Effects of the Apolipoprotein E ε4 Allele on Functional MRI during n-Back Working Memory Tasks in Healthy Middle-Aged Adults

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Fig 1.
Activation maps of n-back task of APOE4 carriers and non-APOE4 carriers in a surface-rendered projection displayed on a standardized brain atlas (display threshold, P < .01; extent, 3 voxels). Increased activation in bilateral frontal and parietal regions is noted, consistent with activation of WM circuitry in both groups.
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Fig 2.
Activation maps of 1-back > 0-back, 2-back > 1-back, and 3-back > 2-back conditions of APOE4 carriers and non-APOE4 carriers in a surface-rendered projection displayed on a standardized brain atlas (display threshold, P < .01; extent, 3 voxels). In both groups, an increase in brain activation occurred in response to each increase in WM load. The degree of increased brain activation was different in both groups. It was greatest in 2-back > 1-back conditions in non-APOE4 carriers, and greatest in 1-back > 0-back conditions in APOE4 carriers. A visual comparison of the between-group difference in 1-back > 0-back conditions shows less extent of activation in the noncarrier group. In 2-back 1-back and 3-back > 2-back conditions, less increase in activation is seen in the carrier group.

Demographic information, cognitive function, and accuracy rates of n-back WM in participants

	Total (n = 110)	ApoE4− (n = 9)	ApoE4+ (n = 9)	ApoE4− versus ApoE4+
	Total (n = 110)	ApoE4− (n = 9)	ApoE4+ (n = 9)	t	p
Sex (male/female)	53:57	4:5	4:5	–	–
Mean age (SD) (yr)	57.60	42.78 (9.63)	42.11 (9.13)	0.53	.34
Mean MMSE score (SD)	28.49 (2.65)	29.56 (0.73)	28.89 (1.17)	0.42	.38
Mean AD8 score (SD)	0.54 (1.20)	0.44 (0.73)	0.11 (0.33)	0.09	.76
0-Back accuracy rate		90% (17)	92% (15)	−0.19	.85
1-Back accuracy rate		93% (6)	89% (17)	0.50	.63
2-Back accuracy rate		80% (11)	85% (9)	−0.82	.43
3-Back accuracy rate		80% (9)	85% (13)	−0.86	.41