Using transcranial direct-current stimulation (tDCS) to understand cognitive processing

Noninvasive brain stimulation methods are becoming increasingly common tools in the kit of the cognitive scientist. In particular, transcranial direct-current stimulation (tDCS) is showing great promise as a tool to causally manipulate the brain and understand how information is processed. The popularity of this method of brain stimulation is based on the fact that it is safe, inexpensive, its effects are long lasting, and you can increase the likelihood that neurons will fire near one electrode and decrease the likelihood that neurons will fire near another. However, this method of manipulating the brain to draw causal inferences is not without complication. Because tDCS methods continue to be refined and are not yet standardized, there are reports in the literature that show some striking inconsistencies. Primary among the complications of the technique is that the tDCS method uses two or more electrodes to pass current and all of these electrodes will have effects on the tissue underneath them. In this tutorial, we will share what we have learned about using tDCS to manipulate how the brain perceives, attends, remembers, and responds to information from our environment. Our goal is to provide a starting point for new users of tDCS and spur discussion of the standardization of methods to enhance replicability.     

Automatic and strategic effects in the guidance of attention by working memory representations

Theories of visual attention suggest that working memory representations automatically guide attention toward memory-matching objects. Some empirical tests of this prediction have produced results consistent with working memory automatically guiding attention. However, others have shown that individuals can strategically control whether working memory representations guide visual attention. Previous studies have not independently measured automatic and strategic contributions to the interactions between working memory and attention. In this study, we used a classic manipulation of the probability of valid, neutral, and invalid cues to tease apart the nature of such interactions. This framework utilizes measures of reaction time (RT) to quantify the costs and benefits of attending to memory-matching items and infer the relative magnitudes of automatic and strategic effects. We found both costs and benefits even when the memory-matching item was no more likely to be the target than other items, indicating an automatic component of attentional guidance. However, the costs and benefits essentially doubled as the probability of a trial with a valid cue increased from 20% to 80%, demonstrating a potent strategic effect. We also show that the instructions given to participants led to a significant change in guidance distinct from the actual probability of events during the experiment. Together, these findings demonstrate that the influence of working memory representations on attention is driven by both automatic and strategic interactions.     

Selective storage and maintenance of an object’s features in visual working memory

It has been shown that we have a highly capacity-limited representational space with which to store objects in visual working memory. However, most objects are composed of multiple feature attributes, and it is unknown whether observers can voluntarily store a single attribute of an object without necessarily storing all of its remaining features. In this study, we used a masking paradigm to measure the efficiency of encoding, and neurophysiological recordings to directly measure visual working memory maintenance while subjects viewed multifeature objects and were required to remember only a single feature or all of the features of the objects. We found that measures of both encoding and maintenance varied systematically as a function of which object features were task relevant. These experiments show that individuals can control which features of an object are selectively stored in working memory.     

Implicit memory influences the allocation of attention in visual cortex

The visual environment is highly regular, with particular objects frequently appearing in specific locations. Previous studies of visual search have shown that people take advantage of such regularities, detecting targets more quickly when they appear at a predictable location within a given spatial configuration. Moreover, this effect depends on implicit rather than explicit memory for the configurations. These studies have suggested that implicit long-term memory for contextual information influences the allocation of attention, modulating the flow of information through visual cortex. The present study used event-related potentials to provide the first direct support for this proposal. We suggest that this guidance of attention by implicit memory is important in the natural environment because it allows environmental regularities to influence perception without the intervention of limited-capacity conscious processes.     

Competition-specific preparation and expert performance

ObjectiveThe objective of the study was to identify and describe the extent, function, nature, and timeline of practice and preparation activities undertaken by experts in order to adapt to constraints unique to a specific upcoming competition.MethodA content analysis was conducted of data from interviews with 15 expert orienteers and six experienced orienteering coaches about competition-specific preparation in the sport of orienteering.ResultsThe analysis revealed several key concepts. First, competition-specific preparation is necessary because the constraints of a given orienteering competition vary across competitions. Second, owing to such variance, orienteers have limited advance information about the specific constraints of an upcoming competition, which impedes their preparation for that competition. Third, expert orienteers engage in a range of activities designed to gather information about the constraints of an upcoming competition. Fourth, this information is then used to identify or create practice environments that represent these constraints. Practice within these environments enables expert orienteers to adapt to these constraints before competing.ConclusionsCompetition-specific preparation appears critical to performance in sports in which environmental constraints change considerably between competitions.     

A comparison of the environments of day care centers and group day care homes for 3 year olds

Caregiver-child interaction and social participation were compared in community-based day care centers and group day care homes for three year olds. Use of group day care homes made it possible to control for group size and adult-child ratio. Day care homes were found to be more structured in terms of curriculum, and more flexible in terms of overall schedule and social-emotional climate. Adult child interaction was of higher quality during structured periods in day care homes. Social participation was of higher quality in day care homes. The adult-child interaction in both types of day care was impersonal and neutral in affective tone.     

Relationships between Growth need Strength and selected individual differences measures employed in job design research

The present study examines the degree to which the Growth Need Strength scales (Job Choice and Would Like formats) of the Job Diagnostic Survey (Hackman & Oldham, Journal of Applied Psychology, 1975, 60, 159–170) correlate with (a) other measures of needs and values employed in research as moderators of the job scope-job satisfaction relationship and (b) a measure of social desirability. Results showed (a) only moderate correlations between the Growth Need Strength scales and the other measures of needs and values and (b) a relatively high degree of correlation between social desirability and the Would Like measure of Growth Need Strength. Implications of these findings for job design research are considered.     

Seeking meaning in late stage dementia

The author uses case studies to illustrate the effectiveness of two techniques which pastoral caregivers may teach to family carers of dementia patients. In the last stages of dementia, it is important to seek meaning and keep in significant contact as long as possible, both for family members as well as for the dementia patients. After a brief literature review, implications for care theory, practice, and policy are reviewed, and a scientific bias is illustrated. These techniques build on the work of C. G. Jung and James Hillman, utilizing metaphor in non-rational uses of language. It is suggested that pastoral caregivers could teach these techniques to families of this population, in the hope of prolonging meaningful connection with their loved one.     

Visual Search Remains Efficient When Visual Working Memory is Full

Many theories of attention have proposed that visual working memory plays an important role in visual search tasks. The present study examined the involvement of visual working memory in search using a dual-task paradigm in which participants performed a visual search task while maintaining no, two, or four objects in visual working memory. The presence of a working memory load added a constant delay to the visual search reaction times, irrespective of the number of items in the visual search array. That is, there was no change in the slope of the function relating reaction time to the number of items in the search array, indicating that the search process itself was not slowed by the memory load. Moreover, the search task did not substantially impair the maintenance of information in visual working memory. These results suggest that visual search requires minimal visual working memory resources, a conclusion that is inconsistent with theories that propose a close link between attention and working memory.     

Do the contents of visual working memory automatically influence attentional selection during visual search?

In many theories of cognition, researchers propose that working memory and perception operate interactively. For example, in previous studies researchers have suggested that sensory inputs matching the contents of working memory will have an automatic advantage in the competition for processing resources. The authors tested this hypothesis by requiring observers to perform a visual search task while concurrently maintaining object representations in visual working memory. The hypothesis that working memory activation produces a simple but uncontrollable bias signal leads to the prediction that items matching the contents of working memory will automatically capture attention. However, no evidence for automatic attentional capture was obtained; instead, the participants avoided attending to these items. Thus, the contents of working memory can be used in a flexible manner for facilitation or inhibition of processing.