Cognitive functions of the posterior parietal cortex: top-down and bottom-up attentional control

Abstract

Although much less is known about human parietal cortex than that of homologous monkey cortex, recent studies, employing neuroimaging, and neuropsychological methods, have begun to elucidate increasingly fine-grained functional and structural distinctions. This review is focused on recent neuroimaging and neuropsychological studies elucidating the cognitive roles of dorsal and ventral regions of parietal cortex in top-down and bottom-up attentional orienting, and on the interaction between the two attentional allocation mechanisms. Evidence is reviewed arguing that regions along the dorsal areas of the parietal cortex, including the superior parietal lobule (SPL) are involved in top-down attentional orienting, while ventral regions including the temporo-parietal junction (TPJ) are involved in bottom-up attentional orienting.

Keywords: attention; bottom-up attention; capture; inferior parietal lobule (IPL); parietal cortex; superior parietal lobule (SPL); temporo-parietal junction (TPJ); top-down attention.

Figure 1

Schematic depiction of relevant anatomical landmarks projected onto the lateral surface of the human brain. Superior parietal lobule (SPL) and inferior parietal lobule (IPL) are regions within the dorsal part of the parietal cortex subserving top-down attentional orienting. Temporo-parietal junction (TPJ) is a region within the ventral parietal cortex subserving bottom-up attentional orienting. Both, SPL and TPJ, are thought to elicit control signals responsible for subsequent attentional modulations observed over sensory regions, in this case modulating (labeled with dark blue arrows) visually evoked activity in the occipital lobe (OL). Additionally, areas along the inferior frontal gyrus (IFG) and inferior frontal junction (IFJ) are thought to serve as convergence areas for stimulus-driven and top-down attentional control (marked by light blue bi-directional arrows).

Figure 2

Results of the neuropsychological study aimed at investigating the relative contribution of SPL and TPJ to top-down and bottom-up orienting. (A) Lesion overlaps (purple minimal overlap; red maximal overlap) for patients grouped by behavioral deficits in top-down attentional orienting, labeled the SPL group (top panel); and patients grouped by behavioral deficits in bottom-up orienting, labeled the TPJ group (lower panel). (B) Behavioral performance on the top-down task summarized with a “Top-down Index” which quantifies differences between spatial top-down shifts made from left to right and vice versa. Controls and the TPJ lesioned group show similar efficiencies in executing spatial shifts, while patients with SPL lesions show decreased efficiency. Group control and individual patient data (labeled with patient initials) are plotted on the abscissa. (C) “Capture index” is a measure of bottom-up attention and quantifies the extent to which task-irrelevant distractors capture attention away from the task. Controls and the SPL lesioned group show similar capture values, such that both groups are captured by the task-irrelevant distractors. TPJ lesioned group show much reduced capture index (failure to be captured). Note that patients were placed in the SPL or TPJ group based on behavior, rather than based on the lesion, thus note the consistency with which patients end up in the corresponding group.