USO DEL PENSAMIENTO - DISPERSIÓN, DISCREPANCIA

Figure 8.4. Elaboration of sniffing during free fixed-interval 20-second administration of rewarding LH stimulation. During the beginning of training (first 10 trials), animals exhibited only generalized overall energization of sniffing throughout the interstimulation interval. By the end of training (trials 190-199), animals were exhibiting a scalloped pattern, which is reminiscent of animals working for conventional rewards on a fixed interval schedule (see Figure 1 .4). An important point to note is that all of these stimula tions were free, and the animals did not have to change their behavior patterns to obtain all "rewards." However, the system spontaneously developed an instrumental pattern of behavioral output. This can explain how patterns of behavior emerge on the schedules of reinforcement that have long been described in the behavioral literature. (Adapted from Panksepp, 198 1 ; see chap. 3, n. 25.)

do anything systematic to obtain rewards. The under� lying neural system spontaneously exhibited a scalloped response pattern. Thus, since this acquired behavior served no formal instrumental function, it could be deemed delusional. 80 Of course, it could be assumed that the behavior helps animals prepare for receiving avail able rewards efficiently. Indeed, that is why I originally called this the "expectancy system."

To determine whether this spontaneous form of an ticipatory conditioning has primacy over scalloped op erant responding, the spontaneous sniffing of rats was monitored while they were working for sugar water on an FI schedule.s1 It was of special interest to detennine what happened during the moment just prior to the first "voluntary" lever press within each FI response segment. In fact, the rats exhibited an invigoration of sniffing just before they made their first lever press. Sniffing contin

ued to increase further after this initial "optimistic" but invariably ineffective response (Figure 8.5). Thus, the brain system that generates sniffing became engaged a

moment before the animal emitted its first operant re sponses. This suggests that the spontaneous arousal of the SEEKING system helped arouse the instrumental behavior. If we understood the mechanisms that allow the SEEKING system to spontaneously generate scal loped sniffing patterns, we would gain a profound under standing of how the brain spontaneously mediates antici patory states. Presumably this occurs through the ability of LH circuits to generate theta rhythms that sensitize both the associative abilities of the hippocampus and DA-mediated timing functions of the striatum. A neuro physiological understanding of these brain systems can explain how animals spontaneously generate solutions to the various environmental contingencies they encoun ter in their lives. Presumably, these same systems allow us to devel<?P a sense of causality -from the perception of correlated environmental events. This type of spontane ous associative ability characterizes nonnal human think ing, as well as the delusional excesses of schizophrenic thinking. Indeed, as highlighted in the "Afterthought" of

SNIFFING WHEN RATS WORK ON A

FIXED-INTERVAL SCHEDULE OF R EI N FO R C E M ENT

0 z 6 0

A MARKED ELEVATION OF SNIFFING OCCURS 1 Sec

BEFORE FIRST OPERANT RESPONSE ON A FIXED·INTERVAL SCHEDULE OF REINFORCEMENT 0 w C/) 0: w 5 n. (/) LL

�

4 FIRST LEVER PRESS OF A FIXED INTERVAL

COMPONENT

4 3 2 2 3 4

Seconds Before and After First Lever Press Figure 8.5. Elaboration of sniffing in rats working for rewarding brain stimulation on a fixed-interval schedule of reinforcement. It is noteworthy that spontaneous sniffing increased markedly one second prior to the first lever press within each response segment. This suggests that the brain substrates that arouse sniffing, namely, the circuits of the SEEKING system, mediate appetitive behavior patterns seen when animals are required to exhibit operant responses in order to obtain food. It should be noted that the theta rhythm, which invades the hippocampus when it is integrating information, is of the same frequency as sniffing, and the neuronal systems that activate theta arise from the brain stem and course through the lateral hypothalamus. (Reprinted with permission from Panksepp, 198 1 ; see chap. 3, n. 25.)

this chapter, profound relationships exist between the neural underpinnings of SS in rats and schizophrenia in humans.82

The SEEKING System and Sources of Delusional Behaviors in Animals

Arousal of the SEEKING system spontaneously con� structs causal "insights" from the perception of corre� Iated events. Some of the relationships may be true, but others are delusional. Indeed, all forms of inductive thought, including that which energizes scientific pur suits, proceed by this type of logically flawed thinking (see Figure 2.3). An intrinsic tendency for "confirma tion bias" appears to be a natural function of both human and rat minds. 83 Indeed, the classically conditioned confirmation bias that characterizes many brain learn ing systems, including the SEEKING system, perplexed investigators when it was first discovered.

