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The neural signature and cognitive architecture of how a visual stimulus reaches conscious awareness have not been conclusively determined. Recently, we have reported an ERP activity corresponding with a period of perceptual persistence which has been typically reported in working memory research, known as the contralateral delay activity (CDA). Specifically, we reported how the CDA can be used to track how on object fades in out of consciousness. Here, we report on the behaviour of the CDA when the type of item in this paradigm is manipulated between face, animal and object stimuli. We recorded EEG activity while participants viewed a bilateral Shape-from-Motion display and analyzed where and how large a CDA is observed. Our findings show that the CDA is generalizable to different item types fading from awareness, with no differences between item conditions. This work supports the content-invariant involvement of working memory processes in sustaining conscious awareness.

The neural signature and cognitive architecture of how a visual stimulus reaches conscious awareness have not been conclusively determined. Recently, we have reported an ERP activity corresponding with a period of perceptual persistence which has been typically reported in working memory research, known as the contralateral delay activity (CDA). Specifically, we reported how the CDA can be used to track how on object fades in out of consciousness. Here, we report on the behaviour of the CDA when the type of item in this paradigm is manipulated between face, animal and object stimuli. We recorded EEG activity while participants viewed a bilateral Shape-from-Motion display and analyzed where and how large a CDA is observed. Our findings show that the CDA is generalizable to different item types fading from awareness, with no differences between item conditions. This work supports the content-invariant involvement of working memory processes in sustaining conscious awareness.

The present study investigates the intersection of working memory and emotion recognition in young adults with autism spectrum disorders (ASD) and neurotypical controls. The executive functioning theory of autism grounds key impairments within the cognitive realm, whereas social-cognitive theories view social functioning impairments as primary. Executive functioning theory of ASD has been criticized because executive functioning is too broad and is composed of separable, component skills. In the current study, the focus is narrowed to one of those components, working memory. It has been suggested that executive functioning may play a role in effective social interactions. Emotion recognition is an important aspect of social reciprocity, which is impaired in ASD. The current study investigates this hypothesis by combining working memory and emotion recognition into a single task, the n-back, as a model of social interaction and comparing performance between adults with ASD and controls. A validates set of facial expression stimuli (NimStim) was modified to remove all extraneous detail, and type of emotion was tightly controlled across 1-, 2-, and 3-back conditions. Results include significantly lower accuracy in each of the working memory load conditions in the ASD group compared to the control group, as well as in a baseline, maintenance memory task. The control group's reaction time increased as working memory load increased, whereas the ASD group's reaction time did not significantly vary by n-back level. The pattern of results suggests that the limit for n-back with emotional expressions is 2-back, due to near chance level performance in both groups for 3-back, as well as definitive problems in short term memory for facial expressions of emotion in high-functioning individuals with ASD, in contrast to previous findings of near perfect short term memory for facial expressions of emotion in controls.

There is a large range of models of working memory, each with different scopes and emphases. Current interest focuses strongly on the interaction of working memory with long-term memory, as it has become clear that models of working memory alone are incapable of capturing some of our complex cognitive abilities. Most models have contrasting views on how this interaction is implemented. In this thesis, three classes of models are defined, each proposing a different type of interaction. The first model proposes that working memory acts as a gateway for perceptual input on its way to long-term memory. In the unitary model, working memory is seen as comprising the activated portion of long-term memory. The workspace model views working memory as a workspace that is separate from, and deals with the activated contents of long-term memory. The main aim of this thesis was to address the differences between these three models experimentally. Experiments 1 – 7 employed a dual-task paradigm to investigate the effects of irrelevant visual input on visuo-spatial working memory tasks. Two main findings emerged: (1) maintenance of images in working memory was largely insensitive to the effects of concurrent perceptual input; (2) mental imagery was susceptible to interference from irrelevant visual input. This interference effect was selective, as demonstrated by a lack of disruption of imagery by other secondary tasks. Experiment 8 further tested the three models by investigating implicit processing of visual information by neglect patients. It was found that implicit processing is mediated by the activation of long-term memory, in the absence of a conscious representation in working memory. These results together converge to support the workspace model, and suggest a view in which perceptual input activates the contents of long-term memory, prior to these activated representations being made available in a functionally separate working memory system for further processing. The gateway model and unitary model are unable to accommodate all findings. The implications of these results for existing theories about working memory are discussed.

