Backup circuits are available in the injured hemisphere but are b

Backup circuits are available in the injured hemisphere but are blocked from use by the spared hemisphere. Altering activity in specific ipsi- and contralesional brain

areas through temporary deactivation or subsequent lesion unmasks the backup circuits and restores visual function (Sprague, 1966; Wallace et al., 1990; Durmer & Rosenquist, 2001; Lomber et al., 2002). In particular, invasive cooling deactivation of the contralesional visuoparietal cortex produces recovery of function, but restoration of function is only observed during deactivation of the cortex; when the deactivation ceases, the recovery disappears (Lomber et al., 2002). The current study applied cathodal tDCS to the contralesional visuoparietal cortex to reduce excitability and restore visual function. Unlike cooling deactivation, tDCS is non-invasive and exhibits lasting effects that may accrue with repeated application.

Therefore, 70 sessions of cathodal tDCS were administered over the course of 14 weeks. The results support the utility of using multiple sessions to maximise the effect of tDCS on neural function, and represent the first demonstration that a large number of tDCS sessions can improve recovery from brain injury. Experiments were performed on four domestic short-haired female adult cats (> 6 months old) obtained from a licensed USDA-approved cat breeder (Liberty Labs, Waverly, NY, USA). All procedures were performed in accord with the

NIH guidelines governing laboratory animal use, and were approved by the Institutional Animal Care and Use Committee at the Boston DNA Damage inhibitor University School of Medicine. The cats were housed together in an enriched environment and placed on a 12-h light–dark cycle. Data from this cohort were also compared to three control animals with equivalent unilateral lesions that did not undergo any form of tDCS. Metalloexopeptidase Over a 2-month period, cats (n = 4) were trained and tested (~ 8500 trials) on tasks designed to assess their ability to detect, orient to and approach moving visual targets (Lomber & Payne, 1996; Payne et al., 1996; Rushmore & Payne, 2004; Valero-Cabré et al., 2006). All testing and training was performed in an 88-cm-diameter semicircular white arena that was enclosed by 28-cm-high walls and that contained evenly spaced openings at the union of the floor and the wall (Fig. 1). When the lateral canthi of the animal’s eyes were lined up with the most eccentric openings and the midline of the animal was in line with the cynosure of the semicircle, each of the holes then corresponded to 15° increments of visual angle, extending from left 90° to right 90°. The standard moving perimetry task was designed to test the subject’s visual spatial performance on targets presented at the horizontal meridian representation of the left and right visual hemifields (Fig. 1A; Sprague, 1966; Lomber & Payne, 1996; Payne et al., 1996, 2003).

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