Two groups of brain cells together help to filter visual information before it reaches the brain's higher processing regions, a Nature paper suggests. The study offers a mechanism for visual attention shifts and provides support for a hypothesis that was put forward by Francis Crick nearly 25 years ago.
The eye is bombarded with a vast array of visual information, and in order to make sense of our environment, attention needs to be focused on particular parts by boosting activity in relevant cells in the cortex. Kerry McAlonan and colleagues show that attention modulates visual signals before they even reach the cortex by triggering increased activity in a brain area called the lateral geniculate nucleus (LGN). At the same time, attention decreases neuronal activity in an adjacent cell group called the thalamic reticular nucleus, which is known to make inhibitory connections onto LGN.
On the basis of the anatomy, Crick had proposed that 'if the thalamus is the gateway to the cortex, the reticular complex might be described as the guardian of the gateway.' The reciprocal activity demonstrated here between the two cell groups finally offers support for this idea.
Kerry McAlonan (National Eye Institute, Bethesda, MD, USA)
(C) Nature press release.
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