The effect of cognitive load on hemispheric asymmetries in true and false memory.

Studies examining hemispheric asymmetries in false memory have shown that the right hemisphere (RH) is more susceptible to false memories compared to the left hemisphere (LH). Theories suggest that hemispheric asymmetries in true and false memory may be due to differences in representational coding and the use of top-down mechanisms in each hemisphere. In the current study, the Deese-Roediger-McDermott false memory paradigm was used in conjunction with divided visual field presentation to examine the role of top-down mechanisms in hemispheric asymmetries of true and false memory. In Experiment 1, participants studied lists of related words while completing secondary cognitive load tasks. In Experiment 2, the secondary tasks were administered during memory retrieval instead of memory encoding. Results revealed that cognitive loads imposed during the study phase influenced veridical memory in the LH more than the RH, but cognitive loads imposed during retrieval did not influence veridical memory in either hemisphere. Surprisingly, false memory rates were not influenced by cognitive loads and were higher in the LH. These data provide evidence that, at least for veridical memory, top-down control mechanisms are used more readily for the encoding of information into memory in the LH compared to the RH.

What forgetting tells us about remembering: the influence of top-down control on hemispheric asymmetries in verbal memory.

It has been suggested that left hemisphere (LH) advantages in verbal processing is due to superior top-down control of verbal information. It is not clear how top-down mechanisms affect the encoding and retrieval of verbal information from hemispheric memory and whether they only influence activation or also encompass the inhibition of verbal information. The directed forgetting method, in conjunction with divided visual field presentation, was used to examine the influence of top-down control mechanisms on hemispheric asymmetries in verbal memory. Participants were cued to remember or forget words. Cues were presented either simultaneously with targets or after a short delay. A recognition memory test using divided visual field presentation was then given. Response times (RTs) revealed effects of cue timing in the LH. With simultaneous cues, RTs were faster to "Remember" words compared to "Forget" words. With delayed cues, RTs for "Remember" and "Forget" words were equivalent. In the right hemisphere (RH), "Remember" words were consistently faster than "Forget" words, regardless of cue timing. These data provide evidence that top-down mechanisms influenced LH verbal memory retrieval more than RH verbal memory retrieval. Finally, there was little evidence to suggest the hemispheres differ in inhibitory processing.

Supportive Care for Dementia: A Replicable Model to Reduce Neurobehavioral Symptoms, Caregiver Stress, and Hospitalizations, and Increase Hospice Referrals.

Objective: This report describes a hospice-supported no-fee program to support patients living with all levels of dementia and their caregivers. Background: Our medical system struggles to serve the rapidly increasing numbers of patients with dementia. Hospice of the Valley developed a low-cost six-month program to reduce caregiver stress and reduce neurobehavioral disturbances of patients living with dementia, reduce costs for insurers, and increase hospice referrals. Methods: Data were analyzed from 532 patients living with caregivers admitted over 22 months. Caregiver burden, behaviors, hospitalization, and hospice admissions were tracked. Results: Severity of neurobehavioral disturbances and burden to caregivers decreased significantly. Hospitalizations decreased during and after the program, resulting in cost savings for insurance programs. Twenty-five percent of participants were admitted to hospice. Discussion: The Supportive Care for Dementia program was welcomed by community physicians, leading to improved supportive care and increased hospice referrals. The program is replicable and has been adopted by one health plan and is being evaluated by others.

The effect of traumatic brain injury on sustained attention and working memory.

PRIMARY OBJECTIVE: The aim of the study was to evaluate working memory (WM) and sustained attention (SA) following severe traumatic brain injury (TBI). RESEARCH DESIGN: The study was a quasi-experimental design with two dependent measures. METHODS AND PROCEDURES: Nine individuals with severe TBI and nine non-injured controls completed two visual tasks containing alphabetic stimuli: a WM task (2-back task) and a 10-minute SA task. MAIN OUTCOMES AND RESULTS: Participants with TBI had lower hit rates and higher false alarm rates than controls on the WM task. Quantitative analysis of the group data did not reveal a differential deficit in SA; however, post-hoc qualitative visual analysis of individual data revealed considerable variability in four participants with TBI, indicating evidence of impaired SA in select individuals. The hit rates for both tasks were positively correlated, supporting the contention that WM and SA are inter-related. CONCLUSIONS: This study provides further evidence of WM deficits following TBI as well as possible SA deficits in some individuals. The results also suggest that WM and SA are inter-related processes. Future studies are needed to replicate the results with larger sample sizes. Based on these findings, patients with TBI may present with WM and SA deficits.

