Motor maps, seizures, and behaviour.

Abstract

Atypically organised motor maps have been described in some people with epilepsy and we have modelled this in rats. Our goal is to more fully understand the mechanisms responsible for seizure-induced functional brain reorganisation and to reverse their effects. Here we present an overview of the relationship between neocortical motor maps, seizures, and interictal behaviour. To begin we summarise the observations of atypical motor maps with epilepsy and in animal models following experimentally induced seizures. Our novel experiments have established that motor map expansion is linked to a functional alteration of motor behaviour. Evidence for some of the putative brain mechanisms responsible for motor map size is discussed. Our successes reversing seizure-induced map expansion by two different methods are also briefly reviewed. Lastly, unanswered questions for possible future experimentation are posed.

Peripheral and central changes combine to induce motor behavioral deficits in a moderate repetition task

“…Extensive repetition of digit movements without motor learning in primate or unskilled pellet reaching in rats did not significantly alter the M1 forelimb map, while motor skill learning was associated with an expansion of the representation of distal forelimb movements (Kleim et al, 1998; Plautz et al, 2000). The M1 skill-related expansion has been shown to depend upon functional synaptogenesis (Kleim et al, 2002, 2004), long term potentiation (Rioult-Pedotti et al, 2000), excitation-inhibition balance (see Teskey et al, 2008 for a review), synchronous firing (Schieber, 2002), tuning, and signal-to-noise changes of M1 cells (Kargo and Nitz, 2003, 2004). In rats that reached for bundles of pasta strands, skilled reaching with targeting and grasping components requires coordinated forelimb joint movements (Remple et al, 2001).…”

Optimal parameters for microstimulation derived forelimb movement thresholds and motor maps in rats and mice

“…Like primates, rats and mice are dexterous mammals that can expertly manipulate their digits to quickly learn skilled reaching tasks with accuracy and proficiency (e.g., Whishaw and Pellis, 1990;Whishaw, 1992;Kleim et al, 1998;Farr and Whishaw, 2002). Because rodents are easily trained on skilled motor tasks and their motor maps are easily derived, the rodent motor system provides an excellent animal model to study the relationship between the brain and motor behaviour (e.g., Bury and Jones, 2002;Kleim et al, 2002), which is useful in assessing motor function in models of CNS injuries or diseases like stroke and epilepsy (Gonzalez et al, 2004;Teskey et al, 2002Teskey et al, , 2008Gharbawie et al, 2008;Young et al, 2009). Moreover, genetic manipulations such as knock-out strains and cloning techniques in mice and more recently rats (Guerts et al, 2009) allow for investigation of genetic contributions to motor cortex plasticity and motor behaviour.…”

Persistent enhancement of functional MRI responsiveness to sensory stimulation following repeated seizures

“…Experimental animal models of seizures have been useful in addressing how seizures affect the functional organization of various brain structures (Pitkänen et al., 2006). Seizures can induce changes in neocortical movement representations and behavior (for a review see Teskey et al., 2008). We have shown previously that seizure activity in the neocortex can result in larger motor maps of the forelimb (Teskey et al., 2002; van Rooyen et al., 2006; Ozen et al., 2008; Young et al., 2009) as well as nonforelimb areas (Henderson et al., 2011) and can lead to alterations in forelimb performance on specific motor tasks (Henry et al., 2008; Flynn et al., 2010).…”