It is generally agreed that language interpreting is cognitively demanding; how- ever, to date there is little evidence to indicate how working memory is involved in the task, perhaps due to methodological limitations. Based on a full considera- tion of key components of interpreting, two series of experiments were conducted to explore how working memory might play a role in discourse and sentence inter- preting. If working memory is implicated both in grammatical encoding into the target language, and in temporary storage of the discourse content, then higher demand in one function might compromise the other. Thus discourses that di er in word orders between languages could increase the processing load and leave less resource for memory maintenance, a ecting recall performance. In Experiment 1, Chinese-English bilingual participants' memory performance was compared when they translated passages from Chinese to English and from English to Chinese, where the expected word order was either congruent or incongruent between source and target. Recall was not sensitive to word order or direction of translation. Per- haps surprisingly, memory for incongruent discourses was numerically better than that for congruent sentences. Experiment 2 showed that interpreting trainees per- formed just like the participants in Experiment 1 did, suggesting that memory performance was not modulated by translation direction in pro cient translators. Experiment 3 explored the relationship between surface form transformation and recall. As discourse paraphrasing did not result in better recall than verbatim recall, it was concluded that the better memory performance for incongruent discourse in- terpreting suggested by Experiment 1 was not the result of active manipulation of word form or word order in interpreting. Finally, a free recall task among native English speakers showed that the incongruent discourses tested in earlier experi- ments were intrinsically more memorable than congruent discourses (Experiment 4). Despite this confound, this series of experiments highlighted the importance of comprehension in interpreting, but it did not rule out the role of working memory in the task. The role of working memory in interpreting was further explored using on-line measures in Experiments 5-8. Experiment 5 replicated a self-paced reading study by Ruiz, Paredes, Macizo, and Bajo (2008), comparing participants’ times to read sentences for translation to those to read them normally. The data showed that participants accessed lexical and syntactic properties of a target language in the reading-for-translation condition when resources were available to them. In order to explore the role of working memory in sentence interpreting, a dual-task paradigm was used in Experiment 6. When participants' working memory was occupied by a secondary task (digit preload), reading times were only different numerically between congruent and incongruent sentences. Crucially, reading times decreased as digit preload increased. Since there were no differences in the interpretations produced or in digit recall, it appears that participants were flexible in their resource allocation, suggesting that processing can be tuned up to optimise performance for concurrent tasks. Experiment 7 refined the procedure in the order of responses for the dual tasks but replicated the results of Experiment 6. A closer examination of participants’ interpretation responses showed that devices that could reduce processing load in target language production may have been strategically employed. Finally, another set of sentences were used in Experiment 8 in an attempt to replicate Experiment 5. A failure to replicate the earlier findings suggested that working memory demand might differ for different syntactic structures in sentence interpreting. All in all, this thesis shows that research in language interpreting benefits by taking a full account of the key components of interpreting. The use of on-line measures allowed us to take a ne-grained approach to the investigation of interpretation processes. It is proposed in this thesis that interpreting research may gain more insight from the data by incorporating some of the theories and methods typically used in research into language production.

This study investigated the effects of working memory constraints on the comprehension of expository texts by adolescents with severe Traumatic Brain Injury (TBI). The performance of adolescents with TBI will be compared against a group of typically developing (TD) gender and age-matched peers. The research questions are: (1) How does the performance of adolescents with TBI compare to typically developing gender and age-matched peers on tasks examining comprehension of expository texts?; and (2) Does comprehension of expository text decrease when working memory constraints are increased for adolescents with TBI? Fifteen participants will participate in the study. One group of five adolescents with severe TBI and a second group of ten gender and age-matched typically developing adolescents without TBI completed a battery of assessments including: Test of Nonverbal Intelligence 3rd Edition (TONI-3), Clinical Evaluation of Language Fundamentals 4th Edition (CELF-4), Peabody Picture Vocabulary Test 3rd Edition (PPVT-3) and the Working Memory Span Task (Tompkins et al 1994). All participants also completed an experimental task which involved listening to an expository passage and answering comprehension questions. Scores were then submitted to statistical analysis using ANOVA methodology to determine the significance of any within and between group differences. Results showed that there was no significant group by task interaction effect. The study did show that there was a significant difference between the TBI and TD groups on the measure of working memory. Results of the study will enhance our understanding of how adolescents with TBI comprehend expository information. This study will also help to create a foundation for further research into this area which is critical for student’s success in secondary education.

