Frequency-Limiting Effects on Speech and Environmental Sound Identification for Cochlear Implant and Normal Hearing Listeners

BACKGROUND AND OBJECTIVES: It is important to understand the frequency region of cues used, and not used, by cochlear implant (CI) recipients. Speech and environmental sound recognition by individuals with CI and normal-hearing (NH) was measured. Gradients were also computed to evaluate the pattern of change in identification performance with respect to the low-pass filtering or high-pass filtering cutoff frequencies. SUBJECTS AND METHODS: Frequency-limiting effects were implemented in the acoustic waveforms by passing the signals through low-pass filters (LPFs) or high-pass filters (HPFs) with seven different cutoff frequencies. Identification of Korean vowels and consonants produced by a male and female speaker and environmental sounds was measured. Crossover frequencies were determined for each identification test, where the LPF and HPF conditions show the identical identification scores. RESULTS: CI and NH subjects showed changes in identification performance in a similar manner as a function of cutoff frequency for the LPF and HPF conditions, suggesting that the degraded spectral information in the acoustic signals may similarly constraint the identification performance for both subject groups. However, CI subjects were generally less efficient than NH subjects in using the limited spectral information for speech and environmental sound identification due to the inefficient coding of acoustic cues through the CI sound processors. CONCLUSIONS: This finding will provide vital information in Korean for understanding how different the frequency information is in receiving speech and environmental sounds by CI processor from normal hearing.

Association between Frontal-Executive Dysfunction and Speech-in-Noise Perception Deficits in Mild Cognitive Impairment

BACKGROUND AND PURPOSE: Speech-in-noise perception deficits have been demonstrated in patients with mild cognitive impairment (MCI). However, it remains unclear whether the impairment of speech perception varies between MCI subtypes. The purpose of this study was twofold: 1) to compare speech perception performance among MCI subgroups, and 2) to identify the cognitive domains specifically related to speech-in-noise perception. METHODS: We studied 46 patients with MCI and 39 hearing-threshold-matched cognitively normal elderly (CNE) subjects. Two different patient classifications were used: 1) patients with amnestic mild cognitive impairment (aMCI) (n=21) or nonamnestic mild cognitive impairment (naMCI) (n=25), and 2) patients with frontal-executive dysfunction (FED) (n=16) or without FED (n=30). All of the subjects underwent audiometric, neuropsychological, and speech perception assessments. Speech-in-noise perception was measured using sentence recognition tests in the presence of two types of background noise at four levels. RESULTS: First, as the level of background noise increased, the MCI with FED group scored lower than both the MCI without FED and CNE groups under both types of noise. Second, both the naMCI and aMCI groups scored lower than the CNE group, but there were no differences between the naMCI and aMCI groups in sentence recognition under any noise conditions. Third, significant correlations were found between sentence recognition and executive function scores both in the MCI groups and in the CNE group. CONCLUSIONS: Our findings suggest that frontal-executive function is strongly related to speech-in-noise perception and that MCI patients with FED have greater deficits in speech-in-noise perception compared to other subgroups of MCI.

Characteristics of Language Comprehension in Normal Elderly and the Mild Cognitive Impaired

BACKGROUND: Healthy aging is characterized by declines in language function and it is important to differentiate language comprehension difficulties due to pathological aging (i.e., mild cognitive impairment) from those due to normal aging. The purposes of this study were to review the literature on characteristics of language comprehension in normal elderly and the mild cognitive impaired, and to compare their performances on different language domains. METHODS: A comprehensive literature search identified numerous studies on language comprehension in both groups, and we analyzed them according to each language domain. RESULTS: The results indicated that the normal elderly show more difficulties in the comprehension of grammatically or lexically complex sentences and in text/discourse comprehension than words or simple sentences. Compared to normal elderly, MCI shows significantly lower performance on text/discourse comprehension and other tasks demanding higher cognitive function. In both groups, there are many different factors affecting language comprehension, such as hearing sensitivity, speech rate, literacy, and cognition. CONCLUSIONS: The results may provide insight into useful language comprehension tasks for differential diagnosis between normal aging and MCI. Further research on various compensatory strategies in daily life to facilitate language comprehension for both groups is warranted.

