R ats were fixed with a chronically indwelling electrode fo r in tracranial stimulation (ICS) of a site of stimulation that elicited posit ive affect. After recovery from surge ry, ea ch ra t was forced to avo id or escape footshock for 100 tr ials/day for 10 days in an au toma ted one-wa y avo ida nc e chamber. After 1,000 trials, footshock Was discontinued and trials measured to extinction. Between shock discontinuance and extinction trials, one group received time on the grid with the ledge removed, a response prevention treatment. Another group spent the sam e time in response prevention and also received periodic ICS , a counterconditioning treat m en t. A t h ird group sp e nt time outside t he chamber , a no-treatment control. The group of counterconditioning responded re liably less during extinc tio n. T h ese data confirm the conclusion drawn from similar studies using only limited avo ida nce training that counterconditioning is a superior treatment for reducing persisting avoidance.Avoidance responding, norm ally highly resist ant to ext inct ion , can be redu ced by forcing the organism to remain in the situ ation which pr eviously elicited active a voi d a nc e (response p revention) (Baum , 1970). Cha nging th e affec tive state of th e anim al through the intro duction of a positive affec tive stim ulus duri ng respons e prevention (c ou ntercond itioning) attenua tes per sistent avoida nce even more (Wilson & Davison, 1971 ; Reid , 197 3). Posit ive in tracran ial stimulation (ICS) of th e lat eral hypotha lam us has been used in some of th e studies dem onstrati ng the effective ness o f cou nte rcondit ioning (Buss & Reid , 1973 ; G ordon & Baum , 1971 ;Hunsicker, Nelson , & Reid , 1973 ; Prad o-Alcala, Bush , Steele , & Reid , 197 3).In nearly all lab oratory studies test ing vario us ways t o redu ce persisting avoidance, Ss are tested after o nly minim al training (in th is paradigm, usually after 25 or so tra ining tri als) . Baum (196 8) gave rats eit her 50 or 100 additional trials afte r the avoidance was acquired. Th is overtraining increased persistence of responding only if the rat failed to avoid and therefore received a fo otshock during th e additional training. Th is study was designed to t est th e effi ciency of treatme n ts kn own to redu ce avoida nce resp ond ing aft er minim al training with rats in which the avoida nce was well esta blished ( after over 1,000 traini ng tri als). METHOD Subjects and ApparatusFifteen adult male Sprague-Dawley rats were each fixed with chronically indwelling bipolar electro des or received sham surge r ies. Electro de tips were aimed for the lateral hypothalamus-medial forebrain bundl e. Subsequent histological inspection verified that sites of ICS, the activation of which were " Thi s stud y wa s su p ported b y Bradley Uni versity's Bo ard for Res earch w hic h adm in ist ers NSF G rant G U 3320. We t ha nk Cindy Ro yer , Angela Sp ears, and Fred eric Sautter fo r assist ance with the d ail y testing of Ss. This study is p art o f a resea...