Communication of Appetitive Emotion in Rats:

Exploring the nature of 50KHz Ultrasonic Vocalizations

Steve MahlerPsych 787, Fredrickson

Emotions and Communication

Emotion vs. Communication of Emotion--Different Basic Functions

Often together, but…

Also separable--Emotion without communication--Communication without emotion

Appetitive Emotion vs. Communication Thereof

• “Appetitive Emotion” (AKA appetitive state, motivational state, and/or desire in humans)--Functions to motivate organisms toward achieving rewards (work, anticipation, etc)

• Why communicate it?--Social appetite (The reward is social)

--sex, play, cooperation, social bonding, --Sharing large rewards

--Reciprocal Altruism, Kin Selection

Why Not Share it?

• Selfishness (esp. for small rewards)

• Energy Expenditure

--To communicate, and to be able to do so

• Potential for Cheaters– “Freeloaders,” hidden intentions, etc.

A Balance is Best

• Despite the consequences of communicating appetitive emotion, under some circumstances it is adaptive to do so.

• For some species, then, communication of motivation should be conditional based on:– Type of reward– Presence of (suitable) listeners

Communication in Lab Rats

• Olfactory

• Visual

• Tactile

• Ultrasonic Vocalizations:– 22KHz—Aversive “complaining”– 50KHz—Appetitive “joyful” or “appetitive”

50 KHz Vocalizations• Emitted by Socially Housed Rats:

– By juveniles before and during play– By males and females before ‘desired’ sex– In environments previously associated with play and sex– During aggressive encounters by losers (?)

• Emitted by Individually Housed Rats:– In anticipation of and during tickling (to a point)– In anticipation of MOR, AMPH, ICS, food – After systemic and intra-NAc injection of the

dopamine agonist AMPH (and intra-VTA glutamate)

– In environments previously associated with these

Panksepp’s InterpretationEvolutionary Antecedant of Laughter?

“HAHAHA”

Appetitive Social Motivation? “Let’s Play, bond, etc…”

Appetitive States in general (including drug ‘craving?’ “IWantItIWantItIWantIt…”

My Interpretation

• 50KHz vocalizations occur mostly in appetitive situations

• They are communication, so they are probably inherantly social

• Not all motivation should be communicated all the time, so these calls may be conditional

My Interpretation, Ctd.• For the social rewards, 50KHz’s functions are

obvious: “Let’s play/get it on/cooperate”

• In non-social reward studies, rats were isolated. --Experimenter the partner? --Abundant rewards, communicating availability?

• Therefore, rats might not be ‘saying’ “I want it!,” they’re saying “I want to interact” or “Come ‘n get it!”

How to test this?

• If 50KHz calls are fundamentally communicative and conditional, you might not hear them when:

– Rats have no one to talk to– The resources available are not enough to

share

Hypothesis 1

• If Panksepp and collegues’ experiments using non-social rewards (drugs, EBS, food) were replicated using socially-housed rats, these rats would not consider the experimenter as someone to talk to. Therefore, we would see fewer 50KHz calls in appetitive states for non-social rewards under these conditions

Experiment 1, eg.

Group Housed

Who cares?

Solo Housed

50KHz50KHz, friend!

Experiment 1, Ctd.

• If the group housed rats vocalized less than isolated rats, this would help support my theory.

Hypothesis 2

• If systemic or intra-NAc AMPH were administered totally in the absence of other rats and the experimenter, we would see few 50 KHz calls because there is no one to talk to.

Experiment 2• Choose socially housed rats that have had

little contact with humans.

• Insert a jugular catheter or intra-NAc brain cannulle under anesthesia.

• After recovery, transfer the rat to an “isolation chamber” free of the smells, sounds and sights of other rats or humans.

• Remotely inject AMPH, and record vocalizations.

Experiment 2, eg.

AMPHAMPH

Come ‘n Get

It!

I want it!

Experiement 2, Ctd.

• If less vocalizations occur than under the isolation chamber condition, this supports the idea that the calls are uniquely communicative

Hypothesis 3

• Appetitive calls are contingent of the ‘sharability’ of the reward. When a reward is scarce and ‘hoggable,’ rats will not tell others it is there.

Experiment 3• Train rats to forage in one of two types of

sandboxes:

Food Rich Food Poor

Experiment 3

• …With the food buried in the sand…

Food Rich Food Poor

Experiment 3 Ctd.

Food Rich Food Poor

Bring in the first rat’s cagemate, who has never been tested, and who has been de-vocalized.

Experiment 3, Ctd.

• Do the “Food Rich” rats vocalize more than the (selfish) “Food Poor” rats?

Food Rich Food Poor

Come ‘n Get it!

------

????Mmmm!

Experiment 3, Ctd.

• If the “Food Rich” rats do advertise their appetitive emotional state more than “food Poor” rats, this is evidence that appetitive communication is conditional, not inherant to appetitive states.

Summary

These experiments will help test whether 50KHz calls in rats are linked unconditionally to appetitive states, as Panksepp believes, or if they are conditional based on social factors and reward type, as evolutionary theory might predict them to be.

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