A meta-analysis of studies reporting brain activity in individuals with a diagnosis of PTSD has revealed differences between the brain activity of individuals with PTSD and that of groups of both trauma-exposed (those who had experienced trauma but didn't have a diagnosis of PTSD) and trauma-naïve (those who hadn't experienced trauma) participants.
The critical difference between those who developed PTSD and those who experienced trauma but didn't develop PTSD lay in the basal ganglia. Specifically:
- PTSD brains compared with trauma-exposed controls showed differentially active regions of the basal ganglia
- trauma-exposed brains compared with trauma-naïve controls revealed differences in the right anterior insula, precuneus, cingulate and orbitofrontal cortices, all known to be involved in emotional regulation
- PTSD brains compared with both control groups showed differences in activity in the amygdala and parahippocampal cortex.
The finding is consistent with other new evidence from the researchers, that other neuropsychiatric disorders were also associated with specific imbalances in specific brain networks.
The findings suggest that, while people who have experienced trauma may not meet the threshold for a diagnosis of PTSD, they may have similar changes within the brain, which might make them more vulnerable to PTSD if they experience a subsequent trauma.
The finding also suggests a different perspective on PTSD — that it “may not actually be abnormal or a 'disorder' but the brain's natural reaction to events and experiences that are abnormal”.
A couple of years ago I reported on a finding that walking in the park, and (most surprisingly) simply looking at photos of natural scenes, could improve memory and concentration (see below). Now a new study helps explain why. The study examined brain activity while 12 male participants (average age 22) looked at images of tranquil beach scenes and non-tranquil motorway scenes. On half the presentations they concurrently listened to the same sound associated with both scenes (waves breaking on a beach and traffic moving on a motorway produce a similar sound, perceived as a constant roar).
Intriguingly, the natural, tranquil scenes produced significantly greater effective connectivity between the auditory cortex and medial prefrontal cortex, and between the auditory cortex and posterior cingulate gyrus, temporoparietal cortex and thalamus. It’s of particular interest that this is an example of visual input affecting connectivity of the auditory cortex, in the presence of identical auditory input (which was the focus of the research). But of course the take-home message for us is that the benefits of natural scenes for memory and attention have been supported.
Many of us who work indoors are familiar with the benefits of a walk in the fresh air, but a new study gives new insight into why, and how, it works. In two experiments, researchers found memory performance and attention spans improved by 20% after people spent an hour interacting with nature. The intriguing finding was that this effect was achieved not only by walking in the botanical gardens (versus walking along main streets of Ann Arbor), but also by looking at photos of nature (versus looking at photos of urban settings). The findings are consistent with a theory that natural environments are better at restoring attention abilities, because they provide a more coherent pattern of stimulation that requires less effort, as opposed to urban environments that are provide complex and often confusing stimulation that captures attention dramatically and requires directed attention (e.g., to avoid being hit by a car).
Older news items (pre-2010) brought over from the old website
Healthy older brains not significantly smaller than younger brains
A study using healthy older adults from Holland's long-term Maastricht Aging Study found that the 35 cognitively healthy people who stayed free of dementia showed no significant decline in gray matter, but the 30 people who showed substantial cognitive decline although still dementia-free showed a significant reduction in brain tissue in the hippocampus and parahippocampal areas, and in the frontal and cingulate cortices. The findings suggest that atrophy in the normal older brain may have been over-estimated in earlier studies, by not screening out people whose undetected, slowly developing brain disease was killing off cells in key areas.
Burgmans, S. et al. 2009. The Prevalence of Cortical Gray Matter Atrophy May Be Overestimated In the Healthy Aging Brain. Neuropsychology, 23 (5), 541-550.
Brain's problem-solving function at work when we daydream
An imaging study has revealed that daydreaming is associated with an increase in activity in numerous brain regions, especially those regions associated with complex problem-solving. Until now it was thought that the brain's "default network" (which includes the medial prefrontal cortex, the posterior cingulate cortex and the temporoparietal junction) was the only part of the brain active when our minds wander. The new study has found that the "executive network" (including the lateral prefrontal cortex and the dorsal anterior cingulate cortex) is also active. Before this, it was thought that these networks weren’t active at the same time. It may be that mind wandering evokes a unique mental state that allows otherwise opposing networks to work in cooperation. It was also found that greater activation was associated with less awareness on the part of the subject that there mind was wandering.
Christoff, K. et al. 2009. Experience sampling during fMRI reveals default network and executive system contributions to mind wandering. Proceedings of the National Academy of Sciences, 106 (21), 8719-8724.
Processing speed component of intelligence is largely inherited
A new kind of scanner used on the brains of 23 sets of identical twins and 23 sets of fraternal twins has revealed that myelin quality is under strong genetic control in the frontal, parietal, and left occipital lobes, and that myelin quality (in the cingulum, optic radiations, superior fronto-occipital fasciculus, internal capsule, callosal isthmus, and corona radiata) was correlated with intelligence scores. Myelin governs the speed with which signals can travel along the axons of neurons, that is, how fast we can process information. The researchers are now working on finding the genes that may influence myelin growth.
Chiang, M-C. et al. 2009. Genetics of Brain Fiber Architecture and Intellectual Performance. Journal of Neuroscience, 29, 2212–2224.
New brain region associated with face recognition
Using a new technique, researchers have found evidence for neurons that are selectively tuned for gender, ethnicity and identity cues in the cingulate gyrus, a brain area not previously associated with face processing.
Ng, M. et al. 2006. Selectivity for the configural cues that identify gender, ethnicity, and identity in human cortex. Proceedings of the National Academy of Sciences, 103 (51), 19552-19557.