The Role of Subcortical Regions in Speech Production

BACKGROUND: Speech production requires accurate coordination of the speech musculature, and is dependent upon cooperation among cortical and subcortical structures. Multiple subcortical structures, including the basal ganglia, thalamus, and cerebellum, are involved in several parallel and segregated cortical-subcortical-cerebellum circuits. These circuits serve critical functions in integrating neural networks that modulate speech motor behaviors. Previous studies on speech disorders linked to subcortical lesions have been limited to perceptual evaluations of speech in patients with lesions. However, more recent studies using neuroimaging have confirmed the results of the lesion studies and provided further evidence of the important contributions of the subcortical structures to speech motor control. METHODS: We reviewed recent research literature on both behavioral and functional neuroimaging to reveal the role of subcortical structures in speech production. A review of this topic was conducted by searching the literature and electronic databases. RESULTS: Based on numerous articles, we found that the basal ganglia, thalamus, and cerebellum make different contributions to the modulation of speech-related variables. The cerebellum is the structure that is most strongly associated with speech rate, complexity, and timing. CONCLUSIONS: We conclude that the subcortical structures may play critical functions in speech production. The function of each structure involves the stimulation of cortical regions through the neural circuits and neurotransmitters. Thus, the function of the subcortical structures should be understood within the paradigm of neural networks.

Language Profiles of Transcortical Aphasia

BACKGROUND: The term "transcortical aphasia" is applied to primary lesions not involving the receptive and expressive language areas, but rather the areas connected to the association cortex. By definition, patients with transcortical aphasia can repeat what they have heard, but they have difficulty producing spontaneous speech or understanding speech. This paper reports the clinical features of stroke patients with transcortical aphasia to delineate the language profiles of its subtypes. METHODS: Eighty patients with stroke were divided into three subtypes of transcortical aphasia: transcortical sensory aphasia, transcortical motor aphasia, and mixed transcortical aphasia. A Korean version of the Western Aphasia Battery was used to compare the subdomains of language ability among the three groups. RESULTS: The patients showed a relatively preserved repetition ability, but the performances in repetition and generative naming, and the aphasia quotient were highest in the transcortical sensory aphasic group, followed by the transcortical motor aphasic and mixed transcortical aphasic groups. CONCLUSIONS: The present study provides detailed information on the language profiles of the three subtypes of transcortical aphasia, which can be differentiated based on the aphasia quotient and generative naming scores.

Effects of Subthalamic Nucleus Deep Brain Stimulation on the Phonation and Articulation of the Patients with Parkinson's Disease

BACKGROUND: The purpose of this study was to investigate the effects of the subthalamic nucleus (STN) deep brain stimulation (DBS) on the phonation and articulation of patients with Parkinson's disease (PD). METHODS: Seven PD patients who underwent bilateral STN DBS were included. The patients were asked to make and sustain the vowel sounds /a/ and /i/ as long as possible and to repeat nonsense syllables, /pa/, /ta/, /ka/ and /pataka/ as quickly as possible for 3 seconds. When the patients were administered levodopa `on' and `off' treatments, we evaluated the effect of DBS on the maximum phonation time (MPT), jitter (pitch perturbation), shimmer (intensity perturbation), tremor index and diadochokinetic rate (DDK). In each condition, using a Unified Parkinson's Disease Rating Scale score, we also measured the motor disability of the patients. RESULTS: During levodopa `off', both the DBS and levodopa treatment caused significant prolongation of the MPT of the vowels /a/ and /i/. Acoustic analysis showed that DBS had an effect on shimmer only when the patients were levodopa `off'. At the articulatory level, no significant changes were found in the diadochokinetic rate under any conditions. However, there was a correlation between the amount of improvement of voice tremor and sum of UPDRS scores measuring `tremor at rest' and `postural tremor'. CONCLUSIONS: In patients with advanced PD, STN DBS improves phonation, but had limited effects on articulation.

