Speech Rate and Syntactic Complexity as Multiplicative Factors in Speech Comprehension by Young and Older Adults

An experiment is reported in which young and older adults heard short English sentences that differed in syntactic complexity and speech rate. The syntactic contrast pitted center-embedded sentences with a subject-relative clause against sentences with center-embedded object-relative clauses. Speech rate was varied using computer time-compression of the speech signal. Both young and older adults showed poorer comprehension accuracy for the more complex object-relative clause sentences than subject-relative sentences, with an age difference appearing only when sentences were presented at a very rapid rate. By contrast to accuracy scores, older adults took longer than the young adults to give their comprehension responses at all speech rates tested, with this age difference amplified by both speech rate and syntactic complexity.     

Neural basis for sentence comprehension deficits in frontotemporal dementia

Many patients with frontotemporal dementia (FTD) have impaired sentence comprehension. However, the pattern of comprehension difficulty appears to vary depending on the clinical subgroup. The purpose of this study was to elucidate the neural basis for these deficits in FTD. We studied patients with two different presentations: Three patients with Progressive Non-Fluent Ahasia (PNFA), and five non-aphasic patients with a dysexecutive and social impairment (EXEC). The FTD patient subgroups were compared to a cohort of 11 healthy seniors with intact sentence comprehension. We monitored regional cerebral activity with blood oxygen level dependent (BOLD) functional magnetic resonance imaging (fMRI) while subjects read sentences featuring both a grammatically complex object-relative center-embedded clause and a long linkage between the head noun phrase (NP) and the gap where the NP is interpreted in the center-embedded clause. Subjects decided whether the agent of the action is a male or a female. Healthy seniors activated both ventral portions of inferior frontal cortex (vIFC) and dorsal portions of IFC (dIFC) in the left hemisphere, often associated with grammatical and working memory components of these sentences, respectively. PNFA patients differed from healthy controls since they have reduced activation of left vIFC, while EXEC patients have less recruitment of left dIFC. We conclude that FTD subgroups have distinct patterns of sentence comprehension difficulty in part because of selective interruptions of a large-scale neural network for sentence processing.     

The effects of slowed speech on auditory comprehension in aphasia

The present study investigates the effects of slowed speech on auditory comprehension in aphasia. Specifically, an attempt was made to isolate the effects of added time on comprehension at the language processing stages of auditory perception, by increasing the duration of the vowel segments in each word; word recognition and semantic analysis, by adding silences between words; and syntactic analysis, by adding silences at constituent phrase boundaries. Sentences were also read at a slow rate to see the effects of naturally slowed speech on sentence comprehension. Test sentences consisted of simple active and passive declarative sentences, and complex sentences with embedded medial and final relative clauses. Sentences were either semantically reversible or nonreversible. Thirty-four aphasic patients who varied in both severity and type of aphasia were tested on a picture verification task. Results indicated that slowing facilitated language comprehension significantly only in the syntactic condition. Neither syntactic complexity nor semantic reversibility interacted with slowed speech to facilitate auditory language comprehension. Further, it was only the Wernicke's aphasics who showed significant improvement with time added at constituent boundaries. These results suggest that time alone does not facilitate language comprehension in aphasia, but that rather it is the interaction of time with syntactic processing which improves comprehension.     

Brain imaging of tongue-twister sentence comprehension: twisting the tongue and the brain

This study used fMRI to investigate the neural basis of the tongue-twister effect in a sentence comprehension task. Participants silently read sentences equated for the syntactic structure and the lexical frequency of the constituent words, but differing in the proportion of words that shared similar initial phonemes. The manipulation affected not only the reading times and comprehension performance, but also the amount of activation seen in a number of language-related cortical areas. The effect was not restricted to cortical areas known to be involved in articulatory speech programming or rehearsal processes (the inferior frontal gyrus and anterior insula), but also extended to areas associated with other aspects of language processing (inferior parietal cortex) associated with phonological processing and storage.     

