INTER-RESPONSE INTERFERENCE CONTRIBUTES TO THE SEQUENCING DEFICIT IN FRONTAL-LOBE LESIONS

In this study we investigated the contribution of inter-response inter ference to the sequencing deficit in frontal lobe lesions. We examined inter-response interference in choice sequences through the reduction in inter-response interval produced by stimulus preview when compared with sequences performed without preview If frontal lobe lesions resu lt in a stronger inter-response interference, the facilitative effect of preview on inter-response interval should be attenuated We compared nine patients with a frontal excision with nine patients with a tempo ral excision and nine controls in a task requiring rapid keypress resp onses to each of five letters in a sequence. In the no-preview conditi on, the Jive letters were presented one at a time, immediately followi ng the previous response. In the preview condition the Jive letters we re presented simultaneously before the response sequence. Patients wit h a frontal lesion showed slower response times than the other groups. In normal subjects and patients with a temporal lesion, stimulus prev iew produced the expected reduction of inter-response time and the slo wing of sequence initiation. In frontal lesions, however preview did n ot reduce inter-response time and exacerbated the slowing of sequence initiation. The results indicate that patients with a frontal lobe les ion show increased interference between adjacent responses as well as a sequence initiation problem.