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Remembering the sound of a new word when it is first encountered is an important skill which plays a critical role in the development of vocabulary (Gathercole & Baddeley, 1989), yet the mechanisms underlying this form of verbal short-term memory are not well understood. Errors in the repetition and serial recall of nonwords indicate that structural properties of the syllable are represented in short-term memory, but existing accounts of serial learning and recall do not incorporate any representation of linguistic structure. Models of speech production implicate syllable structure in the representation of phonological form, but do not explain how such representations are acquired. This thesis draws together theories of speech production and serial memory to develop a computational model of nonword repetition based on the novel idea that short-term memory for the serial order of a sequence of speech sounds is constrained by a syllabic template. The results of simulations using the model are presented and compared with experimental findings concerning short-term memory for nonwords. The interaction of short- and long-term phonological memory systems and the aquisition of vocabulary are discussed in terms of the model. The model is evaluated in comparison with other contemporary theories.

A vast literature and our own common sense tell us that free recall (i.e., recalling information without hints) is harder and less successful than cued recall (i.e., recalling information with hints). In this dissertation, I argue that in past work free and cued recall has not been directly comparable because cued recall procedures encourage guessing and the nature of the cues promotes accurate guesses. These biases often inflate cued recall performance above free recall, creating the illusion that cued recall is superior to free recall. To control for these issues, I introduce the recognized recall procedure. Recognized recall requires subjects to produce a word on every test trial and subsequently to recognize those produced words as “old” or “new.” Across eight experiments with recognized recall, it is demonstrated that cueing does help subjects produce more studied words than in free recall, however, subjects are often unable to recognize those extra words produced. Worse yet, false memories are observed to rise in all cases of cueing. Three subsequent experiments demonstrate that cueing fails to improve recall consistently because cues do not always cue the same meaning of the word as was encoded at study. A final experiment demonstrates that free associates of studied words produced by subjects can be highly effective at improving memory if used as cues at test. It is concluded that cues can improve memory if they are specific to the study episode but can often lead to a rise in false memories. Thus, in terms of consistently optimizing accurate recall while minimizing false memories, free recall may actually be superior to cued recall.

Masters Research - Master of Medical Science / Introduction: Between 6-10% of women attending breast screening are recalled to investigate an unclear area on the mammogram. Image quality is known to affect image interpretation and it has been suggested that the number of recalls could be reduced with improved image quality. Aim: This study aimed to investigate the effect image quality has on recall rates, to assess reader consistency using the PGMI classification system and to establish factors leading to recall. Materials and Methods: A six member panel assessed 904 sets of images (698 recalled; 206 non-recalled) through a BreastScreening Program during three separate phases (pilot, main and non-recall). The pilot study was conducted without additional training in PGMI. Levels of agreement and Kappa statistics were calculated to assess intra- and inter-consistency. The percentage of and reasons for inadequate images was calculated; while a case-control study was conducted to establish factors increasing the likelihood of a client being recalled. Results: The level of agreement between panel members significantly increased from the pilot to the main study (45.5% to 57.7%) before decreasing slightly for the non-recall (57.7% to 52.2%). Overall, 3.3% of the 904 sets of images were classed as inadequate; the most common PGMI reason was exposure (31%); the left MLO was considered the most common inadequate projection (30%), with more privately produced (66%) images considered inadequate compared to public images (34%). Inadequate image quality did not hinder the cancer detection rates. The case-control component demonstrated current and previous HRT use, increased breast density, better image quality and images being taken at a public site all contributed to a client being recalled. Conclusion: The results of this study demonstrated that inadequate image quality was not a major factor leading to recall; although twice the number of recalled images were considered inadequate compared to the non-recalled images. The use of the PGMI classification system is highly subjective, with low levels of agreement amongst users. The use of HRT, breast density, imaging site and image quality all contribute to a client being recalled.

Spiking neural networks (SNNs) are a more biologically realistic model of the brain than traditional analog neural networks and therefore should be better for modelling certain functions of the human brain. This thesis uses the concept of deriving an SNN from an accepted non-spiking neural network via analysis and modifications of the transmission function. We investigate this process to determine if and how the modifications can be made to minimize loss of information during the transition from non-spiking to spiking while retaining positive features and functionality of the non-spiking network. By comparing combinations of spiking neuron models and networks against each other, we determined that replacing the transmission function with a neural model that is similar to it allows for the easiest method to create a spiking neural network that works comparatively well. This similarity between transmission function and neuron model allows for easier parameter selection which is a key component in getting a functioning SNN. The parameters all play different roles, but for the most part, parameters that speed up spiking, such as large resistance values or small rheobases generally help the accuracy of the network. But the network is still incomplete for a spiking neural network since this conversion is often only performed after learning has been completed in analog form. The neuron model and subsequent network developed here are the initial steps in creating a bidirectional SNN that handles hetero-associative and auto-associative recall and can be switched easily between spiking and non-spiking with minimal to no loss of data. By tying everything to the transmission function, the non-spiking learning rule, which in our case uses the transmission function, and the neural model of the SNN, we are able to create a functioning SNN. Without this similarity, we find that creating SNN are much more complicated and require much more work in parameter optimization to achieve a functioning SNN.

