Helsinki University of Technology

About: Helsinki University of Technology is a based out in . It is known for research contribution in the topics: Artificial neural network & Finite element method. The organization has 8962 authors who have published 20136 publications receiving 723787 citations. The organization is also known as: TKK & Teknillinen korkeakoulu.

The human auditory sensory memory trace persists about 10 sec: Neuromagnetic evidence

Abstract: Neuromagnetic responses were recorded to frequent "standard tones of l000 Hz and to infrequent 1100-Hz "deviant" tones with a 24-channel planar SQUID gradiometer. Stimuli were presented at constant interstimulus intervals (ISIs) ranging from 0.75 to 12 sec. The standards evoked a prominent 100-msec response, N100m, which increased in amplitude with increasing ISI. N100m could be dissociated into two subcomponents with different source areas. The posterior component, N100m2, increased when the ISI grew up to 6 sec, whereas the more anterior component, N100m2, probably continued its growth beyond the 12-sec ISI. At ISIs from 0.75 to 9 sec, the deviants elicited additionally a mismatch field (MMF). The equivalent sources of both N100m and MMF were at the supra-temporal auditory cortex. We assume that auditory stimuli leave in the auditory system a trace that affects the processing of the subsequent stimuli. The decrement of the N100m amplitude as well as elicitation of MMF can be considered as indirect evidence of active traces. A behavioral estimate of the persistence of the sensory auditory memory was obtained in a separate experiment in which the subject compared, without attending to the stimuli, tones presented at the daerent ISIs. The subjects discriminated the stimuli better than merely by chance at ISIs of 0.75-9 sec. The ISI dependence of the behavioral estimate as well as of N100m2 and MMF are similar enough to suggest a common underlying mechanism that retains information for a period of about 10 sec.

Impaired visual word processing in dyslexia revealed with magnetoencephalography.

Abstract: Dyslexia is most often attributed to phonological impairments, manifested in abnormal activation of the left temporal and temporoparietal cortex in response to auditorily presented language and possibly associated with anomalies in the cytoarchitecture and hemispheric symmetry of the plana temporale. The immediate cortical correlate of the severely impaired reading process has, however, remained obscure. Here we report on the distinct time courses of cortical activation in dyslexic and control subjects during passive viewing of single words, tracked with whole-head magneto-encephalography. A striking difference was found in the left inferior temporo-occipital region where intracranial recordings have recently identified word-specific responses within 200 msec after stimulus onset : controls showed a sharp activation at about 180 msec after word presentation, whereas dyslexics failed to activate this area entirely, or showed a slowly increasing late response. Perception of words as specific units thus seems to be impaired in dyslexics.