Semantic relatedness effects in conjoined noun phrase production: implications for the role of short-term memory

Abstract

Speech error data and empirical studies suggest that the scope of planning is larger for semantic than for phonological form representations in speech production. Previous results have demonstrated that some patients show dissociable impairments in the retention of semantic and phonological codes. The effect of these STM deficits on speech production was investigated using a phrase production paradigm that manipulated the semantic relatedness of the words in the phrase. Subjects produced a conjoined noun phrase to describe two pictures (e.g., "ball and hat") or produced the same phrases in response to pairs of written words. For the picture naming condition, control subjects showed an interference effect for semantically related pictures relative to unrelated pictures. This interference effect was greatly exaggerated for two patients with semantic short-term memory deficits but not for a patient with a phonological STM deficit. For the written words, control subjects showed a small facilitatory effect for the onset of phrases containing semantically related words. One of the patients with a semantic STM deficit who was tested on picture naming was also tested on these materials and showed a small facilitatory effect within the range of controls. The findings support the contention that speech planning is carried out at a phrasal level at the lexical-semantic level and that the capacities that support semantic retention in list recall support speech production planning.     

On the role of phonological short-term memory in sentence processing: ERP single case evidence on modality-specific effects

The present study explored a possible interaction between distinct language processes and components of phonological short-term memory (pSTM) in a patient with a pSTM profile. Event-related brain potentials (ERPs) were recorded while HG and age-matched controls engaged in auditory and visual sentence correctness tasks. Stimulus onset asynchrony (SOA) was varied in the visual modality. Controls showed an early anterior negativity followed by a P600 for syntactic violations and an N400 for semantic violations in the auditory and the short visual SOA condition. In the long visual SOA condition only a P600 and an N400 were observed. Across all tasks, HG displayed a comparable early anterior negativity and N400 pattern to controls. However, the P600 was replaced by a centro-parietal negativity (500-800?ms) that was followed by a very late positivity (900-1300?ms) in the visual modality, indicating that late syntactic processes are sensitive to SOA manipulation. This result implies that the cortical regions lesioned in HG may be part of a neural network that engages the pSTM system during "temporally variable" late syntactic processing in the visual modality. The combined results indicate that the pSTM system differentially impacts semantic and late syntactic processes.     

On the role of phonological short-term memory in sentence processing: ERP single case evidence on modality-specific effects

The present study explored a possible interaction between distinct language processes and components of phonological short-term memory (pSTM) in a patient with a pSTM profile. Event-related brain potentials (ERPs) were recorded while HG and age-matched controls engaged in auditory and visual sentence correctness tasks. Stimulus onset asynchrony (SOA) was varied in the visual modality. Controls showed an early anterior negativity followed by a P600 for syntactic violations and an N400 for semantic violations in the auditory and the short visual SOA condition. In the long visual SOA condition only a P600 and an N400 were observed. Across all tasks, HG displayed a comparable early anterior negativity and N400 pattern to controls. However, the P600 was replaced by a centro-parietal negativity (500–800 ms) that was followed by a very late positivity (900–1300 ms) in the visual modality, indicating that late syntactic processes are sensitive to SOA manipulation. This result implies that the cortical regions lesioned in HG may be part of a neural network that engages the pSTM system during “temporally variable” late syntactic processing in the visual modality. The combined results indicate that the pSTM system differentially impacts semantic and late syntactic processes.     

Temporal capacity of short-term visuomotor memory in continuous force production

The focus of this article is on the temporal capacity of short-term visuomotor memory as reflected by changes in the time and frequency patterns of force output. In experiment 1, subjects produced continuous force output (isometric index finger flexion) to a target force level (from 5 to 75% of maximum voluntary contraction, MVC) displayed on a video monitor for 20 s. In the full visual feedback condition, visual feedback was displayed throughout each trial, while, for the visual feedback-withdrawal condition, visual feedback was occluded for the final 12 s of each trial. With visual feedback present, subjects matched their force output to the target force level for 20 s. When visual feedback was removed, participants continued to match the target force level for approximately 0.5-1.5 s; thereafter force output decayed exponentially. In line with this decay, short time-frequency analysis revealed a decrease in force intensity in the 0- to 5-Hz band. Force level did not influence the time before decay; however, greater forces led to larger decay. Experiment 2 assessed whether the force decay in experiment 1 was a property of visual or motor short-term memory by having participants set their own target force levels with no visual information provided throughout. In agreement with the findings of experiment 1, force output decayed, emphasizing the importance of a motor memory source. It is concluded that the 0.5- to 1.5-s time period represents a limit on the temporal capacity that precise visuomotor information is held in short-term memory.     

