| Abstract: | In the blocking paradigm, prior training to 1 conditioned stimulus (CSA) blocks the ability to attend to a 2nd conditioned stimulus (CSB) when the 2 form a compound (CSAB) in subsequent training. Blocking is an associative process by which animals learn to ignore CSB because it contains no new information regarding the reinforcing event. In Exp I, dopamine (DA) receptor supersensitivity was induced in 20 male Sprague-Dawley rats by prolonged pretreatment (21 days) with haloperidol (0.5 mg/kg). 20 control Ss received saline injections for 21 days. Results show that Ss with DA receptor supersensitivity failed to show blocking by responding equivalently to both elements of the CSAB compound (tone and light). This effect was replicated in Exp II, which also tested for an arousal interpretation of disrupted blocking by introducing a novel stimulus following training. 10 male Sprague-Dawley rats were randomly assigned to either saline or haloperidol pretreatment groups, and following 21 days of treatment and a 7-day drug free period, Ss were run in the 3-stage blocking procedure used in Exp I over 2 days. Findings indicate that supersensitive Ss were no more responsive to the novel stimulus than were controls, which supports a selective attention deficit interpretation of disrupted blocking with DA receptor supersensitivity. It is suggested that this attentional deficit resembles behavioral perseverations induced by DA agonists. (24 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) |
