It is not yet clear whether humans are able to learn while they are sleeping. Here we show that full-term human newborns can be taught to discriminate between similar vowel sounds when they are fast asleep. It is possible that such sleep training soon after birth could find application in clinical or educational situations.
The aim of this follow-up study was to examine the long-term disabilities and handicaps caused by severe head injuries and their effects on the everyday life of patients and their relatives. The group studied consisted of 19 subjects who had suffered a severe closed-head injury during 1984 and had been rehabilitated in the Käpylä Rehabilitation Center. In 1989 a thorough functional assessment of these patients was carried out. In addition, information concerning the quality of life, activities of daily living (ADL) and social situation was gathered by means of questionnaires filled in by the patient and, if possible, by a close relative. The results indicated the importance of changes in cognitive functions, personality and emotional reactions. Changes in personality and emotional reactions were especially emphasized by the relatives. We also correlated the patients' and their relatives' estimates of the occurrence of memory problems, whereas tests of visual memory, though able to discriminate the brain-injured from normal subjects, did not correlate on a statistically significant level with the estimates of patients and relatives. The implications of the results for methods of assessment and the planning of rehabilitation programmes are discussed.
Most right-handers perceive an octave illusion when they are presented with a 400 Hz tone to one ear and with a 800 Hz tone to the other ear simultaneously, and when the tones continuously reverse between the ears: instead of the correct sound sequence, the subjects typically report a high tone in the right ear alternating with a low tone in the left. To study the neural basis of the illusion, we recorded neuromagnetic responses to binaural 400 and 800 Hz tones in different combinations. In the auditory cortex of each hemisphere, the 100 ms response (N100m) was stronger to pairs where the 800 Hz tone was presented to the contralateral ear and the 400 Hz tone to the ipsilateral ear than vice versa. The sustained fields tended to behave in an opposite manner. We suggest that the perceived locations of the sounds in the octave illusion follow the N100m lateralization, and the percept is contributed by streaming by the ear.
Traumatic brain injury (TBI) causes damage through complex pathophysiological mechanisms. Deficits related to traumatic axonal injury persist in a subset of patients with no macroscopic lesions on conventional MRI. We examined two event-related brain potentials, mismatch negativity (MMN) and P3a, to identify possible electrophysiological anomalies in this subset of TBI patients in comparison with TBI patients with focal abnormalities on MRI/computed tomography and healthy controls. Each group consisted of 10 individuals. A passive oddball paradigm, in which the individuals were instructed to ignore auditory stimuli while watching a silent movie, consisted of non-native speech sounds presented in a random order. Patients with no discernible lesions on conventional MRI showed a significantly augmented amplitude of the brain's involuntary change-detection response MMN, relative to that of the two other groups. In patients with focal neuroradiological abnormalities, this MMN anomaly was not found, whereas the subsequent orientation-related P3a response was significantly enlarged when compared with that of the controls. The present findings demonstrate that MMN is indicative of a functional abnormality in the mechanisms of involuntary attention in chronic TBI patients with normal conventional MRI findings, indexing their increased distractibility associated with the traumatically-induced loss of neural integrity.
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