Evidence of cue use and performance differences in deciphering dysarthric speech.

There is substantial performance variability among listeners who transcribe degraded speech. Error patterns from 88 listeners who transcribed dysarthric speech were examined to identify differential use of syllabic strength cues for lexical segmentation. Transcripts from listeners were divided into four groups (ranging from Better- to Poorer- performing). Phrases classified as Higher- and Lower-intelligibility were analyzed separately for each performance group to assess the independent variable of severity. Results revealed that all four listener groups used syllabic strength cues for lexical segmentation of Higher-intelligibility speech, but only the Poorer listeners persisted with this strategy for the Lower-intelligibility phrases. This finding and additional analyses suggest testable hypotheses to address the role of cue-use and performance patterns.

Don't shoot the messnger: memory for misspellings in context.

Misspellings in sentences are usually easy to understand by readers due to top-down influences. Although top-down processing allows for fluent reading of misspelled items, the nature of their representations in memory is not known. If representations of misspellings are distinct from representations of correctly spelled words, their influence should be seen in later recognition decisions. In this set of experiments, participants read words and misspellings embedded in sentences and were later given a recognition test. The sentences contained semantically biased or neutral contexts. In Experiment 1, misspellings were created by removing a single letter (e.g., drveway). In Experiment 2, the recognition items probes were presented in uppercase letters (e.g., DRVEWAY) to reduce the visual similarity between study and test items. In Experiment 3, the misspellings were created by substituting visually similar letters (e.g., driweway). In contrast to the previous experiments, in Experiment 4, participants were explicitly told about the memory test to see how response strategies affect performance. Overall, the results indicate that people retain surface feature information about misspellings which seem to inform their memory judgments, and that the processing of this information cannot be strategically controlled.

Words Versus Pictures: Bilingual Performance on Verbal and Pictorial Measures of Executive Functions.

PURPOSE: This study examined bilinguals' performance on functional executive function map tasks such as the Zoo Map from the Behavioural Assessment of the Dysexecutive Syndrome and the extent to which working memory, set-shifting, and inhibition measures predicted bilinguals' performance on these tasks. Additionally, we explored the utility of pictorial map tasks as a measure of complex executive function in bilinguals. We hypothesized that bilinguals would perform better on the pictorial map tasks due to the reduced language processing demand. METHOD: The analyses included 131 bilingual young adults who completed a comprehensive language history questionnaire, an English proficiency test, a battery of working memory and executive function tasks, and verbal and pictorial map tasks. RESULTS: Contrary to predictions, bilinguals' performance on the verbal maps did not differ significantly from that on the pictorial maps. Two multiple regression models significantly predicted performance on the verbal and pictorial maps, accounting for 7%-25% of the variance in the map scores. Working memory and interference control were the most prominent predictors within these models. CONCLUSIONS: In our study, bilinguals' performance on the verbal maps did not differ significantly from that on the pictorial maps. Additionally, English proficiency did not correlate with the participants' verbal map scores. These results suggest that executive function map tasks (e.g., the Zoo Map) are a useful clinical tool for assessing executive function in bilinguals. The findings of this study are discussed in light of the current literature on executive functions in bilinguals.

The effects of stimulus modality, task complexity, and cuing on working memory and the relationship with speech recognition in older cochlear implant users.

