Differential effects of target height on immediate and delayed pointing actions: an ERP study

  • Author / Creator
    Moukhaiber, Rayan
  • Visually guided actions are those that are completed using available visual information, such as reaching for a cup of coffee while looking at it. In the absence of visual information, our hand actions are guided by previously stored visual information; these are known as memory-guided actions. Naturally, memory-guided actions are less accurate and slower than visually guided actions. Existing neuropsychological literature has proposed that immediate, visually guided actions are controlled by dorsal-visual stream processes in the parietal cortex, whereas delayed, memory-guided actions are reliant on ventral-visual stream processes in the inferior temporal cortex. It has been shown that the N170, an event-related potential (ERP) component linked to perceptual processes associated with object and face recognition and memory, also reflects processing needed for delayed actions to remembered targets. However, the greater part of studies investigating the N170 ERP, have used experimental paradigms reliant on actions conducted within the lower visual field. This is understandable given the fact that a significant portion of behaviours are conducted within the lower visual field, including typing on a keyboard or reaching for a cup of coffee. The present experiment measured the N170 ERP as a function of the height of a target to-be-reached-to, in order to determine how stimulus locality in upper and lower visual fields will affect immediate and delayed actions. We hypothesized that if delayed actions require more perception-based processes compared to immediate actions, they will also differ between target locations in the upper and lower visual fields. That is, delayed actions to targets in the upper visual field may be more perceptually taxing, take longer to execute, and be associated with a greater amplitude N170. Right-handed participants (N=28) were instructed to, reach out and touch a black target appearing on a touchscreen monitor in front of them, whenever they heard an auditory cue. The experiment consisted of two conditions, an immediate condition, and a delayed condition. The two conditions differed in timing by an average of 350 milliseconds. This has been shown in the literature to significantly alter behavioral and neural processing for targets in the lower visual field. The target location was manipulated so that targets can appear anywhere in the upper and lower visual field while simultaneously recording behavioral and electroencephalography (EEG) data. Our results indicated that memory-guided actions were initiated faster than visually guided actions but the two conditions were equivalent in terms of accuracy and movement time. Moreover, the N170 ERP exhibited a greater difference between conditions in the left hemisphere versus the right hemisphere, which replicates previous visuomotor literature. Contrary to our hypothesis, there was not an interaction between reach-height and either reaching type. This suggests that hand-arm kinematics and the neural circuitry underlying visually- and memory-guided actions may be relatively unchanged for targets in the upper visual field.

  • Subjects / Keywords
  • Graduation date
    Spring 2021
  • Type of Item
  • Degree
    Master of Science
  • DOI
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.