cognitive psychology psyc231 cognition and the brain: basic principles 2 dr. jan lauwereyns, ea619,...
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Cognitive PsychologyPSYC231
Cognition and the Brain:
Basic Principles 2
Dr. Jan Lauwereyns, EA619, ext. 5042
Broca:Production,Syntax
Wernicke:Comprehension,Meaning
Figure 2.22 (p. 46)(a) When a monkey is looking at the X and is not paying attention to the flashing light that is off to the side, a neuron in the cortex fires slowly; (b) when the monkey pays attention to the light (while still looking at the X) firing of the neuron increases.
Techniques for Studying the Physiology of Cognition
Electrical recording techniques
Human electrophysiology
• Electro-encephalo-graphy (E.E.G.): e.g., used for detecting different sleep phases
• Recording electrical signal from the scalp• Faint, noisy• Moderate spatial resolution, but very accurate
temporal resolution (ms)• Can be used for cognitive experiments: ERP
– Averaging– Relating to events: “Event-Related Potential”
Less popular now, but…
• ERP research was very popular in the 80s and early 90s, now losing momentum
• Related technique of MEG (magneto-encephalo-graphy), better spatial resolution but too expensive
Invasive techniques
• Electrode in the brain
Deep-brain stimulation in patients with Parkinson’s disease
Self-stimulation of subthalamic nucleus (in the basal ganglia): Patients can move
their arms and legs again
Animal models
• Single-unit studies, recording electrical discharges of individual neurons
• Cat (Hubel & Wiesel)• Monkey• Rat• Correlate neuronal activity with task events in
simple behavioural paradigms• Best possible temporal and spatial resolution• But: cost, external validity• Well defined, hypothesis driven
Neural robotics: Miguel Nicolelis
Functional imaging studies
• Functional imaging: record brain activity during task performance
• As opposed to Structural imaging, measuring tissue density only (for diagnostic purposes)
• Put S in scanner, the whole brain lights up• Data are only as good as the logic of the
experiment – this is where Psychology steps in• Subtraction method with task components• Let’s look at “spec sheet” of PET and fMRI…
Positron Emission Tomography (PET)
• Inject radioactively tagged substance (e.g., O2, glucose)
• Map the uptake of the substance (photocells)
Pro’s and con’s of PET
• Not only cerebral blood flow:– Example: Koepp et al,
1998, Nature: Measure dopamine release while participants play a video game (reduced binding in ventral striatum)
• Drawbacks: – involves radiation– poor temporal resolution
(tens of seconds, minutes)
functional Magnetic Resonance Imaging (fMRI)
• Map rates of O2 uptake
– Loss of O2 causes magnetic changes to blood
– Non-invasive
Most important pro:– Temporal resolution better– With the most powerful scanners it is possible to map
changes in blood flow in a few seconds (event fMRI)
But:
– Noise: even small movements (eye blink)– Requires averaging across samples– Problems with inter-individual differences– Preferably multiple samples from the same S
Doesn’t come cheap…
Transcranial magnetic stimulation
• Deliver a fairly localized magnetic current while participants perform a task
• Not really “invasive” in the sense that nothing mechanical is put in the brain
• Long-term effects not known
Lesion or subtraction method(Neuropsychology)
• Dr. Carolyn Wilshire• Patients with specific brain
damage• Compared with normals• How do the patients perform differently in
behavioral/cognitive tests?• Single or double dissociation (broken TVs)
• No control over size and site of damage• Animal models