An example of this type of spontaneous learning is called "autoshaping," which reflects an animal's ten dency to spontaneously behave as if correlated cue reward contingencies reflect causal relationships. In the classic demonstration of this phenomenon, pigeons were exposed to an illuminated key just prior to the deliVery offood.84 With repeated exposure to this con tingency, pigeons exhibited anticipatory pecking at the illuminated key, even though there was no formal con nection between anything the animal did and the appear ance of food. It was as if the animal believed its behav ior was instrumental in procuring the food, although, in fact, it was not. Of course, this is a very effective way to train animals to do various things, even though at a formal level such behaviors reflect delusional thinking. Comparable phenomena have now been observed in all mammalian species that have been studied. The "rain dances" of Indian shamans and the prayers of the de vout may reflect such processes in humans. If performed long enough, such rituals are bound to "work," even though there may be no causal relationships between the dances or prayers and events in the world. None theless, we should note that it is possible that the dust kicked up during hours of rain dancing may help seed colloidal suspensions of moisture that can promote pre cipitation. Also, prayer may put individuals in a frame of mind to behave in ways that may change the social world. However, to the best of our current knowledge, most of such autoshaped behaviors simply reflect a form of classical conditioning within the SEEKING system of the brain. The role of DA in the generation of this type of behavior is affirmed by the ability of DA block ing agents to reduce autoshaping.85

Another bizarre behavior generated by the SEEK ING system is schedule-induced polydipsia (SIP). This is the excessive drinking that can be produced in hun gry rats by giving them small portions of food on an Fl schedule; using about two-minute intervals between

food delivery produces the maximal response.86 If water is not available, the animal will exhibit other be haviors such as compulsive shredding of available ob jects or schedule-induced wheel running. One can even obtain aggression if another animal is nearby. Animals appear to vent the frustration of neuroernotional energy emerging from unfulfilled expectations on any avail able target.

As a group, these behaviors are called ''adjunctive" or "displacement" behaviors, and they resemble the "superstitious" behaviors that Skinner described in his pigeons when they worked on FI schedules of reinforce ment. 87 During the interreinforcement intervals, some would strut around the cage and flap their wings in pre dictable patterns, as if their dance had some meaning ful consequence for world events. These behaviors were explained by "adventitious reinforcement"-the chance pairing of randomly emitted behaviors with the deliv ery of rewards. A deeper cause may be overarousal of the brain's SEEKING system. Adjunctive behaviors probably emerge from the same neural substrates as the "stimulus-bound" behaviors evoked by electrical stimu lation of the LH: Animals can dissipate their appetitive "energies" on any of a number of goal-directed behav iors. Indeed, rats that exhibit the most intense SIP be havior are also the most likely to develop intense "stimulus-bound" behaviors.88 In other words, hungry animals may experience sustained foraging arousal, and if they cannot satisfy this urge by homeostatically appropriate consummatory behavior, they will start to exhibit alternative consummatory behaviors that can partially alleviate feelings of excessive appetitive arousal. The fact that LH lesions as well as DA receptor block ade can markedly reduce schedule-induced behaviors affirms such a conclusion.S9

Such adjunctive behaviors may resemble the obses sive-compulsive (OC) behavior patterns that humans exhibit under stressful circumstances. However, one of the cardinal attributes of OC psychopathology in hu mans is the conscious desire to avoid the compulsions. Since we cannot measure the thoughts of animals, the obsessive component of OC disorders may never be properly evaluated in animal models, although adjunc tive behaviors may help highlight the nature of impulse control disorders: compulsive acts that are not accom panied by the internally experienced need to withhold behavior.90

Another remarkable finding in this area is that most of the behaviors evoked by LH stimulation in rats can also be evoked by applying mild pressure to their tails.91 Behaviors induced by tail pressure include feeding, drinking, and gnawing, all of which can be diminished by DA receptor blocking agents. This suggests that the phenomenon also arises from excessive activity of the SEEKING system.

