Abstracts

It has been suggested that aphasia during the intracarotid amytal procedure (IAP or Wada test) may interfere with later recall of memory stimuli. This has been used as an argument for varying the timing of stimulus presentation during IAP, or perfusion of amytal via the posterior cerebral artery. Logically, however, any effect of aphasia should be mitigated by use of stimuli amenable to multimodal encoding, such as real objects. The purpose of this study was to evaluate the effect of aphasia on recognition of objects presented during IAP.
Subjects were 30 patients with left temporal lobe seizure onset (LSO), and 32 with right temporal lobe seizure onset (RSO). All subjects underwent IAP and all were left language dominant. IAP memory was tested with recognition of 9 objects presented with 18 foils. Objects were presented as soon as possible after amytal injection, once unilateral EEG slowing and contralateral hemiparesis were established, and typically while global aphasia was still present. Measures of interest were duration of speech arrest on left injection (SPEECH), recognition memory score, corrected for false positive errors, on left and right injections (LMEM, RMEM), and duration of EEG slowing on left and right injections (LEEG, REEG).
For LSO patients, LMEM was correlated with both SPEECH (r = -.36, p [lt] .05) and LEEG (r = -.45, p [lt] .05). However, SPEECH and LEEG were also correlated (r = .39, p [lt] .05). Multiple regression analysis (MRA) using SPEECH and LEEG as predictors, and LMEM as the criterion, was significant (F[2,27] = 4.37, p [lt] .05), but only LEEG made a significant contribution to the model (r[sub]LMEM[SPEECH.LEEG][/sub] = -.20, n.s.; r[sub]LMEM[LEEG.SPEECH] [/sub]= -.34, p [lt] .05). The identical pattern of results was found for RSO patients. LMEM was correlated with SPEECH (r = -.46, p [lt] .01) and LEEG (r = -.58, p [lt] .01), but MRA (F[2,28] = 8.09, p [lt] .01) showed that only LEEG contributed significantly to the prediction of LMEM (r[sub]LMEM[SPEECH.LEEG][/sub] = -.19, n.s.; r[sub]LMEM[LEEG.SPEECH] [/sub]= -.35, p [lt] .05). Congruent with LMEM findings, for both LSO and RSO patients, RMEM was correlated with REEG (r = -.41, p [lt] .05, and r = -.45, p [lt] .05, respectively).
Recognition memory for objects during IAP is not affected by aphasia. Although patients with more severe speech disturbance do tend to have lower memory scores, this is incidental to duration of EEG slowing. Resistance to the confounding effect of aphasia suggests that objects are preferable to verbal stimuli for IAP memory testing.