Neurological Basis for Placbeo effect*

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1 Placebo Effect* Occurs if patients given a placebo treatment will have a perceived or actual improvement in a medical condition a wide variety of things can be placebos and exhibit a placebo effect. Pharmacological substances administered through any means can act as placebos, including pills, creams, inhalants, and injections. Medical devices such as ultrasound can act as placebos. Sham surgery and sham acupuncture, either with sham needles or on fake acupuncture points, have all exhibited placebo effects. Can a physician be a placebo?

2 Theories* One theory behind the placebo effect is the subject-expectancy effect. When people already know what the result of taking a pill is supposed to be, they might unconsciously change their reaction to bring about that result, or simply report that result as the outcome even if it wasn't. Others believe that people who experience the placebo effect have become classically conditioned to expect relief when they take medication. In the case of people and placebos, the stimulus is the medicine (or what's perceived to be medicine) and the response is relief from their symptoms. The subject-expectancy effect and classical conditioning are pretty similar. In both, the patient has a built-in expectation of the outcome. Remember last week s discussion of the orbital frontal region and its role in reward evaluation and expectancy

3 Neurological Basis for Placbeo effect* In 2004 it was demonstrated that the placebo effect is related to endorphins, the brain's own natural pain relievers healthy subjects were given a painful but harmless injection in the jaw while their brains were scanned The subjects were then given what they thought was a pain reliever, and all of them experienced a decrease in their pain levels after receiving the placebo. they also showed a change in brain activity in the brain's opioid receptors (which receive endorphins) and its areas related to processing and responding to pain. That is why the naloxone mentioned before has an effect The expectation of pain relief caused the brain's pain relief system to activate.

4 Neurological Basis for Placbeo effect* Examples of studies trying to go beyond subjective verbal reports. In a 2002 study two groups of patients received experimental antidepressants, while the third was given a placebo. After several weeks of taking pills, each group's brain activity was measured using EEG. The patients who had been on the placebo and reported a positive effect showed a greater increase of brain activity than those who had responded well to the drug. That activity was also centered in a different area of the brain, the prefrontal cortex suggesting that the brain isn't being "fooled" by a placebo after all -- it actually responds in a different way to a drug and a placebo. (orbital frontal and expectancy of the value of a rewardlast week in context of wine tasting)

5 The ultimate brain fooling- or Is the brain fooling us? Seeing* We are so familiar with seeing - why is there a problem to be solved? - well, because The eyes give us tiny distorted, upside down images that activate chains of electrical impulses to brain and somehow we see solid objects in surrounding space. In some respects even better than the external reality from which it was created The photons s energy in light has become information. These particles of light alter the delicate molecular structure of the receptors in the retina starting the electrical information (colour and form) to the brain Avoid the temptation of thinking the eye produces a picture in the brain - as this suggests we need an internal eye to see it and another eye to see that picture etc. So different from a photograph

6 Brain reconstruction* Rather than pictures in the brain -Hubel & Weisel -nobel prize receptive fields from different parts of visual field - cells respond not to dots of light (like visual pointillism of Seurat A Sunday Afternoon on the Island of La Grande Jatt) but rather edges, contrast This is what the world looks like in the early processing in the visual cortex- before it is seen - more like Cézanne (Forest with the rock caves above the Château Noir)

7 The importance of organization of sensory data - contribution of Gestalt theories of Perception* Gestalt psychology attempts to understand psychological phenomena by viewing them as organised and structured wholes rather than the sum of their constituent parts Falsely believed in isomorphism (electrical fields in the brain that copied the form of perceived objects) But they did provide the important emphasis on the brain trying to organize sensory data into objectsalmost like mental shortcuts for solving problems Real world example - grouping by colour (light grey under preferences etc)

8 Perceptual constancy* tendency see familiar objects as having standard shape, size, colour, or location regardless of changes in the angle of perspective, distance, or lighting. The impression tends to conform to the object as it is or is assumed to be, rather than to the actual stimulus. Perceptual constancy is responsible for the ability to identify objects under various conditions, which seem to be "taken into account" during a process of mental reconstitution of the known image.

9 After image* An afterimage is an optical illusion that refers to an image continuing to appear in one's vision after the exposure to the original image has ceased. E.g. bright glow that seems to float before one's eyes after looking into a light source for a few seconds. Afterimages come in two forms,a positive (retaining original color) and a negative- in the latter one views complementary colours negative afterimages are a retinal phenomenon

10 Colour perception* 3 types of Cones in retina different wavelengths cause chemical changes in different cones. Opponent colours: Red-green; blue- yellow; black-white. Essentially when a wavelength of one of the pairs stimulates the appropriate cone, perception arises from a chemical reaction in one direction, the perception of the other member of the pair is antagonistic.