Which of the following tracts carries proprioceptive and discriminative touch information from the lower limbs and lower trunk?

Explanation

## Fasciculus Gracilis — Lower Body Proprioception **Key Point:** The fasciculus gracilis is the medial column of the dorsal column–medial lemniscus system and carries fine touch, vibration sense, and proprioception from the **lower limbs and lower trunk** (below T6 vertebral level). ### Anatomical Organization The dorsal columns are somatotopically organized: - **Fasciculus gracilis** (medial) — lower body (sacral, lumbar, lower thoracic) - **Fasciculus cuneatus** (lateral) — upper body (cervical, upper thoracic) ### Pathway 1. First-order neurons: peripheral receptors → dorsal root ganglia → dorsal column 2. Synapse in nucleus gracilis (medulla) 3. Second-order neurons cross as internal arcuate fibers → medial lemniscus 4. Ascend to VPL thalamus → primary sensory cortex **High-Yield:** Fasciculus gracilis damage causes loss of proprioception and fine touch in the **lower limbs** (e.g., Friedreich ataxia, dorsal column degeneration). **Clinical Pearl:** Patients with fasciculus gracilis lesions develop sensory ataxia and a positive Romberg sign due to loss of proprioceptive feedback. ### Comparison Table: Dorsal Column Organization | Feature | Fasciculus Gracilis | Fasciculus Cuneatus | | --- | --- | --- | | **Location** | Medial dorsal column | Lateral dorsal column | | **Body region** | Lower limbs, lower trunk (below T6) | Upper limbs, upper trunk (above T6) | | **Medullary nucleus** | Nucleus gracilis | Nucleus cuneatus | | **Modality** | Fine touch, vibration, proprioception | Fine touch, vibration, proprioception | **Mnemonic:** **"Gracilis = Lower limbs"** — *gracilis* is a medial thigh muscle; gracilis tract is medial and carries lower-body sensation.