Thus, the SEEKING system can promote many dis tinct motivated behaviors, and the underlying neural system is prepared to jump to the conclusion that cor-

162 BASIC EMOTIONAL AND MOTIVATIONAL PROCESSES

related environmental events reflect causal relation ships. It is easy to appreciate how this may yield a con sensual understanding of the world when the underly ing memory reinforcement processes are operating normally (i.e., yielding a "reality" that most of the so cial group accepts). It is also easy to understand how it might yield delusional conclusions about the world. If the system is chronically overactive, it may be less con strained by rational modes of reality testing. The fact that the meso limbic DA system is especially responsive to stress could explain why paranoid thinking emerges more easily during stressful periods, and why stress may promote schizophrenic thinking patterns.

One critical task for better understanding how this system operates is to identify which neural change actu ally constitutes reinforcement within the dynamic op eration of such brain circuits. In line with the suggestion that positive reinforcement may be linked to reductions in firing within the SEEKING system, we might antici pate that in schizophrenics bursting patterns and inter nally generated cessations of such patterns may occur with abnormal frequency in response to internal cues rather than to real-life events.92 Perhaps neurons of the VTA-DA system exhibit excessive bursting, leading to many cessations of bursting for internal as opposed to external reasons. If the spontaneous, internally generated relationships between certain perSistent thoughts and the modulation of neuronal bursting are sufficiently system atic, then we can envision how schizophrenics might de velop delusional insights from poor regulation of neu ronal firing in the SEEKING system.

Relationships of the SEEKING System to Schizophrenia

Some psychobiologists believe that SS of the LH cir cuitry is an excellent model for type I, or paranoid, schizophrenia, as opposed to type II schizophrenia, which is characterized by demonstrable brain damage (CAT technology reveals ventricular enlargement, sug gesting deterioration of surrounding brain tissues).93 There is general agreement that paranoid schizophre nia is characterized by excessive brain DA activity. The most commonly observed biochemical correlate is an increase ofDA receptors (the 02 variety), especially in the ventral striatum,94 with occasionally reported abnor malities such as elevated DA levels in the amygdala of the left hemisphere.95 All antipsychotic drugs reduce DA activity at D2 receptors, and here is where the par allel between schizophrenia and SS circuitry becomes striking: Virtually all drugs that reduce schizophrenic symptoms also reduce SS along the SEEKING system. Conversely, drugs that worsen schizophrenic symptoms generally increase SS behavior.96 For instance, psycho stimulants facilitate SS and, when administered re peatedly, eventually precipitate symptoms of paranoid

schizophrenia that are psychiatrically indistinguishable from the spontaneously occurring variety.97

Since schizophrenic breaks can also be precipitated by stress, it is especially noteworthy that the meso limbic DA system (AIO) is highly stress-responsive, more so than the other brain DA systems.98 During stress, cer� tain ascending DA systems become rapidly depleted of DA, with consequent development of hypersensitivity in the receptors to the little that is left, causing increases in psychological symptoms resembling schizophrenia. Functionally, this may reflect an adaptive process: One should exhibit increased amounts of seeking behaviors when one is under stress in order to ferret out resources to alleviate the stressful situation.

