Cerebral Cortex Advance Access originally published online on August 21, 2006
Cerebral Cortex 2007 17(6):1486-1492; doi:10.1093/cercor/bhl060
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Human Ventral Parietal Cortex Plays a Functional Role on Visuospatial Attention and Primary Consciousness. A Repetitive Transcranial Magnetic Stimulation Study
1 Dipartimento Fisiologia Umana e Farmacologia, Università degli Studi di Roma "La Sapienza," 00185 Rome, Italy, 2 IRCCS "Centro S. Giovanni di Dio-F.B.F.," 25125 Brescia, Italy, 3 A.Fa.R. Dipartimento Neuroscienze, Osp. FBF, Isola Tiberina, 00186 Rome, Italy, 4 Dipartimento di Neuroscienze, Sezione Neurologia, Università Siena, 53100 Italy, 5 Dipartimento di Neuroscienze, Sezione Psichiatria, Università Siena, 53100 Italy, 6 Clinica Neurologica, Campus Biomedico, Università di Roma, 00155 Italy
Address correspondence to Dr Claudio Babiloni, Dipartimento di Fisiologia Umana e Farmacologia, Università degli Studi di Roma "La Sapienza", P.le Aldo Moro 5, 00185 Rome, Italy. Email: claudio.babiloni{at}uniroma1.it.
In this paper, we used repetitive transcranial magnetic stimulation (rTMS) in 18 normal subjects to investigate whether the ventral posterior parietal cortex (PPC) plays a causal role on visuospatial attention and primary consciousness and whether these 2 functions are linearly correlated with each other. Two distinct experimental conditions involved a similar visual stimuli recognition paradigm. In "Consciousness" experiment, number of consciously perceived visual stimuli was lower by about 10% after rTMS (300 ms, 20 Hz, motor threshold intensity) on left or right PPC than after sham (pseudo) rTMS. In "Attentional" Posner's experiment, these stimuli were always consciously perceived. Compared with sham condition, parietal rTMS slowed of about 25 ms reaction time to go stimuli, thus disclosing effects on endogenous covert spatial attention. No linear correlation was observed between the rTMS-induced impairment on attention and conscious perception. Results suggest that PPC plays a slight but significant causal role in both visuospatial attention and primary consciousness. Furthermore, these high-level cognitive functions, as modulated by parietal rTMS, do not seem to share either linear or simple relationships.
Key Words: primary consciousness repetitive transcranial magnetic stimulation (rTMS) ventral posterior parietal cortex visuospatial attention
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