Localization of human intraparietal areas AIP, CIP, and LIP using surface orientation and saccadic eye movement tasks

Abstract

In monkeys, areas in the intraparietal sulcus (IPS) play a crucial role in visuospatial information processing. Despite many human neuroimaging studies, the location of the human functional homologs of some IPS areas is still a matter of debate. The aim of the present functional magnetic resonance imaging (fMRI) study was to identify the distinct locations of specific human IPS areas based on their functional properties using stimuli adapted from nonhuman primate experiments, in particular, surface orientation discrimination and memory guided saccadic eye movements (SEM). Intersubject anatomical variability likely accounts for much of the debate. By applying subject by subject analysis, we can demonstrate that sufficient intersubject anatomical and functional commonalities exist. Both the lateral bank of the anterior part of IPS, the putative human homolog of the area AIP, and the caudal part of the IPS (putative CIP) showed activation related to spatial discrimination of surface orientation. Eye tracking conducted during fMRI data acquisition allowed us to show that both areas were separated by an area related to SEM. This area was located in the middle region of the IPS (most probably including LIP), i.e., similar to the location observed in nonhuman primates. In 10 of 11 subjects our putative CIP activation was located in a medial side branch of the posterior part of the IPS, on the opposite side as described in nonhuman primates, making this landmark a useful anatomical marker for the location of CIP.

Morphological patterns of the intraparietal sulcus and the anterior intermediate parietal sulcus of Jensen in the human brain

“…Functional activity related to saccadic eye movements and attentional processing, reflecting putative area LIP, and activity related to pointing and reaching hand movements in the putative area PRR were observed in the posterior ramus of the IPS that lies caudal to the sulcus of Jensen. By contrast, activity related to grasping hand movements, reflecting putative area AIP, was located in the anterior ramus of the IPS (anterior to the sulcus of Jensen) and close to the junction of the IPS with the post-central sulcus, not only in the average-group data [24,56] (also see table 1 in [21] and table 1 in [22]), but also consistently observed in the individual subjects (see fig. 4 in [21]; [22][23] 8).…”

“…By contrast, activity related to grasping hand movements, reflecting putative area AIP, was located in the anterior ramus of the IPS (anterior to the sulcus of Jensen) and close to the junction of the IPS with the post-central sulcus, not only in the average-group data [24,56] (also see table 1 in [21] and table 1 in [22]), but also consistently observed in the individual subjects (see fig. 4 in [21]; [22][23] 8). These coordinates place the activity close to the gyral passage separating the post-central sulcus from the anterior ramus of the IPS [38].…”

“…This sulcus appears at the intersection of the posterior end of the IPS and the paroccipital sulcus, and therefore the available information localizes the putative area CIP in the human brain to this intersection of the posterior end of the IPS with the paroccipital sulcus (figure 1). We therefore interpret the data provided by Shikata et al [22] for the human homologue of area LIP to be the posterior ramus of the IPS until its connection with the paroccipital sulcus. Beyond this point starts the CIP region.…”

“…The issue of the cortical topography of the homologues of areas AIP, PRR and LIP in the human brain has been addressed in functional neuroimaging studies investigating activation foci in the parietal cortex during the performance of hand movements (grasping, reaching or pointing), saccadic eye movements and visuospatial attentional processes [16][17][18][19][20][21][22][23][24][54][55][56][57][58][59][60] (for reviews, see [25][26][27]; also see electronic supplementary material, tables S1-S3). We projected the average coordinates of the putative AIP, LIP and PRR activity reported in these functional neuroimaging studies onto an average brain template (ICBM152 nonlinear sixth-generation model [48]) and examined the location of the peaks with respect to the IPS morphology as established in this study.…”

“…In the human brain, Shikata et al [22] localize the intraparietal region involved in saccadic eye movements (putative area LIP) at x ¼ 225.6, y ¼ 257, z ¼ 58.4 and x ¼ 26.1, y ¼ 259.4, z ¼ 57.6. These MNI space coordinates would place LIP in the posterior ramus of the IPS as defined in this study.…”