Syntactic predictions and asyntactic comprehension in aphasia: Evidence from scope relations

People with aphasia (PWA) often fail to understand syntactically complex sentences. This phenomenon has been described as asyntactic comprehension and has been explored in various studies cross-linguistically in the past decades. However, until now there has been no consensus among researchers as to the nature of sentence comprehension failures in aphasia. Impaired representations accounts ascribe comprehension deficits to loss of syntactic knowledge, whereas processing/resource reduction accounts assume that PWA are unable to use syntactic knowledge in comprehension due to resource limitation resulting from the brain damage. The aim of this paper is to use independently motivated psycholinguistic models of sentence processing to test a variant of the processing/resource reduction accounts that we dub the Complexity Threshold Hypothesis. According to this hypothesis, PWA are capable of building well-formed syntactic representations, but, because their resources for language processing are limited, their syntactic parser fails when processing complexity exceeds a certain threshold. The source of complexity investigated in the experiments reported in this paper is syntactic prediction. We conducted two experiments involving comprehension of sentences with different types of syntactic dependencies, namely dependencies that do not require syntactic prediction (i.e. unpredictable dependencies in sentences that require Quantifier Raising) and dependencies whose resolution requires syntactic predictions at an early stage of processing based on syntactic cues (i.e. predictable dependencies in movement-derived sentences). In line with the predictions of the Complexity Threshold Hypothesis, the results show that the agrammatic patients that participated in this study had no difficulties comprehending sentences with the former type of dependencies, whereas their comprehension of sentences with the latter type of dependencies was impaired

Single case studies are a powerful tool for developing, testing and extending theories

Psychology embraces a diverse range of methodologies. However, most rely on averaging group data to draw conclusions. In this Perspective, we argue that single case methodology is a valuable tool for developing and extending psychological theories. We stress the importance of single case and case series research, drawing on classic and contemporary cases in which cognitive and perceptual deficits provide insights into typical cognitive processes in domains such as memory, delusions, reading and face perception. We unpack the key features of single case methodology, describe its strengths, its value in adjudicating between theories, and outline its benefits for a better understanding of deficits and hence more appropriate interventions. The unique insights that single case studies have provided illustrate the value of in-depth investigation within an individual. Single case methodology has an important place in the psychologist’s toolkit and it should be valued as a primary research tool

THE EFFECTS OF LOCALITY ON SENTENCE COMPREHENSION IN PERSONS WITH APHASIA AND NORMAL INDIVIDUALS

The first aim of the current study was to investigate the effects of the distance manipulation on sentence comprehension in normal individuals (NI) and persons with aphasia (PWA). Consistent with Gibson¡¯s (1998; 2000) locality theory, when distance was manipulated by varying the syntactic dependency (subject-verb: SV and filler-gap: FG) and type of modifier (No, prepositional-phrase: PP, and relative-clause: RC), NI demonstrated an increase in the number of errors and response times to the yes/no questions as the distance increases. NI also exhibited a relatively systematic increase of reading times on the verb (RT-V) and response times (RT) as a function of distance manipulation except for the most complex condition (FG-RC) in which 77% of NI performed at chance-level. More than 60% of normal individuals performed at chance-level in sentences with FG-dependency. Consistent with the previous literature on syntactic comprehension in aging, older adults showed decreased performance on the filler-gap computations. PWA generated more errors in the FG- than SV-dependency. However, their sentence comprehension was not affected by the manipulation of the modifiers. Their RT-V data were difficult to interpret due to the very limited observations for FG-dependency conditions after chance-level performers were excluded from the analyses. One can argue that the high rate of chance-level performance in PWA, especially in the FG conditions, is consistent with the specific impairments hypotheses. However, chance-level performance was observed in majority of individuals with aphasia and even in normal individuals, which was not predicted by those hypotheses. The current results were more consistent with resource-related hypotheses which suggested that sentence comprehension deficits will manifest themselves regardless of the type of aphasia when their capacity is taxed to be exceeded. When distance-based integration cost was held constant between the two dependencies, FG-dependency generated more errors across the groups. However, the RT-V was not significantly different between the two conditions in older adults. These results are consistent with the locality theory. Considering the longer RT-V differences between FG- and SV-dependency in older adults than younger adults, the non-significant group results might be due to the large variability of older adults¡¯ performance and the limited sample size

Semantic radical consistency and character transparency effects in Chinese: an ERP study

BACKGROUND: This event-related potential (ERP) study aims to investigate the representation and temporal dynamics of Chinese orthography-to-semantics mappings by simultaneously manipulating character transparency and semantic radical consistency. Character components, referred to as radicals, make up the building blocks used dur...postprin

Three symbol ungrounding problems: Abstract concepts and the future of embodied cognition

A great deal of research has focused on the question of whether or not concepts are embodied as a rule. Supporters of embodiment have pointed to studies that implicate affective and sensorimotor systems in cognitive tasks, while critics of embodiment have offered nonembodied explanations of these results and pointed to studies that implicate amodal systems. Abstract concepts have tended to be viewed as an important test case in this polemical debate. This essay argues that we need to move beyond a pretheoretical notion of abstraction. Against the background of current research and theory, abstract concepts do not pose a single, unified problem for embodied cognition but, instead, three distinct problems: the problem of generalization, the problem of flexibility, and the problem of disembodiment. Identifying these problems provides a conceptual framework for critically evaluating, and perhaps improving upon, recent theoretical proposals

Using fMRI and Behavioural Measures to Investigate Rehabilitation in Post-Stroke Aphasic Deficits

In this thesis I investigated whether an intensive computerised, home-based therapy programme could improve phonological discrimination ability in 19 patients with chronic post-stroke aphasia. One skill specifically targeted by the treatment demonstrated an improvement due to the therapy. However, this improvement did not generalise to untreated items, and was only effective for participants without a lesion involving the frontal lobe, indicating a potentially important role for this region in determining outcome of aphasia therapy. Complementary functional imaging studies investigated activity in domain-general and domain-specific networks in both patients and healthy volunteers during listening and repeating simple sentences. One important consideration when comparing a patient group with a healthy population is the difference in task difficulty encountered by the two groups. Increased cognitive effort can be expected to increase activity in domain-general networks. I minimised the effect of this confound by manipulating task difficulty for the healthy volunteers to reduce their behavioural performance so that it was comparable to that of the patients. By this means I demonstrated that the activation patterns in domain-general regions were very similar in the two groups. Region-of-interest analysis demonstrated that activity within a domain-general network, the salience network, predicted residual language function in the patients with aphasia, even after accounting for lesion volume and their chronological age. I drew two broad conclusions from these studies. First, that computer-based rehabilitation can improve disordered phonological discrimination in chronic aphasia, but that lesion distribution may influence the response to this training. Second, that the ability to activate domain-general cognitive control regions influences outcome in aphasia. This allows me to propose that in future work, therapeutic strategies, pharmacological or behavioural, targeting domain-general brain systems, may benefit aphasic stroke rehabilitation.Open Acces