加工速度对晚期第二语言学习者句法加工的影响

两个实验通过操纵句子呈现的速度,考察加工速度因素对于晚期第二语言学习者句法加工的影响。实验1采用视觉方式呈现句子,实验2采用听觉方式呈现句子。被试的母语为汉语,第二语言为英语,属于晚期第二语言学习者,实验任务为句法判断。两个实验的结果表明,加工速度缓慢是导致晚期第二语言学习者句法加工困难的重要因素之一。加工速度缓慢对第二语言句法加工的影响,不是局限于少数一两种句法形式,而是作用于多数句法形式。研究还发现,视觉和听觉两种呈现方式下,不同句法形式的加工难度既存在共性的一面,也存在差异性的一面。     

晚期汉-英二语者英语被动句句法加工的ERP研究*

选取二语中等熟练者和高熟练者两类中国大学生被试,共40人(27女,13男),年龄为20~29岁,平均年龄23.88岁。采用ERP技术,以直译型英语被动句和意译型英语被动句作为实验材料,通过比较无违例、―句法违例句1‖(动词过去分词形式错误)、―句法违例句2‖(动词过去分词错误用为动词原形而造成的句法违例)以及―句法违例句3‖(动词过去分词误用为动词现在分词形式)条件下的行为数据和ERP多维数据变化的基础上,探讨了二语熟练度和语言间句法结构相似性对汉-英双语者英语被动句句法加工过程的影响。结果表明：高熟练者的反应时和正确率整体上优于中等熟练者;难易度不同的句法错误信息会直接影响被动句的加工,对明显有错误的句法信息的反应速度最快,―正确的局部句法信息‖反应时最长。对明显有错误的句法信息的正确反应率最高,最根本的句法结构的错误信息最低。最根本的句法结构的错误信息引发的P600最大,无违例条件引发的P600最小;高熟练者对最根本的句法结构的错误信息引发最大的P600效应,中等熟练者的P600效应未受不同句法错误信息的影响。行为指标支持句法加工相似性效应——直译句反应快、正确率高;意译句反应慢、正确率低。并且此效应在中等熟练者身上表现更加明显。但是脑神经活动模式未表现出句法结构相似性效应,说明二语熟练度在英语被动句加工中具有更为显著的作用。     

Sentence processing in Lewy body spectrum disorder: the role of working memory

Prior work has related sentence processing to executive deficits in non-demented patients with Parkinson's disease (PD). We extended this investigation to patients with dementia with Lewy bodies (DLB) and PD dementia (PDD) by examining grammatical and working memory components of sentence processing in the full range of patients with Lewy body spectrum disorder (LBSD). Thirty-three patients with LBSD were given a two-alternative, forced-choice sentence-picture matching task. Sentence type, working memory, and grammatical structure were systematically manipulated in the sentences. We found that patients with PDD and DLB were significantly impaired relative to non-demented PD patients and healthy controls. The deficit in PDD/DLB was most pronounced for sentences lengthened by the strategic placement of an additional prepositional phrase and for sentences with an additional proposition due to a center-embedded clause. However, there was no effect for subject-relative versus object-relative grammatical structure. An MRI voxel-based morphometry analysis in a subset of patients showed significant gray matter thinning in the frontal lobe bilaterally, and this extended to temporal, parietal and occipital regions. A regression analysis related sentence processing difficulty in LBSD to frontal neocortex, including inferior prefrontal, premotor, and dorsolateral prefrontal regions, as well as right superior temporal cortex. These findings are consistent with the hypothesis that patients with PDD and DLB have difficulty processing sentences with increased working memory demands and that this deficit is related in part to their frontal disease.     

句法歧义消解影响因素、认知机制及其神经基础

句法歧义消解主要是指人们在面临多种句法分析可能性的情况下,句法分析器抑制不正确的句法分析而选择正确句法分析的认知过程。研究表明,该过程受到工作记忆、认知控制能力、语言分布频率、语境、韵律等因素的影响。为有效说明人们是如何完成句法歧义消解的,研究者们建构了诸如花园路径模型、约束满意理论、弱交互作用句法分析理论等相关模型。另外,基于脑成像技术研究表明,左侧额下回、左侧颞叶后部、中部和前部在句法消歧任务中都有显著激活。未来研究当围绕着句法消歧中的语义效应、句法和词汇歧义消解机制的异同、句法消歧中抑制能力的效应等方面展开。     

Event-related responses to pronoun and proper name anaphors in parallel and nonparallel discourse structures.

