The spinothalamic tract (STT) is the major ascending pathway for information about pain, temperature, and "simple" touch and is localized in the anterolateral quadrant of the spinal cord. The STT mediates the discriminative components of these sensations into the "fast" (discriminative aspect) and "slow" (affective aspect) components of pain in different regions of the tract that are transmitted in parallel to the thalamus.
The STT is divided into the lateral STT (fast and slow pain and temperature) and the anterior STT (simple touch). The STT ascends the entire length of the cord and then enters the brainstem where the fast pain STT axons terminate in the ventroposterior nucleus. The slow pain STT axons terminate in the nonspecific intralaminar nuclei of the thalamus and the reticular formation in the brainstem, and these axons transmit information about the affective quality (unpleasantness and fear of further injury) of pain. The projections to the reticular formation are involved in the arousal effects of painful stimuli that activate noradrenergic neurons in the locus coeruleus and decrease the upward pain transmission by a negative feedback loop.
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