Dead Salmon Social Perspective Taking

I read a paper today in the British Medical Journal presenting a compelling case for a randomized controlled trial to measure the effectiveness of parachute use as a medical intervention to prevent injury when jumping from an aeroplane (Smith & Pell, 2003).

Their reasoning was as follows:

  • No such trial has been done before
  • The perception of the success of the parachute is based solely on anecdote
  • Natural history studies show that free fall without does not always result in an adverse outcome, therefore there is not a 100% chance of mortality when not using a parachute
  • There is also not a 100% chance of survival when using a parachute
  • In all other medical interventions not having a randomized controlled trial would be unacceptable
  • Current industry trials are subject to selection and reporting bias, as well as conflicts of interest.

All in all, there seems to be plenty of reasons why a randomised controlled trial should be carried out, so as to determine more appropriately the efficacy of the parachute… Except for the fact it would be stupid. And that, leads me on to the post-mortem Atlantic salmon.

Bennet, Baird, Miller and Wolford (2009) compared fMRI results of a dead Atlantic Salmon to a group of normal participants in a social perspective taking task.

Image Credit: Bennet, Baird, Miller and Wolford, 2009

The blood-oxygen-level-dependent (BOLD) signal experienced a significant change during the presentation of stimuli compared to at rest (t(131) > 3.15, p(uncorrected) < 0.001). An 81mm3 cluster of active voxels was identified on the Salmons brain cavity, and another smaller cluster was identified in the Salmons dorsal spinal column.

After the same t-tests were done using Benjamimi-Hochberg and family-wise corrections, both with a type 1 error rating of 0.05, no significant results were found. With those error ratings adjusted to 0.25, there was still no brain activity in Mr Salmon.

So, we have two daft studies here, both of which tickled me. It shows the importance of the correct use of advanced (and less advanced) statistics. It’s important to have a firm grasp of the statistical techniques you are working with, or you can very easily end up with errors. This is especially so in the case of the Salmon where such a large number of fine readings are recorded that without an element of realism being considered during the analysis, obvious statistical errors pop up.

And of course, the same level of realism is required at the opposite end of the spectrum, when you ask if we really need experimental control at all. I am impressed with how statistics allow researchers in the social sciences to measure population variables with precision. I don’t even pretend for one minute that I have an in depth understanding of all the methods covered even at undergraduate level, but I have learnt the value of getting stats right. It is important to properly reflect on what statistical tools are genuinely necessary to answer the research question, and of the ones you choose to use, it is important to understand the intricate details.

Mechanisms of Memory

You will have seen a lot of cover on the science of education recently. Certainly that topic has been taking a lot of my time. However the other module I am enrolled in this semester is the ‘biological foundations of memory’.

I’ve been studying today the encoding of memories; specifically the electroencephalogram (EEP) readings for the encoding of memories. In this domain, the encoding of memories can be identified by a simple test. One presents images during a study phase, and then presents those images again, along with some novel ones, and asks participants if they have seen the said images before. By subtracting the brain waves recorded during the encoding phase (discriminated by the results of the test phase) of images subsequently recognised from those forgotten, one can measure the brain activity at given locations that represent memory encoding. Differences are discovered, as you might expect, but there’s more to it than that.

Another comparison, carried out by Yovel and Paller (2004) compared difference waves between familiar items, and recalled items, compared to items forgotten of the respective categories. Familiar items represent semantic memory (of meaning), whereas recalled items represent episodic memory. This is because as items are recalled, the participant remembers memorising them in the test phase. Indeed, as you can see below, there are some unique patterns for each category.

Yovel & Paller (2004)

Yovel & Paller (2004)

As far as our class goes, it is now mine to judge whether this represents a general unspecific mechanism or a number of specialised mechanisms.

Topographically, the recollection brain activity (which indicates episodic memory) completely encompasses the familiarity brain activity. Certainly the components of any episodic memory contain semantic components, so it is entirely logical that the components to process the episodic memories will activate semantic areas.

I don’t see any dissociations, however at the same time, these topographies span the entire brain, which is a bit big for one general mechanism. Based on that, I think the system breaks down into specific components which are actively connected during the episodic encoding experience.

So that is my synthesis. I don’t know what the most groundbreaking research might be saying about these concepts. It is likely that further experiments might be able to break this down and dissociate things further, however our lecturer is an active researcher in the field, so I imagine things are largely up to date. However I am going to leave matters at this conclusion for now.