Dataset Information

Visuotopic organization of macaque posterior parietal cortex: a functional magnetic resonance imaging study.

ABSTRACT: Macaque anatomy and physiology studies have revealed multiple visual areas in posterior parietal cortex (PPC). While many response properties of PPC neurons have been probed, little is known about PPC's large-scale functional topography-specifically related to visuotopic organization. Using high-resolution functional magnetic resonance imaging at 3 T with a phase-encoded retinotopic mapping paradigm in the awake macaque, a large-scale visuotopic organization along lateral portions of PPC anterior to area V3a and extending into the lateral intraparietal sulcus (LIP) was found. We identify two new visual field maps anterior to V3a within caudal PPC, referred to as caudal intraparietal-1 (CIP-1) and CIP-2. The polar angle representation in CIP-1 extends from regions near the upper vertical meridian (that is the shared border with V3a and dorsal prelunate) to those within the lower visual field (that is the shared border with CIP-2). The polar angle representation in CIP-2 is a mirror reversal of the CIP-1 representation. CIP-1 and CIP-2 share a representation of central space on the lateral border. Anterior to CIP-2, a third polar angle representation was found within LIP, referred to as visuotopic LIP. The polar angle representation in LIP extends from regions near the upper vertical meridian (that is the shared border with CIP-2) to those near the lower vertical meridian. Representations of central visual space were identified within dorsal portions of LIP with peripheral representations in ventral portions. We also consider the topographic large-scale organization found within macaque PPC relative to that observed in human PPC.

SUBMITTER: Arcaro MJ

PROVIDER: S-EPMC3074253 | biostudies-literature | 2011 Feb

REPOSITORIES: biostudies-literature

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Visuotopic organization of macaque posterior parietal cortex: a functional magnetic resonance imaging study.

Arcaro Michael J MJ Pinsk Mark A MA Li Xin X Kastner Sabine S

The Journal of neuroscience : the official journal of the Society for Neuroscience 20110201 6

Macaque anatomy and physiology studies have revealed multiple visual areas in posterior parietal cortex (PPC). While many response properties of PPC neurons have been probed, little is known about PPC's large-scale functional topography-specifically related to visuotopic organization. Using high-resolution functional magnetic resonance imaging at 3 T with a phase-encoded retinotopic mapping paradigm in the awake macaque, a large-scale visuotopic organization along lateral portions of PPC anterio ...[more]

PMID: 21307244

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Project description:BackgroundRecent studies have shown that patients with disorders of consciousness (DoC) can benefit from repetitive transcranial magnetic stimulation (rTMS) therapy. The posterior parietal cortex (PPC) is becoming increasingly important in neuroscience research and clinical treatment for DoC as it plays a crucial role in the formation of human consciousness. However, the effect of rTMS on the PPC in improving consciousness recovery remains to be studied.MethodWe conducted a crossover, randomized, double-blind, sham-controlled clinical study to assess the efficacy and safety of 10 Hz rTMS over the left PPC in unresponsive patients. Twenty patients with unresponsive wakefulness syndrome were recruited. The participants were randomly divided into two groups: one group received active rTMS treatment for 10 consecutive days (n = 10) and the other group received sham treatment for the same period (n = 10). After a 10-day washout period, the groups crossed over and received the opposite treatment. The rTMS protocol involved the delivery of 2000 pulses/day at a frequency of 10 Hz, targeting the left PPC (P3 electrode sites) at 90% of the resting motor threshold. The primary outcome measure was the JFK Coma Recovery Scele-Revised (CRS-R), and evaluations were conducted blindly. EEG power spectrum assessments were also conducted simultaneously before and after each stage of the intervention.ResultrTMS-active treatment resulted in a significant improvement in the CRS-R total score (F = 8.443, p = 0.009) and the relative alpha power (F = 11.166, p = 0.004) compared to sham treatment. Furthermore, 8 out of 20 patients classified as rTMS responders showed improvement and evolved to a minimally conscious state (MCS) as a result of active rTMS. The relative alpha power also significantly improved in responders (F = 26.372, p = 0.002) but not in non-responders (F = 0.704, p = 0.421). No adverse effects related to rTMS were reported in the study.ConclusionsThis study suggests that 10 Hz rTMS over the left PPC can significantly improve functional recovery in unresponsive patients with DoC, with no reported side effects.Clinical trial registrationwww.ClinicalTrials.gov, identifier: NCT05187000.

Project description:The posterior parietal cortex (PPC) in rodents is reciprocally connected to primary somatosensory and vibrissal motor cortices. The PPC neuronal circuitry could thus encode and potentially integrate incoming somatosensory information and whisker motor output. However, the information encoded across PPC layers during refined sensorimotor behavior remains largely unknown. To uncover the sensorimotor features represented in PPC during voluntary whisking and object touch, we performed loose-patch single-unit recordings and extracellular recordings of ensemble activity, covering all layers of PPC in anesthetized and awake, behaving male rats. First, using single-cell receptive field mapping, we revealed the presence of coarse somatotopy along the mediolateral axis in PPC. Second, we found that spiking activity was modulated during exploratory whisking in layers 2-4 and layer 6, but not in layer 5 of awake, behaving rats. Population spiking activity preceded actual movement, and whisker trajectory endpoints could be decoded by population spiking, suggesting that PPC is involved in movement planning. Finally, population spiking activity further increased in response to active whisker touch but only in PPC layers 2-4. Thus, we find layer-specific processing, which emphasizes the computational role of PPC during whisker sensorimotor behavior.SIGNIFICANCE STATEMENT The posterior parietal cortex (PPC) is thought to merge information on motor output and sensory input to orchestrate interaction with the environment, but the function of different PPC microcircuit components is poorly understood. We recorded neuronal activity in rat PPC during sensorimotor behavior involving motor and sensory pathways. We uncovered that PPC layers have dedicated function: motor and sensory information is merged in layers 2-4; layer 6 predominantly represents motor information. Collectively, PPC activity predicts future motor output, thus entailing a motor plan. Our results are important for understanding how PPC computationally processes motor output and sensory input. This understanding may facilitate decoding of brain activity when using brain-machine interfaces to overcome loss of function after, for instance, spinal cord injury.

Dataset Information

Visuotopic organization of macaque posterior parietal cortex: a functional magnetic resonance imaging study.

Publications

Visuotopic organization of macaque posterior parietal cortex: a functional magnetic resonance imaging study.

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