Investigating the Characteristics of Covert Unilateral Spatial Neglect Using the Modified Posner Task: A Single-subject Design Study

Abstract

Objectives: Patients identified as asymptomatic for unilateral spatial neglect (USN) based on paper-and-pen tests nonetheless often collide with objects to their left while walking. This study aimed to investigate chronic USN in subjects who experienced collisions while walking. Methods: Two patients with chronic USN who experienced collisions while walking were evaluated using the Behavioral Inattention Test-conventional (BIT-c). Additionally, the modified Posner task (MPT) was used to evaluate the left and right reaction times. MPT targets randomly appeared either on the side indicated by the cue (valid condition) or on the opposite side (invalid condition). This study used an alternating treatments single-case design. The valid and invalid conditions of the MPT alternated rapidly and randomly to determine differences in reaction time. Statistical analysis compared left and right reaction times using a one-tailed randomization test to study valid and invalid conditions. Results: The total BIT-c score was in the normal range for both subjects, whereas MPT reaction times were higher on the left side than on the right side for the invalid condition. However, for the valid condition, only Case B had increased reaction times on the left side. Conclusions: The MPT valid condition evaluates voluntary attention, whereas the invalid condition evaluates the reorientation of attention. Consequently, for Case A, a left reorientation of attention deficit was observed, whereas, for Case B, left voluntary attention and left reorientation of attention deficits were observed. The MPT results revealed the characteristics of covert neglect signs. USN evaluation would benefit from additional research using MPT.

Effects of Functional Electrical Stimulation on Attentional Function: A Study on Healthy Young Participants

“…The setting of the modified Posner task was according to previous studies [18,19], and a 1,000-2,000 ms delay occurs between the cue and the target appearance. We selected this long timing because we ultimately intended to apply the intervention to patients with USN; however, the time is sufficiently long to trigger some inhibition of return in healthy young…”

“…However, the conventional "paper and pencil tests" for USN and the Posner task are unsuitable for detecting vertical neglect. Therefore, Osaki et al [18] developed a modified Posner task, wherein the target presentation time was extended, and the target was presented at four locations (upper left, lower left, upper right, and lower right). The modified Posner task was used for patients with USN; the RT to target the left side was significantly more than that required to target the right side under invalid conditions [18].…”

“…Therefore, Osaki et al [18] developed a modified Posner task, wherein the target presentation time was extended, and the target was presented at four locations (upper left, lower left, upper right, and lower right). The modified Posner task was used for patients with USN; the RT to target the left side was significantly more than that required to target the right side under invalid conditions [18]. Reorientation of attention is necessary to react to unpredictable movements, such as the sudden appearance of a person crossing the street while walking.…”

Effects of standing and walking training using a laser pointer based on stimulus-driven attention for behavioural outcome in spatial neglect: A single-case study

“…Outcomes were measured using the BIT-c (Ishiai, 1999), CBS (Azouvi et al, 2003), and modified Posner task (MPT) (Osaki et al, 2021).…”

“…Moreover, this task is a method for measuring RT, which is delayed in the neglected space in cases of USN (Posner, 1980;Posner et al, 1984). Although the usual Posner task only consists of two frames in which the target appears to the left and right of the fixation point, Osaki et al (2021) reported using an MPT with four frames (right up, right down, left up, and left down) (Figure 4). We used a 17-inch computer (ROG STRIX GL703VM SCAR Edition, ASUS, Taipei, Taiwan) and software (Cedrus Corporation SuperLab 5.0, San Pedro, CA, USA) for the MPT.…”