Table 1.

Military service data.

Group	Age in Vietnam	Duration (months)	% Drafted	AFQT (%ile)	AFQT Change	Combat Exposure	Combat Exposure (% high)
Amygdala	20.4 (2.2)	6.1 (3.1)	50	65.6 (28.1)	−15.2 (23.9)	3.9 (1.6)	64
vmPFC	20.3 (3.1)	5.8 (3.5)	36	55.0 (22.6)	−9.7 (17.9)	3.2 (0.8)	43
Non-vmPFC/non-amygdala	20.6 (2.9)	5.6 (3.8)	31	61.3 (25.9)	−8.2 (19.0)	3.3 (1.1)	58
No brain damage	20.6 (3.1)	>10	52	65.4 (22.9)	3.9 (14.5)	2.6 (1.2)	33

"Age in Vietnam" is the age when arrived in Vietnam; "Duration" is the period between arrival in Vietnam and injury (in the case of the brain-injured) or end of service in Vietnam (in the case of the non brain-injured); "% Drafted" is the percentage of individuals drafted into military service; AFQT (Armed Forces Qualifying Test) is a measure of basic intellectual function; "AFQT (%ile)" is the AFQT percentile at the time of enlistment; "AFQT Change" is the difference between AFQT score at the time of enlistment and the Phase 3 evaluation; "Combat Exposure" is the frequency of exposure to enemy contact: 0=no contact (support unit); 1=occasional mortar attack (support unit); 2=intermittent enemy contact (support unit); 3=intermittent enemy contact (combat unit); 4=constant enemy contact (combat unit). "Combat Exposure (% high)" is the percentage of individuals who experienced constant enemy contact in a combat unit. For "Age in Vietnam," "Duration," "AFQT (%ile)," "AFQT change," and "Combat Exposure" mean values are given with standard deviations in parentheses.