Laterality defects in conjoined twins: implications for normal asymmetry in human embryogenesis

We evaluated six pairs of conjoined twins: four pairs were dicephalus, and two were of the ischiopagus type. In three of the four dicephalus pairs, the right twin had an abnormality of laterality that included a right aortic arch, reversed great vessel orientation, bilateral right-sided isomerism of the lungs, asplenia, and situs inversus of the viscera. The left twin had normal great vessel orientation and situs solitus in each case. The finding that was unique in these three dicephalus twin pairs was their fused hearts, which were similar in orientation and configuration. The fourth dicephalus twin pair had one normally rotated heart, which was located in the midline and had normally placed chambers and great vessels. Each twin of this pair had normal visceral situs. In the two pairs of ischiopagus twins, each pair had two separate hearts, with normal cardiac structure and great vessel relationships. The viscera expressed normal laterality. Documentation of a defect in laterality in the right twin in three conjoined twin pairs with fusion of the hearts, combined with the presence of normal laterality in three pairs without cardiac fusion, has implications regarding the mechanisms leading to laterality of the human embryo. We suggest that rotation of the heart initiates the embryo's process of lateralization and that the laterality defects of the viscera seen in the right twin are a result of their abnormal cardiac rotation.     

Proactive interference effects on short-term memory in rats: I. Basic parameters and drug effects

An operant delayed-matching task was used to assess the role of proactive interference (PI) effects on short-term memory capacity of rats. Task performance was analyzed in terms of the influence of the sample positions and response choices on previous trials. PI was predominantly attributable to the influence of the immediately previous trial but not preceding trials and was abolished by increasing the intertrial intervals from 5 to 15 s. Nicotine induced a decline in choice accuracy only on trials in which the previous response had been to the side opposite the current sample and correct response, suggesting an increased susceptibility to PI. Physostigmine induced a mild, relatively nonspecific decline in response accuracy. Clonidine induced delay-dependent impairments irrespective of responses on previous trials. None of these drugs enhanced choice accuracy at any dose tested.     

Long-term memory is the representational basis for semantic verbal short-term memory

The present study supports activation models of verbal short-term memory that include a semantic contribution to the retention process. Event-related brain potentials were used to probe the level of activation of semantic representations of a series of words in a delay interval following their presentation. The levels of activation were compared in two tasks: (1) a short-term memory task that involved a semantic judgment in the recall phase following the delay interval, and (2) a nonmemory control task. The level of semantic activation during the delay interval was higher in the short-term memory task, indicating that enhanced activation of semantic representations is involved in the short-term storage of verbal information. This result implies that activated long-term memory provides a representational basis for semantic verbal short-term memory, and hence supports theories that postulate that short- and long-term stores are not separate.     

Semantic relatedness between words in each individual brain: an event-related potential study

The relationship between 2 words is judged by the meanings of words. Here, we examined how the semantic relatedness of words is structured in each individual brain. During measurements of event-related potentials (ERPs), participants performed semantic-relatedness judgments of word pairs. For each participant, we divided word pairs into 2 groups - related and unrelated pairs - and compared their ERPs. All of the participants showed a significant N400 effect. However, when we applied an identical grouping of pairs, this effect was observed only in half the number of the participants. These results show that our single-subject analysis of N400 extracted semantic relatedness of words in the individual brain. Future studies using this analysis will clarify the organization of the mental lexicon.     

The noun/verb dissociation in language production: varieties of causes

We report the performance of two patients who presented with complementary deficits in naming nouns relative to verbs: EA performed far worse with nouns than verbs, while MR performed worse with verbs than nouns. The two patients' grammatical category-specific deficits could not easily be explained in terms of damage to specific types of semantic knowledge prototypically associated with nouns (visual properties) and verbs (action features). One of the two patients, MR, also presented with a selective deficit in processing verbal as opposed to nominal morphology, in line with her impairment in naming verbs. The other patient, EA, showed no impairment in producing nominal and regular verbal morphology. The contrasting patterns of grammatical category-specific deficits in naming and morphological processing, along with other recently reported patterns, are interpreted as providing support for the claim that semantic and grammatical properties independently contribute to the organisation of lexical processes in the brain.     

The effects of blood sludging upon short-term memory in rats and rhesus monkeys: an evaluation of its role in age-related cognitive declines.

