The thalamus - its halves connected by the intermediate mass, the thalamus receives all conscious sensations and acts as a relay center. Sensations from the spinothalamic tract and the fasciculus gracilis and fasciculus cuneatus synapse in the thalamus before continuing to the cortex. Afferent impulses are routed by the thalamus to their proper destinations. The thalamus also lies at the top of the reticular formation and is part of the alert mechanism of the reticular activating system. The thalamus also helps to filter out unwanted stimuli.