Aerobic Exercise Stalls Brain Atrophy in Parkinson’s Disease

Post by Anastasia Sares

The takeaway

Compared to a regimen of stretching, aerobic exercise (riding a stationary bike) helped people with Parkinson’s disease maintain cognitive control. It also changed the connectivity within cognitive and motor regions of the brain. This offers us some clues as to how exercise can stall the progression of symptoms in Parkinson’s disease.

What's the science?

In Parkinson’s disease, dopamine-producing cells in a brain region called the substantia nigra begin to atrophy and die. This leads to many different symptoms, including tremors, difficulty with movement, emotional changes, and cognitive decline. The substantia nigra is part of the basal ganglia, a series of nuclei (clusters of neurons) near the middle of the brain, which have strong connections to the motor cortex, helping us decide when and how to perform movements. In Parkinson’s, researchers have observed a shift in which basal ganglia regions are connected to the motor cortex. Specifically, the posterior putamen inevitably deteriorates over the course of the disease, and its function is gradually taken over by the anterior putamen.

Some drugs can slow the progression of Parkinson’s, but lately, researchers are looking into non-drug therapies to complement a patient’s medication. Simple aerobic exercise is an example of such a therapy: it has been shown to slow the progression of Parkinson’s symptoms in both animal and human studies. This week in Annals of Neurology, Johansson and colleagues compared aerobic exercise to stretching, this time asking: what exactly does this kind of exercise do to the brain?

How did they do it?

The study was part of a clinical trial, which was designed to evaluate the effect of exercise on Parkinson’s symptoms. The trial was carefully designed: all the participants had mild to moderate Parkinson’s, and were randomly assigned to a therapy involving either aerobic exercise or stretching. They were evaluated before and after the therapy. This is called an active control study—the goal is to compare two active groups, as opposed to one active group and one passive group. This way, both groups go through the same experience of being in contact with the researcher, scheduling their therapy, and following up— which can have placebo effects of their own that aren’t of interest to the researcher.

A subset of the participants volunteered to undergo MRI scans. The authors measured their brain structure as well as recording brain activity at rest. Finally, participants performed a cognitive control test, where they had to stare at a screen and then move their eyes towards a small dot or away from it, depending on the color of another dot in the center of the screen. The authors measured their eye movements and recorded correct/incorrect responses.

What did they find?

First, the authors looked at measures of overall gray matter (brain tissue that houses neuronal cell bodies). In Parkinson’s and other degenerative diseases, thinning gray matter can be a sign of neural atrophy. In the group that had done the aerobic exercise, however, there was no sign of this atrophy for the 6-month period of the study. Next, the authors looked at neural connectivity. As mentioned above, in the normal course of Parkinson’s, they expected to see a shift in connectivity of the motor cortex—after six months, the motor cortex should shift from being more connected with the posterior putamen to being more connected with the anterior putamen. This compensatory mechanism was strengthened in patients from the aerobic exercise group. Finally, the patients in the aerobic exercise condition improved on the cognitive control test. This came along with increased connectivity in frontal networks in the brain (executive control).

What's the impact?

This study is among many others showing how body and brain health are connected, and how exercise has far-reaching benefits beyond mere physical strength. These findings have important implications for the impact of aerobic exercise on stabilizing disease progression. Future studies could test whether these insights also apply to other neurodegenerative conditions. 

Access the original scientific publication here

A Massive 7T fMRI Dataset to Bridge Neuroscience and Artificial Intelligence

Post by Andrew Vo

The takeaway

To understand the complex brain networks that underlie human sensory and cognitive behaviors, enormous amounts of high-quality imaging data are required. The introduction of such a dataset will be invaluable in studying processes such as vision or memory and will bridge the gap between cognitive neuroscience and artificial intelligence.

What's the science?

To successfully understand human brain function, we need to build comprehensive models of how information is processed by the brain. Such models require massive amounts of high-dimensional and context-specific data. However, most existing human brain imaging studies have been limited by small amounts of low-resolution data collected from varying numbers of individuals. This week in Nature Neuroscience, Allen et al. introduced the Natural Scenes Dataset (NSD), a publicly available brain imaging dataset of unprecedented scale and quality.

How did they do it?