The present study investigated event-related potential (ERP) effects of pronoun and proper name anaphors in both parallel and nonparallel discourse structures. Thirty-seven students processed 400 semantically different text passages. Each trial consisted of two sentences and a comprehension question. The first sentence introduced a protagonist who was referred to by an anaphoric word in the second sentence. The anaphoric word was either a pronoun or a repetition of the proper name of the protagonist and had either the same or a different syntactic role as its antecedent (subject or object). The sentences were presented word by word as rapid serial visual display. Event-related potentials were recorded from 61 scalp electrodes. In agreement with the parallel function strategy, nonparallel discourse structures required longer decision times and exhibited higher error rates than parallel structures. The ERPs revealed two effects: First, pronoun anaphors evoked a more pronounced negativity than proper name anaphors between 270 and 420 ms latency over the frontal cortex electrodes. Another relative negativity occurred between 510 and 600 ms over the parietal cortex electrodes. Second, anaphors in nonparallel positions were accompanied by a more pronounced negativity over the parietal cortex. These data support the idea that an anaphor in nonparallel position triggers extra processing steps, probably search processes in working memory which integrate currently encountered information with previously activated representations.     

Rapid extraction of gist from visual text and its influence on word recognition

Two experiments explored rapid extraction of gist from a visual text and its influence on word recognition. In both, a short text (sentence) containing a target word was presented for 200 ms and was followed by a target recognition task. Results showed that participants recognized contextually anomalous word targets less frequently than contextually consistent counterparts (Experiment 1). This context effect was obtained when sentences contained the same semantic content but with disrupted syntactic structure (Experiment 2). Results demonstrate that words in a briefly presented visual sentence are processed in parallel and that rapid extraction of sentence gist relies on a primitive representation of sentence context (termed protocontext) that is semantically activated by the simultaneous presentation of multiple words (i.e., a sentence) before syntactic processing.     

句子语境中语义联系启动作用的研究

通过对比研究正序和乱序两种句子语境对目标词加工的不同影响,来探讨句子语境中语义联系启动作用及作用点问题。实验一采用词汇命名任务研究发现,句法成分影响命名任务,句法违反对命名任务产生较大的抑制作用。语义违反则对命名任务没有产生显著的抑制作用。实验二利用词汇决定任务发现,词序影响决定任务,乱序对词汇决定产生很大的抑制作用。语义违反对决定任务地产生较大的抑制作用。结果表,中义联系启动是短暂的,它的保持和传递需要句法成分的支持。     

Influence of linguistic complexity,rate of presentation,and interphrase pause time on auditory-verbal comprehension of adult aphasic patients

Among the variables affecting comprehension of linguistic stimuli by aphasic subjects are syntactic complexity and processing time. Comprehension performance of 15 aphasic adults was studied while altering the rate of speech presentation and varying the pause time between the major phrases within sentences of increasing grammatical complexity.Simple Active Affirmative Declarative Sentences, Negative, and Passive sentences were presented (1) at the rate of 150 words per minute (wpm) with 1-sec interphrase pause time (IPT); (2) 150 wpm with no pauses; (3) 120 wpm with 1-sec IPT; (4) 120 wpm with no pauses added.Performance was seen to vary with increasing syntactical complexity and as a function of processing time. Greater comprehension was seen with active affirmative than negative; greater with passive affirmative than with active negative. Clinical implications are discussed. Subjects demonstrated greater comprehension when sentences were presented at slower than normal rate; addition of interphrase pause time intervals aided comprehension. Combining slower rate of presentation and IPT intervals provided greatest increase in auditory processing time and showed concomitant increase in comprehension performance.     