Blood sludging or intravascular erythrocyte aggregation was induced in male, hooded rats by intravenous injection of the high molecular weight polysaccharide, Dextran 500 (mean mol. wt.=370,000). Analysis of blood sludging produced by dextran, using erythrocyte sedimentation rate (ESR), showed profound sludging after doses of 300 mg/kg, which persisted for several days. In contrast to the effects on ESR, a second study showed that Dextran 500 had no effect upon the accuracy of short-term memory (STM) in rats trained on a delayed spatial alternation task. The behavioral effects of dextran under these procedures were limited to a general, dose-dependent suppression of responding. Finally, the incidence and extent of blood sludging in behaviorally impaired, aged Rhesus monkeys was compared with that of normal, young monkeys using ESR. No significant difference in sludging between the two age groups was found. Thus, blood sludging was not associated with the STM impairment present in old monkeys. These results, taken together, do not support the notion that age related cognitive impairments (specificially in STM), are due to gross changes in blood sludging. The clinical reports of salutary effects in senile patients resulting from long-term anticoagulant therapy may therefore be due to factors unrelated to the antisluding properties of those drugs.     

Timing of bimanual movements and deafferentation: implications for the role of sensory movement effects

In a repetitive tapping task, the within-hand variability of intertap intervals is reduced when participants tap with both hands instead of single-handedly. This bimanual advantage has been attributed to timer as opposed to motor variance (according to the Wing-Kristofferson model; Helmuth and Ivry 1996) and related to the additional sensory consequences of the movement of the extra hand in the bimanual case (Drewing et al. 2002). In the present study the effect of sensory feedback of the movement on this advantage was investigated by comparing the results of a person (IW) deafferented below the neck with those of age-matched controls. IW showed an even more pronounced bimanual advantage than controls, suggesting that the bimanual advantage is not due to actual sensory feedback. These results support another hypothesis, namely that bimanual timing profits from the averaging of different central control signals that relate to each effectors movements.     

Processing of syntactically complex sentences relies on verbal short-term memory: evidence from a short-term memory patient

The role of the phonological loop in auditory sentence comprehension was examined in a 35-year-old woman with a selective deficit of verbal short-term memory (STM). More specifically, the objective of the experiment was to test whether sentence comprehension is limited by number of propositions, as suggested by Rochon, Waters, and Caplan (2000), or whether it depends on syntactic complexity. In an offline task, severe impairment was present on cleft objects and centre-embedded structures; the deficit on object relatives in right peripheral position was less relevant, and the patient was able to handle sentential coordination easily. In an online task, her processing of centre-embedded structures and object relatives in right peripheral position was significantly slower than that in controls. She was also significantly slower in processing the verb of the object relative in centre-embedded structures. The results obtained do not support the claim that the difficulties encountered by patients with limited working-memory resources are due to the number of propositions in the sentence; they do, however, suggest a direct involvement of the phonological loop in processing syntactically complex sentences.     

Processing of syntactically complex sentences relies on verbal short-term memory: Evidence from a short-term memory patient

The role of the phonological loop in auditory sentence comprehension was examined in a 35-year-old woman with a selective deficit of verbal short-term memory (STM). More specifically, the objective of the experiment was to test whether sentence comprehension is limited by number of propositions, as suggested by Rochon, Waters, and Caplan (2000), or whether it depends on syntactic complexity. In an offline task, severe impairment was present on cleft objects and centre-embedded structures; the deficit on object relatives in right peripheral position was less relevant, and the patient was able to handle sentential coordination easily. In an online task, her processing of centre-embedded structures and object relatives in right peripheral position was significantly slower than that in controls. She was also significantly slower in processing the verb of the object relative in centre-embedded structures. The results obtained do not support the claim that the difficulties encountered by patients with limited working-memory resources are due to the number of propositions in the sentence; they do, however, suggest a direct involvement of the phonological loop in processing syntactically complex sentences.     

Age-related cognitive impairments as assessed with an automated repeated measures memory task: implications for the possible role of acetylcholine and norepinephrine in memory dysfunction

Although there exists a general agreement that certain aspects of learning and memory, and certain associated neuronal systems may be impaired with aging, systematic parametric studies are needed to characterize the nature and limits of these age-related impairments and to identify the underlying neuronal mechanisms. We review a series of experiments that examined the effects of aging and experimental treatments on rats' performance of a continuous nonmatching-to-sample, working memory task. In these studies, disruption of cholinergic transmission produced robust impairments that increased with retention interval duration, but could be observed even at the shortest intervals tested. In contrast, age-related impairments were less robust. With tone and light discriminative stimuli age-related impairments were not observed under conditions that were sensitive to disruption of cholinergic transmission, but were observed with increased retention interval duration. Finally, disruption of noradrenergic transmission produced a marginal disruption of memory performance, at worst. The generality of these results, and possible implication for future studies and animal models of dementia are discussed.     

