View Full Version : "the seeking system and a sense of time"

02-05-14, 07:29 PM
Lateral Hypothalamus (LH)


There is, however, one very special way in which the SEEKING system is able to learn spontaneously.

It is not the kind of traditional conditioned learning we have been talking about, and it does not appear to involve thinking.

Rather, it reflects the way that this system is able to gauge the passage of time.

This system can learn to anticipate spontaneously various events, especially rewarding events that are highly predictable.

When we discussed classic "schedules of reinforcement" that are commonly used in behavior experiments, we mentioned one schedule that is of particular interest to the present discussion.

These are the fixed interval experiments, where animals are allowed to obtain rewards by pressing levers,, poking their noses into holes (that have photocells to automatically record those investigations), or performing any of a variety of other tasks at fixed intervals of time.

Animals press their various "operant buttons"--lever-presses, nose-pokes, and such--quite slowly after just having received a reward on a fixed interval schedule, but they gradually speed up until, during the second half of the interval, they press the lever with ever-increasing frequency.

When these patterns of operant behaviors are plotted on a graph, they form a scalloped shape--an apparent upward curve of anticipation.

And this happens spontaneously.

Animals also show such scalloped responding when working for a self-stimulation reward.

But this type of pattern also emerges spontaneously in animal brains and bodies, when rewards are given freely.

Suppose that a rat is given totally free LH stimulation at regular fixed intervals, say at every 20 seconds, so that it has to do nothing at all in order to get each reward.

In this experiment, the rat is not given a lever or any other device for performing operant behaviors.

All rewards are free.

The animal has the option of being "cool as a cucumber" and to sit back like a philosopher, and relax.

Still, a remarkable anticipatory pattern emerges.

The fixed interval brain "reward" produces spontaneous sniffing behaviors in the same scalloped pattern (Clarke & Trowill, 1971, Panksepp, 1981a).

Indeed, aroused sniffing is one of the cardinal unconditioned signs of SEEKING arousal in rats (Ikemoto & Panksepp, 1994; Rossi & Panksepp, 1992).

Thus, it appears that some kind of intrinsic learning occurs during highly periodic SEEKING arousal that gradually produces the scalloped pattern of the sniffing response.

As another spontaneously emerging indicator of the same process, more recently we have found that rats also exhibit scalloped patterns of 50-kHz ultrasonic vocalizations (Burgdorf, et al, 2000)--the excited chirping sounds that young rats make when they play (see Chapter 10).

These sounds, just like invigorated exploratory sniffing, are know to be unconditioned responses of the dopamine-energized SEEKING system (Burgdorf, et al., 2001).

In other words, in an animal that has experienced this fixed interval schedule of free rewards for a while there is very little sniffing and chirping right after the brain stimulation; but as the fixed intervals proceeds, sniffing and chirping rates both go up systematically at an ever-accelerating rate, until the next brain stimulation is received (see Figure 3.2).

Then the measures drop down to a very low level again.

In other words, the system automatically shapes into an anticipatory curve, with nothing being explicitly "reinforced."

Clearly, the brain is an organ that is designed to spontaneously anticipate the future, perhaps because this system mediates "psychological time" as described at the end of this chapter.

Because an aroused SEEKING system produces both elevated sniffing and chirping, and this naturally shapes into an anticipatory pattern, then it would seem that the SEEKING system is somehow intrinsically responsive to the timing of rewarding affects.

It becomes ever more aroused as the moment of reward delivery approaches.

How might the SEEKING system be able to gauge this passage of time?

No one knows for sure, but it is well known that many neurons have self-generated firing patterns.

Although some neurons fire only when they are excited by some external influence, other neurons have some background level of activity that arises from some type of "internal pacemaker"--in other words, a clocking mechanism.

The dopamine-containing neurons of the SEEKING system have such endogenous pacemakers that normally keep them firing at a stable monotonous rate, like the ticking of a clock, especially when nothing special is happening to an animal.

