Research Methods of Biopsychology

Research Methods of Biopsychology


It’s Professor Dave, let’s check out some
research. Now that we have some of the basics down in
terms of how the brain works, it’s time to start diving into some of the specific
capabilities of the brain. How do we learn? What are emotions? These are bold questions with fascinating
answers, but before we get into all that, we have to talk a bit about how exactly scientists
come to know these things. What kinds of experiments are done to gather
information about the human brain? What kinds of instruments are used? Let’s take a moment to gather a basic vocabulary
and understanding of the research methods associated with biopsychological research. Given the dual nature of biopsychology, research
will focus on one of two things. Sometimes it is the nervous system that is
studied, when examining biological aspects of the brain, and sometimes it is human behavior
that is studied, when examining psychological aspects of human behavior. Starting with the first of these, how exactly
is it that we study the brain? Fortunately modern technology is powerful,
so we have many ways of visualizing the brain and documenting its activity. The 1970s saw the development of computed
tomography, which utilizes X-rays to produce what we commonly refer to as a CT scan. This revolutionized the field, as it was then
finally possible to get actual images of the brain inside a living person, and even three-dimensional
representations when many cross-sectional images are combined. But much more relevant to psychology was the
development of positron emission tomography, or PET. This utilizes a radioactive compound which
is injected into the neck and accumulates in active neurons, tracking cerebral bloodflow. In this way, PET allows for the visualization
of brain function. Analyzing the regions of the brain that show
activity while a person performs a specific task tells us what part or parts of the brain
are involved in the execution of that task. A related technique is called magnetic resonance
imaging, or MRI. This utilizes the way that hydrogen atoms
interact with a magnetic field to produce images. Of particular importance to biopsychology
is functional MRI, or fMRI, which identifies the regions of the brain experiencing increased
oxygen usage. We can refer to this as BOLD, or blood oxygen
level dependent imaging. This technique is very practical because it
provides both structural and functional information, all without injecting anything into the patient. There is also diffusion tensor imaging, or
DTI, which looks at the diffusion of water molecules as an indicator of white matter structure. With imaging in general, we should note the
difference between structural imaging and functional imaging. This is essentially the difference between
a photo and a video, since the first of these gives good resolution and allows us to zoom
in on specific areas, in order to get very specific data. By contrast, the latter allows us to see the
brain in motion, in order to get the bigger picture. That covers the primary brain imaging techniques,
so let’s move on to methods of recording psychophysiological data. The most familiar of these will be the electroencephalogram,
or EEG. This technique places electrodes on the scalp
in a non-invasive fashion to measure electrical brain activity that originates from the cortex
and conducts to the scalp. Thus, EEG is actually measuring voltage differences
between different scalp areas that result from underlying brain activity. The data appears as waveforms called brain
waves that look like this, and the thing that is very useful about this method is that different
states of consciousness will produce quite different and rather distinct waveforms, as
will different cognitive activities, brain disorders, and pharmacological manipulations. Looking at the following data, we can first
identify alpha waves. These are waves of a frequency of around eight
to thirteen hertz, which means cycles per second. Beta waves fall at around fourteen to thirty hertz. Theta waves fall at around four to seven hertz. And delta waves are those around four hertz or less. These are high-amplitude waves associated
with a state of deep sleep or being under anesthesia. With this technique, we can also identify
the perception of a stimulus when it happens. This is called a sensory evoked potential,
and in this case we can see the signal as being distinct from the background activity,
which we call the noise. If the noise is too great, it becomes more
difficult to distinguish such sensory evoked potentials from the noise. Methods such as signal averaging work to reduce
noise, by recording noise in absence of stimulus and mathematically removing it when the stimulus
is present. Other similar techniques also exist, like
magnetoencephalography, or MEG, which measures changes in magnetic fields at the scalp due
to changes in neural activity below. That covers the basics regarding non-invasive
techniques for studying the brain. Let’s take a look at a few that are quite
a bit more direct, meaning techniques where physical contact is made with the brain itself
in some way, typically on a laboratory animal like a rat. Stereotaxic surgery is a method in which an
experimental device, like an electrode, is implanted in the brain. If this electrode is placed somewhere in particular,
like the amygdala, it can then stimulate that area of the brain electrically, causing nearby
neurons to fire, often having very specific behavioral effects. This can give us information about that part
of the brain. And of course small sections of the brain
can be removed entirely, which produces similarly valuable information about brain function,
by examining how behavior changes in its absence. These kinds of lesion studies are responsible
for a lot of our knowledge regarding certain regions like the amygdala. The brain can also be manipulated chemically,
by administering drugs which have an impact on the levels of certain neurotransmitters. We can then measure the chemical activity
of the brain by a number of methods. One method involves using a molecule called
2-deoxyglucose that has been labelled with a radioactive isotope. This is similar enough to glucose that neurons
will absorb it, but because of the missing hydroxyl, it can’t be metabolized, so it
remains in the cell intact. So upon performing autoradiography, we can
see how the compound is distributed, and identify things like tumor cells, which will have a
higher glucose uptake. Cutting edge techniques include genetic engineering. We can produce organisms that overexpress
a particular gene, or even completely lack a particular gene, and thus lack the protein
that would be produced when that gene is expressed. We can therefore gain clarity on the role
of a particular protein in carrying out some physiological function. We can even perform gene replacement, where
a human gene is placed in a mouse so as to perform studies on certain disorders. Another important technique is called optogenetics,
where light-activated ion channels are inserted into neurons, and then blue or yellow light
can be used to excited or inhibit specific neurons. Innovations like these may hold the key to
better understanding a wide variety of neurological disorders. Lastly, a wide variety of experiments deal
not with brain function, but strictly with the behavior of an organism. There are many tests relating to brain damage
that work by examining the performance of specific tasks to see how they line up with expectation. This can include repeating sequences of digits,
arranging blocks, performing arithmetic, or improvising a story given a set of images. These may assess memory, spatial reasoning,
language skills, or other such things. With animals like rats, certain types of behavior
may be observed and measured. This can relate to aggressiveness, defensiveness,
sexual behavior, or the anxiety associated with navigating a maze. Later we will examine such studies in a more
rigorous and quantitative way, in order to contextualize certain information regarding
human psychology. But for now, with a basic knowledge of research
methods acquired, let’s move forward into the mind.

6 thoughts on “Research Methods of Biopsychology

  1. Hi Prof. Speaking of ECG and blood oxygen, what's your take on all those smart fitness watches that can take your ECG, heart rate, blood oxygen, and blood pressure? 🙂

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