Early occipito-parietal activity in a word recognition task: an EEG and MEG study

OBJECTIVE We investigated early brain activity (under 200 ms after the stimulus onset) related to the encoding and the retrieval of verbal information. METHODS First, we compared ERPs produced by words which were encoded to ERPs produced by words from following test phases (correctly identified repetitions and correctly classified new words) in two different experiments. Experiment 1 consisted of an intentional learning paradigm and experiment 2 consisted of an incidental learning paradigm. In addition, we conducted a control experiment (experiment 3), which was a continuous recognition task with two different repetition intervals. Secondly, we conducted a magnetoencephalographic (MEG) study to further investigate early brain activity (experiment 4). The same intentional learning paradigm as in experiment 1 was used. RESULTS We found that ERPs elicited by correctly classified test words (repeated words and new words) of both experiment 1 and experiment 2 were significantly more negative going than the ERPs elicited by the study words. This effect was apparent between 100 ms and 200 ms after the stimulus onset and was distributed over occipital and parietal scalp locations. In the control task (experiment 3), these early potential differences were missing (for both repetition intervals). Early event-related fields (ERFs) were also found to depend on the situation of the study phase and the test phase. This activity difference peaked at 120 ms after the stimulus onset. The distributions of the difference magnetic fields were occipito-parietal and thus consistent with the findings of experiment 1 (EEG-experiment). CONCLUSION Whether the effect we defined in the present study is due to an increase of activity during the test situation or due to a decrease of activity during the study situation remains unclear. However, it might reflect attentional processes within a word recognition task depending on whether a word is encoded or an effort of word retrieval has to be made.

[1]  S. Hillyard,et al.  Event-related brain potentials in the study of visual selective attention. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[2]  H Bauer,et al.  Technical requirements for high-quality scalp DC recordings. , 1989, Electroencephalography and clinical neurophysiology.

[3]  S. Houle,et al.  Activation of medial temporal structures during episodic memory retrieval , 1996, Nature.

[4]  G. Mangun,et al.  ERP and fMRI measures of visual spatial selective attention , 1998, Human brain mapping.

[5]  L. Deecke,et al.  Localization of brain activity during auditory verbal short-term memory derived from magnetic recordings , 1991, Brain Research.

[6]  R. Hari.  On Brain's Magnetic Responses to Sensory Stimuli , 1991, Journal of clinical neurophysiology : official publication of the American Electroencephalographic Society.

[7]  W Lang,et al.  Cortical DC potential shifts accompanying auditory and visual short-term memory. , 1992, Electroencephalography and clinical neurophysiology.

[8]  A. Gevins.  The future of electroencephalography in assessing neurocognitive functioning. , 1998, Electroencephalography and clinical neurophysiology.

[9]  S. Kuriki,et al.  Neural processing of words in the human extrastriate visual cortex. , 1998, Brain research. Cognitive brain research.

[10]  R. Eason.  Visual evoked potential correlates of early neural filtering during selective attention , 1981 .

[11]  Steven A. Hillyard,et al.  Mechanisms and models of se-lective attention , 1995 .

[12]  F. Craik,et al.  Levels of Pro-cessing: A Framework for Memory Research , 1975 .

[13]  E. Donchin,et al.  Psychophysiology : systems, processes, and applications , 1987 .

[14]  M. Coles,et al.  Event-related brain potentials: An introduction. , 1995 .

[15]  H. Jasper,et al.  The ten-twenty electrode system of the International Federation. The International Federation of Clinical Neurophysiology. , 1999, Electroencephalography and clinical neurophysiology. Supplement.

[16]  P Walla,et al.  Early cortical activation indicates preparation for retrieval of memory for faces: an event-related potential study , 1998, Neuroscience Letters.

[17]  Richard S. J. Frackowiak,et al.  Brain regions associated with acquisition and retrieval of verbal episodic memory , 1994, Nature.

[18]  M. Rugg.  ERP studies of memory. , 1995 .

[19]  C. Michel,et al.  Evidence for rapid face recognition from human scalp and intracranial electrodes , 1997, Neuroreport.

[20]  H. Begleiter,et al.  A neurophysiologic correlate of visual short-term memory in humans. , 1993, Electroencephalography and clinical neurophysiology.

[21]  P. Svasek,et al.  PC-Supported 64-Channel DC-EEG Amplifier , 1991, MIE.

[22]  P. Brodal.  The Central Nervous System , 1992 .

[23]  Astrid M. Schloerscheidt,et al.  Neural correlates of depth of processing effects on recollection: evidence from brain potentials and positron emission tomography , 1998, Experimental Brain Research.

[24]  T. Allison,et al.  Word recognition in the human inferior temporal lobe , 1994, Nature.

[25]  R Salmelin,et al.  Information processing in the human brain: magnetoencephalographic approach. , 1996, Proceedings of the National Academy of Sciences of the United States of America.

[26]  G H Glover,et al.  Separate neural bases of two fundamental memory processes in the human medial temporal lobe. , 1997, Science.

[27]  R. Dolan,et al.  Differential activation of the prefrontal cortex in successful and unsuccessful memory retrieval. , 1996, Brain : a journal of neurology.

[28]  J. G. Snodgrass,et al.  Pragmatics of measuring recognition memory: applications to dementia and amnesia. , 1988, Journal of experimental psychology. General.