The posterior parietal cortex is a brain region involved in complex cognitive functions. It plays a role in integrating sensory information, contributing to our understanding of the world and our ability to interact with it. This area is involved in planning actions, spatial reasoning, and directing attention, which are fundamental to how we perceive and navigate our surroundings.
Where the Posterior Parietal Cortex is Located
The posterior parietal cortex is situated in the parietal lobe, behind the central sulcus, a deep groove separating the frontal and parietal lobes. It is positioned between the visual cortex and the somatosensory cortex, which processes touch and body sensations.
This region is subdivided into the superior parietal lobule and the inferior parietal lobule by the intraparietal sulcus. It receives sensory input from the visual, auditory, and somatosensory systems, gathering information about the body’s position and external objects in space.
The Posterior Parietal Cortex’s Role in Spatial Awareness and Attention
The posterior parietal cortex is involved in processing spatial information and guiding attention. It helps individuals understand the location of objects and navigate their environment. It integrates sensory data to construct a spatial map of the surroundings, used for various cognitive functions.
The superior parietal lobule and inferior parietal lobule are active in spatial awareness. The right posterior parietal cortex plays a role in maintaining sustained spatial attention. This area also processes visual stimuli and contributes to decisions about images within the field of view.
This region helps in selectively focusing on relevant stimuli while filtering out distractions. For instance, activity in the posterior parietal cortex reflects shifts in covert attention, even without eye movements, indicating its involvement in mental shifts of focus. The integration of visual, tactile, and proprioceptive information in the posterior parietal cortex contributes to our perception of body ownership and self-perception, as demonstrated by phenomena like the rubber hand illusion.
The Posterior Parietal Cortex’s Role in Guiding Movement
The posterior parietal cortex is an area for planning and executing goal-directed movements. It acts as an interface between sensory input and motor commands, transforming information about an object’s location into instructions for movement. This region contains specialized areas for planning different types of movements, such as eye movements (saccades), reaching, and grasping.
For instance, neurons in subdivisions like the lateral intraparietal area (LIP) show activity before and during visually guided saccades, which are rapid eye movements. Other neurons in the parietal reach region (PRR) are activated when planning arm movements. This suggests specialization within the posterior parietal cortex for different body effectors.
The posterior parietal cortex is involved in learning motor skills and selecting actions. It processes visual information and merges it with motor information, often referred to as “vision for action.” This allows for actions like reaching to a target, translating the visual location of the target into a precise motor plan.
How Damage to the Posterior Parietal Cortex Affects Cognition
Damage to the posterior parietal cortex can lead to effects on cognition. One common symptom is spatial neglect, also known as hemispatial neglect, where individuals may ignore one side of space, typically the left side following damage to the right posterior parietal cortex. This can manifest as shaving only half of the face or dressing only one side of the body.
Another consequence of posterior parietal cortex damage is apraxia, which involves difficulty with skilled movements despite intact motor function. Patients might struggle with complex action sequences even if they can perform elementary movements. Such damage can also impair spatial reasoning and navigation, making it challenging to understand spatial relationships or find one’s way around.
Individuals with posterior parietal cortex damage may experience deficits in visual working memory and the perception and memory of spatial relationships. In severe cases, patients may report their environment appearing “confused or blurred,” and these spatial defects can be more debilitating than blindness. These impairments underscore the posterior parietal cortex’s role in integrating sensory information for coherent spatial perception and guiding motor actions.