Konorski's definitions:

• Emotion: The subjective experience that accompanies a drive.
• Mood: The subjective experience that accompanies an anti-drive.

  An anti-drive is the neural activity that opposes or inhibits a drive. It typically occurs when a drive has been fulfilled, and unlike a drive is not goal-oriented (i.e., behavior is not directed toward a goal object). For example, hunger is a drive, satiety is the hunger anti-drive; fear is a drive, relief is the fear anti-drive.

Theoretical approaches to the biology of emotion:

Cannon-Bard theory: Cannon & Bard, writing in the 1920's and 1930's, dismissed the James-Lange theory by focussing instead on the brain. A stimulus evokes activity in the thalamus (most neuroscientists today would look elsewhere), which causes both the subjective experience of emotion "upstream" in the cortex and the appropriate behavioral response via "downstream" lower brain structures. The bear is perceived, and the perception leads to the emotion and the response.

Classic studies in the psychobiology of emotion:

1. Visual agnosia (K-B called it "psychic blindness"): Monkeys could see, but were apparently blind to the meaning of what they saw. They could no longer identify objects visually.
2. Increased orality: All objects were placed in the mouth (perhaps appropriately, as food could not be recognized visually).
3. Increased exploration (K-B called it "hypermetamorphosis"): Monkeys constantly explored their environment (orally).
4. Tameness & placidity: Monkeys became uncharacteristically tame and docile, very easy to handle.
5. Hypersexuality: Monkeys would copulate constantly with receptive partners. Species unimportant. If no partner available, constant masturbation occured.

Tameness and placidity represents a profound emotional change, but what part of brain was responsible? Many regions were removed or damaged in the surgery.

Papez' Circuit (The Limbic System)

Papez (1937) suggested that a complex circuit including the cingulate gyrus, hippocampus, mammillary bodies, and anterior n. of the thalamus might underly emotion. He based this theory on two sorts of evidence: people with damage to the anterior n. or to the cingulate gyrus often experience disturbances of emotion, and rabies (with its concommittant emotional changes) affects the hippocampus. Papez was the first to focus attention on the limbic system in emotions.

However, Papez left out the septum and the amygdala, two structures now believed to play important roles in the control of emotion.

Amygdala:

Lesions of the amygdala lead to tameness in most animals (Shreiner & King, 1953). Stimulation of the amygdala can produce aggression that appears predatory, defensive, or rageful, depending on exactly what part of the amygdala is activated. LeDoux has demonstrated over the past 10 years that the amygdala is involved in fear (so that lesions produce tameness by reducing or eliminating the fear response).

When the taming effect of amygdala lesions was first demonstrated in animals it prompted inappropriate human applications. People convicted of especially violent crimes were given amygdala lesions in an effort to "tame" them, as were children with (what was then known as) hyperactivity. There is no evidence that these people benefitted, nor should they have been expected to benefit. In the animal studies damage inflicted on a normal brain produced abnormal behavior. Why in humans should damage cause behavior to become more normal?

Septum:

Brady & Nauta (1953) discovered that a septal lesion in a rat produced a profound emotional change, a change that came to be known as "septal rage." The rat attacked everything, including the experimenter (including me, doing my first experiments in the 1970's) aggressively and emotionally. Stimulation of the septum (in an unlesioned rat) appeared to produce tameness. The initial interpretation held that the septum and amygdala were mutually inhibitory, with the amygdala producing rage and the septum inhibiting it.

This interpretation proved overly simplistic. Septal rage appears to occur only in rats, not in cats, dogs, or monkeys, suggesting that the septum's role must not be the inhibition of rage. Thomas has conducted several experiments indicating that a more likely interpretation is that the septum normally produces relief (the fear anti-drive). In rats the lack of relief expresses itself as an increased likelihood of attack; in other species it does not.

The evidence linking the septum to relief is pretty compelling:

• Rats find septal stimulation rewarding (that is, they will work to artificially activate the septum) in conditions when relief would be welcome (e.g., in the presence of a fear-inducing stimulus) but not at other times.
• Unit activity in the septum increases when relief would be expected to occur, and decreases in fearful situations: when a stimulus signalling shock delivery is presented, septal activity decreases dramatically, and when a safety signal (signalling the nondelivery of an expected shock) occurs, septal activity increases dramatically.

It is likely that the amygdala is largely responsible for fear, and the septum for relief, in a mutually inhibitory way. Oddly, these two brain structures most implicated in emotion were omitted by Papez from his emotional circuit, even though the septum and amygdala are intimately connected to the other components of his circuit.

Emotions other than fear (and the offsetting mood, relief) are less well understood. The neural substrates of happiness, affection, curiosity, and lust require further study. [By the way, which of these should be characterized as emotions and which as moods, according to Konorski?]