Defensive behavior is a function of specific survival circuits, the “aversive brain system”, that are thought to be conserved across vertebrates, and involve threat detection and the organization of defensive responses to reduce or eliminate threat. In mammals, these circuits involve amygdalar and hypothalamic subnuclei and midbrain circuits. The increased interest in teleost fishes as model organisms in neuroscience created a demand to understand which brain circuits are involved in defensive behavior. Telencephalic and habenular circuits represent a “forebrain circuit” for threat processing and organization of responses, being important to mounting appropriate coping responses. Specific hypothalamic circuits organize neuroendocrine and neurovegetative outputs, but are the less well-studied in fish. A “midbrain circuit” is represented by projections to interneurons in the optic tectum which mediate fast escape responses via projections to the central gray and/or the brainstem escape network. Threatening stimuli (especially visual stimuli) can bypass the “high road” and directly activate this system, initiating escape responses. Increased attention to these circuits in an evolutionary framework is still needed.

防御行为是特定生存回路的功能，即“攻击性大脑系统”，被认为在整个脊椎动物中都是保守的，并且涉及威胁检测和组织防御反应以减少或消除威胁。在哺乳动物中，这些回路涉及杏仁核和下丘脑亚核和中脑回路。人们对硬骨鱼类的兴趣日益浓厚，成为神经科学中的典范生物，这就要求人们了解哪些大脑回路参与了防御行为。端脑回路和哈贝状回路代表了“脑回路”，用于威胁处理和响应组织，对于建立适当的应对响应非常重要。特定的下丘脑回路组织神经内分泌和神经营养输出，但在鱼类中的研究较少。“中脑回路”由对光学中枢中的中间神经元的投射来表示，该投射通过介导对中央灰色和/或脑干逃逸网络的投射来介导快速逃逸响应。威胁性刺激（尤其是视觉刺激）可以绕过“高速公路”并直接激活该系统，从而引发逃生反应。仍然需要在进化框架中增加对这些电路的关注。