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Cognitive Psychology PSYC231 Cognition and the Brain: Basic Principles 2 Dr. Jan Lauwereyns, EA619, ext. 5042
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Broca: Production, Syntax Wernicke: Comprehension, Meaning
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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.
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Techniques for Studying the Physiology of Cognition
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Electrical recording techniques
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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”
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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
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Invasive techniques Electrode in the brain
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Deep-brain stimulation in patients with Parkinson’s disease
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Self-stimulation of subthalamic nucleus (in the basal ganglia): Patients can move their arms and legs again
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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
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Neural robotics: Miguel Nicolelis
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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…
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Positron Emission Tomography (PET) Inject radioactively tagged substance (e.g., O 2, glucose) Map the uptake of the substance (photocells)
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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)
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functional Magnetic Resonance Imaging (fMRI) Map rates of O 2 uptake –Loss of O 2 causes magnetic changes to blood –Non-invasive
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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)
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But: –Noise: even small movements (eye blink) –Requires averaging across samples –Problems with inter-individual differences –Preferably multiple samples from the same S
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Doesn’t come cheap…
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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
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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
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