What is the parietal lobe?
The parietal cortex is located posterior to the frontal lobe. It is structurally divided into the superior, middle and inferior gyri. The most anterior portion of the parietal lobe forms the post-central gyrus, the somatosensory cortex. Posterior to this are the parietal association regions and the visual regions of the posterior parietal cortex involved in visuospatial processing.
What is the evidence for parietal lobe alterations?
Moderate to high quality evidence found decreased parietal grey matter volume in medicated people with schizophrenia compared to controls. There were reductions in the left inferior parietal gyrus in chronic patients, and reductions in bilateral postcentral gyrus of both chronic and first-episode patients. Reductions in the right postcentral gyrus were greater in people with chronic schizophrenia than in people with first-episode schizophrenia. Reductions in parietal white matter were found over time (1-10 years). Parietal grey matter reductions over time were found only in first-episode patients. Increased antipsychotic dose was associated with decreased parietal lobe volume over time (>2 years).
Moderate quality evidence found decreased activation in the precuneus of people with schizophrenia while at rest compared to controls at rest. Relatives of people with schizophrenia also showed decreased resting-state activity in the left precuneus.
During hallucinations, there was increased activity in the postcentral gyrus and the inferior parietal lobule of people with schizophrenia. During episodic memory encoding and executive functioning tasks, there was decreased activity in the right inferior parietal lobe compared to controls. The left inferior parietal cortex of people with schizophrenia showed increased activity during executive functioning and theory of mind tasks and decreased activity during cognitive control tasks. The right inferior parietal cortex of people with schizophrenia showed increased activity during theory of mind tasks, and the left postcentral gyrus showed increased activity during episodic memory encoding. Bilateral superior parietal gyri showed increased activity during timing tasks and increased activity in the parietal cortex in general during inhibition and emotion tasks. Compared to people with an autism spectrum disorder, there was increased activity during face emotion recognition in the left inferior parietal region of people with schizophrenia. After cognitive remediation, moderate to low quality evidence found increased activity in the right superior parietal lobe and the right postcentral gyrus.
In relatives of people with schizophrenia, there was increased activity in the left inferior parietal gyrus and the left precuneus during executive functioning and working memory tasks, and increased activity in the right parietal precuneus and the right inferior parietal lobule during cognitive tasks. There was decreased activity in relatives in the right parietal cortex during executive functioning tasks. During emotion tasks, there was increased activity in relatives in the left sub-gyral parietal region and the left precuneus, and decreased activity in the right inferior parietal lobule.
Green - Topic summary is available.
Orange - Topic summary is being compiled.
Red - Topic summary has no current systematic review available.