Where are the images and ideas from dreams located in the brain, and is there any way to capture them?

—Derek Meier, Chicago

Mark A. W. Andrews, director and professor of physiology at Lake Erie College of Osteopathic Medicine at Seton Hill University in Greensburg, Pa., replies:

THE ANSWER to the latter part of your question is simply, “No.” Although we have technology that can measure general brain activity, we have no method for assessing or capturing our individual thoughts and dreams.

To evaluate our future potential to do so, it is important to understand which areas of the brain are associated with dreaming. Most dreams occur during the stage of sleep when slumberers start making rapid eye movements, called REM sleep. The imagery a sleeping brain concocts appears to originate in the reticular formation (RF), a diffuse, intricate collection of more than 100 networks of neurons arranged throughout the brain. The RF helps to regulate essential processes, including waking and sleeping cycles and cardiac function. The RF’s neural networks link up with the cerebral cortex, which regulates how we think and remember. But the widespread connections between the RF and the rest of

the brain make dreams difficult to study.

In addition to the RF, dreaming involves the limbic system, often referred to as the emotional brain. Areas of the visual cortex responsible for recognizing complex visual scenes as well as the anterior cingulate gyrus, which governs attention and motivation, are also active during REM sleep. Interestingly, regions of the frontal cortex involved in thought

and judgment while we are awake remain relatively calm throughout REM sleep, possibly accounting for the bizarre and illogical content of some dreams. Currently scientists are able to probe human brain activity in several ways. We can record brain waves using EEG. With PET scans and functional MRI, we can observe fluctuations in brain activity by measuring changes in blood flow and levels of nutrients.

These established techniques are not powerful enough to document dreams, but a newer method may enable a breakthrough. Recently neuroscientists have implanted single electrodes in the cortex to record the activity of single neurons believed to be associated with a single thought or image. One day such implanted electrodes might let us log and

play back our thoughts and dreams.

How much can the brain recover from years of excessive alcohol consumption?

—Paul Howlen, London

Richard Ridderinkhof, professor of neurocognitive development and aging at the University of Amsterdam, answers:

Evidence shows that heavy alcohol use modifies the structure and physiology of the brain, although the extent of recovery after years of abstinence is unclear.

Recent neuroimaging studies have revealed that chronic alcoholism can damage the cerebellum, which plays an important role in regulating motor control, attention and language. It can also cause the prefrontal cortex to shrink and degrade, potentially impairing decision-making skills and social behavior. Studies have also found damage in the white matter of the brain, which connects these regions.

The question remains, however, whether such extensive damage can be reversed after abstaining from alcohol. Researchers have studied the effects of abstinence on the brains of alcohol-dependent individuals by comparing subjects recovering from years of alcohol abuse with those who do not drink or drink minimally. Scientists have also investigated changes in brain volume in initial versus sustained abstinence in one set of subjects.

Several of these studies have shown that years of abstaining from booze can allow brain regions to return to their original volume and can repair neural connections across different regions. Much of this restoration occurs in the system most adversely affected by chronic alcoholism—the frontocerebellar circuitry, which regulates decision making, reasoning and problem solving.

Other reports, however, have found sustained injury in certain areas. Some former alcohol abusers show permanent damage to the hippocampus, a brain region that regulates long-term memory and spatial navigation, and only partial resolution of lesions on the white matter.

Although the effects of abstinence on the alcohol-abused brain vary, it appears that we display at least some ability to recover from the effects of excessive drinking. Future neuroimaging studies should clarify the full extent and potential for recuperation.