常大量的食物，以及（2）主观上的失控感——而不仅仅是一顿饭吃多了。
• 严重暴食症：约每日一次；中度：约每周3–4次。
• 失控性进食（未达到完整暴食标准）每周可发生数十次。
• 餐前负性情绪——感到压力、焦虑或情绪低落——通常先于暴食发作；进食暂时缓解这种状态，从而强化该循环。
• 暴食症与肥胖密切相关，但并不等同——并非所有暴食症患者都肥胖，也并非所有肥胖者都暴食。

宾大针对失控性进食的 DBS 试验

• 研究设计：由 NIH 资助、FDA 批准的人类首次先导研究；招募胃旁路手术失败的患者，推测原因为暴食症。
• 靶点：伏隔核——具体为通过纤维束追踪图谱（connectomics，连接组学）定位的、与前额叶皮质相连的区域。
• 术中方案：
  • 患者保持清醒且处于空腹状态
  • 展示个人精选的高渴望食物图片以诱发渴望
  • 单单元和多单元神经记录识别**“渴望细胞”**
  • 给予刺激以评估安全性和情绪提升效果
  • 实时术中 CT 成像确认电极放置精度约为 0.5 mm
• 刺激参数：短暂、间歇性爆发，持续 5–10 秒，仅在检测到渴望信号时触发（响应性/闭环刺激）。
• 间歇性刺激的理由：小鼠数据（发表于 PNAS）显示，持续刺激会随时间失效；间歇性、信号触发刺激产生更持久的暴食阻断效果。
• 刺激所短暂诱发的正性情绪被假设为能够打断从渴望到暴食的循环。
• 宾大计划纳入六名患者；录制时已有两名患者接受了治疗。

神经性厌食症与共享回路假说

• 神经性厌食症在所有精神疾病中死亡率最高

---

English Original 英文原文

Biology & Treatments for Compulsive Eating & Behaviors

Summary

Dr. Casey Halpern, Chief of Stereotactic and Functional Neurosurgery at the University of Pennsylvania, discusses the neuroscience underlying compulsive behaviors including binge eating disorder, OCD, and addiction. His laboratory develops and applies engineered devices — particularly deep brain stimulation (DBS) — to directly modulate brain circuits responsible for loss-of-control behaviors. The conversation covers the role of the nucleus accumbens, current treatment approaches, and a groundbreaking first-in-human trial using responsive DBS for compulsive eating.

---

Key Takeaways

• The nucleus accumbens is a central hub of reward circuitry that becomes dysregulated after repeated exposure to highly palatable foods, drugs, or other powerful rewards — potentially within as little as two weeks in animal models.
• Binge eating disorder is the most common eating disorder, affecting an estimated 3–5% of the population, and is likely underdiagnosed in people with obesity.
• A defining feature of binge eating disorder, OCD, and addiction is loss of control — pursuing a reward despite known risks — which Dr. Halpern views as a common neurological denominator across these conditions.
• Responsive (intermittent) DBS — triggered only when a craving signal is detected — appears more effective and durable than continuous stimulation, which loses efficacy over time due to the brain’s homeostatic regulation.
• Obesity is a phenotype, not a uniform diagnosis; roughly 20% of people with obesity have a binge eating component, but not all obesity is behaviorally driven.
• High-fat and highly refined foods can hijack normal nucleus accumbens function within weeks, predisposing continued compulsive eating behavior.
• A “two-hit hypothesis” is proposed for developing binge eating disorder: a biological/genetic predisposition combined with a recurring environmental stressor.
• Anorexia and obesity-related compulsive overeating may be more neurologically similar than different, both involving compulsive behavior driven by societal pressures and brain circuit vulnerabilities.
• Deep brain stimulation for OCD achieves a responder rate of roughly 50%, and even responders remain symptomatic — motivating more targeted, disease-specific approaches.
• Social stigma around obesity and eating disorders worsens outcomes by causing shame, discouraging treatment-seeking, and reinforcing the cycle of disordered behavior.

---

Detailed Notes

What Neurosurgeons Do vs. Other Brain Specialists

• Neurosurgery covers the entire central and peripheral nervous system — tumors, aneurysms, spinal disorders, and functional/movement disorders.
• Stereotactic and functional neurosurgery is a subspecialty focused on precise, physiology-driven interventions rather than purely structural ones.
• DBS involves implanting a thin insulated wire into a target brain region, connected to a subcutaneous pulse generator (similar to a cardiac pacemaker). The electrical stimulation itself — not the wire placement — is the therapy.
• Focused ultrasound (transcranial) is an FDA-approved, non-invasive ablation method currently approved for essential tremor.

