Memory Secrets: Where the Brain Stores and Processes Words
- Lidi Garcia
- Mar 24
- 5 min read
Verbal memory involves several areas of the brain, including the temporal lobe and hippocampus. Patients with temporal lobe epilepsy often have difficulty with this function, and surgery to treat the condition can further affect memory. One study showed that reduced volume in certain brain regions is linked to poorer performance in word learning. These findings help to better understand how the brain processes verbal memory and may lead to more effective treatments and safer surgeries.
Verbal memory, or the ability to understand, remember and use spoken words and information, is a critical function of our brain. However, we still do not fully understand how this ability is structured and which brain areas are most important for its functioning.
We do know that the temporal lobe, a region of the brain located near the temples, plays a crucial role in memory. People with temporal lobe epilepsy (TLE), a neurological condition in which abnormal electrical discharges affect this region, often have memory difficulties.
In more severe cases, when medications do not control seizures, many patients need to undergo a surgery called anterior temporal lobe resection (ATLR), in which part of the lobe is removed.
The problem is that this surgery can have a significant side effect: up to 60% of patients experience a worsening of their verbal memory after the procedure.
However, the impacts vary greatly from person to person, while some suffer major memory loss, others experience little or no problems. This suggests that the brain can compensate for the loss of some areas, or that different parts of the brain may contribute in different ways to verbal memory.
Scientists have been studying this question for years and know that verbal memory does not depend solely on the temporal lobe. Word processing involves several regions of the brain, such as the prefrontal cortex, responsible for reasoning and planning, and the cingulate cortex, which helps with communication between different brain areas.
The hippocampus, a structure located within the temporal lobe, also plays a fundamental role, being considered a kind of "archiver" of our memories.
But what exactly is the relationship between these areas and verbal memory?
To answer this question, a group of researchers from the National Hospital for Neurology and Neurosurgery, UK, conducted a study analyzing brain scans of 84 patients with temporal lobe epilepsy and comparing them with those of 43 healthy people.
They used advanced MRI scans to measure the size of different brain regions and checked how the participants performed on verbal memory tests.
The results showed that patients with smaller volumes in certain brain areas performed worse on tasks involving word learning. Specifically, the reduction of gray matter in regions such as the temporal lobe, frontal lobe and cingulate cortex was directly linked to difficulties in verbal memory.
Furthermore, within the hippocampus, specific substructures, such as the dentate gyrus and areas called CA3 and CA4, have also been associated with verbal learning difficulties.
These findings are very important because they show that verbal memory does not depend on a single region of the brain, but rather on an interconnected network of brain areas. This discovery could have significant clinical implications, helping to develop more effective treatments for people with memory difficulties.
It could also contribute to making brain surgeries safer, allowing doctors to try to preserve as much of the areas responsible for verbal memory as possible when removing parts of the temporal lobe affected by epilepsy.
In summary, this study advances our understanding of how the brain processes verbal memory and reinforces the idea that multiple areas are involved in this function.
By identifying which regions are most critical, it opens up the possibility of developing therapeutic approaches that minimize the impacts of epilepsy and brain surgeries on the ability to learn and recall words.
The image illustrates the main areas of the brain involved in processing and storing verbal memory (heard words). Auditory verbal information enters the brain and goes through different stages until it is stored and integrated with existing knowledge.
The arrows indicate how information flows between these areas, showing the path that words take in the brain from the moment they are heard until they are stored as memory.
Input First-Processing: Parietal-Temporal-Occipital Junction (blue) and Superior and Middle Temporal Gyri (orange). These regions receive and process the sounds of words, helping us recognize and understand the meaning of what we hear.
Input Representation: Processed information goes to other areas of the brain (pink arrow), where it gains meaning and is organized for future retrieval.
Encoding: Dorsolateral and Ventrolateral Prefrontal Cortex (dark blue and purple). These areas help organize and structure information so that it can be stored correctly in memory.
Schema Integration: Middle Prefrontal Cortex and Anterior Cingulate Cortex (purple). These areas integrate new information with existing knowledge, helping to form connections for easier recall later.
Learning and Storage: Hippocampus (dark red) and Posterior Cingulate Cortex (pink). The hippocampus is essential for transforming information into long-term memory, ensuring that we can remember words and their meanings in the future.
READ MORE:
Cortico-hippocampal networks underpin verbal memory encoding in temporal lobe epilepsy
Giorgio Fiore, Davide Giampiccolo, Fenglai Xiao, Matthias J Koepp, Juan E Iglesias, Sjoerd B Vos, Jane de Tisi, Andrew W McEvoy, Giulio A Bertani, Marco Locatelli, Roisin Finn, Lorenzo Caciagli, Meneka Sidhu, Marian Galovic, Sallie Baxendale, John S Duncan, and Anna Miserocchi
Brain Communications, Volume 7, Issue 2, 2025, fcaf067
Abstract:
Knowledge of the structural underpinnings of human verbal memory is scarce. Understanding the human verbal memory network at a finer anatomical scale will have important clinical implications for the management of patients with verbal memory impairment. In this cross-sectional study, we aimed to assess the contributions of cerebral cortex and hippocampal subfields to verbal memory encoding in temporal lobe epilepsy. We included consecutive patients (n = 84) with radiologically and pathologically defined hippocampal sclerosis (HS) (44 left-sided) and unilateral temporal lobe epilepsy, and healthy volunteers (n = 43) who were comparable regarding age and sex. The morphometric and volumetric measures of cerebral cortex and hippocampal subfields were extracted from high-resolution MRI scans. People included in this study underwent standardized neuropsychological evaluation, including measures of verbal memory assessed through the Adult Memory and Information Processing Battery. Verbal memory performances were Z-scores corrected by using means and standard deviations published for sample standardization. Associations between verbal learning Z-scores and the grey matter volume of the cerebral cortex and hippocampal subfields were investigated. Reduction of grey matter volumes in the left and right medial and dorsolateral prefrontal cortex (Pcorr < 0.0001), superior and middle temporal gyri (Pcorr < 0.0001), anterior and posterior cingulate cortex (Pcorr < 0.0001) and of the left ventrolateral prefrontal cortex (Pcorr < 0.0001) and parietal–temporal–occipital junction (Pcorr < 0.0001) were associated with worse verbal learning. These findings were consistent across both the entire cohort and in a subgroup analysis focused exclusively on HS patients. Within hippocampi, smaller volumes of the left dentate gyrus (P = 0.003), cornu ammonis 4 (P = 0.005) and cornu ammonis 3 (P = 0.03) were associated with worse verbal learning Z-scores. This study demonstrates that verbal learning in patients with temporal lobe epilepsy is strongly related to the volume of distinct regions of the prefrontal, temporal and cingulate cortices and left dentate gyrus, cornu ammonis 4 and cornu ammonis 3 hippocampal subfields. It provides the basis to suggest a corticohippocampal network for verbal learning in these patients, improving our understanding of human verbal memory. These biomarkers may inform attractive targets for forthcoming modulating therapies. Future work may also analyse the impact of sparing part of the left dentate gyrus, cornu ammonis 4 and cornu ammonis 3 as a protective measure against verbal memory impairment after surgery for temporal lobe epilepsy.
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