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Anesthesia awareness is a rare, but severe complication of anesthesia with possible severe long-term effects that is more commonly reported after trauma and emergent surgery. Anesthesia awareness in trauma patients who require emergency surgery has not been researched on since Bogetz and Katz’s study in 1984. This landmark study reported a higher risk of anesthesia awareness due to multiple factors, including intolerance of anesthetic agents in these patients who often present with hemodynamic instability and low blood pressure. Given the reported risk of awareness in this population, clinicians continue to administer standard doses of anesthetic agents despite the associated hemodynamic effects and the concern for other anesthesia-related complications. Therefore, it is important to determine if the risk factors and incidence of awareness remains high despite recent advances in anesthetic techniques and monitoring. We hypothesized that awareness under general anesthesia in trauma patients is less common with the use of modern-day anesthetic agents and monitoring devices. To examine this hypothesis, the incidence of anesthesia awareness was retrospectively studied in all trauma patients requiring emergency surgery at Boston Medical Center (BMC) between January 2020 and February 2022. The patients were asked a 5-minute questionnaire which included questions from the modified Brice questionnaire to determine the incidence of perioperative awareness. It was found that the incidence of awareness during general anesthesia in trauma surgery patients at BMC from January 2020 through February 2022 was significantly lower (with an incidence of 0%) than the previously reported incidence of 11% by Bogetz and Katz, (p = 0.028, CI -0.22-0.00). Further research is warranted to confirm our findings and further explore the incidence and impact of awareness in this vulnerable population. Future prospective studies should examine a greater number of trauma patients, associated risk factors, and the role of processed EEG monitoring in preventing awareness during general anesthesia.

A series of 5 experiments investigated whether false memory in associated word lists present with serial position effects (SPE) and how any such effects behave in response to manipulations of true recall SPE. Recall for a series of events is typified by SPE such that items nearer the beginning, primacy effect, and end, recency effect, of a series are remembered better than middle items. Recall is also typified by the intrusion of falsely remembered information. Word-lists segmented into trimesters of either semantically (e.g., hot, snow, warm.../ bed, rest, awake.../ looking, lens, shatter...) or phonologically (e.g., code, called, fold.../ sweep, sleet, steep.../ class, grass, glad...) associated words produced false recall (e.g., cold, sleep, glass), allowing for the simultaneous investigation of SPE for true and false recall. Typical SPE for true recall were observed for each of the five Experiments. For immediate free recall, semantic false recall declined from early to late study trimesters whereas phonological false recall displayed a false primacy and recency effect similar to true recall SPE. Phonological false recall was significantly reduced when a 15 second distractor task was implemented during the retention interval. Dividing attention during study using a concurrent handwriting task reduced true recall whereas semantic false recall increased at primacy and phonological false recall increased at recency. This suggests distinct processes underlying the two forms of false recall. Dividing attention using an articulatory suppression task produced less true recall and less false recall than using concurrent handwriting. This research indicates that false recall SPE exist and that the semantic and phonological forms of false recall SPE are distinct. Current theories of false memory and of true recall SPE are considered.

A series of 5 experiments investigated whether false memory in associated word lists present with serial position effects (SPE) and how any such effects behave in response to manipulations of true recall SPE. Recall for a series of events is typified by SPE such that items nearer the beginning, primacy effect, and end, recency effect, of a series are remembered better than middle items. Recall is also typified by the intrusion of falsely remembered information. Word-lists segmented into trimesters of either semantically (e.g., hot, snow, warm.../ bed, rest, awake.../ looking, lens, shatter...) or phonologically (e.g., code, called, fold.../ sweep, sleet, steep.../ class, grass, glad...) associated words produced false recall (e.g., cold, sleep, glass), allowing for the simultaneous investigation of SPE for true and false recall. Typical SPE for true recall were observed for each of the five Experiments. For immediate free recall, semantic false recall declined from early to late study trimesters whereas phonological false recall displayed a false primacy and recency effect similar to true recall SPE. Phonological false recall was significantly reduced when a 15 second distractor task was implemented during the retention interval. Dividing attention during study using a concurrent handwriting task reduced true recall whereas semantic false recall increased at primacy and phonological false recall increased at recency. This suggests distinct processes underlying the two forms of false recall. Dividing attention using an articulatory suppression task produced less true recall and less false recall than using concurrent handwriting. This research indicates that false recall SPE exist and that the semantic and phonological forms of false recall SPE are distinct. Current theories of false memory and of true recall SPE are considered.

I detta arbete undersökts det huruvida ergodiska texter kan ge ett bättre stöd för att minnas en fabula av en text gentemot en traditionell text. Med två versioner av en text, en ergodisk och en traditionell, har deltagare fått ge ett återgivande av den version de tog del av. För att analysera deltagarnas återgivanden gjordes en lista av hållpunkter baserade på berättelsens fabula. Utifrån resultaten kom det fram att den ergodiska versionen var lättare att ta till sig, men på grund av det låga deltagarantalet ger detta inte ett representativt resultat. Vidare studier skulle kunna ge mer representativa resultat.