Table 2. Morphological variability in humans.

Structure	Morphology	Left hemisphere	Right hemisphere	Total
ipcs	One segment	100% (30)	(90%) 27	95% (57)
	Two segments	0	10% (3)	5% (3)
	Three segments	0	0	0
ifs	One segment	56.7% (17)	63.3% (19)	60% (36)
	Two segments	43.3% (13)	36.6% (11)	40% (24)
	Three segments	0	0	0
ar	Vertical	83.3% (25)	80% (24)	81.7% (49)
	Oblique	6.7% (2)	10% (3)	8.3% (5)
	Diagonal	(10%) 3	10% (3)	10% (6)
ds	Not present	30% (9)	16.7% (5)	23.3% (14)
	No connection	26.7% (8)	33.3% (10)	30% (18)
	Connection	43.3% (13)	50% (15)	46.7% (28)

ar, Anterior ascending ramus of the Sylvian fissure; ds, diagonal sulcus; ifs, inferior frontal sulcus; ipcs, inferior precentral sulcus. An oblique as is one that is neither vertical or diagonal and tends to curl in different directions through parasagittal sections. Some diagonal ar may become more vertical medially (supplemental Appendix, available at www.jneurosci.org as supplemental material). The ds may be connected to one or a combination of the ar, ifs, or ipcs. For an individual breakdown of values, see supplemental material (available at www.jneurosci.org).