The posterior parietal cortex and serial visual search: a tDCS study
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1
Australian National University, Research School of Psychology, Australia
Intro: Serial visual search models suggest that people scan potential targets in a cluttered scene sequentially, and is the leading cognitive explanation of how people process potential targets in a visual scene. However, the relative contributions of attention and memory in facilitating serial visual search are poorly understood, as the two concepts have not been dissociated experimentally.
Aims: The posterior parietal cortex (PPC) is believed to be involved in visual search, though its underlying cognitive contributions remain unclear. The current study aimed to explore the cognitive role of the PPC in serial visual search by directly manipulating PPC activity via transcranial direct current stimulation (tDCS), during memory and attention based search conditions.
Methods: Anodal, cathodal and sham tDCS were applied during a serial visual search task, within subjects across three blocks. Manipulations were made to the search condition to maximise the contributions from attention or memory.
Results: Results confirmed that tDCS stimulation significantly affected reaction time in serial visual search, though these results varied by block. While stimulation did not significantly affect RT in the first block, anodal stimulation significantly increased RT in the second block (t = 2.557, p = .022), while in the third block, anodal stimulation significantly decreased RT (t = -2.781, p = .011). Significant interactions between search condition and stimulation were observed in blocks 2 (F = 3.089, p = .046) and 3 (F = 4.98, p = .007). These interactions showed that the effect of anodal stimulation had a greater impact on the memory condition; significantly increasing RT in the memory condition in block 2 (t = 2.441, p = .015), and decreasing RT in block 3 (t = - 2.532, p = .011), relative to the attentional search condition.
Conclusions:The current project suggests PPC activity may be causally involved in serial visual search. This research also highlights the largely uninvestigated (and unanticipated) effects of task learning on tDCS, providing insight for future cortical stimulation research. Results suggest that PPC is playing a WM role; and that the direction of stimulation effects vary with task learning.
Keywords:
tDCS,
Visual Cortex,
dorsal stream,
Visual attention networks,
visual working memory
Conference:
Australasian Society for Psychophysiology, Inc, Coffs Harbour, Australia, 26 Nov - 28 Nov, 2014.
Presentation Type:
Oral Presentation
Topic:
Psychophysiology
Citation:
Blunden
HR and
Pammer
K
(2014). The posterior parietal cortex and serial visual search: a tDCS study.
Conference Abstract:
Australasian Society for Psychophysiology, Inc.
doi: 10.3389/conf.fnhum.2014.216.00012
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Received:
15 Oct 2014;
Published Online:
02 Dec 2014.
*
Correspondence:
Ms. Holly R Blunden, Australian National University, Research School of Psychology, Canberra, ACT, Australia, holly.blunden@anu.edu.au
Dr. Kristen Pammer, Australian National University, Research School of Psychology, Canberra, ACT, Australia, Kristen.Pammer@anu.edu.au