Abstract
Patients affected by right parietal lesions have impairments in visual timing tasks (Battelli et al. 2008) and may also show an extended attentional blink (AB, Husain et al. 1997), an impairment in detecting the second of two targets appearing in close temporal succession. This overall disturbance of temporal attention may have distinct components that are differentially altered in patients. We used a rapid serial visual presentation (RSVP) display containing a stream of 26 letters presented at 8.6 items/sec. Two letters were targets cued by an annulus, and the number of items (the lag) between the first target (T1) and second target (T2) was varied. Participants were asked to report both targets. For each participant we measured accuracy for T1, and for T2 contingent on correct report of T1. By analyzing the serial position of non-target items reported as targets, we also derived estimates for three distinct components of attentional selection: (i) efficacy, comparable to the probability of reporting an item in a time window around the target; (ii) latency; and (iii) temporal precision. We tested three right parietal patients (FC, RR and PP). All showed an extended AB—in terms of both contingent T2 accuracy (i.e. exactly correct) and T2 efficacy (approximately correct)—replicating previous findings. FC and PP showed low T1 accuracy but normal T1 efficacy; in contrast, RR showed both low accuracy and low efficacy. For PP and RR, T1 and T2 selections were systematically delayed and less temporally precise relative to controls, whereas latency and precision were relatively spared for FC. Interestingly, patient PP showed lag-1 sparing, which was not evident for FC nor for RR. These results confirm that parietal patients show an extended blink, but point to substantial individual differences in component attentional processes. We discuss how these differences may relate to lesion site.
Meeting abstract presented at VSS 2014