I feel weird about posting this, as things are don’t feel like things are actually real. But I have been offered an Assistant Professor position at an awesome university, in an awesome psychology department, which will support my research. I’m just terrified that’s all! It’s another international relocation (back to the motherland), another fight for funding, but… a continuing (tenured) position. Woah.
Other things… I’m off to Denver in a week to present at the Society for the Study of Ingestive Behavior, then to Toronto for some down time with one of my BFF’s.
My lab is turning out some interesting research, so I don’t feel too bad abandoning them for a couple of weeks. Plus I’ve been setting up my beautiful new touchscreens and can’t wait to smash out some pilot data for future grants in the UK before I relocate.
For the last year my lab have been studying the effects of dietary sugar on cognition. We have found some pretty exciting results, and some dramatic cognitive deficits. However, I will admit that I have been somewhat of a “Do as I say, don’t do as I do” researcher. I work out regularly, and eat pretty well (by the looks of my bank account, I spend a small fortune on food each week). However, I’ve decided that I should clean up my diet a bit more. It’s hard, because academia is demanding and stressful, and I find it hard to contain my emotions often when my job involves something like 80+ hours of my life a week.
In general, I eat a lot of fruit, I like smoothies, have a weakness for ginger beer and I deep love of granola for breakfast. I don’t have sugar in my tea or coffee, and don’t bake anything requiring sugar ever. However, I was genuinely horrified to find out that a small bottle of ginger beer has 45g of sugar in it, which is basically double the WHO’s recommended daily intake of 25g for an adult. Sugar isn’t evil by itself. Our bodies need glucose to function and power our cells. However, when I worked out that I was consuming probably 2 to 3 times my recommended amount per day, whilst wondering why I’m still getting spots in my thirties and never losing weight despite going to the gym 3 to 4 times a week, I probably should address the cold hard facts.
To start with, I’m avoiding breakfast cereal in favour of an omelette. This has been easy, and actually takes less time to prepare than cereal, and I haven’t been hungry by 10am as I thought I’d be. I’m not eating fruit as a snack (other than blueberries and raspberries – which are low in sugar) – swapping instead for nuts, and no more fruit juices – instead I’m drinking water. It’s been a week now, I lapsed on Friday night when I drank whiskey and ginger ale, but other than that I’ve been pretty good, I feel a lot less bloated, and my skin hasn’t had a random grant writing breakout. GO ME!
Throughout our lives we have multitudes of experiences that shape how we then behave in the world. Some of these lessons are learnt rapidly, such as why we shouldn’t put our hand on a hot pan on the stove. Other, more autobiographical experiences can be stored and recalled explicitly as our memories.
These memories can be recalled and described, such as what we did for certain birthdays, or experiences from our holidays. We can also learn to perform certain actions and behaviours that are totally new to us – for example, learning to ride a bike and drive a car. These actions can be thought of as muscle memories, or “non-declarative” memory.
Forgotten – but not gone
However, it seems we don’t retain all of our memories and experiences. There are times in your life when you find yourself pondering basic general knowledge questions and wonder where these gaps in information have sprung from. Despite all those hours of study at school, many of us can’t remember how to say “two beers please” in Spanish when we are on holiday, or how to work out a specific angle of a triangle, despite being proficient in these skills some years ago.
Why is it that we lose the information that we have learnt? Is it still there but inaccessible, or is it gone forever?
Short-term memory has a limited capacity (about seven items) and duration (15-30 seconds). There are two ways in which capacity is tested, one being span, the other being recency effect. Miller’s (1956) “magic” number 7 (plus or minus two) provides evidence for the capacity of short-term memory.
Most adults can store between five and nine items in their short-term memory. The duration of short-term memory seems to be between 15 and 30 seconds, according to the researchers Atkinson and Shiffrin (1971). After this time the information decays and fades away unless repeated verbally (rehearsal), which keeps the information in short-term memory. Then information that survives in short-term memory can pass into long-term memory.
So a piece of information can be learnt through practice, making it easy to be recalled in a test a few days later. However, the strength of a memory at the time is misleading when it comes to predicting whether we will remember it in the future.
‘Every time I learn something new, it pushes some old stuff out of my brain’ – Homer Simpson
He might not be too wide of the mark, since new memories can block the recall of older memories. Rev. Xanatos Satanicos Bombasticos, CC BY
This suggests that acquiring new memories interferes with previously stored information, and indicates that the human brain has a limit to how much information can be stored. We do not know the capacity of the brain, or the full capacity of our memory.
Theoretically, the capacity of long-term memory could be unlimited, the main constraint on recall being accessibility rather than availability. The brain contains a vast number of cells that are proposed to work together as a network to encode memories and store them.
There is a theory of forgetting in cognitive psychology that suggests the encoding of new memories can cause interference with recall of memories previously encoded (known as retro-active interference). This interference is proposed to prevent the recall of a specific memory by competing for expression. So a new memory blocks the recall of an older memory.
Retrieval failure theory
Retrieval failure is where the information is in long-term memory, but cannot be accessed. When we form a memory we also learn about the situation and environment. These can form retrieval cues.
These cues prompt the retrieval of a memory and without them the information may not be accessible. These cues act as a hint or clue that can assist memory retrieval.
Forgetting is greatest when the situation where the information needs to be recalled is very different from when the information was encoded. This can mean that information that we have learnt in a school environment may not be as easily retrieved when in the “real world”. So, if you had learnt the Spanish phrase for “two beers please” in a bar, you would be able to recall it easily when in the same environment again.
These retrieval cues can be important for people suffering with memory impairments caused by neurodegenerative diseases such as Alzheimer’s disease.
Being unable to recall information is very upsetting. This can, in turn, cause a change in the internal (emotional) state of the person, which makes recalling a memory even more difficult. However, by providing retrieval cues such as old photographs, or returning to a childhood home, a flood of lost memories can be triggered.
So, here’s some hot off the press research that I did…
We exposed rats to a high fat / high sugar “junk food” diet or a standard diet in the control animals and then tested their memories on a task known as trace conditioning which allowed us to determine how different memory systems were functioning – the hippocampus and the amygdala. In this task the rats were exposed to 2 environments, which differed in smell, appearance and size. In one of these environments the rats were exposed to a flashing light signal, and 30 seconds after it’s offset, they received a static shock. So the rats had to learn about 2 things, the flashing light (Conditioned Stimulus) and the environment (context). We found a dissociation in what each group of rats remembered, the standard (healthy) diet rats learned about the environment, which relies on the hippocampus, but the junk food diet consuming rats learned about the flashing light, which does not require the hippocampus, indicating dysfunction of this memory structure.
We then analysed the molecular components of hippocampal tissue of the rats and found a reduction in the neuroplasticity associated protein Reelin in the junk food fed rats. Reelin is important in the developing brain and the adult brain in the arrangement of synapses that allow neurons to connect to each other to form new memories, a process called Long Term Potentiation. It has been implicated in Alzheimer’s disease, schizophrenia and autism, so the fact that junk food reduces it’s expression is important, as these diets may cause long term changes in both adult and developing brains.
I love my job. I love that I can be autonomous and enthusiastic and inspired.
I love that I can travel around the world and talk to people who are probably just as crazy as me with the same passion and drive.
I love that I can think of something I want to test and I can have the means to put it into action..
I love that I get to write for a living. That I get to teach curious minds. That I get to work when I want.
Today is a good day, things are going well. Some days aren’t so good, some days I get shouted at and made to feel small, useless and insignificant. When I all want to do is curl up in a ball and wish I’d made different decisions. I’m writing the good things down to remind me that when my job makes me sad that it’s not all shit.