EFFECTS OF HEMISPHERE SPEECH DOMINANCE AND SEIZURE FOCUS ON PATTERNS OF BEHAVIORAL-RESPONSE ERRORS FOR 3 TYPES OF STIMULI

We used a protocol consisting of a continuous presentation of stimuli with associated response requests during an intracarotid sodium amobar bital procedure (IAP) to study the effects of hemisphere injected (spe ech dominant vs. nondominant) and seizure focus (left temporal lobe vs . right temporal lobe) on the pattern of behavioral response errors fo r three types of visual stimuli (pictures of common objects, words, an d abstract forms). Injection of the left speech dominant hemisphere co mpared to the right nondominant hemisphere increased overall errors an d affected the pattern of behavioral errors. The presence of a seizure focus in the contralateral hemisphere increased overall errors, parti cularly for the right temporal lobe seizure patients, but did not affe ct the pattern of behavioral errors. Left hemisphere injections disrup ted both naming and reading responses at a rate similar to that of mat ching-to-sample performance. Also, a short-term memory deficit was obs erved with all three stimuli. Long-term memory testing following the l eft hemisphere injection indicated that only for pictures of common ob jects were there fewer errors during the early postinjection period th an for the later long-term memory testing. Therefore, despite the inab ility to respond to picture stimuli, picture items, but not words or f orms, could be sufficiently encoded for later recall. In contrast, rig ht hemisphere injections resulted in few errors, with a pattern sugges ting a mild general cognitive decrease. A selective weakness in learni ng unfamiliar forms was found. Our findings indicate that different pa tterns of behavioral deficits occur following the left vs. right hemis phere injections, with selective patterns specific to stimulus type. ( C) 1997 Academic Press.