Why blood flow its an indirect measure of brain activityactive areas need more

Why blood flow its an indirect measure of brain

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Why blood flow: it’s an indirect measure of brain activity—active areas need more oxygen and glucose, hence more blood Good for where, not for when PET—Positron Emission Tomography: radioactive tracer injected into bloodstream; ex) 2DG, similar to glucose; travels through bloodstream and accumulates in active areas consuming glucose; the tracer emits radiation, which is measured and the info is used to create a computer image fMRI—functional Magnetic Resonance Imaging: tracks oxygen consumption to monitor brain activity; oxygenated blood has different magnetic properties than deoxygenated blood; subtractive method used
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- Caution: have to be careful about Type 1 error; False positives, ‘noise’ in the system Thousands or millions of comparisons made, increasing likelihood of false positives Need to do statistical corrections Split Brains - Condition in which the corpus callosum is severed - Effects are more minor than one would think Can still walk and engage in typical motor functions - Optic Chiasm: the anatomical cross-over point at the base of the brain for the optic nerves - Right side- can name the object; left side- can draw or point to the object. 18-10-09 Lecture 9 Chapter 5: Body Rhythms and Mental States What is Consciousness? - Awareness of objects, events, and activities in the world and in your own body and brain. Biological Rhythms - Regular functions in biological systems causing variations in body temperature, blood pressure, hormonal secretions, etc. - Cycles can occur over different time periods (ex. Daily sleep-wake cycle, 28-day menstrual cycle; seasonal changes; changes throughout the day in alertness, energy, hunger, etc.) - Circadian rhythms: 24-hour cycles Why do we have Circadian Rhythms? - Adaptation to earth’s rotation and the changes this causes in light level, temperature, etc. - Entrainment: the rhythm of physiological or behavioral events becomes matched to the environmental rhythm. Study of Biological Rhythms - Chronobiology: the study of biological rhythms - Jurgen Aschoff (1913-1998)- one of the founders of chronobiology - Experiments: Underground bunkers Lack of external cues (‘Zeitgebers’, or ‘time givers’) - Findings: Humans have endogenous circadian oscillators that become synchronized with external cues (biological clocks) Non-light cues can also entrain (ex. Regular meals) No time cues = lengthening/shortening of cycle
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Where is this Biological Clock? - The hypothalamus; mainly in the suprachiasmatic nucleus - Suprachiasmatic Nucleus (SCN): SCN responds to changes in light and dark, detected by cells in the eyes Regulates levels of some NTs and hormones, like melatonin (secreted by the pineal gland) - Melatonin levels in humans: Increases in the evening Peaks in the middle of the night Falls and returns to normal in the morning and stays steady throughout the day Getting ‘Out of Sync’ - Internal desynchronization : body rhythms not in phase with one another - Causes: Irregular sleep patterns Travelling - Effects:
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