Biomedical subjects

Ayşe Pinar Saygin

Publications and source records attributed to Ayşe Pinar Saygin.

6 recordsLinked to original sources

PubMed2005

Analyzing aphasia data in a multidimensional symptom space.

The utility of single-case vs. group studies has been debated in neuropsychology for many years. The purpose of the present study is to illustrate an alternative approach to group studies of aphasia, in which the same symptom dimensions that are commonly used to assign patients to classical taxonomies (fluency, naming, repetition, and comprehension) are used as independent and continuous predictors in a multivariate design, without assigning patients to syndromes. One hundred twenty-six Italian-speaking patients with aphasia were first classified into seven classic aphasia categories, based on fluency, naming, auditory comprehension, and repetition scales. There were two goals: (1) compare group analyses based on aphasia types with multivariate analyses that sidestep classification and treat aphasic symptoms as continuous variables; (2) present correlation-based outlier analyses that can be used to identify individuals who occupy unusual positions in the multivariate "symptom space." In the service of the first goal, group performance on an external validation measure (the Token Test) was assessed in three steps: analyses of variance based on aphasia type, regressions using the same cut-offs for fluency, naming, comprehension and repetition as independent but dichotomous predictors, and regressions using the same subscales as continuous predictors (with no cut-offs). More variance in Token Test performance was accounted for when symptoms were treated as continuous predictors than with the other two methods, though use of independent but dichotomous predictors accounted for more variance than aphasia taxonomies. Thus, if we by-pass classical taxonomies and treat patients as points in a multidimensional symptom space, better predictions are obtained. Outlier analyses show that group results depend on heterogeneity among patients, which can be used as a search tool to identify potentially interesting dissociations. Hence this multivariate group approach is complementary to and compatible with single-case methods.

Aphasia↗

PubMed2005

An on-line task for contrasting auditory processing in the verbal and nonverbal domains and norms for younger and older adults.

Contrasting linguistic and nonlinguistic processing has been of interest to many researchers with different scientific, theoretical, or clinical questions. However, previous work on this type of comparative analysis and experimentation has been limited. In particular, little is known about the differences and similarities between the perceptual, cognitive, and neural processing of nonverbal environmental sounds and that of speech sounds. With the aim of contrasting verbal and nonverbal processing in the auditory modality, we developed a new on-line measure that can be administered to subjects from different clinical, neurological, or sociocultural groups. This is an on-line task of sound to picture matching, in which the sounds are either environmental sounds or their linguistic equivalents and which is controlled for potential task and item confounds across the two sound types. Here, we describe the design and development of our measure and report norming data for healthy subjects from two different adult age groups: younger adults (18-24 years of age) and older adults (54-78 years of age). We also outline other populations to which the test has been or is being administered. In addition to the results reported here, the test can be useful to other researchers who are interested in systematically contrasting verbal and nonverbal auditory processing in other populations.

Adolescent↗

PubMed2004

Listening to speech activates motor areas involved in speech production.

To examine the role of motor areas in speech perception, we carried out a functional magnetic resonance imaging (fMRI) study in which subjects listened passively to monosyllables and produced the same speech sounds. Listening to speech activated bilaterally a superior portion of ventral premotor cortex that largely overlapped a speech production motor area centered just posteriorly on the border of Brodmann areas 4a and 6, which we distinguished from a more ventral speech production area centered in area 4p. Our findings support the view that the motor system is recruited in mapping acoustic inputs to a phonetic code.

Acoustic Stimulation↗

PubMed2004

Action comprehension in aphasia: linguistic and non-linguistic deficits and their lesion correlates.

