Why does nearly every sense pass through the thalamus before reaching the cortex? · Grey Matter

Each sense except smell has a thalamic nucleus that receives it and sends it on to its own area of cortex: the lateral geniculate for vision, the medial geniculate for hearing, the ventral posterior nuclei for touch and taste.

Why does nearly every sense pass through the thalamus before reaching the cortex?

Each sense except smell has a thalamic nucleus that receives it and sends it on to its own area of cortex: the lateral geniculate for vision, the medial geniculate for hearing, the ventral posterior nuclei for touch and taste. Passing everything through one structure lets the brain control the flow, since the cortex sends back more fibres than it receives and the reticular nucleus can mute the relay cells, amplifying what is attended to and damping the rest. The same gate closes in deep sleep, when thalamic cells switch to bursting and the outside world is largely kept out.