Repetition Deficits Research Articles

Repetition Deafness: Repeated Words in Computer-Compressed Speech Are Difficult to Encode and Recall

This research demonstrates a new cognitive phenomenon known as repetition deafness, a difficulty in immediate recall of repeated words in computer-compressed speech Sixty-four subjects heard sentences and lists at four speeded rates 70, 55, 35, and 28 ms/phoneme Each target word in the materials followed a pretarget word that was either identical (repeated-target condition) or different (unrepeated-target condition), and targets were harder to recall when repeated than unrepeated Repetition deafness was rate-limited, occurring only with rapid rates of presentation (55 ms/phoneme or less), and decreased in magnitude as structure increased from lists to sentences Implications for current theories of repetition deficits are discussed

Tc-99m HMPAO Brain Perfusion SPECT in Acute Aphasia Correlation With Clinical and Structural Findings

Tc-99m hexamethylpropylene amineoxime (HMPAO) brain perfusion SPECT was correlated with CT, MRI, and clinical findings in 17 patients with acute and subacute aphasia to determine its diagnostic potential in the early phases of stroke-associated language dysfunction. SPECT was performed using a dedicated brain imaging system after intravenous injection of 20 mCi (740 MBq) of Tc-99m HMPAO. Transaxial and three-dimensional surface rendered images were evaluated visually, and perfusion defects were correlated with CT, MRI, and a standard battery of clinical tests for aphasia. Clinical examination was insufficient for anatomic localization of aphasia in more than 40% of patients. CT exams were normal in 5 patients, although SPECT demonstrated perfusion defects in all 17. Nonfluent aphasia was present in only 6 of 10 patients with perfusion defects in Broca's area and fluent aphasia was present in only 5 of 10 patients with lesions in Wernicke's area. Auditory comprehension defect was associated with perfusion defects in the inferior parietal region in 9 of 12 patients (P = 0.05); reading and writing abnormalities were associated with perfusion defects in the posterior frontal, superior and inferior parietal cortex, and superior temporal gyri, and repetition deficit was associated with defects involving the inferior parietal cortex, the supramarginal and angular gyri, and the ipsilateral thalamus in 8 of 11 patients (P < 0.05). Brain perfusion SPECT should be included in the initial evaluation of aphasic patients, because clinical tests of aphasia and morphological imaging have limited value for accurately determining the extent and location of functional deficits.

Repetition in aphasia

Forty-one Spanish-speaking left hemisphere-damaged patients were taken and divided into seven groups (transcortical motor, Broca aphasia, conduction aphasia, Wernicke aphasia, anomic aphasia, alexia without agraphia, and global aphasia). Three repetition tests (words, high-probability and low-probability sentences) taken from the Boston Diagnostic Aphasia Examination Spanish version (Goodglass and Kaplan, Evaluación de las afasias y de transtomos similares, 1979) were given. Repetition errors were specially associated with perisylvian aphasias (Broca, conduction, and Wernicke). However, in all aphasic groups some repetition errors were observed. They were not only quantitative but also qualitatively different. Depending on the specific repetition task, errors may be evident or unnoticed in a particular aphasic group. Different mechanisms underlying repetition deficits are proposed: limitation of the auditory—verbal short-term memory, difficulties at the level of the phonological production, defects in phoneme recognition, and deficits in semantic and syntactic comprehension.

Repetition deficits in three aphasic syndromes

This study examined the repetition errors of three aphasic subgroups during a repetition task. A total of 95 subjects, including 32 conduction, 38 Broca's, and 25 Wernicke's aphasics, repeated phrases and sentences from the Repeating Phrases Subtest of the Boston Diagnostic Aphasia Examination. Conduction aphasics exhibited a greater number of phonemic attempts, word revisions, and word and phrase repetitions. Broca's aphasics demonstrated more phonemic errors and omissions. Finally, Wernicke's aphasics showed more unrelated words and jargon.

The critical role of Wernicke's area in sentence repetition.

The anatomical correlates of persistent deficits in sentence repetition were studied in a group of 32 right-handed patients with fluent aphasia caused by left hemisphere ischemic stroke. Patients whose ability to repeat remained impaired by 6 months after onset almost without exception had damage to Wernicke's area. Furthermore, all patients with damage to Wernicke's area had impaired repetition 6 months after onset. The most consistent lesion correlating with chronic impairment of repetition, therefore, was one destroying parts or all of Wernicke's area. Lesions outside of this area typically resulted in milder impairment of repetition that resolved within a few months. Only 5 patients had no repetition impairment when tested early (1 month after onset). These patients all had lesions anterior to the rolandic fissure, some including Broca's area.

An investigation of repetition and language processing in a case of conduction aphasia

A study is reported of a single case of conduction aphasia. A battery of tasks designed to investigate the parameters of the patient's severe repetition deficit is supplemented by tests of several language functions. The results provide extensive information on a wide range of the patient's language abilities and are used to evaluate the adequacy of four models that have been offered to account for conduction aphasia. An argument is made in support of the suggestion that the syndrome of conduction aphasia should be divided into two subgroups based on patients' ability to select and realize phonemes in speech output. It is concluded that the best explanation for the disorder of patients with repetition deficit but without significant speech output problems is the hypothesis that repetition ability is compromised by a pathological limitation of auditory-verbal short-term memory. This hypothesis is extended to account for the pattern of results obtained in the language tasks.

Short-term memory impairment and spontaneous speech

The spontaneous speech of a patient with a specific repetition deficit was studied. The amount of pausing and of paraphasic errors was found to be normal. It was concluded that the repetition difficulty arose from an auditory-verbal short-term memory impairment and not a high-level speech production deficit. It was further concluded that the STM store involved was not part of the speech output system.

Behavioral analysis of the repetition deficit in conduction aphasia.

Behavioral analysis of the repetition deficit in conduction aphasia.