Behavioral and Cognitive Effects Produced by Electrical Stimulation in the Medial Prefrontal Cortex:An Experimental Model for High Cortical Activation

An electrical stimulation (ES) session with ten 30-second trains of sine-wave stimuli (30–100 µA, 60 Hz) separated by 30-second intervals was conducted daily in rats with electrodes implanted in the left or right or in both sides of the medial prefrontal cortex (PFC; B = + 2 mmA, + or –0.6 unilateral or 1 mmL bilateral, + 2.7 mmV). The unilateral and bilateral ES in the medial PFC produced abnormal behaviors such as circling spying, body stretching and immobility, and did not affect either the acquisition or the performance of delayed tasks in the 8-arm radial maze conducted 8–10 h after the ES session. However, animals that showed convulsions when the bilateral ES was applied in the medial PFC showed significant deficits in spatial learning and in the performance of short-term (5-second delay) and long-term (1-hour delay) working memory. The behavioral and cognitive effects induced by repeated episodic ES in the medial PFC provide an experimental model to study the effects of increased cortical activation on cognitive processes.