The effect of syntactic structure upon speech initiation times of stuttering and nonstuttering speakers

Past research has shown that adults who stutter tend to be slower than adults who do not stutter at initiating various speech-like movements, nonsense syllables, words, short phrases, and simple sentences. The present study sought to extend this research by examining the effect that syntactic structure has upon stutterers' and nonstutterers' ability to initiate sentences. Eleven persons who stutter (mean age=22.2 years) and 11 nonstuttering controls (mean age=23.3 years) read, rehearsed, and then reproduced a series of 96 sentences within a simple reaction time paradigm. The sentences were presented in four blocks of 24 sentences, and each block contained one version of each of the 24 base sentences. Versions of the base sentences varied, from simple to complex, along four levels of syntactic complexity. Results indicated that speech initiation times (SITs) were significantly longer for participants who stutter than they were for nonstuttering controls for three of the four sentence types. There was no significant difference in SITs across the four sentence types for either group. Among the stuttering participants, there was no significant correlation between stuttering severity and overall initiation time for the sentences. Consistent with other studies, the present findings suggest that persons who stutter are slower than persons who do not stutter at planning and/or initiating motor movements associated with speech production. EDUCATIONAL OBJECTIVES: The reader will be able to (1). describe how persons who stutter typically perform during various reaction time tasks, (2). explain the rationale for examining the effect of syntactic complexity upon speech initiation time, (3). discuss how the speech initiation times of persons who stutter compare to those of persons who do not stutter during the production of various types of sentences, (4). identify future research needs in this area.     

The neural reality of syntactic transformations: evidence from functional magnetic resonance imaging

The functional anatomy of syntactic transformations, a major computational operation invoked in sentence processing, was identified through a functional magnetic resonance imaging investigation. A grammaticality judgment task was used, presented through a novel hidden-blocks design. Subjects listened to transformational and nontransformational sentences in which a host of other complexity generators (number of words, prepositions, embeddings, etc.) were kept constant. A series of analyses revealed that the neural processing of transformations is localizable, evoking a highly lateralized and localized activation in the left inferior frontal gyrus (Broca's region) and bilateral activation in the posterior superior temporal sulcus. The pattern of activation associated with transformational analysis was distinct from the one observed in neighboring regions, and anatomically separable from the effects of verb complexity, which yielded significant activation in the left posterior superior temporal sulcus. Taken together with neuropsychological evidence, these results uncover the neural reality of syntactic transformations.     

Syntactic and semantic contributions to sentence comprehension in agrammatism

Five aphasic subjects, who demonstrated agrammatic speech, and eight control subjects were presented with a sentence-picture matching task in which the factors of syntactic complexity, semantic reversibility, and sentence plausibility were independently varied. A subset of the sentences was patterned after that presented by A. Caramazza and E. Zurif (1976, Brain and Language, 5, 572-583) who concluded that Broca's aphasics rely on semantic constraints instead of syntactic information for sentence comprehension. Our aphasic subjects showed the same pattern of performance on this subset of sentences. However, the results from the full set of sentence materials we tested show that the aphasic subjects could perform some sentence level syntactic analyses, even when syntactic information conflicted with semantic constraints. The aphasic subjects correctly interpreted most active and passive sentences. They failed, however, to assign thematic roles and adjectives in center-embedded relative sentences, and instead relied on nonsyntactic information. These results show that both semantic and syntactic information contributed to sentence comprehension in the aphasic subjects we tested, in contrast to previous claims that syntactic and semantic processes are completely dissociated in this population.     

Building Syntactic Structure in Speaking

We investigated how people produce simple and complex phrases in speaking using a newly developed immediate recall task. People read and tried to memorize a target sentence, then read a prime sentence, then did a distractor task involving the prime sentence. Despite the delay and activity between memory and recall, people could still recall the target sentence although the syntactic form of the recalled sentence was influenced by the syntactic form of the prime sentence. This result replicates the syntactic priming effect found with other experimental paradigms. Using this task, we tested how people used abstract syntactic plans to produce simple and complex noun phrases. We found syntactic priming both when targets and prime sentences matched in complexity and when they did not match, suggesting that simple and complex noun phrases are built by the same syntactic routines during speech production.     

