The Amygdala: Central Component in the Neurological Pathway of Fear

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The Amygdala: Central Component in the Neurological Pathway of Fear

Fear produces physiological symptoms in a wide variety of animals.  Symptoms that are displayed when an animal is afraid include changes in autonomic activity for example changes in heart rate, blood pressure, or respiration.  Fear can also be inferred when an animal freezes or suddenly stops some ongoing behavior such as eating or interacting with other animals.  Also a change in simple reflexes or a change in facial expressions can also be a measure fear.  When an organism is afraid and at the onset of fear these symptoms seem to kick in almost automatically as well as simultaneously.  These highly correlated sets of responses seen during fear along with existing knowledge of the visual and auditory neural pathways suggest that stimuli elicited fear results from activation of a single area of the brain, the amygdala.  Research in primates show that projections to the amygdala from sensory regions of the cortex are important in the processing of emotional significant complex stimuli.  The results of which are then projected to a variety of target areas, which are critical for reacting accordingly to the stimulus. In order for the brain to recognize a fear causing stimulus information from the physical world must reach the brain along a specific pathway.  The pathways in this process are very similar in mammals and possibly all vertebrates, the stating point for the information is the senses.

Generally organisms have five distinct senses that act as information gathering tools which help us experience the world around us.  Our senses are extremely sensitive to the presence or change in an object or event. Our senses are also starting point in detecting the presence of a dangerous stimulus, or a stimulus that elicits fear.

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Optical information is received by the retina in the eye, within the retina are the nerve cells responsible for vision.  Impulse form these nerve cells then travel along the optic nerve to the visual thalamus.  Like the eye auditory information is also important in collecting information about the surrounding environment.  Sound waves reaching the ear are directed along the auditory canal into the tympanic membrane causing it to vibrate.  Vibration of the membrane causes the malleus to move back and forth.  This movement is passed on to the incus and stapes, the oval window is pushed in and out by ...

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