Hippocampal and extrahippocampal systems compete for control of contextual fear: Role of ventral subiculum and amygdala

Two neural systems, a hippocampal system and an extrahippocampal system compete for control over contextual fear, and the hippocampal system normally dominates. Our experiments reveal that output provided by the ventral subiculum is critical for the hippocampal system to win this competition. Bilateral electrolytic lesions of the ventral subiculum after conditioning, but not before conditioning, impaired contextual fear conditioning. Reversibly inactivating this region by bilateral injections of muscimol produced the same results—no impairment when the injection occurred prior to conditioning but a significant impairment when this region was inactivated after conditioning. Thus, the extrahippocampal system can support contextual fear conditioning if the ventral subiculum is disabled before conditioning but not if it is disabled after conditioning. Our experiments also reveal that the basolateral region of the amygdala (BLA) is where the two systems compete for associative control of the fear system. To test this hypothesis we reasoned that the extrahippocampal system would also acquire associative control over the fear system, even if the hippocampal system were functional, if the basal level of plasticity potential in the BLA could be increased. We did this by injecting the D1 dopamine agonist, {"type":"entrez-protein","attrs":{"text":"SKF82958","term_id":"1156217255","term_text":"SKF82958"}}SKF82958, into the BLA just prior to conditioning. This treatment resulted in a significant increase in freezing when the ventral subiculum was disabled prior to the test. These results are discussed in relationship to the idea that D1 agonists increase plasticity potential by increasing the pool of available extrasynaptic GluR1 receptors in the population of neurons supporting acquired fear.It is generally believed that contextual fear conditioning depends on the hippocampus. However, it is now clear that an extrahippocampal system exists that can also support contextual fear conditioning. The last statement is based on the fact that damage to the hippocampus prior to conditioning has a minor impact on contextual fear (Maren et al. 1997; Frankland et al. 1998; Cho et al. 1999; Wiltgen et al. 2006). In fact, the conclusion that the hippocampus is normally involved in contextual fear conditioning is now based primarily on the finding that damage to the hippocampus after conditioning greatly impairs fear to the context in which conditioning occurs (Maren et al. 1997; Frankland et al. 1998; Anagnostaras et al. 1999; Bannerman et al. 1999; Richmond et al. 1999; Fanselow 2000; Rudy et al. 2004; Wiltgen et al. 2006). Maren et al. (1997) were the first to appreciate the implications of this set of findings. Specifically, they proposed that (1) in the normal animal there is competition between the hippocampal system and an extrahippocampal system for support of contextual fear conditioning, and (2) the hippocampal system normally dominates the extrahippocampal system—preventing it from acquiring the information needed to support fear to the context. This competition hypothesis provides a reasonable account of the lesion data. If the hippocampus is damaged prior to conditioning, then the extrahippocampal system will be able to acquire control over the fear system and generate a fear response at the time of testing. However, if the hippocampal system is functional during conditioning, it will (1) acquire control of the fear system, and (2) prevent the acquisition of control by the extrahippocampal system. Thus, if the hippocampal system is damaged after conditioning, the expression of contextual fear will be impaired, because the information that was acquired by the hippocampal system will not be available and the extrahippocampal system never acquired the relevant information.Maren et al.''s competition hypothesis is accepted by a number of other researchers (Wiltgen and Fanselow 2003; Rudy et al. 2004; Driscoll et al. 2005; Wiltgen et al. 2006). Nevertheless, very little is known about the mediators of this competition. The experiments in this study were aimed at filling some of the gaps in our knowledge of the neural basis of this competition. They are organized around two hypotheses:

• The ability of the hippocampal system to dominate the extrahippocampal system depends on information it provides through the ventral subiculum, a major output region of the hippocampus.
• The locus of the competition is the basolateral region of the amygdala (BLA), which is thought to be critical to the acquisition of conditioned fear and is where information from the hippocampal and extrahippocampal system can converge.

     

Relative absence of neuropsychological deficit in patients with low grade astrocytomas

Given the current accuracy and precision of modern brain imaging technology, there is presumed to be little utility in neuropsychological assessment procedures in patients with brain tumors. The primary exposure of many clinical neuropsychologists to patients with brain tumors is during their training, in the form of didactic classroom activities, such as reviewing the brain tumor cases of early investigators in the field. Historically, these brain tumors were the more aggressive and destructive tumors, such as grade III and IV astrocytomas, that could be identified with pre CT and pre MRI technology. With current imaging technology, low grade tumors that might previously have gone undiagnosed for years can be detected and patients followed over time. This series of cases represents documentation of the very unique neuropsychological status of patients with relatively slow growing, infiltrative brain tumors classified as grade II astrocytomas. The potential relevance of neuropsychological assessment for such cases is discussed.     

Ontogeny of second-order odor-aversion conditioning in neonatal rats

In Experimental 1, rat pups 1, 3, 5, or 7 days old received a Phase 1 S1-US (Stimulus 1-unconditioned stimulus) pairing calculated to establish a first-order conditioned aversion to S1 (lemon scent). On the next day each pup received a Phase 2 S2-S1 pairing designed to establish a second-order aversion to S2 (orange scent). Pups at all ages displayed a first-order aversion to S1, but only pups given Phase 2 training when 6 or 8 days old displayed a second-order aversion to S2. Experiment 2 revealed that pups that received the S1-US pairing when 3 days old acquired an aversion to S2 if they were 6 days old when they received the S2-S1 pairing but not if they received the pairing when 4 days old. In Experiment 3, two Phase 2 treatments were compared. One was identical to that employed in Experiments 1 and 2: Pups 4 days old received a sequential exposure to S2 and S1. Another set of pups received a modified treatment: They were exposed first to S2 and then jointly to both S2 and S1. Only pups in the latter set displayed an aversion to S2. It is suggested that these results reflect developmental differences in the memory processes mediating the rat's experience with olfactory stimulation.     