The goal habituation model of vigilance proposed by Ariga and Lleras (2011) posits that it is possible to attenuate the vigilance decrement (the decline in performance that occurs with time-on-task) through dis-habituation of a vigilance task’s goal. The goal in a vigilance task is to detect critical signals. Hence, a switch away from this goal should dishabituate the task goal. When a person resumes the vigilance task, the person’s performance should improve. Follow up studies to the Ariga and Lleras study have not found supporting evidence (Helton & Russell, 2011; 2012). The methods in these follow up studies differed from those of Ariga and Lleras in a number of ways. The present study attempts to replicate the original Ariga and Lleras (2011) work using methods that more closely follow the original study. The present research sought to uncover confounds in the original article through replicating the original task and manipulating variables in line with hypotheses made by attentional resource theory. Overall, the results of this research present a challenge to the goal habituation model. Rest breaks, not goal switching; lessened the magnitude of the decline in sensitivity with time on task, while task switching resulted in a temporary re-correction of increasingly conservative responding that occurred with greater time on task. We also found support for the context dependent relationship of task-unrelated thought, (TUT) and task demand. Given that the vigil was determined to impose relatively low workload, pre-task TUT was associated with average performance rather than post-task TUT. Finally, we discuss the dangers of over compliance with signal detection theory (SDT) measures. We explain that SDT sensitivity and bias measures are not independent given responding floor and ceiling effects during low demanding tasks such as the present. It is argued that this may have distorted the original conclusion arrived at by Ariga and Lleras (2011).

Arbetsminnet är en viktig funktion för människans kognitiva förmåga. Tidigare forskning har visat det finns flera faktorer som kan påverka arbetsminnets kapacitet, ett exempel är inlärning. Den aktuella studien undersöker om om det finns ett samband med att studera på högskola och att förbättra sin arbetsminneskapacitet. I studien deltog 82 ekonomistuderanden varav 42 studeranden från andra terminen och 40 från sjätte terminen. Ett nätbaserat arbetsminnestest visade att det var en signifikant skillnad i arbetsminneskapaciteten (antalet ihågkomna ord) från andra till sjätte terminen. Det visade sig även att motivationen hade en tendens att vara högre att klara testet i sjätte terminen än i andra. Studien kan bidra till vidareforskning om en högre utbildnings effekt på olika faktorer som är förknippade med kognition.

Cannabis has been used medicinally for millennia, but the cannabinoid (CB) field exploded with the identification of its endogenous receptors and endocannabinoids (eCBs). In vitro experimentation established that eCBs alter synaptic plasticity at presynaptic nerve terminals; however, the characterization of the eCB system (ECS) in vivo remains incomplete. This study aimed to determine the mechanism of in vivo eCB-mediated hippocampal synaptic plasticity and to analyze the effects this plasticity had on spatial working memory (SWM). With in vivo recordings of field excitatory postsynaptic potentials (fEPSPs) in anesthetized mice and rats as well as pharmacological manipulation of the ECS and glutamate receptor antagonism, it was found that eCBs, both anandamide (AEA) and 2-arachnidonyl glycerol (2-AG), caused LTD at hippocampal CA3-CA1 synapses. Induction of eCB-LTD occurs via a sequential activation of cannabinoid type-1 receptor (CB1R) and NR2B-containing NMDA receptor (NR2BR) and is expressed through the endocytosis of AMPA receptors (AMPARs). Increased eCB tone also caused an impairment of SWM for over 24 hours in the Delayed Non-Match-To-Sample (DNMTS) T-maze. This study provides the first evidence that an acute administration of eCB degradative enzyme inhibitors not only produces an in vivo LTD at hippocampal CA3-CA1 synapses that requires CB1R, NR2BR, and AMPAR, but also impairs SWM, a phenomenon also caused by an acute injection of exogenous CBs.