Which of the following fiber tracts passes through the posterior limb of the internal capsule?

Explanation

## Anatomy of the Internal Capsule The internal capsule is a major white matter tract containing both ascending and descending fibers. It is divided into three main parts: anterior limb, genu, and posterior limb. ### Posterior Limb Contents **Key Point:** The posterior limb of the internal capsule contains: 1. **Corticospinal tract** — descending motor fibers from motor cortex to spinal cord 2. **Sensory radiations (thalamocortical fibers)** — ascending sensory fibers from VPL/VPM thalamus to somatosensory cortex 3. **Optic radiations** — visual fibers from lateral geniculate nucleus to visual cortex (some sources place this in the retrolenticular part) ### Organization by Limb | Limb | Key Fiber Tracts | |------|------------------| | **Anterior** | Corticobulbar tract, thalamocortical fibers to prefrontal cortex, frontopontine fibers | | **Genu** | Corticobulbar tract, thalamocortical fibers to motor/premotor cortex | | **Posterior** | Corticospinal tract, sensory radiations (VPL/VPM → S1), optic radiations | **High-Yield:** Lesions of the posterior limb classically produce contralateral motor weakness (corticospinal involvement) and contralateral sensory loss (thalamic radiations), often with visual field defect if optic radiations are damaged. **Clinical Pearl:** A lacunar stroke affecting the posterior limb causes pure motor stroke (if corticospinal tract alone) or motor + sensory stroke (if both tracts involved). **Mnemonic:** **PALS** = Posterior limb: **P**yramidal (corticospinal), **A**scending sensory, **L**ateral geniculate (optic), **S**ensory radiations.