The claustrum is a vertical layer of neurons located in each cerebral hemisphere. Surrounded by white matter, it is an elongated structure of grey matter, lying between the lentiform nucleus and the insular cortex. Almost all cerebral cortical areas have connection with the claustrum, specially sensorimotor and visual-auditory regions. The lower part of claustrum is also linked up with the limbic system. Although the claustrum functions are not yet known, bilateral activation of claustrum in laboratory pets was seen to be involved in motivational processes that direct behavior towards a sexual goal.