Computational models of working memory: putting long-term memory into context

Detailed computational modeling of human memory has typically been aimed at either short-term (working) memory or long-term memory in isolation. However, recent research highlights the importance of interactions between these systems for both item and order information. At the same time, computational models of both systems are beginning to converge onto a common framework in which items are associated with an evolving "context" signal and subsequently compete with one another at recall. We review some of these models, and discuss a common mechanism capable of modelling working memory and its interaction with long-term memory, focussing on memory for verbal sequences.     

Performance-related activity in medial rostral prefrontal cortex (area 10) during low-demand tasks

Neuroimaging studies have frequently observed relatively high activity in medial rostral prefrontal cortex (PFC) during rest or baseline conditions. Some accounts have attributed this high activity to the occurrence of unconstrained stimulus-independent and task-unrelated thought processes during baseline conditions. Here, the authors investigated the alternative possibility that medial rostral PFC supports attention toward the external environment during low-demand conditions. Participants performed a baseline simple reaction time (RT) task, along with 3 other tasks that differed in the requirement to attend to external stimuli versus stimulus-independent thought. Medial rostral PFC activation was observed in the baseline task and in a condition requiring strong engagement with external stimuli, relative to 2 conditions with a greater requirement for stimulus-independent thought. An important finding was that activity in this region was associated with faster RTs in the baseline task, ruling out an explanation in terms of task-unrelated thought processes during this condition. Thus, at least under certain circumstances, medial rostral PFC appears to support attention toward the external environment, facilitating performance in situations that do not require extensive processing of experimental stimuli.     

Spatial memory: how egocentric and allocentric combine

Recent experiments indicate the need for revision of a model of spatial memory consisting of viewpoint-specific representations, egocentric spatial updating and a geometric module for reorientation. Instead, it appears that both egocentric and allocentric representations exist in parallel, and combine to support behavior according to the task. Current research indicates complementary roles for these representations, with increasing dependence on allocentric representations with the amount of movement between presentation and retrieval, the number of objects remembered, and the size, familiarity and intrinsic structure of the environment. Identifying the neuronal mechanisms and functional roles of each type of representation, and of their interactions, promises to provide a framework for investigation of the organization of human memory more generally.     

Effects of chronic non-clinical depression on the use of positive and negative words in language contexts

The purpose of this study was to investigate the effects of chronic non-clinical depression (ChD) on the use of ambiguous and unambiguous emotional words in language contexts. Participants with ChD and normal non-depressed (ND) participants' responses to positive and negative stimulus words on a free association word test were compared using the Hyperspace Analogue to Language (HAL) model of memory's context density metric, a measure of the range of contexts in which a word is used in language. ChD participants generated negative words that were used in more restricted contexts than ND participants. However, ND and ChD participants used positive words in a similar range of contexts. The results suggest that people with ChD tend to use negative words that are probably more negative in connotation, yet they are not impaired with respect to using words in contexts where positive words are required.     

Psychopathy and COVID-19: Callousness,impulsivity, and motivational reasons for engaging in prevention behavior

Two direct replication studies were conducted to investigate the associations of psychopathic traits with engagement in COVID-19 prevention behavior and motivational reasons for engaging in such behavior. College undergraduate students completed two self-report measures of psychopathic traits based on the four-factor conceptualization of psychopathy (callous affect, manipulative tendency, erratic lifestyle, criminal tendency) and the triarchic conceptualization of psychopathy (meanness, disinhibition, boldness). Participants then reported the degree to which they engaged in COVID-19 prevention behavior currently and in the past, and reported their self-focused and other-focused motivational reasons for doing so. Results aggregated across both studies (N = 292) revealed that traits reflecting emotional callousness and impulsivity independently predicted lower levels of other-focused reasons for engaging in prevention behavior. Moreover, controlling for other-focused reasons appreciably reduced negative associations of emotional callousness and impulsivity with prevention behavior. The results provide insight into points of convergence in conceptualization and measurement of psychopathy from multiple theoretical perspectives and the importance of considering the impact of divisive personality traits on motivation to protect others during pandemics.     

Illness intrusiveness and quality of life in end-stage renal disease: comparison and stability across treatment modalities

Investigated the degree to which chronic, life-threatening illness and its treatment interfere with continued involvements in valued activities and interests--that is, illness intrusiveness--and its impact on quality of life in end-stage renal disease. Data were collected on two occasions separated by a lag of 6 weeks. Mixed analyses of variance indicated that life domains were affected differentially across treatments. Perceived illness intrusiveness correlated significantly with treatment time requirements, uremic symptoms, intercurrent nonrenal illnesses, fatigue, and difficulties in daily activities. Significant quality-of-life differences were observed across treatment modalities for satisfaction/happiness and pessimism/illness-related concerns but not for depression/distress. Perceived illness intrusiveness correlated significantly with each of these quality-of-life measures. Results were stable over time. These findings substantiate the construct of illness intrusiveness as a mediator of the psychosocial impact of chronic, life-threatening illness.     

Automated offset compensation for DC biopotential measurements

We describe a design for high-gain DC bioamplifiers with automatic offset nulling capability. Taking advantage of state-of-the-art commercially available linear integrated circuits, the design is suitable for low-level measurements such as EEG and event-related potentials. DC input offsets can be nulled instantly, making multichannel DC amplification feasible without time-consuming manual offset compensation. In addition, both signal and DC offset outputs are provided, permitting concurrent monitoring of slow large-scale DC shifts as well as faster small-signal activity . An alternative AC mode with signal and offset outputs is also provided. This approach lends itself to a wide range of applications in which small DC biopotentials must be measured in the presence of larger, variable DC components.     

An aerosol spray alternative to cigarette smoking in the study of the behavioral and physiological effects of nicotine

For studies of the behavioral and physiological effects of nicotine in smokers, delivery of nicotine via cigarette smoking is highly variable and difficult to control. A more precise method of delivery is needed in order to accurately manipulate the amount of nicotine being presented and, thus, to determine its quantitative effects. The objective of the study reported here was to test an aerosol nasal-spray method of delivering measured doses of nicotine. Eleven healthy males were presented 0 mg (placebo), 0.5 mg, 1.0 mg, and 2.0 mg of nicotine over 5 min during four separate sessions, and changes were observed in plasma nicotine concentration and cardiovascular activity. Dose-response relationships were observed between nicotine presented via this method and plasma nicotine, heart rate, systolic blood pressure, and, to a lesser extent, diastolic blood pressure. These results suggest that this aerosol spray method of presenting nicotine provides the measured doses necessary for quantification of nicotine’s effects.