The Occipital Cortex and Visual Memory Development
Post by Amanda McFarlan
What's the science?
The study of learning and memory commonly focuses on brain regions such as the hippocampus and the prefrontal cortex, however, recent studies have provided evidence to suggest that the occipital cortex may be involved in visual memory development. Indeed, age-related differences in cortical thickness indicate that the occipital cortex matures well into adolescence. Researchers postulate that synaptic pruning may occur throughout this maturation process as a way of enhancing visual processing. This week in Neuropsychologia, Yin and colleagues investigated whether the maturation of the occipital cortex played a role in enhancing memory formation of visual stimuli.
How did they do it?
The authors used electrocorticographic recordings (electrodes placed directly on the surface of the brain) to measure brain activity in the occipital cortex in 24 children (6-13 years) and adolescents (13- 20 years) while performing a memory task. The memory task consisted of two parts: the “study” part and the “test” part. During the study part of the memory task, participants were presented with 40 scenic images of both high and low complexity (defined by the number of object categories in the image) and were asked to decide whether the image was of an indoor scene or an outdoor scene. Then, during the test part of the task, the participants were presented with the same 40 scenic images and 20 new scenic images. The participants were asked to classify the scenic images as “old” (ones they had previously studied) or “new” (ones they had not studied). The participants’ brain activity in the occipital cortex during the two parts of the memory task was recorded. To further investigate how visual processing in the occipital cortex might contribute to memory formation, the authors analyzed brain recordings during the study part, focusing on oscillations in the alpha range (7-14 Hz) since these are known to be important in visual processing. Specifically, they measured alpha power, which has been shown to decrease with increased neural activity and memory formation, and instantaneous alpha frequency which have been shown to increase with a higher temporal resolution of perception.
What did they find?
The authors found that the recognition accuracy for high-complexity scenes was greater for adolescents compared to children, which suggests that memory formation for complex visual scenes improves during development. Additionally, decreased alpha power was found to be a predictor of recognition accuracy for high-complexity scenes in adolescents. Next, the authors determined that only high-complexity scenes were associated with both an age-related decrease in alpha power and an increase in instantaneous alpha frequency, suggesting that visual processing in the occipital cortex that is involved in memory formation improves in an age-dependent manner for complex scenic stimuli. Finally, the authors determined that there were no age-related differences in alpha power or frequency for scenes that were later incorrectly identified “new”, which suggests that age-related differences in alpha power and frequency may be predictive of memory formation, but not visual perception as a whole.
What’s the impact?
Using electrocorticographic recordings in children and adolescents, this study showed that developmental changes in the occipital cortex are associated with enhanced memory formation for complex scenic stimuli. The authors found that adolescents were better at recognizing high, but not low-complexity scenes compared to children. Additionally, they found that decreased alpha power was predictive of memory formation for high-complexity scenes in an age-dependent manner. In all, these findings highlight the importance of occipital cortex maturation in the enhancement of visual memory formation.
Yin et al. Direct brain recordings reveal occipital cortex involvement in memory development. Neuropsychologia (2020). Access the original scientific publication here.