These neurons even keep firing when animals are asleep, but the background activity is not normally attended by the release of dopamine.

The regular activity of dopamine neurons in the SEEKING system almost seems to act like the second hand of a clock, marking reasonably accurate mental time in a methodical fashion.

While the system is ticking along in this way, it is in a quiescent, but informative, state.

However, when the system is aroused, dopamine neurons start to "burst" and release dopamine as they fire several times in quick succession.

Now the animal becomes alert and starts to explore its world.

Or if the animal is asleep, it begins to dream, or at least demonstrate a REM pattern, a state characterized by high dopamine activity (Dahan et al., 2007; Solms, 2000).

Although the research has yet to be done, we can suppose that this type of neuronal bursting and increased release of dopamine take place just at the time sniffing and chirping begin to increase spontaneously during fixed interval experiments.

If this system has an internal timing mechanism that can help animals predict when to exhibit eager anticipation--to be "first in line for resources," so to speak--it would be of momentous importance for understanding both the basic behavior and psychology of organisms.

It is presumably this internal shaping of activity within the SEEKING system that helps explain the scalloped pattern of behavior that animals exhibit when they are required to work for their food on fixed interval schedules.

Perhaps this same process is the one that keeps tabs on the passage of psychological time within our minds.

Thus, when the SEEKING system becomes aroused, the regular firing of dopamine neurons shifting into a more rapid bursting pattern may cause the animal's internal sense of time to speed up as well.

We have all heard the adage that time flies when you are having fun, and this has now been empirically demonstrated (Droit-Volet &Meck, 2007).

When we are happily engaged in a activity, especially when we are profitably employed and working toward a desired goal, time seems to flow freely, with no bumpy boredom.

Perhaps this is because during these periods when our SEEKING systems are aroused and our dopamine neurons assume a bursting pattern, our experience of subjective time accelerates--time seems to pass more quickly, and with a mental ease that is a joy to experience.

By the same token, dopamine neurons respond to some aversive events with an inhibition of baseline firing (Schultz, 2006), but this firing also can be increased by various aversive events (Ungless, 2004), which is consistent with the arousal of SEEKING urges when various negative emotions are aroused.

Indeed, if an animal is confronted with affectively negative situations, the dopamine terminal fields tend to show plasticities whereby they are more capable of sustaining negative affects, since this system can mediate both "desire and dread" as noted by Kent Berridge and colleagues (Faure et al., 2008, 2010).

Bad times strengthen negative affective circuits in the brain.

When we are in pain or beset by worries--when we are having a bad time--our sense of time itself tends to slow down.

Likewise, it is well know that people with Parkinson's disease, in which dopamine neurons are degenerated, have an altered sense of time.

Without medicines to facilitate dopamine transmission, these people fall into a waking "sleep"--they feel themselves to be frozen in time and live in a seemingly eventless universe of boredoom, ennui, and psychological emptiness (Sacks, 1973).

Beyond these important observations about dopamine-firing patterns, we do not know how the firing of dopamine neurons computes a sense of time.

In addition, we do not know how this sense of time can regulate the arousal of the SEEKING system, causing it to lie relatively dormant during the first half of a fixed interval schedule and then to become increasingly active during the second half.

Although many aspects of these ideas remain to be formally tested, there are increasing data from rats that their sense of time, as in humans, is controlled by dopamine (Meck et al., 2008)

We are beginning to understand the reasons for why organisms become so marvelously anticipatory during the fixed interval timing of reward delivery, clarifying the profound mysteries about the relationship between the perception of time passing and the arousal of the anticipatory eagerness generated by our SEEKING systems.

For now, we can be confident that our feelings of the passage of time is a basic psychological function that allows us to predict changing events in the environment.

Whether time is also a fundamental property of the universe is more debatable (Barbour, 2000), but it is clear that we cannot coherently discuss the nature of the universe or our place in it without this evolved mental process.

Panksepp/Biven; "The Archaeology of Mind", The SEEKING System, P 137-140.