INTRODUCTION: The role of working memory (WM) in speech recognition of older cochlear implant (CI) users remains unclear. This study 1) examined the effects of aging and CI on WM performance across different modalities (auditory vs. visual) and cuing conditions, and 2) assessed how specific WM measures relate to sentence and word recognition in noise. METHOD: Fourteen Older CI users, 12 Older acoustic-hearing (AH) listeners with age-appropriate hearing loss, and 15 Young normal-hearing (NH) listeners were tested. Participants completed two simple span tasks (auditory digit and visual letter span), two complex WM tasks (reading span and cued-modality WM with simultaneously presented auditory digits and visual letters), and two speech recognition tasks (sentence and word recognition in speech-babble noise). RESULTS: The groups showed similar simple span performance, except that Older CI users had lower auditory digit span than Young NH listeners. Both older groups had similar reading span performance, but scored significantly lower than Young NH listeners, indicating age-related declines in attentional and phonological processing. A similar group effect was observed in the cued-modality WM task. All groups showed higher recall for auditory digits than for visual letters and the advantage was most evident without modality cuing. All groups displayed greater cuing benefits for visual recall than for auditory recall, suggesting that participants consistently allocated more attention to auditory stimuli regardless of cuing. For Older CI users, after controlling for the previously reported spectral resolution, auditory-uncued WM performance was significantly correlated with word recognition but not sentence recognition. CONCLUSIONS: Complex WM was significantly affected by aging but not by CI. Neither aging nor CI significantly affected modality cuing benefits in the WM task. For Older CI users, complex auditory WM with attentional control may better reflect the cognitive load of speech recognition in noise than simple span or complex visual WM.

The impact of mild traumatic brain injury on reading comprehension and eye movements: preliminary results.

INTRODUCTION: Individuals who sustain a mild traumatic brain injury (mTBI) can suffer from executive function, working memory, and attention deficits, which can impact functional task performance, including reading comprehension. Individuals with mTBI commonly report reading difficulties, but such difficulties have been historically difficult to capture using behavioral measures. The current study examined reading performance in those with and without mTBI using eye-tracking measures, which may be more sensitive to reading impairment in mTBI. METHOD/RESULTS: In Experiment 1, 26 participants with a history of mTBI and 26 healthy control participants completed working memory (WM) and reading comprehension tasks. We found no differences in behavioral measures but found that spontaneous eye-blinking frequency was lower during the reading task in the mTBI group. In Experiment 2, we explored the impact of auditory distraction (e.g., multi-talker babble) on reading and memory performance. Twenty-three new participants with a history of mTBI and 26 healthy control participants completed a short-term memory (STM) task, a WM task, and a reading comprehension task under two distraction conditions. As in Experiment 1, we found no differences on behavioral measures, but observed significant differences on spontaneous eye-blinking frequency between those with and without mTBI. Group differences in distraction effects were also observed and performance on the WM task predicted reading comprehension performance. CONCLUSIONS: The lack of differences on behavioral measures between groups, but lower frequencies of spontaneous eye blinking in the mTBI group suggests that while these individuals successfully completed the reading comprehension task, they may require more cognitive resources to do so.

The Effects of Topic Knowledge on Intelligibility and Lexical Segmentation in Hypokinetic and Ataxic Dysarthria.

Benefits to speech intelligibility can be achieved by enhancing a listener's ability to decipher it. However, much remains to be learned about the variables that influence the effectiveness of various listener-based manipulations. This study examined the benefit of providing listeners with the topic of some phases produced by speakers with either hypokinetic or ataxic dysarthria. Total and topic word accuracy, topic-related substitutions, and lexical boundary errors were calculated from the listener transcripts. Data were compared with those who underwent a familiarization process (reported by Liss, Spitzer, Caviness, & Adler, 2002) and with those inexperienced with disordered speech (reported by Liss Spitzer, Caviness, & Adler, 2000). Results revealed that listeners of ataxic speech provided with topic knowledge obtained higher intelligibility scores than naïve listeners. The magnitude of benefit was similar to the familiarization condition. However, topic word and word substitution analyses revealed different underlying perceptual mechanisms responsible for the observed benefit. No differences attributable to listening condition were discovered in lexical segmentation patterns. Overall, the results support the need for further study of listener-based manipulations to elucidate the mechanisms responsible for the observed perceptual benefits for each dysarthria type.

Psychoacoustic and Demographic Factors for Speech Recognition of Older Adult Cochlear Implant Users.

