![[Download GIF ``brain'']](brain.gif)
The parietal cortex is located roughly 'after' vision and 'before' motor control in the cortical information processing hierarchy. See the diagram, in which the front of the brain is to the left.
It corresponds to Brodmann's Areas 5 and 7 in the monkey and 5, 7, 39 and 40 in the human. The posterior region (PPC) is made up of multiple subregions with differing inputs and outputs, thought to be involved in different functions.
The posterior parietal cortex (PPC) receives many and various inputs including visual, auditory, somaesthetic, limbic and motor output signals. Evidence suggests strong links with frontal cortex, the cingulate gyrus, and the motor system (especially the cerebellum and basal ganglia).
Nobody knows. Some of us care. When strokes blow holes in the right-side PPC the result is often neglect, a bizarre syndrome in which the patient seems unaware of the left side of space. Sometimes patients don't acknowledge their surroundings on that side, sometimes their own bodies seem alien to them. So it's been suggested that the PPC may have something to do with spatial processing. Other ideas include motor command generation, visuomotor transformation, multimodal integration, attention, consciousness ...
The question of how the brain attends to visual objects is an old and difficult one. It is clear from what we know of visual cortex that processing a visual scene is a massively complex and resource-intensive task. Nevertheless, humans can rapidly identify and react to visual objects under a wide range of circumstances. Neuroscientific techniques such as MRI and PET imaging, evoked potentials recording and transcranial magnetic stimulation have begun to shed some light on this problem in recent years. They suggest that the posterior parietal cortex (PPC), which appears to be important for spatial processing and the control of eye movements, may also have a central role in visual attention. PPC damage due to stroke often leads to the clinical syndrome of neglect, in which patients seem unable to attend to events in the contralesional hemifield. One hypothesis is that the PPC may contain a 'saliency representation' of the visual scene, in which objects are represented in terms of how 'interesting' (how salient) they are. Current studies in Steinlab aim to investigate the nature of this representation, the factors contributing to the saliency of visual objects, and the mechanisms which may underlie selective attention. To achieve this we are using both computational modelling techniques and human psychophysics (recording eye movements using a scleral coil setup). There are plans to extend this approach to monkeys using cellular recording techniques.
"This is a very exciting area and much work remains to be done." A. Scientist.