Fruit flies that were kept in the dark lost long-term memory of a traumatic stress they were exposed to.

Flies Kept in Dark Lose Traumatic Long-Term Memory

Fruit flies that were kept in the dark lost long-term memory of a traumatic stress they were exposed to. Scientist from Tokyo Metropolitan University also discovered the specific molecular mechanism that affected long-term memory in these flies. These findings may lead to novel treatments in humans in terms of treating, or even erasing traumatic memories.

Traumatic Memory is Crippling

Long-term memory is consolidated in our brain, whereby new proteins are made and neuronal circuits being modified. However, if the long-term memory is of a traumatic event, this usually have a devastating effect on individuals, especially those suffering from post-traumatic stress disorder (PTSD). How memory works in the brain and the mechanism involved are still not a clear process for scientists.

Male Fruit Flies Traumatized by Rejection

In this study, the researchers from Tokyo Metropolitan University studied Drosophila fruit flies. They looked at how light exposure affects the memory of these diurnal fruit flies. They used what is called the courtship conditioning paradigm to create traumatic memory in male fruit flies. In this paradigm, male flies are exposed to female flies which have already mated. The mated female flies will be unreceptive and inflict a kind of traumatic stress on the male flies. This memory is so traumatic that these male flies will not attempt to court female flies again, even if the females were unmated.

Darkness Erased Traumatic Memory

However, if these conditioned male flies are kept in the dark for two or more days, they actually lose the long-term memory of the traumatic stress. These conditioned male flies will again court female flies as if they lost the memory of being “rejected” by the female flies.

Mechanism That Affects Long-Term Memory

The researchers looked at a protein called Pigment-dispersing factor (Pdf), known to be expressed in response to light. They found Pdf that regulated the transcription of a protein called the cAMP response element-binding protein (CREB). This protein is found in the part of insect brains called the mushroom bodies. Mushroom bodies are thoughts to play a role in memory and learning in insects. This is the first time this connection between Pdf and CREB is found. The researchers have thus found the specific molecular mechanism by which light affects the retention of long-term memory in fruit flies.

The study was published in the journal JNeurosci: The Journal of Neuroscience.

This study showed that environmental factors can significantly alter memories. Further studies may give insights into how to apply these findings to help people who suffer from traumatic memories. Treatments may be possible to reduce or even erase these traumatic memories.

The team found that flies kept in the dark were unable to maintain a pre-established long-term memory. This was due to the lack of Protein-dispersing factor (Pdf) release, which in turn results in no cAMP response element-binding protein (CREB) being produced in the memory center of the fly brain. (Photo: Tokyo Metropolitan University )