introduction to vision.docx

September 26 , 2012 Psych 2E03: Sensory Processes Introduction to Vision Principle of brainstem auditory evoked response - far field responses (<25ms): brain stem auditory evoked response, 5 waves - near-field responses (>25ms): cortex later wave - anything wrong in the conduction pathway will affect near responses Brain-stem Auditory Evoked Responses - initial 2 waves: auditory nerve, far field - 3-5: brain stem, far field - 6: cortex, near field Typical Evoked responses to a meaningful stimulus - P1, P2, P3 etc. = 1 , 2 , 3 , etc. positive waves - N1, N2 = 1 2 negative waves - Note: the polarity may vary with reference to the electrode position. It is not important. Latency and amplitude of the peaks are important P300 a marker for Schizophrenia and Bipolar disorder - P300 latencies: patients>relatives>control, takes a longer time then it shouls, latency prolonged and amplitude are reduced - P300 amplitudes: contrl>relatives> patients - A similar trend has been even more consistently reported in schizophrenia literature N170, N250, P300-600 - shown picture of a face, no matter whose face it is you will see N170 - if face belongs to face you’re familiar with N170 and N250 - name of face, depending on how familiar you are P300-600, simpler more P300, complex P600, probably will also get the responses at N170 and N250 What type of ERp may seeing this conflicting/counter-intuitive picture evoke - N600, long latency, longer processing time - Depending on how long the latency is we are using more complex processes - Conflict: longer latency Skin conductance test - P300/N600 - Skin detection signal to test Functional MRI (fMRI)(MRI=Magnetic resonance imaging) - MRI detects levels of deoxyhemoglobin in the blood and bold images (blod- oxygen-level dependant images)