Hanja Alexia with Agraphia After Left Posterior Inferior Temporal Lobe Infarction: A Case Study

Korean written language is composed of ideogram (Hanja) and phonogram (Hangul), as Japanese consists of Kanji (ideogram) and Kana (phonogram). Dissociation between ideogram and phonogram impairment after brain injury has been reported in Japanese, but few in Korean. We report a 64-yr-old right-handed man who showed alexia with agraphia in Hanja but preserved Hangul reading and writing after a left posterior inferior temporal lobe infarction. Interestingly, the patient was an expert in Hanja; he had been a Hanja calligrapher over 40 yr. However, when presented with 65 basic Chinese letters that are taught in elementary school, his responses were slow both in reading (6.3 sec/letter) and writing (8.8 sec/letter). The rate of correct response was 81.5% (53 out of 65 letters) both in reading and writing. The patient's performances were beyond mean-2SD of those of six age-, sex-, and education-matched controls who correctly read 64.7 out of 65 and wrote 62.5 out of 65 letters with a much shorter reaction time (1.3 sec/letter for reading and 4.0 sec/letter for writing). These findings support the notion that ideogram and phonogram can be mediated in different brain regions and Hanja alexia with agraphia in Korean patients can be associated with a left posterior inferior temporal lesion.

Striatocapsular Infarct and Aphasia

BACKGROUND: Determining the mechanism for aphasia following a subcortical infarct involving the striatum and internal capsule has been controversial. The aim of this study was to determine the underlying mechanism, which might clarify the relationship between the severity of aphasia and the cortical hypoperfusion in a striatocapsular infarct. METHODS: We included 33 patients with striatocapsular infarcts in the dominant hemisphere on precontrast CT/MRI. A MR angiography (MRA) was done in all patients. Contrast enhanced MRI and/or triphasic perfusion CT (TPCT) were performed in 26 patients to identify slow collateral blood flows. The regional cerebral blood flow was evaluated in 14 out of 33 patients by perfusion SPECT. The index of aphasia severity was the aphasia quotient, measured by the Korean version-Western Aphasia Battery. RESULTS: Twenty-five of 33 patients (75.7%) showed aphasia with different degrees of severity. The four aphasic subgroups were mild (n=9), mild-to-moderate (n=8), moderate-to-severe (n=3), and severe (n=3) groups. Six patients with moderate-to-severe or severe degree of aphasia showed larger infarcts, occlusions of the middle cerebral artery (MCA) stem or internal carotid artery (ICA) on MRA, and abnormal delayed cortical vascular enhancements on MRI and/or TPCT. The severity of aphasia correlated strongly with the degree of perisylvian cortical hypoperfusion on SPECT. Focal perisylvian cortical atrophy on follow-up MRI was found in two patients with greater than moderate-to-severe aphasia. CONCLUSIONS: Aphasia of greater than moderate-to-severe degree following a striato-capsular infarct may be explained by selective neuronal loss of the perisylvian cortex due to the occlusion of the MCA stem or ICA and insufficient collateral blood flow. (J Korean Neurol Assoc 19(1):10~18, 2001

A Case of Frontotemporal Dementia Presenting with Apraxia of Speech

Apraxia of speech (AOS) is a speech disorder due to an impaired ability to program the positioning of the speech musculature and the sequencing of muscle movements. It differs from dysarthria because speech errors are inconsistent depending on the locus of the sound. We report a 66-year-old man who presented with AOS which evolved into frontotemporal dementia 5 years later. Initial neuropsychological test showed mainly buccofacial apraxia and frontal lobe dysfunction. Brain FDG-PET disclosed hypometabolism in frontotemporal region.

Parallel Short Forms for the Korean-Boston Naming Test (K-BNT)

BACKGROUND: The Korean-Boston Naming Test (K-BNT) is a popular measure of the confrontational naming ability. It is particularly sensitive to the early cognitive changes in Alzheimer's disease (AD) and Vascular dementia (VaD). The current study was conducted to develop parallel short forms for the K-BNT used in repeated assessments as well as in situations where the administration of the complete K-BNT is not practical. METHODS: Four 15-item short forms were newly constructed based on the item difficulties of the K-BNT measured from 565 normal elderly aged over 55. The K-BNT was administered to 130 dementia patients (75 AD, 55 VaD) and 130 healthy community-dwelling elderly whose age, sex, and education level were matched with the dementia patients. Scores for the short forms were derived by dividing up the items of the K-BNT. RESULTS: On each short form, normal elderly performed better than dementia patients, and scores on each could be extrapolated to a complete 60-item K-BNT score. Significant correlations were found between short forms and the K-BNT. To compare the probabilities of correctly identifying dementia, the areas under Receiver Operating Characteristic (ROC) curves of each form and the K-BNT were compared. It was found that all the short forms were as efficient as the 60-item K-BNT in identifying dementia. CONCLUSIONS: These results confirm that the four 15-item short forms developed in the current study are parallel and valid as the short forms of the K-BNT.