Gender differences in caring for infant Cebuella pygmaea: the role of infant age and relatedness

This paper describes a three-part study of the parenting behaviors of 6 family groups of Cebuella pygmaea (pygmy marmosets). In the first part, the parenting patterns of undisturbed family groups housed under laboratory conditions were scored throughout the first 10 weeks following the birth of their second infant(s). To further investigate the role of infant age in determining parental behavior, caretaking patterns were studied after a brief separation of infants of varying ages from their families. Finally, an unrelated infant, age 1-5 weeks, was placed inside the home cage of each family, and caretaking of this novel infant was scored. The main findings that emerged from the study were: (1) sex differences in carrying the infants were dependent upon the age of the infant, i.e., adult females were the predominant carriers of infants less than or equal to 3 weeks of age and males (either adult or juvenile) the main carriers for infants greater than 3 weeks of age; (2) some caretaking behaviors, e.g., grooming and protective retrieval, were performed predominantly by the adult females throughout infancy; and (3) the relatedness of the infant, i.e., one's own vs. another's, appeared to primarily affect the behavior of adult females. In general, experimental manipulations confirmed results of the observational part of the study and thus may be useful paradigms for testing specific hypotheses about parental behaviors.     

Th1 memory: implications for vaccine development

Summary: T‐helper 1 (Th1) cells play a critical role, via interferon‐γ (IFN‐γ) production, in mediating intracellular killing against a variety of infectious pathogens. Thus, understanding the regulation of Th1 responses could provide better insight into vaccine design for infections requiring Th1 immunity. The cellular and molecular mechanisms that control the induction of Th1 effector cells have been well characterized. More recently, there has been substantial progress in furthering our understanding of the factors that regulate the development of Th1 memory cells. It is clear that Th1 responses are functionally heterogeneous, as defined by their ability to produce IFN‐γ. Furthermore, this heterogeneity has profound implications for the capacity of distinct lineages of Th1 cells to develop into memory cells. This review emphasizes the mechanisms controlling the differentiation of naïve CD4⁺ T cells into effector and then memory cells in a progressive manner. It highlights the importance of IFN‐γ as a positive regulator for inducing Th1 responses but a negative regulator for sustaining Th1 effector cells. In conclusion, we discuss how this current understanding of Th1 differentiation will inform vaccine design and better define immune correlates of protection.     

Multiple memory deficits in Alzheimer-type dementia: implications for pharmacotherapy

This paper investigates the memory disorder of Alzheimer-type dementia by comparing the performance of Alzheimer patients on selected memory tests with that of Korsakoff patients and healthy controls. Alzheimer patients have deficits in both primary and secondary memory, and this finding is compared with that which pharmacological studies predict would occur on the basis of cholinergic depletion. The deficits in primary memory are unlikely to be accounted for in terms of cholinergic depletion, and provide a possible explanation for the disappointing results of trials of cholinergic replacement therapy in this disorder. On the other hand, the pattern of deficit in secondary memory is entirely consistent with that expected from cholinergic depletion.     

Specific characteristics of cholinergic mechanisms of short-term memory in monkeys for different types of visual information: The effects of amizil

Experiments on rhesus macaques were used to study the relationship between the characteristics of delayed visual differentiation and stimulus properties in conditions of pharmacological treatment with the m-cholinoreceptor blocker amizil, with the aim of identifying how modification of cholinergic structures affects different types of information. Disturbances to short-term memory for all stimuli consisted of reductions in the duration of retention and increases in motor reaction times, but occurred at different doses of the blocker: amizil at a dose of 0.3 mg/kg significantly decreased the retention duration for information relating to spatial relationships. Delayed discrimination of shape, contrast, and size worsened after treatment with amizil at a dose of 0.45–0.50 mg/kg, while decreases in the duration of short-term storage of information relating to color started after amizil doses of 0.6–0.8 mg/kg. It is suggested that the short-term memory system includes a set of neurophysiological mechanisms in which the cholinergic structures are organized differently and whose specific properties result in differences in the characteristics of short-term storage of different types of visual information. Translated from Rossiiskii Fiziologicheskii Zhurnal imeni I. M. Sechenova, Vol. 83, No. 10, pp. 16–23, October, 1997.