PSYC20006 Lecture Notes - Lecture 1: Transcranial Magnetic Stimulation, Parahippocampal Gyrus, Phineas Gage
12 Jun 2018
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Lecture 1 - Tuesday 28 February 2017
PSYC20006 - BIOLOGICAL PSYCHOLOGY
LECTURE 1
TRANSCRANIAL MAGNETIC STIMULATION (TMS) 1
CHAPTER
TMS
•Using TMS for Biological Psychology research
•The injection of “neural noise” approach using single-pulse TMS (Amassian et al., 1989;
Amassian et al., 1993)
•The “virtual lesion” approach using repetitive TMS
•The “probing excitability” approach using single-pulse TMS (Eisenegger et al., 2007; Bode et
al., 2007)
•Probing information transfer using the “paired-pulse approach” (Fitzgerald et al., 2001;
Pascual-Leone & Walsh, 2001)
•Transcranial Magnetic Stimulation is a “non-invasive” technique to create virtual cortical
“lesions”.
•Studies on patients with real lesions have informed cognitive science for a long time as they allow
studying what patients can’t do anymore.
•E.g., Phineas Gage (1823-1860), an American railroad construction worker, who suffered a
serious injury by an iron rod piercing his head and frontal cortex.
•This led to severe changes in his personality.
•Temporary and reversible, localised lesions (at a far smaller scale) could allow for better
understanding the function of specific brain regions.
WHY CAN’T WE ALWAYS USE PATIENTS?
•E.g., Removing most parts of his hippocampus, parahippocampal gyrus and
amygdala in famous patient H.M. led to severe anterograde amnesia.
•In the same way, lesions in Broca and Wernicke areas have been linked to
impairments of speech production and language comprehension,
respectively.
•However, there might not be enough patients with circumscribed lesions to
study all cognitive functions.
•Lesions in single, specialised areas are rare - Recovery and brain plasticity
might compensate for lesions over time è patients might become quite
‘special’ over time.
HOW DOES TMS WORK?
•TMS can be applied externally, using a coil placed on the scalp that produces a rapidly changing
magnetic field to induce electrical currents in the brain.
•These currents can depolarise neurons in a small, circumscribed area of cortex.
•TMS-induced current causes neurons to fire randomly, increasing the level of neural noise,
thereby masking the neurons that are firing correctly.
•Fritsch & Hitzig (1870) were the first to electrically stimulate the cortex of animals.
•D’Arsonval (1896) discovered that the magnetic stimulation of the visual cortex can elicit
“phosphenes”.
•Magnusson & Stevens (1911) developed the first “head coil” covering the entire head.
