Does diet really affect the brain? And other questions about the cranium, answered by a neurologist

The human brain can seem like a complete mystery, and thinking about how much it controls your life and sense of self is enough to make your head hurt. But science has slowly caught up with our natural curiosity, and let us in on the secrets to how it actually functions. So we called on Dr. Sara Mitchell, neurologist at Sunnybrook Hospital, to answer all our burning questions about the human brain.

What happens in the brain while we sleep, and why are dreams so hard to remember?

We spend about a third of our life sleeping, but while we're asleep our brain isn't offline. In fact, our brains are just as active when we're awake versus when we're asleep. Dr. Mitchell explained that here are two main phases of sleep that the brain cycles through — the first is called slow wave sleep (this is about ¾ of the average sleep-cycle sleep) and the second is called rapid eye movement sleep, REM sleep or dreaming sleep. This is when dreams happen and it accounts for about ¼ of a night's sleep. So, it really depends on which cycle you wake up from as to whether or not you're going to remember your dreams, so if you wake up during slow wave sleep you may not remember some of the dreams you had in REM.

Does brain activity change during sex?

Yes it does. Sexual pleasure is derived from an archaic part of the human brain called the Limbic system, which is the emotional centre of the brain. Dr. Mitchell explained that during sexual intercourse, lots of neurotransmitters and hormones are released and they circulate through the brain. One example is oxytocin, which she referred to as 'the cuddling hormone', and is known to give a feeling of closeness and intimacy after intercourse.

Do our brains ever stop growing?

The brain does stop growing, but it's later than most people think. A lot of maturation and development of the brain happens in infancy and in early adulthood, but as Dr. Mitchell pointed out, there is a part of the brain called the prefrontal cortex that really separates us from other species. It's the area that sits right behind the eyes and allows us to do things like high-order decision making, monitoring behaviour, complex thinking etc. and this particular area doesn't fully mature until you're in your mid-twenties to early thirties. So if you examine the decisions that young adults are making before they have a fully-formed prefrontal cortex, it's interesting to note that they still haven't plateaued in their development.

How do migraines affect the brain's function?

During a migraine, something called cortical spreads depression, which is actually a series of self-propagating waves of electro-physiological hyper-reactivity in the brain. Dr. Mitchell specified that it starts in the back part of the brain which is called the visual or occipital cortex, and for those of you familiar with migraines, this is why you can get that onset of aura, or changes in your visual field. This is also when the actual onset of the migraine begins. It then propagates forward toward the front part of the brain followed by a wave of inhibition of brain function. Ultimately what happens is that the pain-sensitive structures of the brain are the coverings and these are activated at the end — that's why migraine-sufferers often get a headache after the visual symptoms of a migraine. Thankfully, Dr. Mitchell assured us that migraines don't cause any harm to your brain; they just come with a lot of discomfort and symptoms.

Does diet really affect the brain?

Dr. Mitchell says it absolutely can. There is a close interplay between the way that we nourish our bodies and how our brain is functioning. The Mediterranean diet, for example, has been linked to staving off neurodegenerative diseases. She also notes that deficiencies in certain vitamins can cause issues. For instance, a diet lacking in Vitamin B12 could lead to memory troubles and other nervous system manifestations. Dr. Mitchell also pointed out that diet can actually be used to treat certain neurological conditions, such as the ketogenic diet as a possible treatment for certain forms of epilepsy. Simply put, having a complete and varied diet is the key to brain health.