New research suggests that the exercise “sweet spot” found in mice to reverse cognitive decline could be applied to dementia patients. 

In experiments on ageing mice, Australian researchers found exercising for 35 days straight was the ‘sweet spot’ for reversing learning deficits in mice aged 24 months. 

Curiously, longer or shorter periods of exercise proved ineffective for reversing this cognitive decline, the researchers found. 

This opens the doors to human studies that will examine the impact of exercise on dementia. 

University of Queensland researchers have discovered an exercise ‘sweet spot’ that reverses the cognitive decline in ageing mice, paving the way for human studies. Worldwide, around 55 million people have dementia conditions, including Alzheimer's (stock image)

University of Queensland researchers have discovered an exercise ‘sweet spot’ that reverses the cognitive decline in ageing mice, paving the way for human studies. Globally, approximately 55 million suffer from dementia, which includes Alzheimer’s. (stock image).


The umbrella term dementia is used to define a range of symptoms that include behavioural changes, gradually decreasing cognitive and social abilities and gradual declines in cognition.

Alzheimer’s disease is the leading cause of dementia. However, there are other conditions such as vascular dementia, Lewy-body dementia, and frontotemporal. 

An abnormal buildup of proteins within and around brain cells may be the cause of Alzheimer’s disease. 

Alzheimer’s Research UK predicts that one million Americans will develop dementia in 2025. This number is expected to rise to two million people by 2050.  

Worldwide, around 55 million people have dementia conditions, including but not limited to Alzheimer’s disease. 

Researchers at Queensland Brain Institute (QBI) led the new study.

Dr Dan Blackmore said that the research team tested cognitive capacity of older mice in a defined period of exercise. They found a “sweet spot,” or optimal time, which significantly improved spatial learning. 

The brain’s nerve cells, also known as neurons and their connections can cause dementia. 

These nerve cells transmit information via chemical and electrical signals, carrying electrical impulses between places. 

The growth of new neurons – known as neurogenesis – is critical in regions of the brain for maintaining cognitive abilities, including the hippocampus, a seahorse-shaped brain region responsible for learning, emotions and memory.    

The hippocampus is essential for memory consolidation – where recent learned experiences are transformed into long-term memory. 

Dr Blackmore says that the hippocampal function is crucial for contextual and spatial learning and that its decline with age leads to cognitive impairment.

Graphical abstract shows the method and results of the experiments; the team found 35 days of voluntary physical exercise improved learning and memory

The graphic abstract below shows the results and method of the experiment. It was found that 35 days of voluntary exercise increased learning and memory.

“Exercise may improve hippocampal function. However, it is not known how much exercise or what mechanisms are involved in this improvement. 


The task of active place avoidance is a dry task that assesses spatial navigation in rodents. 

A subject must be placed in a rotating circle and avoided an unrelated sector. 

Rotation of the arena means that the subject’s avoidance must be active, otherwise the subject will be moved in the to-be-avoided sector by the rotation of the arena and a slight electric shock will be administered. 

Source: Bahník et al 

In the experiments, the researchers tested mice aged from 10 weeks to 24 months on the active place avoidance (APA) task, which tests the spatial navigation and memory of rodents. 

It involves placing rodents on rotating platforms. Then, they must use their surrounding cues for navigation away from an electrified “shock zone”. 

It was no surprise that mice aged 18 and 24 months performed worse than younger ones over five days.

After being placed into a container with running wheels, the animals could be moved around for different times.

When researchers repeated the APA with the aged mice, they found that only those who had exercised for 35 days showed a significant improvement in learning.

Researchers also discovered that neurogenesis activation by injecting growth hormone to sedentary mice enhanced learning.

Age can negatively affect GH in humans. Exercise, however, increases GH levels. 

‘We’ve been able to demonstrate that artificially raising GH in sedentary mice also was also effective in improving their cognitive skills,’ Dr Blackmore said. 

‘We discovered GH stimulates the production of new neurons in the hippocampus – the region of the brain critically important to learning and memory.’ 

The team was able to further explore the effects of producing new neurons on the brain’s circuitry using magnetic resonance imaging, (MRI) in additional experiments.  

MRI demonstrated that spatial learning improved due to connectivity in the dentate gyrus. (DG), which is part of hippocampal formation. 

Dr Blackmore explained that MRI was used to analyze the brain’s response to exercise. This allowed us to identify for the first-time the structural and functional modifications in the hippocampus’s hippocampus, which are crucial for improving spatial learning.   

Researchers conclude that 35 days of’sweet spots’ is too short for hippocampal activation. 

Dementia is a term used to describe the symptoms that occur when there's a decline in brain function (stock image)

The term dementia is used to refer to the signs and symptoms of a decline in brain function. Stock image

“Rather, they demonstrate that an extensive examination of various exercise periods is critical to understand the mechanisms behind the cognitive improvements that follow exercise,” they state. 

The new research was published in separate papers in the open-access journal iScience. 

The first is entitled, ‘An exercise “sweet spot” reverses cognitive deficits of aging by growth-hormone-induced neurogenesis’.

The second is called ‘Neurogenic-dependent changes in hippocampal circuitry underlie the procognitive effect of exercise in aging mice’.  


An electrically excitable neuron (also known as a nerve cell) is a cell that processes, transmits, and takes in information using chemical and electrical signals. 

It’s one of the most fundamental elements of our nervous system.

The neurons transmit stimuli to the brain so that the human body can respond to its environment.

For example, the stimulation of the fingers at candle flames is carried by ascending neurons to central nervous system. In return, the descending neuron stimulate the arm to take the finger out. 

A neuron’s diameter is approximately tenth of that of a human hair.