ABSTRACT
OBJECTIVE: To investigate the effects of cortical ischemic stroke and aphasic symptoms on auditory processing abilities in humans as indicated by the transient brain response, a recently documented cortical deflection which has been shown to accurately predict behavioral sound detection. METHODS: Using speech and sinusoidal stimuli in the active (attend) and the passive (ignore) recording condition, cortical activity of ten aphasic stroke patients and ten control subjects was recorded with whole-head MEG and behavioral measurements. RESULTS: Stroke patients exhibited significantly diminished neuromagnetic transient responses for both sinusoidal and speech stimulation when compared to the control subjects. The attention-related increase of response amplitude was slightly more pronounced in the control subjects than in the stroke patients but this difference did not reach statistical significance. CONCLUSIONS: Left-hemispheric ischemic stroke impairs the processing of sinusoidal and speech sounds. This deficit seems to depend on the severity and location of stroke. SIGNIFICANCE: Directly observable, non-invasive brain measures can be used in assessing the effects of stroke which are related to the behavioral symptoms patients manifest.
Subject(s)
Aphasia/physiopathology , Auditory Pathways/physiopathology , Auditory Perception/physiology , Cerebral Cortex/physiopathology , Evoked Potentials, Auditory/physiology , Stroke/physiopathology , Acoustic Stimulation , Aged , Aged, 80 and over , Analysis of Variance , Aphasia/complications , Female , Functional Laterality/physiology , Humans , Magnetoencephalography , Male , Middle Aged , Phonetics , Reaction Time/physiology , Severity of Illness Index , Stroke/complicationsABSTRACT
OBJECTIVE: The aim of the study was to investigate the effects of aging on human cortical auditory processing of rising-intensity sinusoids and speech sounds. We also aimed to evaluate the suitability of a recently discovered transient brain response for applied research. METHODS: In young and aged adults, magnetic fields produced by cortical activity elicited by a 570-Hz pure-tone and a speech sound (Finnish vowel /a/) were measured using MEG. The stimuli rose smoothly in intensity from an inaudible to an audible level over 750 ms. We used both the active (attended) and the passive recording condition. In the attended condition, behavioral reaction times were measured. RESULTS: The latency of the transient brain response was prolonged in the aged compared to the young and the accuracy of behavioral responses to sinusoids was diminished among the aged. In response amplitudes, no differences were found between the young and the aged. In both groups, spectral complexity of the stimuli enhanced response amplitudes. CONCLUSIONS: Aging seems to affect the temporal dynamics of cortical auditory processing. The transient brain response is sensitive both to spectral complexity and aging-related changes in the timing of cortical activation. SIGNIFICANCE: The transient brain responses elicited by rising-intensity sounds could be useful in revealing differences in auditory cortical processing in applied research.
