LECTURE 23: EMOTIONS, MOTIVATION, AND DRUGS OF ABUSE

REQUIRED READING: Kandel text, Chapters 50, 51

Emotion and Feeling are two interconnected states.

EmotionEmotion is a group of physiological and motor responses to a set of stimuli.These emotional responses communicate our state to others, prepare us

or drive us for consequent action, and have powerful effects on ourunconscious (implicit)unconscious (implicit) memory of the stimulus events.

FeelingFeeling represent the conscious (explicit)conscious (explicit) awareness of our emotional state.

EXAMPLES:

The taste of a great dessert can elicit the emotionemotion of enjoyment andsatisfaction and the feelingfeeling of having something delicious

Upon hearing a joke, one may experience the emotionemotion of laughterand the feelingfeeling of a funny experience

EMOTIONS EXERT POWERFUL INFLUENCES ON MOTIVATIONAL BEHAVIOR

EMOTIONAL EXPERIENCES CAN BE STEREOTYPICAL OR SUBJECTIVE

Hearing an unanticipated loud explosion triggers a startle emotionstartle emotioncharacterized by heightened awareness, shivering or freezing,

elevated pulse and blood pressure, and a specific facial expression,while triggering the feeling of fearfeeling of fear

Seeing David Ortiz of the Boston Red Sox hit a home run againstthe New York Yankees can trigger exhaltationexhaltation, sadnesssadness,

or nothingnothing depending upon one’s interest in baseball and whetherone is a Red Sox or Yankees fan

Why?:Just as conscious cortical activity can shape our reflexive responses

to stimuli, it can also shape our automaticemotional responses to certain stimuli

Conscious decisions can shape value (ethical) judgmentswhich inform our emotional responses

THE LIMBIC SYSTEM CONTROLS GENERATION OF EMOTIONAL STATES

THE AMYGDALA IS CRITICAL FOR EMOTIONAL RESPONSES,PARTICULARLY TO NEGATIVE EMOTIONS

LEARNED EMOTIONAL RESPONSES ARE PROCESSED IN THE AMYGDALA

AMYGDALA AND HIPPOCAMPUS ARE SEPARATELY NEEDED FOR THE FEARFULAND COGNITIVE COMPONENTS OF PAST EXPERIENCE

Individuals with brain lesions were shown different colored slides, and some slide colors were followed by a loud startling noise

LESION CONSCIOUS MEMORY LEARNED FEAR OF COLORS OF COLORS

NONE YES YES

AMYGDALA AMYGDALA YES NONO

HIPPOCAMPUS HIPPOCAMPUS NONO YES

BOTH NO NOBOTH NO NO

DEAZOPENE (VALIUM) INHIBITS FEAR AND ANXIETY

Valium is a widely used medication used to reduce anxiety and fear,often prescribed prior to surgeries without general anesthesia

Valium interacts with GABA ionotropic receptors, and enhancesGABA-induced chloride conductance. At optimal dosages,valium inhibits firing of neurons in fear and anxiety circuits

Valium is often used, often addictively, as a means torelieve “life” stress

MOTIVATIONAL BEHAVIORS ARE OFTEN DIRECTED TOWARDSMAINTENANCE OF PHYSIOLOGICAL HOMEOSTASIS

The hypothalamus plays a pivotal role in homeostatic motivations,acting as physiological sensor and coordinating autonomic

and motivational responses

Examples:Thermal regulation: Thermal regulation: Certain hypothalamic neurons fire at different

rates at different temperatures. Deviation from set point(37oC in humans) triggers other regions of hypothalamus

initiate autonomic functions and behavioral drives

Appetite:Appetite: Hunger level is driven in part by hypothalamic control.Certain hypothalamic neurons have receptors for a hormone,

leptinleptin, which is produced by fat tissue. Leptin suppresses apetite.

SOME MOTIVATIONS ARE NOT DRIVEN BY DIRECT PHYSIOLOGICAL NEEDS,BUT BY PLEASURABLE EMOTIONS AND ANTICIPATION OF PLEASURE

We (and rats) tend to eat more calories of flavorful food thanbland diet

Sexual behavior is drive towards pleasure fulfillment

Stimuli that are pleasurable are believed to signal “pleasure”by activating certain midbrain dopaminergic neurons in

the ventral tegmental area (VTA) that project to thenucleus accumbens (NA) region of the forebrain

Rats can be implanted with electrodes into the VTA, withstimulation triggered by the animals pressing a lever.

Such animals learn to frequently self-”reward” by pressing the lever

MANY DRUGS OF ABUSE ACT BY PROMOTING THEDOPAMINERGIC PLEASURE CIRCUIT

CocaineCocaine and amphetaminesamphetamines act by blocking dopamine reuptake transporters,resulting in prolonged dopaminergic signaling.

These drugs cause sensory-independent sensation of pleasure andalso enhance pleasure associated with certain stimuli

NicotineNicotine mediates excess release of VTA dopamine by stimulatingpresynaptic cholinergic receptors on VTA axons

Mu opiatesMu opiates (e.g., morphine) act by inhibiting GABAergic neurons thatproject to VTA dopaminergic neurons

DRUG CRAVING CAN BE TRIGGERED BY SENSORY CUES ASSOCIATED WITH DRUG USE: A FORM OF CONDITIONED STIMULUS

Drug exposure follows a sequence of behavioral and sensory cuesthat act as conditioning stimuli to the drug unconditional stimulus

Consequence is conditioned response, whereby the cues alone triggeranticipation of drug “reward”