We tested aphasic patients' comprehension of actions to examine processing deficits in the linguistic and non-linguistic domains and their lesion correlates. Twenty-nine left-hemisphere injured patients and 18 age-matched control subjects matched pictured actions (with the objects missing) or their linguistic equivalents (printed sentences with the object missing) to one of two visually-presented pictures of objects. Aphasic patients performed poorly not only in the linguistic domain but also in the non-linguistic domain. A subset of the patients, largely consisting of severe and non-fluent aphasics, showed a greater deficit in the linguistic domain compared with the non-linguistic domain and across the patient group, deficits in the linguistic and non-linguistic domains were not tightly correlated. Poor performance in pantomime interpretation was associated with lesions in the inferior frontal, premotor and motor cortex, a portion of somatosensory cortex, and the caudate, while poor reading comprehension of actions was associated with lesions around the anterior superior temporal lobe, the anterior insula and the anterior portion of the inferior parietal lobe. Lesion size did not correlate with deficits. The lesion results for pantomime interpretation deficits demonstrate that lesions in the frontal component of the human analog of the "mirror neuron system" are associated with deficits in non-linguistic action understanding. For reading comprehension deficits, the lesion correlates are brain areas known to be involved in linguistic tasks including sentence processing and speech articulation; the parietal lesion site may also correspond to a subpart of the human mirror neuron system. These results indicate that brain areas important for the production of language and action are also recruited in their comprehension. Similar findings have been reported in electrophysiological and neuroimaging studies. Our findings now also lend neuropsychological support to an embodied view of brain organization for action processing.

Adult↗

PubMed2004

Grammaticality judgment in aphasia: deficits are not specific to syntactic structures, aphasic syndromes, or lesion sites.

We examined the abilities of aphasic patients to make grammaticality judgments on English sentences instantiating a variety of syntactic structures. Previous studies employing this metalinguistic task have suggested that aphasic patients typically perform better on grammaticality judgment tasks than they do on sentence comprehension tasks, a finding that has informed the current view that grammatical knowledge is relatively preserved in agrammatic aphasia. However, not all syntactic structures are judged equally accurately, and several researchers have attempted to provide explanatory principles to predict which structures will pose problems to agrammatic patients. One such proposal is Grodzinsky and Finkel's (1998) claim that agrammatic aphasics are selectively impaired in their ability to process structures involving traces of maximal projections. In this study, we tested this claim by presenting patients with sentences with or without such traces, but also varying the level of difficulty of both kinds of structures, assessed with reference to the performance of age-matched and young controls. We found no evidence that agrammatic aphasics, or any other subgroup, are selectively impaired on structures involving traces: Some judgments involving traces were made quite accurately, whereas other judgments not involving traces were made very poorly. Subgroup analyses revealed that patient groups and age-matched controls had remarkably similar profiles of performance across sentence types, regardless of whether the patients were grouped based on Western Aphasia Battery classification, an independent screening test for agrammatic comprehension, or lesion site. This implies that the pattern of performance across sentence types does not result from any particular component of the grammar, or any particular brain region, being selectively compromised. Lesion analysis revealed that posterior temporal areas were more reliably implicated in poor grammaticality judgment performance than anterior areas, but poor performance was also observed with some anterior lesions, suggesting that areas important for syntactic processing are distributed throughout the left peri-sylvian region.

Adolescent↗

PubMed2003

Neural resources for processing language and environmental sounds: evidence from aphasia.

Although aphasia is often characterized as a selective impairment in language function, left hemisphere lesions may cause impairments in semantic processing of auditory information, not only in verbal but also in nonverbal domains. We assessed the 'online' relationship between verbal and nonverbal auditory processing by examining the ability of 30 left hemisphere-damaged aphasic patients to match environmental sounds and linguistic phrases to corresponding pictures. The verbal and nonverbal task components were matched carefully through a norming study; 21 age-matched controls and five right hemisphere-damaged patients were also tested to provide further reference points. We found that, while the aphasic groups were impaired relative to normal controls, they were impaired to the same extent in both domains, with accuracy and reaction time for verbal and nonverbal trials revealing unusually high correlations (r = 0.74 for accuracy, r = 0.95 for reaction time). Severely aphasic patients tended to perform worse in both domains, but lesion size did not correlate with performance. Lesion overlay analysis indicated that damage to posterior regions in the left middle and superior temporal gyri and to the inferior parietal lobe was a predictor of deficits in processing for both speech and environmental sounds. The lesion mapping and further statistical assessments reliably revealed a posterior superior temporal region (Wernicke's area, traditionally considered a language-specific region) as being differentially more important for processing nonverbal sounds compared with verbal sounds. These results suggest that, in most cases, processing of meaningful verbal and nonverbal auditory information break down together in stroke and that subsequent recovery of function applies to both domains. This suggests that language shares neural resources with those used for processing information in other domains.

Adult↗