TABLE 2.

Comparison of the currently available awake-rat-functional magnetic resonance imaging (fMRI) strategies.

Studys	Rat strain	Rat age	Duration and type of habituation	Corticosterone levels	Respiration rate	Type of MRI study	Motion Levels
Present study	Male Lister Hooded	4 weeks	Gradually introduced rats to the experimental conditions, 3 weeks 20–60 min/day	FCM levels return to pre-handling values after habituation	85 ± 7 breaths/min on last habituation day	Task-based auditory fMRI	Mean (± S.E.M.) SD of translations: 5.8 ± 0.9 μm (X), 9.3 ± 2.2 μm (Y). Mean (± S.E.M.) RMS: 0.9 ± 0.05 μm. Mean (± S.E.M.) FD: 11.6 ± 0.4 μm
King et al., 2005	Male Sprague Dawley	/	Rats exposed to the final experimental conditions, 8 days, 90 min/day	Plasma corticosterone levels significantly decreased on day 5 and 8 compared to day 1 of habituation.	∼95 ± ∼7.5 breaths/min on day 8	Resting state fMRI	Mean (± S.E.M.) SD of translations: ∼60 ± ∼50 μm (X), ∼150 ± ∼40 μm (Y).
Febo, 2011	Male Sprague Dawley	/	Rats exposed to the final experimental conditions, 5 days, 20–50 min/day	/	/	stimulus fMRI	/
Chang et al., 2016	Male Sprague Dawley	Adult	Rats exposed to the final experimental conditions, 8–10 days, 30 min/day	Plasma corticosterone levels showed a trend toward decreasing on day 8 of the habituation, but increased significantly during the fMRI scan.	73.9 ± 6.1 breaths/min during fMRI experiments	Resting state and stimulus (air puff) fMRI	/
Ferenczi et al., 2016	Female Long-Evans TH-Cre rats and Wild-type male Sprague Dawley rats	/	Rats exposed to the final experimental conditions, 5–10 days, 5–45 min/day	/	> 100 breaths/min during fMRI experiments	Optogenetic fMRI	Mean (± S.E.M.) RMS: 65 ± 3 μm.
Ma et al., 2017, 2020	Male Long-Evans	Adult	Rats exposed to the final experimental conditions, 7 days	/	∼ 82 breaths/min	Resting state fMRI	Mean (± S.E.M.) FD: 150 ± 20 μm (2017), 50 ± 3 μm (2020)
Stenroos et al., 2018	Male Wistar	Adult	Rats exposed to the final experimental conditions, 4–9 days, 15–45 min/day	Plasma corticosterone levels return to baseline by day 5 of habituation.	∼ 160 breaths/min	Resting state fMRI	/

In this table the habituation strategy presented in the current work (“present study”) is compared with other published strategies. With the exception of our study, none of the strategies used adapted a gradual habituation of the animals to the awake fMRI condition, rather the animals were habituated to all aspects of the final awake condition over a period of days. Differences in stress (reflected by corticosterone levels) and motion levels (far right column) are reported where available, as indicators of the final habituation outcome.