Towards a neural basis of auditory sentence processing

Functional dissociations within the neural basis of auditory sentence processing are difficult to specify because phonological, syntactic and semantic information are all involved when sentences are perceived. In this review I argue that sentence processing is supported by a temporo-frontal network. Within this network, temporal regions subserve aspects of identification and frontal regions the building of syntactic and semantic relations. Temporal analyses of brain activation within this network support syntax-first models because they reveal that building of syntactic structure precedes semantic processes and that these interact only during a later stage.     

The consequences of reduced memory span for the comprehension of semantic versus syntactic information

Aphasic patients with restricted memory spans were assessed on their comprehension of syntactically simple sentences varying in numbers of content words and on their comprehension of sentences matched in content words but varying in syntactic complexity. Three different presentation modes were used: unlimited visual presentation, limited visual presentation, and auditory presentation. The difference between performance in the unlimited and limited modes was used as a measure of the extent to which memory decrements caused comprehension failure. These difference scores were related to memory span in order to assess whether the memory involved in sentence processing overlaps that assessed by a memory span task. For the sentences varying in number of content words, performance was worse for the limited presentation modes than the unlimited mode, and the difference between unlimited and limited presentation modes was highly related to memory span. For the sentences varying in syntactic complexity, there was no clear reduction in performance for limited presentation modes, and the difference scores did not relate to memory span. The results support the view that the processing of sentences with many content words draws on the short-term memory capacity assessed by memory span, while the processing of syntactic complexity does not.     

Auditory language comprehension: an event-related fMRI study on the processing of syntactic and lexical information

The functional specificity of different brain areas recruited in auditory language processing was investigated by means of event-related functional magnetic resonance imaging (fMRI) while subjects listened to speech input varying in the presence or absence of semantic and syntactic information. There were two sentence conditions containing syntactic structure, i.e., normal speech (consisting of function and content words), syntactic speech (consisting of function words and pseudowords), and two word-list conditions, i.e., real words and pseudowords. The processing of auditory language, in general, correlates with significant activation in the primary auditory cortices and in adjacent compartments of the superior temporal gyrus bilaterally. Processing of normal speech appeared to have a special status, as no frontal activation was observed in this case but was seen in the three other conditions. This difference may point toward a certain automaticity of the linguistic processes used during normal speech comprehension. When considering the three other conditions, we found that these were correlated with activation in both left and right frontal cortices. An increase of activation in the planum polare bilaterally and in the deep portion of the left frontal operculum was found exclusively when syntactic processes were in focus. Thus, the present data may be taken to suggest an involvement of the left frontal and bilateral temporal cortex when processing syntactic information during comprehension.     

Auditory language comprehension: an event-related fMRI study on the processing of syntactic and lexical information

The functional specificity of different brain regions recruited in auditory language processing was investigated by means of event-related functional magnetic resonance imaging (fMRI) while subjects listened to speech input varying in the presence or absence of semantic and syntactic information. There were two sentence conditions containing syntactic structure, i.e., normal speech (consisting of function and content words), syntactic speech (consisting of function words and pseudowords), and two word-list conditions, i.e., real words and pseudowords. The processing of auditory language, in general, correlates with significant activation in the primary auditory cortices and in adjacent compartments of the superior temporal gyrus bilaterally. Processing of normal speech appeared to have a special status, as no frontal activation was observed in this case but was seen in the other three conditions. This difference may point toward a certain automaticity of the linguistic processes used during normal speech comprehension. When considering the three other conditions, we found that these were correlated with activation in both left and right frontal cortices. An increase of activation in the planum polare bilaterally and in the deep portion of the left frontal operculum was found exclusively when syntactic processes were in focus. Thus, the present data may be taken to suggest an involvement of the left frontal and bilateral temporal cortex when processing syntactic information during comprehension.