Expansion of receptive fields is a feature of which sensitization process?

• A. Peripheral sensitization
• B. Mechanical sensitization
• C. Chemical sensitization
• D. Central sensitization

Answer: (D)

Expansion of receptive fields is a hallmark of central sensitization. After injury, the neurons in the spinal cord’s dorsal horn become more excitable and respond to inputs from a larger area of skin. Repeated nociceptive input recruits changes in central neural circuits — including wind-up and NMDA-receptor–mediated plasticity — that broaden the receptive fields of these second-order neurons. This leads to pain spreading beyond the original injury site and to phenomena like allodynia and hyperalgesia. Peripheral sensitization, by contrast, heightens sensitivity at the injury site itself without enlarging central receptive fields, and the other terms describe peripheral changes rather than CNS-wide expansion. So the CNS-driven expansion of receptive fields best fits central sensitization.