Sensory and motor processing

G. Caetano, N. Forss, R. Hari, Y. Hlushchuk, M. Illman, O. Jensen, V. Jousmäki, R. Lehtonen, T. Morita, J. Numminen, L. Parkkonen, M. Pohja, H. Renvall,  S. Salenius, M. Schürmann, and C. Simôes

Collaborators:

In daily life, humans typically process stimuli of more than one sensory modality at the same time; one example is audiotactile interaction. We found that vibrotactile stimuli can facilitate hearing, lowering the detection thresholds by about 12%. Our recent fMRI study indicated a 85-mm3 region in the posterior auditory belt area co-activated by auditory and vibrotactile stimuli; this brain region might subserve processing of audiotactile events that arise during dynamic contact between hands and environment.

Our studies on tactile processing have indicated phase-locking between the primary and secondary somatosensory cortices 70–100 ms after median nerve stimuli in the 20-Hz frequency range, as an indication of participation of these distant brain areas in the same large-scale cortical processing circuitry for touch.

By recording simultaneously rhythmic brain activity and electromyographic activity of a contracting muscle, we showed in 1997 that “cortex speaks to the muscle” at about 20 Hz and that cortex always leads in time. This “cortex–muscle coherence” has now become rather popular worldwide. We have shown that the reliability and reproducibility of the signals is good within one recording session but that caution is needed when interpreting absolute levels or changes in the strength of coherence in single subjects between the sessions, for example during follow-up of various patient groups.

Studies have been completed on sensory-level processing deficits in subjects with dyslexia and on the search for brain correlates for behavioural measures of face recognition during spatial noise masking.

Publications

  1. Furey ML, Tanskanen T, Beauchamp M, Avikainen S, Uutela K, Hari R and Haxby JV: Modulation of early and late neural responses to faces and houses by selective attention. Submitted.
  2. Hari R: Magnetoencephalography in Clinical Neurophysiological Assesment of Human Cortical Functions. In E Nieder­meyer and F Lopes da Silva (Eds) Electroencephalography: Basic Principles, Clinical Applications, and Related Fields. 5th edition, Lippincott, Williams & Wilkins 2004, pp. 1165–1197.
  3. Hlushchuk Y, Forss N and Hari R: Distal-to-proximal representation of volar index finger in human area 3b. Neuroimage 2004, 21: 696–700.
  4. Jensen O, Goel P, and Kopell N, Pohja M, Hari R and Ermentrout B: On the human motor-cortex beta rhythm: Sources and modelling. Neuroimage, in press.
  5. Jääskeläinen IP, Ojanen V, Ahveninen J, Auranen T, Levänen S, Möttönen R, Tarnanen I, and Sams M: Adaptation of neuromagnetic N1 rsponses to phonetic stimuli by visual speech in humans. NeuroReport  2004, 15: 2741–2744.
  6. Möttönen R, Schürmann M and Sams M: Time course of multisensory interactions during audiovisual speech perception in humans: A magnetoencephalographic study. Neurosci Lett 2004, 363: 112–115.
  7. Numminen J, Schürmann M, Hiltunen J, Joensuu R, Jousmäki V, Koskinen SK, Salmelin R and Hari R: Cortical activation during a spatiotemporal tactile comparison task. Neuroimage 2004, 22: 815–821.
  8. Näsänen R, Kaukiainen A, Hero V, Päällysaho J, Müller K, Hari R, Akila R, Sainio M: Effects of long-term occupational solvent exposure on contrast sensitivity and performance in visual search. Environ Toxicol Pharmacol 2005, 19: 497-504.
  9. Pohja M, Salenius S and Hari R: Reproducibility of cortex–muscle coherence. Neuroimage, in press.
  10. Schürmann M, Caetano G, Jousmäki V and Hari R: Hands help hearing: Facilitatory audiotactile interaction at low sound-intensity levels. J Am Soc Acoust 2004, 115: 830–832.
  11. Simôes C, Salenius S and Curio G: Short-term (≈ 600 ms) prediction of perturbation dynamics for 10- and 20-Hz MEG rhythms in human primary sensorimotor hand cortices, NeuroImage 2004, 22: 387–393.
  12. Raij T and Jousmäki V: MEG studies of gross-modal integration and plasticity. In The Handbook of Multisensory Processes, Ed. Gemma Galvert, Charles Spence and Barry E. Stein, MIT Press, Cambridge, Massachusetts, USA, 2004, pp 515–528.
  13. Renvall H, Lehtonen R and Hari R: Abnormal response recovery in the right somatosensory cortex of dyslexic adults. Cerebral Cortex 2005, 15; 507–513
  14. Tanskanen T, Näsänen R, Montez T, Päällysaho J and Hari R: Face recognition and cortical responses show similar sensitivity to noise spatial frequency. Cerebral Cortex 2005, 15; 526–534