Activation of a distributed somatosensory cortical network in the human brain: a dipole modelling study of magnetic fields evoked by median nerve stimulation. Part II: Effects of stimulus rate, attention and stimulus detection.

In this study we used a repeated measures design and univariate analysis of variance to study the respective effects of ISI, spatial attention and stimulus detection on the strengths of the sources previously identified by modelling SEFs during the 200 ms following mentally counted left median nerve stimuli delivered at long and random ISIs (Part I). We compared the SEF source strengths in response to frequent and rare stimuli, both in detection and ignoring conditions. This permitted us to establish a hierarchy in the effects of ISI, attention and stimulus detection on the activation of the cortical network of SEF sources distributed in SI and posterior parietal cortex contralateral to stimulation, and in the parietal operculum (SII) and premotor frontal cortex of both hemispheres. In all experimental conditions the SI and parietal opercular sources were the most active. All sources were more active in response to stimuli delivered at long and random ISIs and the frontal sources were activated only in this condition of stimulation. Driving the subject's attention toward the side stimulated had no detectable effect on the activity of SEF sources at short ISI. At long ISIs mental counting of the stimuli increased the responses of all sources except SI. These results suggest that activation of frontal sources during mental counting could reflect a working memory process, and that of posterior parietal sources a spatial attention effect detectable only at long ISIs.

[1]  F. Mauguière,et al.  Somatosensory responses during selective spatial attention: The N120‐to‐N140 trasition , 1995 .

[2]  M Hämäläinen,et al.  Somatosensory evoked cerebral magnetic fields from SI and SII in man. , 1984, Electroencephalography and clinical neurophysiology.

[3]  C. Shagass,et al.  Somatosensory evoked potential changes with a selective attention task. , 1982, Psychophysiology.

[4]  H Pratt,et al.  Mechanically and electrically evoked somatosensory potentials in humans: effects of stimulus presentation rate. , 1980, Electroencephalography and clinical neurophysiology.

[5]  Riitta Hari,et al.  Cortical sources of human short-latency somatosensory evoked fields to median and ulnar nerve stimuli , 1996, Brain Research.

[6]  P M Rossini,et al.  Analysis of interhemispheric asymmetries of somatosensory evoked magnetic fields to right and left median nerve stimulation. , 1994, Electroencephalography and clinical neurophysiology.

[7]  S. Geisser,et al.  On methods in the analysis of profile data , 1959 .

[8]  Patricia T. Michie,et al.  The nature of selective attention effects on auditory event-related potentials , 1990, Biological Psychology.

[9]  C. Rosenkilde,et al.  Functional heterogeneity of the prefrontal cortex in the monkey: a review. , 1979, Behavioral and neural biology.

[10]  J C Mazziotta,et al.  Effects of stimulus rate on regional cerebral blood flow after median nerve stimulation. , 1995, Brain : a journal of neurology.

[11]  M. Taussig.  The Nervous System , 1991 .

[12]  V. Jousmäki,et al.  Activation of a distributed somatosensory cortical network in the human brain. A dipole modelling study of magnetic fields evoked by median nerve stimulation. Part I: Location and activation timing of SEF sources. , 1997, Electroencephalography and clinical neurophysiology.

[13]  T Allison,et al.  The scalp topography of human somatosensory and auditory evoked potentials. , 1977, Electroencephalography and clinical neurophysiology.

[14]  T. Allison.  Recovery functions of somatosensory evoked responses in man. , 1962, Electroencephalography and clinical neurophysiology.

[15]  J E Desmedt,et al.  The cognitive P40, N60 and P100 components of somatosensory evoked potentials and the earliest electrical signs of sensory processing in man. , 1983, Electroencephalography and clinical neurophysiology.

[16]  P. Michie,et al.  The effects of spatial selective attention on the somatosensory event-related potential. , 1987, Psychophysiology.

[17]  R. Hari,et al.  Separate finger representations at the human second somatosensory cortex , 1990, Neuroscience.

[18]  F. Mauguière,et al.  Mapping study of somatosensory evoked potentials during selective spatial attention. , 1991, Electroencephalography and clinical neurophysiology.

[19]  S. Ogawa,et al.  Visualization of information processing in the human brain : recent advances in MEG and functional MRI , 1996 .

[20]  M Hämäläinen,et al.  Early deflections of cerebral magnetic responses to median nerve stimulation. , 1989, Electroencephalography and clinical neurophysiology.

[21]  Riitta Hari,et al.  Interaction between afferent input from fingers in human somatosensory cortex , 1995, Brain Research.

[22]  R. Ilmoniemi,et al.  Magnetoencephalography-theory, instrumentation, and applications to noninvasive studies of the working human brain , 1993 .

[23]  R. Hari,et al.  Evoked responses of human auditory cortex may be enhanced by preceding stimuli. , 1989, Electroencephalography and clinical neurophysiology.

[24]  D Robertson,et al.  Differential enhancement of early and late components of the cerebral somatosensory evoked potentials during forced‐paced cognitive tasks in man , 1977, The Journal of physiology.

[25]  R E Passingham.  Memory of monkeys (Macaca mulatta) with lesions in prefrontal cortex. , 1985, Behavioral neuroscience.

[26]  T. Powell,et al.  An anatomical study of converging sensory pathways within the cerebral cortex of the monkey. , 1970, Brain : a journal of neurology.

[27]  M. Raichle,et al.  Stimulus rate dependence of regional cerebral blood flow in human striate cortex, demonstrated by positron emission tomography. , 1984, Journal of neurophysiology.

[28]  P. Rossini,et al.  Short latency somatosensory evoked responses to median nerve stimulation in healthy humans: electric and magnetic recordings. , 1989, The International journal of neuroscience.

[29]  P. Goldman-Rakic,et al.  Connections of the ventral granular frontal cortex of macaques with perisylvian premotor and somatosensory areas: Anatomical evidence for somatic representation in primate frontal association cortex , 1989, The Journal of comparative neurology.

[30]  T. Yoshimoto,et al.  Neuromagnetic evidence of pre- and post-central cortical sources of somatosensory evoked responses. , 1996, Electroencephalography and clinical neurophysiology.

[31]  R Hari.  MEG in the study of human cortical functions. , 1996, Electroencephalography and clinical neurophysiology. Supplement.

[32]  M G Marciani,et al.  Non-invasive evaluation of input-output characteristics of sensorimotor cerebral areas in healthy humans. , 1987, Electroencephalography and clinical neurophysiology.

[33]  R. Knight,et al.  P300 generation by novel somatosensory stimuli. , 1991, Electroencephalography and clinical neurophysiology.

[34]  Dr. Juhani Hyvärinen.  The Parietal Cortex of Monkey and Man , 1982, Studies of Brain Function.

[35]  R. Hari,et al.  Functional Organization of the Human First and Second Somatosensory Cortices: a Neuromagnetic Study , 1993, The European journal of neuroscience.

[36]  C Tomberg,et al.  Mapping early somatosensory evoked potentials in selective attention: critical evaluation of control conditions used for titrating by difference the cognitive P30, P40, P100 and N140. , 1989, Electroencephalography and clinical neurophysiology.

[37]  F. Mauguière,et al.  Target side and scalp topography of the somatosensory P300. , 1993, Electroencephalography and clinical neurophysiology.

[38]  F. Plum.  Handbook of Physiology. , 1960 .

[39]  C C Wood,et al.  Electrical sources in human somatosensory cortex: identification by combined magnetic and potential recordings. , 1985, Science.

[40]  David J. Hand,et al.  Analysis of Repeated Measures , 1990 .