Deep Brain Stimulation: How It Works

• In Parkinson’s disease, DBS targets the subthalamic nucleus; electrical activity from tremor cells is converted to audio and matched to the patient’s tremor frequency — allowing real-time confirmation of correct electrode placement.
• Patients are often awake during surgery for precise mapping; stimulation effects (e.g., tremor relief, mood elevation, laughter) can be observed in real time.
• Incidental findings: Parkinson’s patients receiving DBS for tremor sometimes report improvements in depression, OCD symptoms, or gambling behavior, pointing to overlapping limbic-motor circuits.

OCD: Neurobiology and Treatment

• Brain areas involved: Orbital frontal cortex (OFC), prefrontal cortex, dorsal striatum (caudate/putamen), and ventral striatum including the nucleus accumbens.
• These regions form a cortical-subcortical loop; in OCD, they appear dysregulated rather than simply hypo- or hyperactive.
• OCD exists on a spectrum — from subclinical obsessive tendencies (common in high-achieving individuals) to severe, treatment-refractory disorder.
• Treatment hierarchy:
  1. SSRIs (first-line pharmacotherapy)
  2. Tricyclic antidepressants
  3. Exposure and Response Prevention (ERP) — considered among the most effective non-surgical options; developed in part by Dr. Edna Foa at Penn
  4. DBS or capsulotomy (ablation) for treatment-refractory cases
• Approximately 30% of OCD patients do not respond adequately to medication and behavioral therapy.
• DBS for OCD achieves roughly a 50% responder rate; even responders remain symptomatic, highlighting the need for improved targeting.
• Capsulotomy (thermal ablation of a small brain region) can be effective with minimal detectable side effects; some regions appear safe to ablate — described as “appendix-like” in terms of necessity.

Nucleus Accumbens and Reward Circuitry

• The nucleus accumbens is nearly 1 centimeter in size — larger than many DBS targets — and contains functionally distinct subregions.
• It gates reward-seeking behavior; when perturbed, it promotes compulsive pursuit of rewards despite negative consequences (analogous to a rat seeking food despite receiving foot shocks).
• In mice exposed to 60% high-fat diet, nucleus accumbens function changes within two weeks — showing both hyperactive and hypoactive regions — predisposing continued compulsive eating.
• A craving/anticipatory signal in the nucleus accumbens appears to precede binge behavior and can be detected with local field potential (LFP) recordings.

Binge Eating Disorder: Definition and Neurobiology

• Prevalence: 3–5% of the general population; likely higher among people with obesity (obesity affects ~35% of the U.S. population).
• A binge is defined by: (1) eating an unusually large amount of food in a brief period, and (2) a subjective sense of loss of control — not simply overeating at a meal.
• Severe binge eating disorder: approximately once daily; moderate: ~3–4 times per week.
• Loss-of-control eating (without meeting full binge criteria) can occur dozens of times per week.
• A pre-meal negative affect — feeling stressed, anxious, or low — commonly precedes binge episodes; eating temporarily relieves this state, reinforcing the cycle.
• Binge eating disorder is strongly linked to obesity but not identical — not all patients with binge eating disorder are obese, and not all obese individuals binge eat.

The Penn DBS Trial for Loss-of-Control Eating

• Study design: NIH-funded, FDA-approved first-in-human pilot study; targeting patients who have failed gastric bypass surgery, presumed due to binge eating disorder.
• Target: Nucleus accumbens — specifically the region connected to the prefrontal cortex via tractography-mapped circuits (connectomics).
• Intraoperative protocol:
  • Patients are awake and fasted
  • Shown personally selected high-craving food images to provoke craving
  • Single-unit and multi-unit neural recordings identify “craving cells”
  • Stimulation is delivered to assess safety and mood elevation
  • Real-time intraoperative CT imaging confirms electrode placement to within ~0.5 mm accuracy
• Stimulation parameters: Brief, episodic bursts of 5–10 seconds, triggered only when the craving signal is detected (responsive/closed-loop stimulation).
• Rationale for intermittent stimulation: Mouse data (published in PNAS) showed that continuous stimulation loses efficacy over time; intermittent, signal-triggered stimulation produces more durable binge-blocking effects.
• The positive affect transiently induced by stimulation is hypothesized to interrupt the craving-to-binge cycle.
• Six patients planned at Penn; two have been treated at time of recording.

Anorexia and the Shared Circuit Hypothesis

• Anorexia nervosa has the **highest mortality of all psychiatric conditions