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PSYC 2230
Frank Marchese

thPSYC2230A Lecture May 15 2014 Chapter 3 Physiological Mechanisms of Arousal I Arousal theory how does the organism become activated Motivation may be viewed on a continuum of behavioural activation Continuum ranges from low levels of arousal coma and sleep to high levels of arousal Fig 31 p62 a Inverted U Function behaviours most efficient at optimal level of arousal YerkesDodson Law a relationship between level of arousal and efficient performance Fig 32 p 63 b Different tasks are related to arousal level and performance higher arousal for simple habitual tasks and lower arousal for complex cognitive task Too much arousal reduces performance c Emotion and motivation related to activation of nervous system There are structures that come into play in emotion and motivation egSeparating the medulla from the spinal cord and organism goes through normal sleepwake cycle encephala isole preparation p 6365Separation of the colliculi from the brainstem the organism is deprived of crucial structures medulla pons and reticular activating systemRAS and organism sleeps constantly cerveau isole preparation D RAS nerve cells in central core of brain stem Fig 35 p65 Moruzzi and Magoun 1949 stimulated RAS electrically Changes in electrical activity of cortex were noted in EEGbrain wave recordingsSynchronousAlpha wave activity related to a related awake organism High slow wavesDesynchronousBeta wave activity related to alter attentive aroused organism Low fast waves RAS receives sensory input from external sensory organs and internal organs and muscles Lindsley 1951 cut all structures around the RAS and sleep is preserved He cut the RAS and organism slept constantly RAS send fibers to cortex RAS arouses cortex Cortex can inhibit RAS activation also excite RASII Hebbs Arousal Theory Sensory information serves two functions a To provide information i a cue function and ii an arousal function If cortex is not aroused cue function has no effect b Sensory stimuli sent to cortex and RAS The stimulus effect at RAS level is to activatetone upthe cortex so that stimulus information coming from the thalamus canbe processed Motivation for Hebb is activation of the cortex via the thalamus and RAS c Cortex sends fivers down to RAS and stimulates it when internal and stimulation is low d Downstream connections from cortex to RAS may explain how thoughts images memories can activate and motivate behaviour While trying to sleep if RAS is activated it in turn activates the cortex and sleep becomes difficulttossing and turning Page 1 of 6
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