Researchers at Aalto University
and the University of Helsinki have succeeded for the first time ever in
affecting metacognition of a tactile working memory task by combining neural
pathway imaging and magnetic stimulation of the brain. Understanding brain
function might help in the development of new treatments for neuropsychiatric
illnesses in the future. By combining different brain research methods in a
versatile manner the researchers showed for the first time that transcranial
magnetic stimulation of the brain targeting the prefrontal cortex can improve a
test subject's ability to evaluate his or her performance in a tactile working
memory task. The ability of human subjects to monitor and control their own
cognitive processes is called metacognition. Metacognition is important for
people and in many neuropsychiatric illnesses, it is possible to recognize that
it has weakened. Transcranial magnetic stimulation refers to a method in which
the nerve cells of the brain are activated from outside the skull with the help
of a magnetic field. When used correctly the method is safe, and it is utilized
in procedures such as pinpointing the location of the primary motor cortex or
the speech area before brain surgery, and in the treatment of depression.
Taking part in the study as test
subjects were 14 healthy volunteers. They first underwent structural magnetic
resonance imaging (MRI) of the brain as well as a diffusion MRI that is
sensitive to the movement of water molecules in the brain. After the MRI, the
neural pathway connections between the primary somatosensory cortex and the
prefrontal cortex were determined for each individual. In the last part of the
study the test subjects completed working memory tasks in which they were asked
to keep in mind the characteristics of touch sensations from the fingertip and
to evaluate whether or not the touch stimulation that was just given was
similar to or different from the previous stimulus. During the test they were
given magnetic pulses to prefrontal cortex areas that had a neural pathway
connection to the part of the somatosensory cortex representing the index
finger. The test subjects also evaluated how certain they were about their
answers, on which basis calculations were made on how well a person's own
evaluation corresponded to the actual performance level. Magnetic stimulation
of the prefrontal cortex improved the test subjects' evaluation of their
performance, as they were able to assess more accurately if their answers had
been correct or incorrect.
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