For the assessment of skilled locomotor function, the horizontal ladder task is one of the most commonly used methods in behavioral neuroscience. The horizontal ladder detects fine impairments in both forelimb and hindlimb function following lesions in the sensorimotor cortex (Antonow-Schlorke, Ehrhardt, & Knieling, 2013; Soblosky, Colgin, Chorney-Lane, Davidson, & Carey, 1997), rhizotomies (Liu et al., 2016; Wieseler et al., 2010), and spinal cord injuries (SCIs) (Bolton, Tse, Ballermann, Misiaszek, & Fouad, 2006; Fagoe et al., 2016; Kanagal & Muir, 2008a; Onifer et al., 2011; Zorner et al., 2010). Performance on the horizontal ladder assesses the neuronal control of movement by cortical and subcortical neural structures to precisely aim
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The main endpoint measure of the horizontal ladder is the amount of foot falls, or errors, that occur per the number of steps taken. A major limitation with this type of measure is that it does not account for any changes in behavioral strategies used to perform the task following an injury (Muir & Webb, 2000). After a SCI, rats develop alternate locomotor patterns and behavioral strategies to compensate for functional deficits (Ballermann, Tse, Misiaszek, & Fouad, 2006; Bolton et al., 2006; Whishaw, 2000). These include uncoupling of the forelimb and hindlimbs, decreased hindlimb stepping, changes in flexion during swing phases, and changes in limb placement strategies (Antonow-Schlorke et al., 2013; Bolton et al., 2006). One of the most obvious behavioral changes that occur after injury, however, is the increase in the amount of time it takes for rats to complete the horizontal ladder task (Bolton et al., 2006). The horizontal ladder task is largely reliant on the motivation of rats to cross from one end to another at their preferred pace (Kunkel-Bagden, Dai, & Bregman, 1993). Early after injury there is usually a decrease in motivation to perform skilled tasks (Zemmar, Kast, Lussi, Luft, & Schwab, 2015) and rats are often unable to cross the ladder with consistent …show more content…
In elderly human populations, speed is a useful marker for assessing fall risk. There is a nonlinear relationship between gait speed and falls, where speeds faster and slower than the normal range of walking speed precipitates falls (Quach et al., 2011). Also, human SCI patients have decreased preferred and maximum walking speeds following injury and walking at faster speeds is often utilized as a strategy to improve balance (van Hedel, Dietz, & Curt, 2007). In the rodent model, changes in walking speed following neurological injuries are known to have an effect on stride length, stance duration, swing duration and stepping patterns during overground locomotion (Hruska, Kennedy, & Silbergeld, 1979; Koopmans et al., 2007; Neckel, Dai, & Bregman, 2013). As such, rodent behavioral studies are now frequently accounting for the relationship between speed, gait, and coordination during assessment of unskilled overground locomotion (Batka et al., 2014; Neckel et al., 2013; Vidal, Badner, Maranon, Galan-Estella, & Caballero-Garrido, 2017). While speed is accepted as an important component in locomotion, it still remains unknown if changes in walking speed following a SCI has an effect on the motor deficits and recovery observed during skilled ladder walking. Not accounting for variability in walking speeds before and after injury increases the likelihood
The main endpoint measure of the horizontal ladder is the amount of foot falls, or errors, that occur per the number of steps taken. A major limitation with this type of measure is that it does not account for any changes in behavioral strategies used to perform the task following an injury (Muir & Webb, 2000). After a SCI, rats develop alternate locomotor patterns and behavioral strategies to compensate for functional deficits (Ballermann, Tse, Misiaszek, & Fouad, 2006; Bolton et al., 2006; Whishaw, 2000). These include uncoupling of the forelimb and hindlimbs, decreased hindlimb stepping, changes in flexion during swing phases, and changes in limb placement strategies (Antonow-Schlorke et al., 2013; Bolton et al., 2006). One of the most obvious behavioral changes that occur after injury, however, is the increase in the amount of time it takes for rats to complete the horizontal ladder task (Bolton et al., 2006). The horizontal ladder task is largely reliant on the motivation of rats to cross from one end to another at their preferred pace (Kunkel-Bagden, Dai, & Bregman, 1993). Early after injury there is usually a decrease in motivation to perform skilled tasks (Zemmar, Kast, Lussi, Luft, & Schwab, 2015) and rats are often unable to cross the ladder with consistent …show more content…
In elderly human populations, speed is a useful marker for assessing fall risk. There is a nonlinear relationship between gait speed and falls, where speeds faster and slower than the normal range of walking speed precipitates falls (Quach et al., 2011). Also, human SCI patients have decreased preferred and maximum walking speeds following injury and walking at faster speeds is often utilized as a strategy to improve balance (van Hedel, Dietz, & Curt, 2007). In the rodent model, changes in walking speed following neurological injuries are known to have an effect on stride length, stance duration, swing duration and stepping patterns during overground locomotion (Hruska, Kennedy, & Silbergeld, 1979; Koopmans et al., 2007; Neckel, Dai, & Bregman, 2013). As such, rodent behavioral studies are now frequently accounting for the relationship between speed, gait, and coordination during assessment of unskilled overground locomotion (Batka et al., 2014; Neckel et al., 2013; Vidal, Badner, Maranon, Galan-Estella, & Caballero-Garrido, 2017). While speed is accepted as an important component in locomotion, it still remains unknown if changes in walking speed following a SCI has an effect on the motor deficits and recovery observed during skilled ladder walking. Not accounting for variability in walking speeds before and after injury increases the likelihood