The authors recruited eight human participants to contribute to the NSD. Each participant underwent whole-brain 7T functional magnetic resonance imaging (fMRI), during which their brain activity was measured as they viewed thousands of distinct natural scene images. 7T refers to the high magnetic field strength of the MRI scanner. Higher field strengths improve the signal-to-noise ratio and spatial resolution of the collected data, as compared to those data obtained at lower field strengths (consider that most hospital MRI scanners are only 1.5-3T). The participants collectively viewed over 70,000 richly annotated natural scenes across more than 300 scanning sessions held over the course of one year. To ensure participants remained attentive and engaged with the images, the authors simultaneously performed a continuous recognition task that involved indicating if a presented image was previously viewed. The authors carefully evaluated the data quality of the NSD and present initial analyses of the data.

What did they find?

The resulting NSD is the largest of its kind to date. High performance on the continuous recognition task indicated that participants were consistently engaged and attentive while viewing the many thousands of natural scene images. Inspection of the imaging data revealed that the signal-to-noise ratio and estimated brain responses across the brain remained stable across scanning sessions for each participant.

The authors demonstrated two initial applications of the NSD: First, they analyzed patterns of brain responses to the content of natural scenes and observed transformations of semantic representations along the ventral visual pathway. For example, brain patterns associated with people and animals were found in different parts of higher visual areas. Second, they applied machine learning techniques to build and train a deep convolutional neural network to predict brain activity in the brain’s visual areas. The large amount of data afforded by the NSD allowed their models to successfully predict brain activity more accurately than existing state-of-the-art models.

What's the impact?

This report introduces the NSD, a large-scale publicly available brain imaging dataset. The NSD is unique from other resources in terms of its massive scale (i.e., large amounts of data collected from individuals at ultra-high field strength), data quality, and novel analysis techniques. This sharable dataset has wide-ranging applications to the fields of cognitive science, neuroscience, artificial intelligence, and their intersection.

Online Single-Session Interventions Can Help Depressed Teenagers

Post by D. Chloe Chung

The takeaway

Accessible, online single-session interventions that teach coping skills can effectively improve symptoms related to depression in teenagers, especially during the COVID-19 pandemic with heightened teen depression.

What's the science?

Rates of depression among teenagers soared during the COVID-19 pandemic as they faced social isolation due to school closure and financial difficulties. While teen depression is the major health risk for young people, more than half of depressed teenagers lacked access to professional help even before the pandemic. As many teenagers find it challenging to seek mental healthcare services due to stigma from family or financial reasons, it is important to create effective and accessible platforms to help those in need. Recently in Nature Human Behaviour, Schleider and colleagues showed that accessible, online single-session interventions that teach coping skills can reduce depression in teenagers.

How did they do it?

The authors used Instagram advertisements to recruit a diverse group of teenagers (13-16 years old) in the United States who were experiencing depressive symptoms. Recruited teenagers were informed that they would be rewarded up to $20 by participating in the minimal-risk, free, confidential online psychology study. Since depressed teenagers often feel uncomfortable telling their guardians about their mental health problems, the study was approved to waive consent from parents for participation. A total of 2,452 eligible teenagers who completed the baseline survey were randomly assigned with one of three web-based, single-session interventions designed by the authors. The first active intervention (“growth mindset”) teaches the participants that symptoms and personal traits can change. The second active intervention (“behavioral activation”) teaches participants how to adapt behaviors to experience positive sensations such as happiness and accomplishment. The third intervention (“supportive therapy”), that encourages sharing emotions with others, acts a placebo as it does not teach specific coping skills. Each of the self-guided interventions included peer narratives and writing activities taking 20-30 minutes to complete. The participants were asked to complete the follow-up survey three months after the interventions. Both pre- and post-intervention surveys assessed a range of symptoms including depression, anxiety, COVID-19-related trauma, hopelessness, eating behaviors, and perceived sense of agency.

What did they find?

The authors compared the depressive symptoms measured during the baseline survey and the follow-up survey. From this analysis, they found that both “growth mindset” and “behavioral activation” interventions substantially decreased depressive symptoms compared to the placebo session. The degree of reduction in depressive symptoms was similar between groups of each active intervention. Both active interventions also improved other aspects in depressed teenagers. Specifically, three months after these interventions, participants reported decreased hopelessness, decreased restrictive eating, and increased sense of agency. However, when it comes to reducing trauma-related to COVID-19 and anxiety, only the “growth mindset” intervention and not the “behavioral activation” intervention was effective.

What's the impact?

This study has shown that even a single online intervention session can help depressed teenagers who may otherwise have difficulties in seeking accessible professional help. Study results were promising as the access to mental healthcare services is even more limited during the global pandemic. Since the reduction in depressive and other symptoms by these active interventions was modest, depressed teenagers should be provided with more intense and long-term help for sustainable care. Still, this non-traditional, highly accessible mental healthcare service can support teenagers who might otherwise have trouble getting appropriate help.