The right parahippocampal gyrus contributes to the formation and maintenance of bound information in working memory

Working memory is devoted to the temporary storage and on-line manipulation of information. Recently, an integrative system termed the episodic buffer has been proposed to integrate and hold information being entered or retrieved from episodic memory. Although the brain system supporting such an integrative buffer is still in debate, the medial temporal lobe appears to be a promising candidate for the maintenance of bound information. In the current work, binding was assessed by comparing two conditions in which participants had to retain three letters and three spatial locations presented either bound or separate. At the behavioral level, lower performance was found for bound information than for separate information. When contrasting the two conditions, activation in the right parahippocampal gyrus was greater for the encoding and maintenance of bound information. No activation was observed in the medial temporal lobe during the retrieval of bound information. Together, our results suggest that the parahippocampal gyrus may underlie the integrative and maintenance functions of the episodic buffer.     

Mediated generalization in discrimination learning by Rhesus monkeys

Monkeys received discrimination training in which the choice of either a simultaneous or a serial compound of two visual images was rewarded before we assessed the monkeys' conditioned preference for one of the images from the compound. This preference was reduced or blocked if the other image had been associated with reward rather than nonreward prior to compound training. By contrast, the preference was enhanced if the other image was associated with reward rather than nonreward after compound training. The magnitudes of the blocking and enhancement were unaffected by the temporal structure, simultaneous or serial, of the stimulus compound. These results are discussed in terms of the representation of stimulus compounds, the role of within-compound associations, and the similarities between serial and simultaneous visual compounds as processed by monkeys.     

Motivational control of instrumental performance: The role of prior experience of the reinforcer

In four experiments we investigated the conditions that are necessary for instrumental performance to adjust appropriately to a change in drive state. Rats were trained to press a lever and pull a chain concurrently, with one action being reinforced by sucrose solution and the other by food pellets. In Experiment 1 for animals that were hungry throughout training the rate of lever pressing in an extinction test under thirst was unaffected by the type of reinforcer produced by this action during training, even though the sucrose solution would maintain a higher rate than the food pellets during training under thirst. In contrast, animals that experienced the instrumental contingencies arranged by the concurrent schedule while thirsty at some point during training pressed the lever more during the extinction test under thirst when this action had been reinforced with the sucrose solution rather than the food pellets. The remaining three experiments demonstrated that for this incentive effect to occur it is sufficient that the sucrose solution be delivered non-contingently under thirst at some stage of training. Thus, it would appear that performance mediated by an instrumental contingency adjusts appropriately to reinforcer revaluation brought about by a drive shift only if the animals have had prior experience with the incentive under the test drive state. This observation was interpreted in terms of Tolman's “cathexis” theory of motivation.     

The effect of the instrumental training contingency on susceptibility to reinforcer devaluation

Two experiments investigated performance of instrumental lever pressing by rats following post-conditioning devaluation of the sucrose reinforcer produced by establishing an aversion to it. In Experiment I rats responded less in an extinction test after being averted from the sucrose following training on a ratio schedule, but not following an equivalent amount of training on an interval schedule. This was true even though the devalued sucrose would not act as an effective reinforcer on either the ratio or interval schedule. Experiment II provided a further investigation of the insensitivity of interval responding to reinforcer devaluation by comparing test performance under simple extinction with responding when the devalued reinforcer was presented on either a response-contingent or non-contingent schedule during the test. Once again simple extinction performance was unaffected by prior reinforcer devaluation. Furthermore, neither non-contingent nor contingent presentations of the devalued reinforcer significantly depressed responding below the level seen in the extinction condition. Ratio, but not interval performance appears to be controlled by knowledge about the instrumental contingency that encodes specific properties of the training reinforcer.     

Working Class Masculinity: Keeping Gay Men and Lesbians out of the Workplace

Recent survey research suggests that heterosexuals’ attitudes toward lesbian and gay rights have become more progressive. However, we find in our research that negative attitudes and barriers against gay men and lesbians in workplaces still remain. Our project represents one case study of hidden animosity toward homosexuals, which varies from “overt disgust” to “don’t ask, don’t tell” policies that reinforce negative attitudes toward gay men and lesbians. As such, we contend that attitudes toward lesbian and gay rights are not becoming more progressive; instead various methods of discrimination are increasingly being used to exclude gay men and lesbians from the workplace. We argue that White working class men have constructed and maintained a form of White male solidarity, a collective practice directed toward women, People of Color, and non-heterosexuals that maintains racism, sexism, and homophobia in the local, national, and global context.     

Spatial asymmetries in viewing and remembering scenes: Consequences of an attentional bias?

Given a single fixation, memory for scenes containing salient objects near both the left and right view boundaries exhibited a rightward bias in boundary extension (Experiment 1). On each trial, a 500-msec picture and 2.5-sec mask were followed by a boundary adjustment task. Observers extended boundaries 5% more on the right than on the left. Might this reflect an asymmetric distribution of attention? In Experiments 2A and 2B, free viewing of pictures revealed that first saccades were more often leftward (62%) than rightward (38%). In Experiment 3, 500-msec pictures were interspersed with 2.5-sec masks. A subsequent object recognition memory test revealed better memory for left-side objects. Scenes were always mirror reversed for half the observers, thus ruling out idiosyncratic scene compositions as the cause of these asymmetries. Results suggest an unexpected leftward bias of attention that selectively enhanced the representations, causing a smaller boundary extension error and better object memory on the views’ left sides.     

Age-based discrimination of rival males in western bluebirds

Adaptive social behavior frequently involves discriminating between classes of individuals such as relatives versus non-relatives, older versus younger individuals, or individuals of different status. In the absence of spatial cues, this discrimination may be based on signals that correlate with fitness-related traits (e.g., older or high-status males may sing higher performance songs) or with identity, for example, when receivers distinguish and classify signalers based on their unique signal structure. Here, we examine vocal age-based discrimination in western bluebirds (Sialia mexicana), a North American songbird in which older males have a significant advantage in obtaining extra-pair fertilizations, and therefore pose a significantly higher threat to paternity than younger males. We asked whether western bluebird males showed a higher response to playback of songs of older males compared to younger males relative to their own age. We prepared song stimuli by removing three potential signals of age that have been identified as important in other species: (1) note consistency (which was achieved by playing a single instance of each note repeatedly), (2) note repertoire size, and (3) singing rate (the latter two were equalized across conditions). Even in the absence of these potential signals of age, young males responded more strongly to playback of older males’ songs than to young males’ songs, suggesting that they are able to discriminate between age classes relative to the threat they pose. Further research is required to determine whether this discrimination is based on individual recognition or signal features that are correlated with age.