Purpose This study aimed to evaluate the effects of aging and cochlear implant (CI) on psychoacoustic and speech recognition abilities and to assess the relative contributions of psychoacoustic and demographic factors to speech recognition of older CI (OCI) users. Method Twelve OCI users, 12 older acoustic-hearing (OAH) listeners age-matched to OCI users, and 12 younger normal-hearing (YNH) listeners underwent tests of temporal amplitude modulation detection, temporal gap detection in noise, and spectral-temporal modulated ripple discrimination. Speech reception thresholds were measured for sentence recognition in multitalker, speech-babble noise. Results Statistical analyses showed that, for the small sample of OAH listeners, the degree of hearing loss did not significantly affect any outcome measure. Temporal resolution, spectral resolution, and speech recognition all significantly degraded with both age and the use of a CI (i.e., YNH better than OAH and OAH better than OCI performance). Although both were significantly correlated with OCI users' speech recognition, the duration of CI use no longer had a significant effect on speech recognition once the effect of spectral-temporal ripple discrimination performance was taken into account. For OAH listeners, the only significant predictor of speech recognition was temporal gap detection performance. Conclusion The preliminary results suggest that speech recognition of OCI users may improve with longer duration of CI use, mainly due to higher perceptual acuity to spectral-temporal modulated ripples in acoustic stimuli.

Analysis of Story Recall in Military Veterans With and Without Mild Traumatic Brain Injury: Preliminary Results.

Purpose: The purpose of this study was to determine whether detailed analysis of story recall performance reveals significant differences between veterans with and without history of mild traumatic brain injury (mTBI). Method: Twenty-one military veterans participated, with 7 reporting history of mTBI. All participants were administered the Logical Memory I and II subtests from the Wechsler Memory Scale-Fourth Edition (Wechsler, 2009). Responses were scored for total correct ideas (TCI) and total words produced (TWP). Results: Although the groups did not differ in scaled scores, other measures did reveal significant differences. After a delay, the mTBI group showed a greater drop in TCI relative to the control group. Additionally, the control group showed an increase in TWP when the recall was delayed versus immediate; a pattern not observed for the mTBI group. Conclusions: The mTBI and control groups did not significantly differ in scaled scores. However, group differences were observed in TCI and TWP. The findings suggest that, relative to the control group, the mTBI group were less successful in retrieving episodic information and eliciting self-cueing. Small sample size limited data interpretation, and larger sample sizes are needed to confirm the findings. The results indicate that veterans with mTBI may present with symptoms persisting beyond the acute state of the injury.

Language control in bilingual adults with and without history of mild traumatic brain injury.

Adults with a history of traumatic brain injury often show deficits in executive functioning (EF), including the ability to inhibit, switch, and attend to tasks. These abilities are critical for language processing in bilinguals. This study examined the effect of mild traumatic brain injury (mTBI) on EF and language processing in bilinguals using behavioral and eye-tracking measures. Twenty-two bilinguals with a history of mTBI and twenty healthy control bilinguals were administered executive function and language processing tasks. Bilinguals with a history of mTBI showed deficits in specific EFs and had higher rates of language processing errors than healthy control bilinguals. Additionally, individuals with a history of mTBI have different patterns of eye movements during reading than healthy control bilinguals. These data suggest that language processing deficits are related to underlying EF abilities. The findings provide important information regarding specific EF and language control deficits in bilinguals with a history mTBI.

Comparing visual search and eye movements in bilinguals and monolinguals.

Recent research has suggested that bilinguals show advantages over monolinguals in visual search tasks, although these findings have been derived from global behavioral measures of accuracy and response times. In the present study we sought to explore the bilingual advantage by using more sensitive eyetracking techniques across three visual search experiments. These spatially and temporally fine-grained measures allowed us to carefully investigate any nuanced attentional differences between bilinguals and monolinguals. Bilingual and monolingual participants completed visual search tasks that varied in difficulty. The experiments required participants to make careful discriminations in order to detect target Landolt Cs among similar distractors. In Experiment 1, participants performed both feature and conjunction search. In Experiments 2 and 3, participants performed visual search while making different types of speeded discriminations, after either locating the target or mentally updating a constantly changing target. The results across all experiments revealed that bilinguals and monolinguals were equally efficient at guiding attention and generating responses. These findings suggest that the bilingual advantage does not reflect a general benefit in attentional guidance, but could reflect more efficient guidance only under specific task demands.

Working memory and perseveration in verbal fluency.

Letter and semantic fluency tasks are often used in neuropsychological assessment and are sensitive to many conditions. Performance is assessed by correct responses and errors, including perseverations. Healthy young adults performed letter and semantic fluency tasks. One group performed these tasks in the conventional manner; 2 other groups performed them while maintaining memory loads. The memory loads consisted either of words from the same category as the fluency task or of words from a different category. The results showed little effect of memory loads on correct responses but significant effects of memory load on perseveration rates: Same-category loads resulted in higher rates, especially in letter fluency. The results are discussed in terms of frontal lobe function in verbal fluency.