A dissociation of number processing between arabic and korean numbers: A case study

The cognitive domain of number processing has been known to be separable from that of language. Further, the number processing consists of Arabic and verbal number systems which could be also separable from each other. We report a 49-year-old woman who showed a dissociation between Arabic and Korean verbal numbers. Her impairment in number processing was characterized by the defective comprehension and expression of Korean verbal umbers, without notable defects in those of Arabic numbers. A follow-up examination revealed a further dissociation within the processing of Korean numbers, showing persistent impairment of number comprehension with improvement of number expression. In dealing with numbers with more than two digits, she showed syntactic errors characterized by uttering a string of single digit numbers(I.e., 365) rather than stating them as a whole number(365). Furthermore, auditory comprehension was also more accurate when the numbers were presented as an array of single digit numbers than a whole number with units. However, these syntactic errors were not observed on an automatic counting task. The evidence of separable representation of Arabic and Korean number system could be drawn from these observations, and therefore we propose the possibility of dual number processing pathways, one for a simple numbering system without semantic mediation and the other for a complex, multidigit numbering with semantic mediation.

Errors of ideomotor apraxia in Alzheimer's disease

BACKGROUND & PURPOSE: Ideomotor apraxia is a gestural deficit which is not due to primary sensory or motor deficit, poor auditory comprehension or incooperation. Previous studies on apraxia in AD patients include advanced AD patients who exhibited marked impairment in auditory comprehension, This might have confounded the results of the studies. The purpose of this study is to observe the frequencies and patterns of gestural errors in the early stage of AD. METHOD: Eighteen patients with AD (M : F = 4 : 14, age 62.6 + 7.2) and eighteen age- and sex- matched controls participated in this research. Patients who scored below 80 % of Western Aphasia Battery comprehension subtest and showed marked cognitive impairments were excluded (MMSE; 19.9 + 4.4, CDR 1.1+/- 0.5). Gestures. In response to commands were videotaped and analyzed by 2 neurologists and 1 speech-language pathologist. Test items included 3 types of movements ; 10 limb intrasitive, 15 transitive, and 10 buccofacial. RESULTS: Limb transitive movements were the most affected while buccofacial was the least. The error patterns most frequently observed were body-part-as-objects (BPO, 20%), external configuration orientation (ECO, 16%), and movement error(M, 9%). In comparision, BPO, ECO, M errors in normal control were 2%, 3%, and 4% respectively. In addition, apraxia item, which are to detecting AD were identified. CONCLUSION: It is suggested that the apraxia is commonly associated with AD even in the early stage of the disease and an accurate anaIysis of errors may contribute to establishing an early diagnosis of AD.

Naming deficits in patients with dementia of the Alzheimer type: Error analysis of korean version-Boston naming test

BACKGROUND & OBJECTIVES: The degree and the nature of performance deficit in confrontation naming tasks of patients with dementia of the Alzheimer type (DAT) are multifaceted depending on the stage of illness. Quantative analysis of patients responses may reveal the gradual deterioration of naming ability as the illness exacerbrates. In addition, based on the cognitive model proposed by Ellis and Young (1988), functional components and network involved in naming can be scrutinized for their integrity. The aim of this study is then two fold: first, it is to determine whether thee are quantitative differences in naming performance among the normal control and three DAT groups of different severities. Secondary it is to observe whether there are qualitative differences among the groups and if so, what categories of errors could differentiate one group from the others. METHOD: The DAT patients were trichotomized (CDR 0.5, CDR 1, and CDR 2) according to the severity of the illness based clinical dementia rating (CDR) scale. The Korean version of Boston Naming Test (K BNT) was administered to each DAT group and the normal. The responses were analysed according to six categories and then by detailed subcategories under each of the six categories. RESULTS & CONCLUSION: The results revealed significant mean value differences between the normal and CDR I & 2 groups. The CDR 0.5 group differentiated from the normal group since indefinite response were more evident in the former. Moreover, semantically unrelated errors and no-response errors became predominant as the illness worsens. These findings explicate that qualitative analysis of naming errors may be a valuable tool for us to understand the nature of naming deficits in DAT patients.