The effects of information processing complexity and interpersonal cue availability on strategic play in a mixed-motive game1

A 60-trial iterated PDG was played by 24 male undergraduates. Half were Abstract Information Processors, and half were Concrete Information Processors. In addition, half of the subject pairs played the game face-to-face, while in the other pairs the game was played in separate cubicles. Rather than allowing for free play, the subjects were given the illusion of playing against one another when in reality they all played against a simulation program. It was found that concrete subjects cooperated most in the presence of another player, and competed most when not facing him. This was apparently due to the tendency for the concrete players to be “caught” by the cooperative pull of the face-to-face condition. The abstract subjects tended to use information-seeking strategies in both conditions. When the information was irrelevant to the game (e.g., presence of a false “partner”) the abstract players did not maximize to the same degree as when the feedback was more meaningful.     

When logic fails: Implicit transitive inference in humans

Transitive inference (TI) in animals (e.g., choosing A over C on the basis of knowing that A is better than B and B is better than C) has been interpreted by some as reflecting a declarative logical inference process. We invert this anthropomorphic interpretation by providing evidence that humans can exhibit TI-like behavior on the basis of simpler associative mechanisms that underlie many theories of animal learning. In this study, human participants were trained on a five-pair TI problem (A+B-, B+C-, C+D-, D+E-, E+F-) and, unlike in previous human TI studies, were prevented from becoming explicitly aware of the logical hierarchy, so they could not employ logical reasoning. They were then tested with three problems: B versus D, B versus E, and C versus E. Participants only reliably chose B over E, whereas the other test conditions yielded chance performance. This result is inconsistent with the use of logical reasoning and is instead consistent with an account developed to explain earlier TI studies with rats that found the same pattern of results. In this account, choice performance is based on differential associative strengths across the stimulus items that develop over training, despite equal overt reinforcement.     

Common irrational beliefs associated with the psychophysiological conditions of low back pain,peptic ulcers and migraine headache: A multivariate study

Low back pain, peptic ulcers, migraine headache and a medical control were examined with respect to their irrational beliefs, age, sex and socioeconomic status. Two hundred and sixty-four subjects were diagnosed as having a psychosomatic condition or comprised the medical control group. Subjects were administered the Common Beliefs Survey III, (CBS III) (Bessai, 1977; 1978) and a personal data sheet. The data were analyzed by a multivariate analysis of variance (MANOVA) with dependent variables consisting of six mean factor scores of the CBS III age and socioeconomic status. The MANOVA found group differences on perfectionism. The psychosomatic groups were next combined and compared to the control by a component analysis of variance (CANOVA). The CANOVA found significance on perfectionism, and self-downing for the psychosomatic groups. Age and sex were analyzed and their results discussed. The results were discussed with respect to the experimental and control groups on the factor scores of the CBS III, age, and socioeconomic status.The study is part of a series of investigations conducted at Riverside Methodist Hospital under Drs. Donald J. Tosi and David R. Rudy. This study is based on a dissertation conducted by Dr. Michael A. Forman under the supervision of Dr. Donald J. Tosi. Reprint requests should be sent to: Dr. Forman     

Determinants of infant visual fixation: evidence for a two-process theory

Three experiments were conducted to investigate the dynamics of the human infant's (4 months old) visual fixation. The general finding that, over a series of trials, infants fixate longer to a complex than to a simple stimulus was replicated. The function relating fixation time to trials was shown to be nonmonotonic when the stimulus was complex (fixation time increased between Trials 1 and 2 and then decreased), but was monotonic when the stimulus was simple (it decreased systematically over trials). Additional experiments indicated that (a) the nonmonotonic function associated with the complex stimulus was eliminated when the interval separating Trials 1 and 2 was increased from 10 to 20 or 30 s (Experiment 2), and (b) the difference in fixation time between the complex and the simple stimulus was eliminated by controlling their effects in a within-subjects design (Experiment 3). These data challenge the prevailing cognitive-schema theories as a complete account of the dynamics of the infant's visual fixation. A two-process theory that accounts for these data was proposed.     

Reliability of a Measure of Temporal Discounting

The Psychological Record - Participants (N = 17) chose between smaller, immediate and larger, delayed hypothetical money amounts in two laboratory sessions separated by 1 week. The choice procedure...     

Contributions to the Content Analysis of Gender Roles: An Introduction to a Special Issue

This special issue on gender-related content analysis is the second of two parts (see Rudy et al. 2010b). The current special issue is more diverse than was the first in the number of countries that are represented and in the variety of media genres and content types that are included. The primary aim of this paper is to outline some of the contributions of the individual papers in this second special issue. Some of these advancements and innovations include (a) examining underresearched measures, countries, time spans, sexual orientations, and individual media programs; (b) addressing both international and intranational differences in gender-role portrayals; (c) comparing multiple content formats within the same media unit; (d) updating past findings to take into consideration the current media landscape; (e) employing established measures in novel ways and novel contexts; (f) uncovering limitations in established intercultural measures and media-effects theories; (g) suggesting variables that could predict additional differences in gender-role portrayals; (h) adopting virtually identical methods and measures across distinct content categories in order to facilitate comparisons; (i) conducting multiple tests of a given hypothesis; (j) examining, from multiple perspectives, the implications of racial differences in gender portrayals; and (k) examining the implications of underrepresentation of women and the perspectives that women hold. In addition to the original content-analytical research presented in this special issue, two reviews, one methodological and the other analytical, offer recommendations of procedures and perspectives to be implemented in future research.