Sensitivity to expectancy violations in healthy aging and mild cognitive impairment.

In this study, individuals with mild cognitive impairment (MCI) were tested to see if executive dysfunction impacts their implementation of expectancy biases in a priming task. Young adults, healthy older adults, and individuals with MCI made speed-related decisions to sequentially presented word pairs. The proportion of category related (e.g., apple-fruit) versus coordinate related (apple-pear) pairs was varied to create different expectancy biases. When the proportion of category pairs was high (80%), the control groups showed an expectancy bias: Significant inhibition was observed for coordinate pairs compared with category pairs. The MCI group also demonstrated an expectancy bias but with much larger costs for unexpected targets. The findings suggest that individuals with MCI are inordinately sensitive to expectancy violations, and these findings are discussed in terms of possible executive dysfunction.

Episodic memory reflected in printed word naming.

Although memory is typically measured by recall or recognition, it is also expressed by fluent or stylized task performance. In this experiment, 12 volunteers (called speakers) completed four experimental stages over a 2-week period. They read printed words aloud in two sessions, before and after exposure to auditory training tokens. They later completed a recognition memory test, discriminating old from new words. Groups of perceptual judges assessed the speakers' vocal imitation by comparing utterances recorded before and after training and deciding which sounded like "better imitations" of the training tokens. The data showed clear evidence of postexposure imitation, with systematic effects that preclude strategic explanations. The contents of episodic memory were reflected by participants' speaking style while they were reading aloud. Together, the imitation and recognition data suggest that memory preserves detailed traces of spoken words; those traces were apparently activated when participants later read the same words in the same context.

Paws + cause = pause? Memory load and memory blends in homophone recognition.

Previous research has shown that separate information sources, activated closely together in time, can induce errors suggestive of memory blends. In Experiment 1, homophones were used to induce such memory errors. In a study task, participants made relatedness judgments to word pairs that included homophones (e.g., PAWS-BEAR). During this task, one group (study-similar) maintained memory loads with words that were orthographically similar to the presented homophones (e.g., JAWS). Another group (test-similar) maintained memory loads similar to those obtained for the study homophone's alternate spelling (e.g., CAUSE). A third group maintained no memory load during the task. In a surprise recognition test, participants were presented both previously viewed homophones (PAWS) and non-presented alternate spellings (PAUSE). We hypothesized that partially activated alternate spellings, in conjunction with the orthographically similar memory words, would result in the creation of blended memories. The results followed suit: The test-similar condition produced significantly elevated false alarms, relative to both the study-similar and the no-load conditions. Experiment 2 replicated these results while including memory loads to control for potential orthographic confusions. The findings are discussed in terms of multiple, episodic memories later activated as single, blended memories.

Resonance within and between linguistic beings.

Pickering & Garrod (P&G) deserve appreciation for their cogent argument that dialogue merits greater scientific consideration. Current models make little contact with behaviors of dialogue, motivating the interactive alignment theory. However, the theory is not truly "mechanistic." A full account requires both representations and processes bringing those representations into harmony. We suggest that Grossberg's (1980) adaptive resonance theory may naturally conform to the principles of dialogue.

Puzzle-solving science: the quixotic quest for units in speech perception.

Although speech signals are continuous and variable, listeners experience segmentation and linguistic structure in perception. For years, researchers have tried to identify the basic building-block of speech perception. In that time, experimental methods have evolved, constraints on stimulus materials have evolved, sources of variance have been identified, and computational models have been advanced. As a result, the slate of candidate units has increased, each with its own empirical support. In this article, we endorse Grossberg's adaptive resonance theory (ART), proposing that speech units are emergent properties of perceptual dynamics. By this view, units only "exist" when disparate features achieve resonance, a level of perceptual coherence that allows conscious encoding. We outline basic principles of ART, then summarize five experiments. Three experiments assessed the power of social influence to affect phoneme-syllable competitions. Two other experiments assessed repetition effects in monitoring data. Together the data suggest that "primary" speech units are strongly and symmetrically affected by bottom-up and top-down knowledge sources.