Early-stage findings on long-term behavioral effects of Transcranial Magnetic Stimulation in cortical blindness in rats.

OBJECTIVE

Generate bilateral cortical lesions to induce blindness in rats and assess the effects of Transcranial Magnetic Stimulation (TMS) on their recovery.

METHODS

A study with Long Evans male rats (250-300 g), N = 20, was divided into four groups (n = 5): Control (CG), Sham Group (SG), Experimental Group I (EG1), and Experimental Group II (EG2). The training for visual discrimination tests (VDT) was conducted in a 'Y' water maze (YWM) created with transparent acrylics, using visual cues (P+, p-). Primary visual cortex (V1) stereotaxic lesions were performed: anteroposterior 5.4-7.5 mm, lateral 2.3-4.3 mm, at different depths, for 8 lesions per cerebral hemisphere. Cortical blindness (CB) was corroborated with VDT. TMS frequency of 60 Hz and intensity of 100 G (10 mT) was administered for 1 hour a day, 3 days per week, for 4 weeks for EG1, and 120 G (12 mT) for EG2 (12 sessions). Post-TMS evaluations were performed 24 hours after therapy, over 4 weeks. T-Student and repeated-measured ANOVA tests were analyzed with a significance (p < 0.05). Histological slides confirmed V1 lesions.

RESULTS

CB was effectively produced in CG and EGs with a visual cortex lesion. After evaluations, EGs showed a highly significant improvement in the average of correct VDT attempts, comparing their performance between Week 1 and Week 4 after using TMS (p < 0.01).

DISCUSSION: The YWM effectively evaluates vision behavior dependent on V1. TMS is a non-invasive neuromodulation method that is effective in treating neurological deficits. Correct VDT attempts in EGs improved by 20-30%, and the difference between them was 8%.