The brain region that helps us interpret our world

Updated: Mar 23

Have you ever wondered how everyone views reality in their own way? Within the nature vs. nurture argument, it has been stated that our environment shapes who we become. Our DNA, on the other hand, is what brings out each person's individuality. An image or a poem can be displayed to two separate individuals. Both will reach their own conclusions about what the image symbolizes or what message is conveyed within the poem.

Over the decades, neuroscientists have learned to grasp the different brain areas responsible for various activities. More recently, they have found out which brain region is responsible for our understanding of reality. Face and object perception in the human brain is mediated by coordinated activity across several neural systems. This activity represents information that is transmitted spatially, both locally and globally, within the brain.

Neuronal activity in the inferior parietal lobe (IPL) has been linked to various cognitive abilities. Spatial attention is one of these, and it is critical in an ever-changing environment that demands a quick behavioural response. Semantic review papers have identified that the right IPL is a vital area for visuospatial attention. The presence of neurological injury to the right IPL results in developing a clinical syndrome known as hemineglect. This is the inability to direct visual stimulation to the opposing side of the brain, which might lead to you not paying attention to the side of your body impacted by the brain damage.

Tissue injury to the left temporoparietal cortex has been linked to problems in semantic processing, which is essential for reading and other complex types of language comprehension. Semantic processing is necessary for humans' capacity to contextualize and behave in response to the meaning of things, events, and circumstances. Semantic processing is most likely linked to social cognition. Previous research on spatial overlap between both cognitive domains in the left IPL supports this viewpoint. However, many human neuroimaging tests have revealed that sophisticated social cognitive processes, such as the ability to infer others' ideas, beliefs, and behavioural tendencies, involve the IPL of both brain hemispheres. Finally, the IPL contains the bulk of the brain's "default mode" network and it is closely related to other key cortical areas for diverse processes.

Despite evidence supporting the importance of this brain region, it is unclear how some of the most fundamental and complex cognitive processes converge and diverge in the IPL to achieve human communication and interaction. To address this unsolved issue through varying angles, Numssen et al., conducted a multi-method study that reveals the functional specialization hidden within the IPL across attention, semantics, and social cognition tasks.

The researchers looked at brain-behaviour links using three activities that the study participants completed while lying in an MRI scanner. In the first assignment, they had to demonstrate their understanding of the English language. To do so, they looked at meaningful words like "pigeon" and "home," as well as words with no meaning (known as pseudowords) like "pulre" and had to judge if it was a legitimate word or not. All activities in this analysis demonstrated enhanced neural activity in a wide range of brain areas, including the IPL. Real-word processing was revealed to be more engaged within the left-hemisphere.

The second challenge put the participant’s visual-spatial attention to the test. The participants had to react to stimuli on one side of the screen while expecting something to happen on the other side. In comparison to controls, they discovered that attentional reorienting significantly influenced neural activity in several default mode network nodes. These nodes included those within the left and right inferior parietal lobes (IPL).

Lastly, the Sally Anne exam was used in the third task to assess their ability to take perspectives. This is a four-panel comic strip depicting two individuals interacting with each other. A question could only be correctly answered if the research participants could put themselves in the shoes of the corresponding people. The findings for the social cognition task were, as predicted, weaker with less activation within the left and right IPL.

These findings show how the IPL's underappreciated hemisphere specificity underpins some of humanity's most unique cognitive abilities. These findings give fresh insight into how previously unknown activity and connection characteristics within the left and right IPL enable some of humanity's most diverse mental skills.

To sum up, this research sheds light on how the human brain works at its most fundamental level. The researchers demonstrate how our brains adjust flexibly to shifting demands. It does this by connecting specialized individual areas, such as the IPL, with more general brain regions. The more difficult the tasks are, the more closely the various regions interact with one another. This enables very complicated activities like language and social skills to be performed. The IPL might end up becoming one of the regions through which we understand the world.

Written by Reem Alzafiri, BSc., MSc.