Primitive people had a variety of answers: Human behavior is governed by spirits, magical spells, the eating of particular parts of certain animals, and so on. The semi primitive Homeric Greeks were only a little more sophisticated; they thought the gods put ideas and impulses directly into their minds. But the Greek philosophers of the sixth and fifth centuries B.C. made a historic leap: they attributed human behavior to internal forces bodily feeling and thoughts (Hunt, 2007, p.553).

Emotion in developmental psychology has had a rather checkered history. Although emotions were a cornerstone of psychoanalytic theories of adult psychopathology, for a time in academic psychology, the study of emotions was almost isolated from feelings. Feelings have increasingly become legitimate foci of study. Aside from clinical studies that have linked adult psychopathology to intense emotional experiences in early infancy, we have very few data on the relations between early emotions and later adaptation (Yarrow, 1979).

The James-Lange Theory of Emotion was one of the first theories to attempt to explain the role of physiological changes in emotion. James defined emotion as the feeling of bodily changes which follow the perception of an exciting event. This definition implied that the emotion felt was the reverberation of bodily changes on the cortex. For James, then, emotion would seem to accompany the behavioral responses to an exciting event. Neither in his account of emotion as a secondary feeling nor in his illustration of his theory in common sense terms did James equate emotion with the initial reflex and/or learned reaction of an organism to an exciting event but rather with the afferent impulses related to the following initial central and peripheral discharge and the manifestation of these verbal and behavioral responses (Fehr & Stern, 1970).

The Cannon-Bard Theory of Emotions can be summarized as the sensory impulses in the thalamic region that are received, regrouped and redistributed either to higher levels or to neighboring motor centers where they performed emotional-response mechanisms are ready for prompt discharge resulting in reflex-like muscular and visceral activities. “The incoming impulses on their way in may directly excite thalamic processes, or they may go on to the cortex and there arouse conditioned responses which in turn excite thalamic processes and in either case the peculiar quality of emotion is assumed to be added to simple sensation when the thalamic processes are aroused. Therefore the experience of emotion and its visceral symptoms are parallel effects of the thalamic messages (Newman, 1936).

The Schachter –Singer Theory of Emotion states that an emotional state is the result of the interaction between two components: physiological arousal and cognition about the arousal situation. Physiological arousal, which is conceptualized as being diffuse in nature, determines which emotion, if any will be experienced. In Schachter’s theory both cognition and arousal are considered necessary for the occurrence of an emotional state; if either is missing, no emotion will be experienced (Reisenzein, 1983).

There is no longer any doubt that images affect physical reactions directly and indirectly. We now observe with an MRI that some images have impact in the areas of the brain that are impacted by awareness of an object. As Francisco Varela describes it "In some kinds of visual imagery the visual cortex is indeed very active, as if you were seeing the image." Check out Destructive Emotions by Daniel Goleman for the latest on the neuroscience of emotion and neurophenomenology.

The idea that emotions are controlled by a particular area of the brain is in disfavor these days. It is obviously not a complete explanation. It was a popular theory until the mid 80's, especially after Wilder Penfield's contributions. Penfield found he could elicit an entire range of emotions when he stimulated the limbic cortex over the amygdala. He was operating on conscious patients during open-brain surgery to stop uncontrollable epilepsy. Later, Elmer Green at Mayo Clinic demonstrated with biofeedback that "Every change in the physiological state is accompanied by an appropriate change in the mental emotional state, conscious or unconscious and conversely, every change in the mental emotional state, conscious or unconscious, is accompanied by an appropriate change in the physiological state."

Candace Pert went on to conclude that "The body is the unconscious mind!" Kandell and associates at Columbia proved that "biochemical change wrought at the receptor level is the molecular basis of memory." And, Paul Ekman demonstrated that each emotion experienced is expressed in facial features. Now we have other scientists contributing to the mix.

Antonio Damasio, probably the world's outstanding neurologist, published The feeling of what happens: Body and emotion in the making of consciousness at the turn of the 21st century. He makes clear that emotions are essential to our survival and describes in a paradigm shifting text, the nature of relationship between consciousness and the biological source of our sense of self. I believe you would find his presentation, aligning theory with life, fascinating. "Drawing on his fluent understanding of the workings of the brain and of evolution, Damasio conjectures the existence of two levels of consciousness: a core consciousness and self, and an extended consciousness and an autobiographical self. He then postulates the crucial roles emotion, memory, and "wordless storytelling" plays in our existence. At its base, Damasio concludes, consciousness means that we feel both pain and pleasure; in its higher manifestations, it enables us to transcend and articulate these feelings through language, creativity, and conscience."

LeDoux's Emotional Brain is a meaningful introduction to the brain mechanisms behind emotion. But to LeDoux the subtitle says it all The Mysterious Underpinnings of Emotional Life. I included his website because he has you enter through the amygdala, the heart of it all. :) His contributions support your question about the unconscious. Anticipatory fear has often been caused by unknowns and points to unconscious determinants.