Similar long-term brain changes can be induced by chronic administration of psychostimulants such as cocaine and amphetamine, reflecting a permanent eleva tion in the sensitivity of the underlying brain systems.99 This "sensitization" may reflect a long-term brain ad justment that is important for understanding not only schizophrenia but also such phenomena as drug crav ing and other obsessions, as well as overall reductions in the ability to tolerate stress. It is now clear that a number of neurochemical influences can facilitate such sensitization, including opiates and other drugs of abuse, while drugs that reduce memory consolidation, such as glutamate receptor antagonists, tend to block sensitization. A different syndrome is precipitated by chronic treatment of animals with the direct DA recep tor agonist apomorphine, which can influence both postsynaptic and presynaptic DA receptors (i.e., ones situated on DA neurons). Rats that have received such drugs eventually begin to exhibit a high spontaneous level of fearlike emotionality as well as aggression.1oo Many investigators believe such findings are of consid erable importance for understanding such psychiatric disorders as mania, but the precise relations have not been determined.

The ideas and facts that presently predominate in bio logical psychiatry are quite astounding. We can finally make some sense of schizophrenic symptoms by concep tualizing SS circuitry as an appetitive emotional system that can become unstable. If the normal function of this system is to mobilize the organism for seeking out re sources in the world, then we begin to appreciate how the SEEKING system might also generate delusional thoughts. Apparently when this emotional system is over taxed and becomes tfee-xunning, it can generate arbitrary and unrealistic ideas about how world events relate to internal events. Is delusional thinking truly related to the unconstrained operation of spontaneously active associa tive networks that are uncoupled from the reality testing that is created by the brain's normal ability to compute relationships among events? If so, we may have a great deal more to learn about schizophrenia from a study of the SEEKING circuits that mediate SS behavior in ani mals. Through a study of this system, we can also begin

SEEKING SYSTEMS AND ANTICIPATORY STATES OF THE NERVOUS SYSTEM _{1 63}

to understand the natural eagerness that makes us the emotionally vibrant creatures that we are. This emotion is harder to visualize than the others, but we have tried to capture the essence of this pervasive emotional pro cess in Figure 8.6.

AFTERTHOUGHT: Self-Stimulation and Dreaming

Jn the previous chapter, I focused on possible relation ships between schizophrenia and dreaming. As we have now seen, there is also a credible linkage between schizophrenia and SS. Accordingly, one might predict that there is an intimate relationship between SS and . dreaming. Indeed, interesting connections between the two have been found in REM-deprived animals. REM deprivation in rats leads to an increased sensitivity of the LH-SS system: Animals work at higher rates for lower current levels, as if REM deprivation sensitized the substrates of the SS system.101 Conversely, it has also been found that allowing animals to self-stimulate for a few hours during the course of ongoing REM dep rivation eliminates the need for subsequent REM recov ery sleep. In other words, the drive for increased levels of REM following REM deprivation is apparently dis charged by allowing animals to self-stimulate during the deprivation period.

It is noteworthy that schizophrenics also fail to ex hibit compensatory elevations of REM sleep following imposed periods of REM deprivation.102 Thus, there appears to be a fundamental relationship between the schizophrenic process and the neuropsychological ( emo-

Figure 8.6. The SEEKING system in action. (Adapted from photograph in Panksepp, 1989; see chap. l 1 , n. 5.)

tional?) discharge that occurs during both REM sleep and SS. These findings suggest that there may yet be considerable substance to psychodynamic theories that relate dreaming mechanisms to symbol- and reality creating mechanisms of the brain.l03

Such findings also bring to mind old theories of the function of REM sleep, for example, that it provides a time for the discharge of excessive "bottled-up" psychic ener gies.1041f we add to these observations the common specu lation that there may be a fundamental relationship be tween REM sleep and schizophrenia, one is led to wonder whether the type of psychic discharge that occurs during SS might also help alleviate schizophrenic symptoms. Could one dissipate the excess energies of this system through various life activities? Could the symptoms of schizophrenia be alleviated simply by providing more outlets for the foraging tendencies of individuals? Can one dissipate SEEKING urges simply through new types of emotional exercises? Of course, speculative ideas such as these-provocative products of brain SEEKING sys tems-will remain without substance until they are evalu ated through rigorous empirical studies.