Table 3.

Summary of the effects of wheel running on fear learning.

Behavioral test	Exercise improves fear conditioning?	Wheel access (d)	Distance ran (km/d)	Sex	Strain/species	Housed	Sed Ctrl	Reference
Fear potentiated startle	Y	14a	4.5	M	C57BL/6J	G	L	(Falls et al., 2010)
Passive avoidance	Y	28a	1b	M	C57BL/6J	G	L	(Samorajski et al., 1985)
	–	28a	2–3c	M	BALB/c	G	L	(Liu et al., 2009)
Fear conditioned freezing	Yd,f and –e	19a	2	M	Long Evans	G	A	(Hopkins and Bucci, 2010b)
	Yd,g	21	7	M	Long Evans	S	A	(Van Hoomissen et al., 2004)
	Yd,h	22	7	M	Long Evans	S	A	(Van Hoomissen et al., 2011)
	Yd,i	26	6–7	M	C57Bl6/N	S	A/L	(Dubreucq et al., 2010b)
	– d	28	10	M	C57BL/6NCrl	S	L	(Cacciaglia et al., 2011)
	Yd and –e	30	2–5	M	Long Evans	S	A	(Baruch et al., 2004)
	Yd	42	4	M	Fisher 344	S	A	(Greenwood et al., 2009)
	– e,j	38–41	5	M	CB1 WT mice	S	L	(Dubreucq et al., 2010a)
	– d,e,k	46	6–7	M	Long Evans	S	nd	(Wojtowicz et al., 2008)
	Yd,l	54	6	M, F	C57BL6/J	S	A	(Clark et al., 2008)
	– d	56	6	M	Sprague	S	L	(Burghardt et al., 2004)
	Yd,m	56	8	M	Sprague	S	L	(Burghardt et al., 2006)
	– d,e	60a	Nd	F	C57BL6/J	G	L	(Pietropaolo et al., 2006)

Abbreviations:–, did not alter fear conditioning; A, absent wheel controls; CB1, cannabinoid type I receptor; F, female; G, group housing; L, locked wheel controls; M, male; N, impaired fear conditioning; nd, no data; S, single housing; Sed Ctrl, sedentary controls; WT, wild type; Y, improved fear conditioning. Footnotes:

^awheel was shared;

^bkm/hour;

^ckm/12 hour;

^dconditioning to context;

^econditioning to cue;

^feffect reversed when testing occurred in PM or end of light portion of the light:dark cycle;

^geffect abolished by non-selective β-adrenergic receptor blocker propranolol;

^heffect was reversed by olfactory bulbectomy;

ⁱeffect present only when compared to no wheel controls, not locked wheel controls;

^jimproved deficits of CB1 receptor knockout mice;

^ktrended towards improving fear conditioning, wherein time spent freezing was positively correlated with the number of cells expressing the young neuron marker PSA-NCAM in the dentate gyrus;

^leffect was not dependent on hippocampal irradiation;

^meffect present only after high, but not low running. Notes: Wheel access is reported at behavioral testing. Distance ran is reported as the mean at behavioral testing and was divided by the number of subjects per cage when the wheel was shared.