LUND (Sweden), Dec 10: There is a noticeable decline in the number of individuals who engage in reading for pleasure. Recent data shows that fifty percent of UK adults report not reading regularly, an increase from 42 percent in 2015. Furthermore, about one in four young adults aged 16-24 admit they have never read for pleasure, as found by research from The Reading Agency.
What does this trend imply? Could the shift towards favoring video content over text potentially impact our cognitive development or evolution? What unique brain characteristics do proficient readers possess? I have explored these questions in my new study published in Neuroimage.
In my research, I examined open-source data from over 1,000 participants and uncovered various brain anatomy traits associated with readers of different proficiency levels.
Notably, two areas in the left hemisphere, which play essential roles in language processing, exhibited structural distinctions in individuals who excel in reading.
The first area is the anterior part of the temporal lobe, which contributes to the association and categorization of meaningful information. For instance, when defining the word leg, this region synthesizes visual, sensory, and motor data regarding the appearance, feel, and movement of legs.
The second area is Heschl’s gyrus, a fold located in the upper temporal lobe that houses the auditory cortex (the outer layer of the brain). Enhanced reading skills were found to correlate with a larger anterior temporal lobe on the left side compared to the right. It follows that a more extensive brain region dedicated to meaning could facilitate word comprehension and improve reading abilities.
It may seem counterintuitive that the auditory cortex is involved in reading, which is primarily a visual activity. However, pairing letters with their phonetic sounds necessitates an understanding of the language’s sounds. This phonological awareness is a well-recognized precursor to reading development in children.
A thinner Heschl’s gyrus on the left has been previously associated with dyslexia, characterized by significant reading challenges. My findings indicate that variations in cortical thickness do not simply differentiate between individuals with and without dyslexia; instead, they exist across a broader spectrum, with thicker auditory cortices linked to improved reading proficiency.
Why does size matter?
Is greater thickness always advantageous? In terms of cortical structure, the answer is no; it’s not that straightforward. It is known that the auditory cortex in most individuals has more myelin in the left hemisphere. Myelin is a fatty substance serving as an insulator for nerve fibers, enhancing neural communication speed and providing insulation to clusters of brain cells. Neural columns are thought to act as small processing units.
The greater insulation and accelerated signaling in the left hemisphere allow for rapid, categorical processing vital for language. For instance, we must discern whether a speaker uses the phonetic category “d” or “t” in the words “dear” or “tear,” without concentrating on the exact moment vocal folds vibrate.
The “balloon model” of cortical growth suggests that increased myelin compresses left-hemispheric cortical regions, rendering them flatter yet more extensive. Thus, while the left auditory cortex may appear thicker in proficient readers, it remains thinner (though significantly more extensive) than its right counterpart.
Does this imply that thinner is better? Again, the answer is not as simple.
Complex abilities requiring information integration typically benefit from a thicker cortex. The anterior temporal lobe, notable for its intricate information integration, is the most pronounced of all cortical structures. This may relate to the prevalence of overlapping, interacting neurons that facilitate more holistic information processing.
Phonology, a complex skill encompassing the integration of various sound and motor features into coherent speech sounds, seems to correlate with a thicker cortex near the left Heschl’s gyrus. Although the processing extent of phonology in Heschl’s gyrus remains uncertain, the prevalence of multiple left Heschl’s gyri in phoneticians suggests a connection to speech sounds.
Clearly, the structure of the brain offers significant insights into reading abilities. Importantly, the brain is adaptable — it transforms with the acquisition of new skills or refinement of existing ones.
For example, young adults who have intensively studied a language showed increased cortical thickness in language-related regions. Likewise, engaging with reading is likely to influence the structural integrity of the left Heschl’s gyrus and the temporal pole. So, to nurture your Heschl’s gyrus, grab a captivating book and immerse yourself in it.
Lastly, it’s essential to ponder the potential consequences for our species if reading and similar skills are deprioritized. Our ability to interpret our surroundings and comprehend the thoughts of others would undoubtedly decline. In summary, that serene moment with a book in hand is not merely a personal indulgence; it serves a greater purpose for humanity. (The Conversation)
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